U.S. patent application number 15/590259 was filed with the patent office on 2017-08-24 for rapid breeding of plants.
The applicant listed for this patent is Elwha LLC. Invention is credited to Mahalaxmi Gita Bangera, Philip A. Eckhoff, Roderick A. Hyde, Edward K. Y. Jung, Wayne R. Kindsvogel, Lowell L. Wood, JR..
Application Number | 20170238488 15/590259 |
Document ID | / |
Family ID | 52109779 |
Filed Date | 2017-08-24 |
United States Patent
Application |
20170238488 |
Kind Code |
A1 |
Bangera; Mahalaxmi Gita ; et
al. |
August 24, 2017 |
RAPID BREEDING OF PLANTS
Abstract
Various embodiments disclosed herein include systems, methods,
compositions, and products by process for Rapid-breeding of plants.
In certain embodiments, the systems and/or methods are at least
partially automated.
Inventors: |
Bangera; Mahalaxmi Gita;
(Renton, WA) ; Eckhoff; Philip A.; (Kirkland,
WA) ; Hyde; Roderick A.; (Redmond, WA) ; Jung;
Edward K. Y.; (Bellevue, WA) ; Kindsvogel; Wayne
R.; (Seattle, WA) ; Wood, JR.; Lowell L.;
(Bellevue, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Elwha LLC |
Bellevue |
WA |
US |
|
|
Family ID: |
52109779 |
Appl. No.: |
15/590259 |
Filed: |
May 9, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13922445 |
Jun 20, 2013 |
9681615 |
|
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15590259 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C12N 5/0025 20130101;
G16C 99/00 20190201; A01H 1/04 20130101; A01H 1/08 20130101; A01H
4/001 20130101; A01H 1/02 20130101; A01H 4/00 20130101; A01H 5/10
20130101; C12Q 1/6895 20130101; A01H 1/025 20130101 |
International
Class: |
A01H 4/00 20060101
A01H004/00; C12Q 1/68 20060101 C12Q001/68; A01H 1/02 20060101
A01H001/02; C12N 5/00 20060101 C12N005/00; A01H 5/10 20060101
A01H005/10 |
Claims
1.-33. (canceled)
34. A method for rapidly breeding plants, comprising: combining at
least two gametes to obtain at least one first round progeny plant
zygote or embryo; isolating one or more stem cells from the at
least one first round progeny plant zygote or embryo having at
least one desirable gene; differentiating the one or more isolated
stem cells into at least one second round gamete having at least
one desirable gene; combining the at least one second round gamete
with a third gamete such that at least one second round progeny
plant zygote or embryo is obtained.
35. The method of claim 34, further including: isolating one or
more stem cells from the at least one second round progeny plant
zygote or embryo; differentiating the one or more isolated stem
cells into at least one third round gamete having at least one
desirable gene; and combining the at least one third round gamete
with a fourth gamete such that at least one third progeny plant
zygote or embryo is obtained.
36. The method of claim 34, further including analyzing the
genotype of the at least one first round or the at least one second
round progeny plant zygote or embryo.
37. The method of claim 36, wherein analyzing the genotype includes
at least one of genetic sequencing, mRNA sequencing, or protein
sequencing.
38. The method of claim 37, wherein genetic sequencing includes at
least one of sequencing cell nucleus DNA, sequencing mitochondrial
DNA, characterizing DNA methylation, or characterizing telomere
length.
39. The method of claim 36, further including identifying at least
one desired transcription or translation characteristic from the
sequence of the at least one first round or the at least one second
round progeny plant zygote or embryo.
40. The method of claim 34, further including applying at least one
of a polymer or fungicide to the at least one first round or the at
least one second round progeny plant zygote or embryo.
41. The method of claim 34, further including inserting one or more
markers into the at least one first round or the at least one
second round progeny plant zygote or embryo.
42. The method of claim 41, wherein the marker includes one or more
of a colorimetric marker, electronic marker, protein marker or
genetic marker.
43. The method of claim 34, wherein isolating the one or more stem
cells includes selecting the one or more stem cells based on at
least one of genetic sequence analysis, mRNA sequence analysis, or
gene or protein marker selection.
44. The method of claim 34, further including modifying at least
one of the one or more stem cells prior to differentiating.
45. The method of claim 44, wherein modifying the at least one of
the one or more stem cells includes at least one of gene insertion,
gene deletion, gene mutation, alteration in methylation, protein
insertion, or manipulation of cell cytoplasm.
46. The method of claim 44, wherein modifying the at least one of
the one or more stem cells includes modifying at least one
telomere, disrupting or removing the outer cell membrane, or
disrupting or removing the cell nucleus membrane.
47. The method of claim 34, wherein at least one gamete of the at
least two gametes combined to obtain at least one first round
progeny plant zygote or embryo is differentiated from a stem cell
line or stem cell tissue.
48. The method of claim 34, wherein at least one step of the method
is automated.
49. The method of claim 48, wherein the at least one automated step
is controlled by a computing device.
50. The method of claim 34, further including storing at least one
of the progeny plant zygotes or embryos.
51. The method of claim 34, further including culturing at least
one of the progeny plant zygotes or embryos.
Description
[0001] If an Application Data Sheet (ADS) has been filed on the
filing date of this application, it is incorporated by reference
herein. Any applications claimed on the ADS for priority under 35
U.S.C. .sctn..sctn.119, 120, 121, or 365(c), and any and all
parent, grandparent, great-grandparent, etc. applications of such
applications, are also incorporated by reference, including any
priority claims made in those applications and any material
incorporated by reference, to the extent such subject matter is not
inconsistent herewith.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] The present application claims the benefit of the earliest
available effective filing date(s) from the following listed
application(s) (the "Priority Applications"), if any, listed below
(e.g., claims earliest available priority dates for other than
provisional patent applications or claims benefits under 35 USC
.sctn.119(e) for provisional patent applications, for any and all
parent, grandparent, great-grandparent, etc. applications of the
Priority Application(s)). In addition, the present application is
related to the "Related Applications," if any, listed below.
PRIORITY APPLICATIONS
[0003] None.
RELATED APPLICATIONS
[0004] U.S. patent application Ser. No. ______, entitled RAPID
BREEDING OF PLANTS, naming MAHALAXMI GITA BANGERA, PHILIP A.
ECKHOFF, RODERICK A. HYDE, EDWARD K. Y. JUNG, WAYNE R. KINDSVOGEL
AND LOWELL L. WOOD, JR. as inventors, filed 20 Jun. 2013 with
attorney docket no. 0205-004-001-000000, is related to the present
application.
[0005] If the listings of applications provided above are
inconsistent with the listings provided via an ADS, it is the
intent of the Applicant to claim priority to each application that
appears in the Priority Applications section of the ADS and to each
application that appears in the Priority Applications section of
this application.
[0006] All subject matter of the Priority Applications and the
Related Applications and of any and all parent, grandparent,
great-grandparent, etc. applications of the Priority Applications
and the Related Applications, including any priority claims, is
incorporated herein by reference to the extent such subject matter
is not inconsistent herewith.
SUMMARY
[0007] Described herein for various embodiments include systems,
methods, compositions, and products by process for rapid breeding
of plants. In certain embodiments, the systems and/or methods are
at least partially automated.
[0008] The foregoing summary is illustrative only and is not
intended to be in any way limiting. In addition to the illustrative
aspects, embodiments, and features described above, further
aspects, embodiments, and features will become apparent by
reference to the drawings and the following detailed
description.
BRIEF DESCRIPTION OF THE FIGURES
[0009] FIG. 1 illustrates a partial view of an embodiment disclosed
herein.
[0010] FIG. 2 illustrates a partial view of a seed.
[0011] FIG. 3 illustrates a partial view of an embodiment disclosed
herein.
[0012] FIG. 4 illustrates a partial view of an embodiment disclosed
herein.
[0013] FIG. 5 illustrates a partial view of an embodiment disclosed
herein.
[0014] FIG. 6 illustrates a partial view of a sexual reproduction
cycle in plants.
[0015] FIG. 7 illustrates a partial view of an embodiment disclosed
herein.
DETAILED DESCRIPTION
[0016] In the following detailed description, reference is made to
the accompanying drawings, which form a part hereof. In the
drawings, similar symbols typically identify similar components,
unless context dictates otherwise. The illustrative embodiments
described in the detailed description, drawings, and claims are not
meant to be limiting. Other embodiments may be utilized, and other
changes may be made, without departing from the spirit or scope of
the subject matter presented here.
[0017] It is highly beneficial to evolve plant breeding to include
characteristics that are desirable without the time-scales usually
required for growing plants to maturity for such plants that
reproduce sexually. Described herein include various embodiments
related to a focused means for selecting and breeding desired
cultivars with pre-determined or naturally resulting desired
characteristics. Various embodiments disclosed herein provide a
higher rate of improvement of desired characteristics, such as
increased yield, or drought resistance, among others, which assists
in sustainable agriculture practices. In this way, certain
embodiments disclosed herein realize multi-generation sequences of
gametes by the classic sexual reproductive route, without
intervening phenotypes with their attendant complexities and
latencies. Furthermore, various embodiments disclosed herein may be
utilized to derive new cultivars particularly amenable to certain
environmental conditions, or needs for obtaining plant products.
Additionally, the disclosed embodiments herein allow for a
reduction of labor and field resources for plant breeding,
increased capacity to rapidly breed a large number of plants per
field unit, as well as an increased capacity to analyze a larger
number of plants prior to breeding for desirable
characteristics.
[0018] Various embodiments disclosed herein relate to
genotype-to-genotype generational stepping without an intervening
phenotype but instead result from generating male and female
gametes directly from plant stem cells. For example, first
generation stem cells are induced to derive gametes, which are
bred. The resulting fertilized seed includes an embryo from which
second generation stem cells may be obtained, if additional
breeding is desired. This multi-generational cycling of gametes in
vitro (CoGiV) allows for allele valuation and selection for rapid
and efficient directed evolution of the particular plant species
toward one or more desired characteristics. For example, for
specific agricultural crops it is desirable to increase the number
of progeny and decrease the amount of time needed to screen and
select the particular progeny. In another example, it is desirable
to increase the precision of breeding-generated phenotypes or the
breadth of accessible genetic variation. As described herein,
multiple cycles of breeding and/or selecting are conducted
depending on genetic complexity, and desired characteristics.
[0019] As disclosed herein, in an embodiment described are an
increase in efficiency of Rapid-breeding, and do not require
genetic or other modification of the plant genome. However, in an
embodiment, modification of plant cells (genetic, epigenetic,
transcriptional or translational, etc.) is utilized with the
Rapid-breeding process.
[0020] At any number of steps, standard breeding techniques may be
implemented in conjunction with the steps of the Rapid-breeding
methods and systems disclosed herein. For example, in conjunction
with the steps of Rapid-breeding of plants, conventional plant
crossing may be conducted for selecting starting material (e.g.,
plant stem cells, gametophytes, or sporophytes, etc.), or once a
first, second, third, etc. generation of progeny have been
developed. Standard plant crossing includes, for example, obtaining
seeds of the first parent plant (may be modified, such as
transgenic, or not modified) and a second parent plant and growing
the seeds into second generation mature parent plants. Next,
pollinating a flower from the first parent with pollen from the
second parent and harvesting seeds produced on the parent plant
bearing the fertilized flower is conducted. As described herein,
introgressing target genes by backcrossing may be accomplished, for
example, by first crossing a superior inbred plant (recurrent
parent A) to a donor inbred plant (non-recurrent parent B), which
carries the suitable gene(s) for the desired characteristic, and
the progeny of this cross are selected for the desired
characteristic for transference from parent B and selected progeny
are mated back to parent A. Following five or more backcross
generations with selection for the desired characteristic, the
progeny are hemizygous for loci controlling the characteristics
being transferred but are similar to the recurrent parent A for
almost all other genes. The final backcross generation is
self-pollinated to generate progeny which are purebred for the
desired gene. However, as described herein, this conventional
backcross breeding technique is laborious and time consuming, while
the Rapid-breeding methods and systems disclosed herein are able to
accomplish the same task in a much more efficient manner. Still, in
certain instances one or more backcrosses may be implemented, for
example, in conjunction with the Rapid-breeding steps of certain
disclosed embodiments.
[0021] In an embodiment, a method for plant breeding includes
selecting one or more plant stem cells; inducing at least one of
the plant stem cells to differentiate into at least one first
gamete; combining the at least one first gamete with at least one
second gamete of opposite gender for fertilization; and molecularly
or microscopically analyzing the progeny resulting from the
fertilization.
[0022] In an embodiment, the plant stem cell includes a cell
isolated from the meristem of a plant (e.g., the apical meristem or
lateral meristem). In an embodiment, the plant stem cells are
isolated from meristematic tissues such as the root apical
meristem, shoot apical meristem, or vascular system ((pro) cambium
or vascular meristem, for example). In an embodiment, plant stem
cells are isolated from cambium.
[0023] As described herein with regard to various embodiments,
plant stem cells, similarly to animal stem cells, are totipotent
cells that facilitate plant growth and production of plant tissues.
Plant stem cells have the ability to self-renew, as well as
differentiate into the various different cell types of the
plant.
[0024] In an embodiment, callus (dedifferentiated cells) is
utilized to give rise to totipotent embryogenic cells for
utilization with one or more processes described herein. Callus can
be initiated from various plant tissues, including but not limited
to, immature embryos or parts of embryos, seedling apical
meristems, microspores, etc. and result in recipients of genetic
information and give rise to fertile plants.
[0025] In an embodiment, the cell wall of the plant cell is
disrupted or removed (e.g., enzymatically) prior to modification or
other use with Rapid-breeding. In an embodiment, meristematic
tissue including one or more plant stem cells is utilized for
modification as described in the various embodiments disclosed
herein.
[0026] In an embodiment, a method includes selecting one or more
plant stem cells; inducing at least one of the plant stem cells to
differentiate into at least one first gamete; combining the at
least one first gamete with at least one second gamete of opposite
gender for fertilization; and molecularly or microscopically
analyzing the embryo resulting from the fertilization.
[0027] In an embodiment, microfluidics devices or systems may be
utilized for selecting plant stem cells (e.g., by markers) or
selecting progeny generated by various embodiments disclosed
herein.
[0028] In an embodiment, a method includes selecting one or more
plant stem cells; inducing at least one of the plant stem cells to
differentiate into at least one first gamete of first genetic
composition; combining the nucleus of the at least one first gamete
with the nucleus of the at least one second gamete of second
genetic composition for fertilization; and molecularly or
microscopically analyzing the seed resulting from the
fertilization. In this particular embodiment, the gametes may be
from the same or opposite gender. In an embodiment, the gamete may
be from different genetic composition if diversity is desired, or
the same genetic composition if the "ideal" or goal genetic
composition has already been determined or obtained, or there are
particular characteristics desired to be preserved and passed on to
the progeny. In an embodiment, the progeny is/are generated by
combining the nuclei containing the chromosomes that yield a cell
having the ability to sustain itself long enough to be utilized in
an additional round of breeding, and/or to go on to develop into a
plant. For example, nuclei may be extracted from pollen by
purification from the pollen wall by enzymatic, chemical,
mechanical, or osmotic means. See, for example, Dewitte, et al.,
Ch. 4, "Use of 2n Gametes in Plant Breeding," (2012) available
online at intechopen dot com, the subject matter of which is
incorporated herein by reference. For example, the outer exine
layer on the pollen surface is a biopolymer highly resistant to
enzymatic or hydrolytic breakdown, as it has evolved to withstand
environmental stresses. However, several physical techniques, such
as bead beating or chopping of pollen grains, has allowed for
release of nuclei from pollen grains sufficient to study the nuclei
by flow cytommetry. Id.
[0029] In an embodiment, inducing gametes includes inducing plant
stem cells first to differentiate to sporophyte stage. In an
embodiment, gametes are derived from sporophyte stages without
first being induced from stem cells. In an embodiment, inducing
gametes includes inducing plant stem cells first to differentiate
to gametophyte stage. In an embodiment, gametes are derived from
gametophyte stage without first being induced from stem cells.
[0030] For example, culturing microspores gives rise to pollen,
doubled haploid embryos, and apoptotic cells, depending on the
culture conditions, including hormones, and sugars. See Wang et
al., Plant Physiol. (2000), 124: 523-530, which is incorporated
herein by reference. Furthermore, since induction of
differentiation is considered a stress condition, specific stress
hormones, such as abscisic acid (ABA) and its signal transduction
pathway are important factors, as well as lipid transfer proteins,
heat shock proteins, and peroxiredoxin anti-oxidant. Id.
[0031] In an embodiment, the gametes and/or stem cells are
genetically analyzed. Genetic analysis for embodiments described
herein includes genetic sequence analysis, ploidy analysis, or
marker selection, for example. In an embodiment, mRNA sequence
information is obtained at one or more steps in the plant breeding
process, for one or more cell types (e.g., stem cells, fertilized
seed, gametes, etc.). In an embodiment, marker assisted selection
is utilized to screen genetic markers in the very early progeny
(zygote, blastocyst, embryo, etc. stage).
[0032] In an embodiment, the plant stem cells are treated with one
or more transcription factors in order to derive gametes therefrom.
For example, MADS-box genes, encoding MADS-domain family of
transcription factors that bind DNA, are involved in controlling
various cell development and proliferation processes. See Gramzow
and Theissen, Genome Biol., 2010, 11:214, which is hereby
incorporated by reference. For example, two main types of
MADS-domain transcription factors have been characterized,
including Type I and Type II, whereas Type I MADS-box genes have
usually one or two exons, Type II genes have an average of seven.
Id. Likewise, MIKC-type MADS-box genes have been identified as
being involved in plant reproductive organ formation, particularly
MIKC* and MIKC.sup.c. Id. The MADS-box genes are regulated in
various ways, including transcriptional regulation by transcription
factors (including feedback and feed-forward loops), epigenetic
control, and microRNA regulation. Id.
[0033] In an embodiment, selecting one or more plant stem cells
includes choosing at least one plant stem cell tissue (e.g.,
meristem tissue) containing plant stem cells based at least one one
criteria. In an embodiment, selecting one or more plant stem cells
includes choosing from at least one plant stem cell tissue, one or
more single cells isolated from the remaining tissue. In an
embodiment, one or more single plant cells may be isolated from the
plant stem cell tissue, for example, by physical or chemical means
(e.g., dissection, flow cytommetry, enzymatic extraction, lysis of
tissue, etc.).
[0034] In an embodiment, inducing at least one of the plant stem
cells to differentiate into at least one first gamete includes
inducing to differentiate to at least one of a plant ovule,
megagametophyte, or egg cell in the case of a female gamete; or at
least one pollen grain, microgametophyte, or plant sperm cell in
the case of a male gamete.
[0035] For example, light intensity, light/dark period, and
temperature influence sexual reproduction in plants. See for
example, Hohe, et al. (2002), Plant Biol. 4: 595-602, which is
incorporated herein by reference. As another example, MADS-box
genes are involved in development of sexual reproduction plant
components as well as seed development, and root, flower, and fruit
development.
[0036] In an embodiment, a plant somatic cell is
inverse-differentiated into a germ cell precursor and
forward-specialized into pre-gametes of either sex and matured in
appropriate cellular milieu into fertilization-ready gametes. In an
embodiment, plant stem cells are utilized in the process, rather
than inverse-differentiated somatic cells. Post-fertilization, in
an embodiment the zygote resulting from fertilization is analyzed
directly, or cultured to at least a blastula stage, at which stage
multiple cells are provided for next-generation pre-gametes.
Following maturation into gametes of both sexes, each of these may
be employed (in potentially quite wide) crossings aimed at
realization of specific allelic traits and/or the exclusion of
others, as determined in near-real time by endosperm and/or polar
body analysis. As described herein, such Rapid-breeding and
analyses may be done at each generation step, and in parallel
and/or with highly-automated means that allows for rapid trait
selection at each generational step. In an embodiment, the
germination viability of the analyzed plant or plant tissue (such
as a seed portion or in its entirety) is maintained.
[0037] For any given round of breeding, the method includes
selecting naturally occurring characteristics that emerge in the
crossing of the parent cells. Multiple rounds of such a selection
process without the necessity of culturing the resulting offspring
yields a rapid-breeding approach that reduces the time needed for
natural selection of desirable characteristics to a fraction of
that required for traditional plant breeding that allows the
offspring to grow up to plantlets or sexually mature adult
plants.
[0038] For any given round of breeding, one or more genes may be
inserted, deleted, or mutated in order to produce a resulting seed
bearing the gene or stacks of genes of interest. In an embodiment,
for example, the plant stem cells are modified prior to induction
of gametes. In another embodiment, the gametes are modified prior
to fertilization. In an embodiment, the plant stem cells are
modified transgenically by one or more gene insertions, deletions,
or mutations. In an embodiment, the plant stem cells are modified
epigenetically by altering gene expression through changes in
methylation, for example. See for example, Dowen et al., PNAS, pp.
1-9, 2012 available online at pnas.org. For example, in
Arabidopsis, DNA methylation is deposited at CC, CHG, and CHH
sequences (where H is A, C, or T) through three genetically
separable pathways to regulate transposon silencing, genomic
imprinting, and stable gene silencing. Id. Furthermore,
simultaneous disruption of the chromatin remodeling enzymes KYP,
SUVH5, and SUVH6 in Arabidopsis results in concomitant decrease in
cytosine methylation and H3K9me2 levels, and consequently
transcriptional reactivation of heterochromatic transposons.
Cytosince methylation is established in all sequence contexts by de
novo methyltransferases (DRM1/2) through a small RNA-directed DNA
methylation (RdDM) pathway. Id. DICER-dependent 21 to 24 nucleotide
siRNAs guide Argonaute proteins (AGO4/AGO6) to complementary
sequences within the genome, likely through a siRNA:nascent RNA
base pairing mechanism, to direct cytosine methylation. Id.
Methylation of CGs and CHGs are maintained through DNA replication
by MET1, a homologue of the mammalian DNA methyltransferase DNMT1,
and the plant-specific CMT3 methyltransferase, respectively. Id.
Conversely, active demethylation of methylcytosines is catalyzed by
DEMETER (DME) family of DNA glycosylases. Id. Moreover, methylation
alterations also assist in immune response to pathogens. Id.
[0039] In an embodiment, the one or more modifications of plant
cells described herein are reversible. In an embodiment, the one or
more modifications occur in DNA of the plant cell nucleus. In an
embodiment, the one or more modifications occur in DNA of the
mitochondria of the plant cells. In an embodiment, the plant stem
cells or gametes are modified by the addition, deletion, or
mutation of one or more mRNA molecules or proteins utilized in cell
transcription or translation, respectively. In an embodiment, the
genetic or epigenetic modification of the plant cells yields
transformed progeny plants with a genome that has been altered by
the stable integration of a recombinant DNA.
[0040] Various embodiments described herein are applicable to a
number of plants, including but not limited to grass, fruit,
vegetable, flowering trees and plants (e.g., ornamental plants,
fruit plants, such as apple and cherry, etc.), grain crops (e.g.,
corn, soybean, alfalfa, wheat, rye, oats, barley, etc.), other food
or fiber crops (e.g., canola, cotton, rice, peanut, coffee,
bananas, sugar cane, melon, cucumber, sugar beet, quinoa, cassava,
potato, onion, tomato, strawberry, cannabis, tobacco, etc.), or
other plants (including but not limited to banana, bean, broccoli,
castorbean, citrus, clover, coconut, Douglas fir, Eucalyptus,
Loblolly pine, linseed, olive, palm, pea, pepper, poplar, truf,
Arabidopsis thaliana, Radiata pine, rapeseed, sorghum, or Southern
pine. Most of the calories consumed by humans come from members of
the grass family (e.g., wheat, corn [maize], rice, oats, barley,
sorghum, millet, rye, etc.), and grasses make up at least a quarter
of all vegetation on Earth, rendering these important food crops
worldwide. Various embodiments described herein are applicable to
plant cells, seeds, pollen, fruit, zygotes, etc., as disclosed.
[0041] Various embodiments disclosed herein are utilized to improve
one or more characteristics of a plant by way of rapid selection of
desirable naturally occurring characteristics. Various embodiments
disclosed herein are utilized to improve one or more
characteristics of a modified plant (e.g., genetic, or epigenetic
modification) and include rapid selection of desirable
characteristics introduced into the plant by modification as
described. For example, such characteristics include but are not
limited to increased telomere(s), improved agronomic characteristic
(e.g., improved yield, nutritional content, physiology, growth or
development, stress resistance or tolerance (e.g., disease, pest,
or chemical resistance or tolerance), increased seed oil or protein
content. In an embodiment, for example, such characteristics
include one or more of resistance or tolerance to drought, fungal,
bacterial, or viral disease, temperature fluctuation, light
fluctuation, exposure to extreme temperature (e.g., heat exposure,
or cold exposure), exposure to extreme light conditions (e.g.,
abundance of light, shade or too little light), insect or worm
infestation, low nutrient environment (e.g., low nitrogen or
phosphorous availability), osmotic stress, or high plant density.
For example, the plant yield includes such properties as plant
height, plant structure, assimilation of nutrients (e.g., carbon),
pod number or position on the plant, pod shatter, grain size,
number of internodes, efficiency of nitrogen fixation, resistance
to abiotic or biotic stress, seedling vigor, overall percentage of
seed germination, resistance to lodging, growth rate, seed number
or size, or seed composition.
[0042] In an embodiment, analyzing the resulting progeny (e.g.,
fertilized seed or resulting plant(let) therefrom) includes
analyzing for an improvement in a particular characteristic,
whether such characteristic is attributed to a naturally occurring
trait or is the result of a modification (e.g., physical, chemical,
genetic, epigenetic intervention, etc.). In an embodiment an
improvement in a particular characteristic includes an increased
level of a particular characteristic in the progeny, relative to a
control plant (in certain instances, the control plant may be a
parent plant). For example, an increased level of a particular
characteristic may be measured as described herein, including
increased seed size or increased number of seeds per unit
measured.
[0043] In an embodiment, analyzing the resulting progeny includes
evaluating one or more characteristics including a genetic marker,
a single nucleotide polymorphism, a simple sequence repeat, a
restriction fragment length polymorphism, a haplotype, a tag single
nucleotide polymorphism, a gene, an allele of a genetic marker, a
DNA-derived sequence, an RNA-derived sequence, promoter,
5'-untranslated region of a gene, 3'-untranslated region of a gene,
microRNA, siRNA, a QTL, satellite marker, transgene, mRNA,
high-resolution chromosomal structure and content analyses with
microarrays, double stranded mRNA, transcriptional profile, or
methylation pattern.
[0044] In an embodiment, an improvement in a particular
characteristic includes a decreased level of a particular
characteristic in the progeny, relative to a control plant (again,
in certain instances, the control plant is the parent plant). For
example, a decreased level of a particular characteristic may be
measured as described herein, including decreased use of water or
nutrients from the soil.
[0045] The various characteristics described may be analyzed for
improvement in several ways. For example, chemistry, cell biology,
or molecular biology techniques may be utilized for measuring
telomere changes, ploidy, or gene, protein, or mRNA changes, seed
biomass, seed content (e.g., oil, carbohydrate, protein, nitrogen,
phosphorous, etc. or ratios of one or more of these seed
components), epigenetic changes, etc. As another example, ploidy
may be evaluated by flow cytommetry or microscopic analysis. In an
embodiment, the desired ploidy plants or plant tissues (including
seeds) are selected and those that are not of the desired ploidy
are removed from the desired ploidy plants/plant tissues. In an
embodiment, the plant tissue is analyzed for one or more alleles,
or ploidy level of at least one locus.
[0046] As another example, an immunoreactive antibody may be
utilized to detect the presence or absence of a protein that is
expressed or suppressed in the progeny seed or plant tissue.
[0047] Other changes, including improvements, in the various
characteristics described may be measured by physical means, for
example, plant weight, seed weight, seed number per plant, seed
number or seed weight per acre, bushels per acre, tons per acre,
kilo per hectare, etc. As another example, a small portion of
tissue is removed from the fertilized seed without disturbing the
viability of the seeds, and such tissue is analyzed by means
described herein.
[0048] In an embodiment, when autoploid plants (such as alfalfa)
are utilized in the described methods, gametes are optionally
selected depending on their ploidy, for example, gametes that are
bivalents or quadrivalents resulting from meiosis may be selected
(univalent or trivalents resulting from triploids are usually
sterile). If polyploidy plants are desired for use with various
embodiments described herein, inhibition of mitosis artificially
induces polyploids. For example, high temperatures or use of
chemicals to inhibit mitosis (such as colchicine, EMS, GA.sub.3,
temperature, trifluralin, N.sub.2O, or dinitroanilines) may be used
to induce polyploids.
[0049] In an embodiment, a polyploidy plant may be desired due to
the increased cell size or cell volume (including, for example,
enlarged plant organs) that is a result of additional chromosomes.
For example, tetraploid grapes yield greater juice content than
their diploid counterparts, and ornamental crops with increased
numbers of chromosomes have higher quality and size of blossoms.
See, for example, Olmo (1952) American. Soc. Hort. Sci. 59:
285-290, which is incorporated herein by reference.
[0050] Likewise, in an embodiment doubled haploid cells are desired
and may be generated in over 250 plant species. See, for example,
Malunszynski, et al., 2003 Doubled haploid production in crop
plants. A manual. Kluwer Acad. Pub. Dordrecht, Boston, London,
which is incorporated herein by reference. Doubled haploid plants
may be produced in vivo or in vitro, for example. Haploid embryos
are produced in vivo, for example, by parthenogenesis, pseudogamy,
or chromosome elimination following wide crossing.
[0051] Doubled haploid plants save time in generating homozygous
lines essentially without the need for conventional breeding. In
certain embodiments disclosed herein, doubled haploids are utilized
for Rapid-breeding. For example, typically the first step for
doubled haploid production includes haploidization of the plant
with production of haploid seed. Non-homozygous lines are crossed
with an inducer parent, resulting in the production of haploid
seed, and selection of seed that contains a haploid embryo
independent of the ploidy of the endosperm (the process of which
normally results in triploid endosperm). Subsequently, selected
haploid seeds (that is haploid embryo in the seed) undergo
chromosome doubling to generate doubled haploid seeds. Spontaneous
chromosome doubling leads to normal gamete production or production
of unreduced gametes from haploid cell lineages, while addition of
colchicine or other mitotic disruptor can also be used to increase
the rate of diploidization. The chimeric plants are self-pollinated
to produce diploid (doubled haploid) seed, which is cultivated
and/or evaluated and used in hybrid testcross production.
[0052] In an embodiment, plant tissue from the doubled haploid is
analyzed, and utilized further in methods described herein.
Furthermore, by utilizing endosperm tissue derived from a diploid
plant, the ploidy level of the particular genetic marker is
determined, with a diploid level indicating maternal inheritance
and a haploid level indicating paternal inheritance. This is due to
the endosperm tissue being triploid, with two copies of the gene
derived from the female gamete, which allows for analysis of
linkage phase of the parental line by evaluating heterozygous
progeny genotypes that indicates different allele frequencies in
DNA samples.
[0053] For example, maize embryo zygosity includes triploid
endosperm and diploid embryo tissue, thus endosperm copy number
indicates the zygosity of the embryo, that is, a homozygous
endosperm accompanies a homozygous embryo, while a heterozygous
endosperm indicates a heterozygous embryo. For example, endosperm
that is homozygous for an internal control gene will contain three
copies of the gene, whereas the gene of interest varies from 0 to
3, depending on the heritability and zygosity of the resulting
progeny.
[0054] It is useful to determine zygosity of one or more loci
during plant breeding in order to evaluate the degree of fixation,
or inbreeding, segregation distortion (i.e., in transgenic
germplasm, maternal inheritance testing of for loci that affect
gametes).
[0055] For example, determination of allelic frequencies assists in
determining parental linkages for a specific marker, and comparing
allele frequency data between two or more germplasm pools provides
guidance with selection of targeted desired characteristics in such
a way that as alleles increasing in frequency in conjunction with a
shift in distribution of one or more characteristics, such is
presumed to be linked to the trait of interest. Furthermore,
determining relative allele frequency data assists in construction
of genetic linkage maps. For example, several species of plants
have had full or partial genomic sequence analysis conducted,
including rice varieties, eucalyptus varieties, strawberry
varieties, apple varieties, grape varieties, tomato varieties,
potato varieties, wheat varieties, maize varieties, oil plants,
cereal crops, biodiesel crops, various algaes, and others. Thus,
genetic sequences for particular plants, or the homologs from other
species, are readily available or attainable for use with various
embodiments described herein.
[0056] In certain embodiments, selected progeny are bulked,
depending on the analysis of the resulting genotype. Conversely, if
multiple characteristics are analyzed by way of QLT or genomic
selection, for example, with varying effects being selected for a
particular population, the progeny may keep individual identity
preserved, and cultivate the progeny for determination of various
combinations of the desired QTL.
[0057] In an embodiment, methods disclosed herein relate to
introgressing a characteristic into a plant, for example, by
removing a sample of cells or nucleic acids from plant tissue
(e.g., seeds), and analyzing the nucleic acids extracted from each
seed for the presence or absence of at least one genetic marker,
selecting seeds from the population based on the results of the
nucleic acid analysis, and cultivating a plant for use with a
second generation of breeding.
[0058] In an embodiment, cycling of gametes in vitro, as described
herein, accelerates the introgression of a specific gene or genes
into a plant and allow for greater precision by more cycles of
recombination.
[0059] Likewise, genetic recombination can involve "gene
conversion" or the non-reciprocal transfer of DNA from one genotype
to another. Utilizing various embodiments disclosed herein, vast
populations for rare zygotes with gene conversion at a target locus
may be screened to identify a true isogenic derivative rather than
a nearly-isogenic backcross derivative in which flanking alleles
from the donor may confer undesirable characteristics. Gene
conversion may be especially useful for manipulating exotic
germplasm in which a desirable gene is often surrounded by
undesirable ones and thus methods disclosed herein assist in
avoiding intermediate phenotypes.
[0060] Sexual plant breeding results in the addition and transfer
of chromosomes, which allows for increased diversity in the
progeny, and allows for selection of particular desirable
characteristics. Chromosome doubling in vitro induces polyploidy,
by utilizing mitotic inhibitors such as dinitroaniles and
colchicine. As described herein, ploidy status may be determined in
a number of cell or molecular biology techniques, including, for
example, chloroplast count in guard cells, examining morphological
features such as leaf, flower, or pollen size (termed the gigas
effect) and flow cytommetry.
[0061] Further as described herein, various embodiments disclosed
herein utilize polyploidy induction for Rapid-breeding techniques.
For example, allopolyploids may be generated from hybridization of
two or more genomes followed by chromosome doubling or by fusion
with unreduced gametes between or within species. For example,
meiosis or mitosis takes a diploid cell and reduces it to 4 haploid
cells (one copy of each gene and chromosome). However, an unreduced
gamete has not undergone the reduction (e.g., by inhibiting cell
division) and remains diploid. See Figures disclosed herein. In an
embodiment, a method disclosed herein includes inducing at least
one plant stem cell to differentiate into at least one first
gamete. In an embodiment, the at least one first gamete is
unreduced (i.e. has not yet undergone meiosis) such that ploidy is
induced upon fertilization with a second gamete. In an embodiment,
the nuclei are combined instead of the entire gamete(s).
[0062] For example, a dominant mutation coding for AGO104, a member
of the ARGONAUTE family of proteins, results in formation of
functional unreduced gametes. See Singh, et al., Plant Cell vol.
23: 443-458 (2011), which is incorporated herein by reference. The
mutant shows defects in chromatin condensation during meiosis and
subsequent failure to segregate chromosomes when screened in Zea
mays. Id. AGO104 is needed for non-CG methylation of centromeric
and knob-repeat DNA. Thus, in an embodiment, a mutant AGO104 is
utilized for differentiating unreduced gametes.
[0063] In certain instances, the hybridized genomes may differ in
their degree of homology such that some genomes are able to pair
during mitosis and/or meiosis, while others are not. For example,
in certain instances only segments of the chromosomes of the
combining genomes differ (termed segmental alloploidy), and in
order to achieve a "pure cross" a bridge cross, or intervening
cross, may be utilized to achieve the desired hybrid.
[0064] Likewise, the multiallelic nature of loci in polyploids
allows for masking deleterious alleles that may arise during
modification or polyploidy induction. Further, polyploids are able
to tolerate deleterious allele modifications post-mutation and they
have increased mutation frequency due to their large genomes.
Polyploids typically have larger cells and/or plant organs than
their traditional counterparts, however the larger cell volume is
usually due to higher water retention, rather than an increase in
biomass.
[0065] In an embodiment, the progeny are analyzed for example, by
statistical sample testing of plant tissue(s) (including seeds) for
further use. In an embodiment, a portion of the plant tissue(s) are
utilized while maintaining the germination viability of the
progeny. For example, a portion of the endosperm, zygote, embryo,
blastocyst, or other seed portion may be obtained by mechanical or
chemical means and utilized for analysis. For example, an automated
seed sampler may be used with various embodiments disclosed herein.
See for example, U.S. Pat. No. 7,941,969, which is incorporated
herein by reference.
[0066] In an embodiment, the one or more desired characteristics
are quantified based on the analyzed plant tissue. In an
embodiment, the one or more quantified desired characteristics are
compared with control plant tissue samples or known germplasm pools
in order to identify frequency shifts. Likewise, DNA and RNA may be
extracted from plant tissue(s) sufficient to yield DNA or RNA
adequate for PCR, RT-PCR, TaqMan assays, sequencing, arrays or
blots, or other amplification.
[0067] Several criteria may be established in order to determine
whether additional breeding is desired. For example, a small flake
from the fertilized seed (optionally retaining the embryo intact
for planting, if desired) is removed for genetic analysis of a
desired characteristic, whether the corresponding gene(s) are
naturally occurring in the seed or artificially inserted, deleted,
or mutated.
[0068] As described herein, in certain aspects a method disclosed
includes molecularly modifying a plant cell. In an embodiment, a
DNA construct is utilized to modify a plant cell. Assembly of DNA
constructs may be done using standard methods, typically with a
promoter operably coupled to the DNA, and optionally other
regulatory elements such as 5' leaders, introns, 3' untranslated
regions (such as polyadenylation signals), signal peptides, or
repressor or enhancer sequences.
[0069] For example, promoter elements include non-constitutive
promoters (such as spatially specific promoters, temporally
specific promoters, inducible promoters, etc.), or constitutive
promoters. For example, spatially specific promoters include
organelle, cell, tissue, or organ-specific promoters functional in
a plant (such as plastid-specific, root-specific, pollen-specific,
or seed-specific promoter for suppressing expression of the target
RNA in plastids, roots, pollen, or seeds, respectively). In an
embodiment, a seed-specific, embryo-specific, gamete-specific, stem
cell-specific, aleurone-specific, or endosperm-specific promoter is
utilized with an embodiment. For example, temporally specific
promoters can include promoters that favor promoter expression
during certain developmental stages in a plant's growth or
reproductive cycle, or during different times of day or night, or
different seasons of the year. Inducible promoters include
promoters induced by chemicals such as exogenous or synthetic
chemicals as well as endogenous pheromones and other signaling
molecules) or by environmental conditions such as but not limited
to biotic or abiotic stress (e.g., water deficit or drought,
temperature fluctuations or extremes, nutrient fluctuations or
extremes, salt levels, light levels, pest or pathogen infection, or
physical damage, etc.). An expression-specific promoter also
includes generally constitutively expressed promoters that vary on
the degree of expression.
[0070] In addition to promoter elements, in certain instances
terminator elements may be utilized in the embodiments disclosed
herein, including for example, polyadenylation signals as described
herein. Additionally, spacer DNA segments (found, for example,
between parts of a gene suppression element or between different
gene suppression elements) may include translatable DNA encoding a
target gene, translatable DNA encoding a marker or reporter gene,
transcribable DNA derived from an intron, transcribable DNA
encoding RNA that forms a structure such as a loop, stem, or
aptamer capable of binding to a specific ligand, spliceable DNA
including introns and self-splicing ribozymes, transcribable DNA
encoding a target gene detectable by molecular biology
techniques.
[0071] Promoter and enhancer elements that are active in plants
include but are not limited to nopaline synthase (NOS) promoter,
octopine synthase (OCS), CaMV35S promoter (cauliflower mosaic
virus), rice actin promoter, maize chloroplast aldolase promoter,
maize aldolase promoter, napin, maize L3 oleosin, zein Z27,
globulin I, glutelin 1, peroxiredoxin antioxidant (Per 1), maize
nicotianamine synthase promoter, etc. Numerous other promoters that
function in plant cells (whether plant cell or another cell was the
original source) may be utilized in assembling constructs for use
in modifying plant cells as described herein.
[0072] Likewise, various enhancer sequences, such as 5' introns of
rice actin 1 and rice actin 2 genes, maize alcohol dehydrogenase
gene intron, maize heat shock protein 70 gene intron, maize
shrunken 1 gene, etc. may be used to assist in increasing gene
expression.
[0073] In various aspects, one or more genes or other modifications
may be implemented with various embodiments disclosed herein, by
for example, making multiple modifications to a single cell or by
making single mutations in a cell and crossing those cells to
result in a transformed plant. Such modifications may be stacked
into the resulting plant with various modifications. For example,
characteristics for increasing drought resistance may be stacked
with characteristics for increasing yield, or tolerating
herbicides. For example, transgenic plants have been produced that
have demonstrated tolerance to glyphosate, dicamba, glufosinate,
sulfonylurea, bromoxynil, and norflurazon, and such plants may be
further modified utilizing various embodiments described
herein.
[0074] Some non-limiting examples of 3' polyadenylation signals
include nos 3', tml 3', tmr 3', tms 3', ocs 3', tr7 3', and others
from Agrobacterium tumefaciens genes, heat shock protein 17 3' from
wheat (triticum aesevitum), wheat ubiquitin gene, wheat fructose-1,
6-biphosphatase gene, rice glutelin gene, rice lactate
dehydrogenase gene, rice beta-tubulin gene, pea ribulose
biphosphate carboxylase gene (rbs 3'), etc.
[0075] With regard to gene suppression, various modes may be used,
for example, including anti-sense, co-suppression, and RNA
interference (miRNA, dsRNA, siRNA, and other forms of double
stranded RNA that block translation). Several microRNA genes have
been characterized in plants, including promoters for the same. See
for example, U.S. Pat. No. 8,395,023, which is incorporated herein
by reference. Transposable elements can also be utilized to
suppress gene function. In certain instances, mutations by
insertion of one or more transposable elements disrupts protein
translation from a particular gene.
[0076] Modification of plant cells by transformation with molecular
constructs may be used with various embodiments described herein.
For example, agrobacterium-mediated transformation and
microprojectile bombardment have been described for use with
soybean, corn, wheat, rice, and sugar beet. See U.S. Pat. No.
8,410,336, which is incorporated herein by reference. Culturing
conditions for transforming plant cells includes, for example,
nutrient media, kept at conditions which facilitate transformation
of the cells. Plant cell targets for transformation include at
least one of meristem cells, calli, hypocotyls, gametes
(microspores, pollen, sperm, egg, etc.), or immature embryos. In
addition, callus may be differentiated from tissues such as
immature embryos, hypocotyls, microspores, seedling apical
meristems, etc. and can be grown into a plantlet or mature plant.
Since typically not all cells are transformed when modified in this
manner, one or more markers (e.g., marker genes) are generally
utilized to provide an efficient system for identification of the
cells that are stably transformed with DNA constructs. Further, if
conferring resistance to an antibiotic or herbicide, for example,
transformation may be screened by application of the antibiotic or
herbicide to the plant (or plant cells).
[0077] In an embodiment, a target sequence includes at least one of
amino acid catabolic genes (such as maize LKR/SDH), maize zein
genes, fatty acid synthesis genes (such as plant microsomal fatty
acid desaturases or plant acyl-ACP thioesterases), genes involved
in multi-step biosynthesis pathways (such as genes encoding enzymes
for polydydroxyalkanoate biosynthesis), genes encoding cell-cycle
control proteins (such as proteins with cyclin-dependent kinase
(CDK) inhibitor-like activity, genes from undesirable proteins
(such as allergens or toxins), or enzymes for the biosynthesis of
undesirable compounds (such as undesirable flavor or odor
components). For example, a modified plant disclosed herein
includes a plant with decreased allergenicty (such as peanut),
regulated fruit ripening, a pest or pathogen resistant plant, or an
herbicide tolerant plant.
[0078] For example, several non-limiting examples of pathogens
include but are not limited to fungal, bacterial, or viral
pathogens. For example, Phakospora pachirhizi (Asian soy rust),
Puccinia sorghi (corn common rust), Puccinia polysora (corn
Southern rust), Fusarium oxysporum and other Fusarium spp.,
Alternaria spp., Penicillium spp., Pythium aphanidermatum and other
Pythium spp., Rhizoctonia solani, Exserohilum turcicum (Northern
corn leaf blight), Bipolaris maydis (Southern corn leaf blight),
Ustilago maydis (corn smut), Fusarium graminearum (Gibberella
zeae), Fusarium verticilliodes (Gibberella moniliformis), F.
proliferatum (G. fujikuroi var. intermedia), F. subglutinans (G.
subglutinans), Diplodia maydis, Sporisorium holci-sorghi,
Colletotrichum graminicola, Setosphaeria turcica, Aureobasidium
zeae, Phytophthora infestans, Phytophthora sojae, Sclerotinia
sclerotiorum, Pseudomonas avenae, Pseudomonas andropogonis, Erwinia
stewartii, Pseudomonas syringae pv. syringae, maize dwarf mosaic
virus (MDMV), sugarcane mosaic virus (SCMV, formerly MDMV strain
B), wheat streak mosaic virus (WSMV), maize chlorotic dwarf virus
(MCDV), barley yellow dwarf virus (BYDV), banana bunchy top virus
(BBTV), etc. See for example, U.S. Pat. No. 8,395,023, which is
incorporated herein by reference.
[0079] For example, several non-limiting examples of pests capable
of destroying plants include but are not limited to northern corn
rootworm (Diabrotica barberi), southern corn rootworm (Diabrotica
undecimpunctata), Western corn rootworm (Diabrotica virgifera),
corn root aphid (Anuraphis maidiradicis), black cutworm (Agrotis
ipsilon), glassy cutworm (Crymodes devastator), dingy cutworm
(Feltia ducens), claybacked cutworm (Agrotis gladiaria), wireworm
(Melanotus spp., Aeolus mellillus), wheat wireworm (Aeolus mancus),
sand wireworm (Horistonotus uhlerii), maize billbug (Sphenophorus
maidis), timothy billbug (Sphenophorus zeae), bluegrass billbug
(Sphenophorus parvulus), southern corn billbug (Sphenophorus
callosus), white grubs (Phyllophaga spp.), seedcorn maggot (Delia
platura), grape colaspis (Colaspis brunnea), seedcorn beetle
(Stenolophus lecontei), and slender seedcorn beetle (Clivinia
impressifrons), as well as parasitic nematodes. Id.
[0080] For example, several non-limiting examples of target genes
related to pests include but are not limited to major sperm
protein, alpha tubulin, beta tubulin, vacuolar ATPase,
glyceraldehyde-3-phosphate dehydrogenase, RNA polymerase II, chitin
synthase, cytochromes, miRNAs, miRNA precursor molecules, miRNA
promoters, etc. Id.
[0081] In an embodiment, modification of plant cells is conducted
with one or more aptamers, which include DNA or RNA sequences that
recognize and specifically bind to a particular ligand or molecule,
often with high affinity. Aptamers have been utilized similarly to
antibodies for binding specific antigens or receptors as well as
for protein antagonists, as molecular escorts for delivery of an
agent to a particular cell or tissue, as well as part of a
riboswitch. Riboswitches include complex folded RNA sequences that
contain an aptamer domain for a specific ligand and can operate as
"cis" or "trans" elements. Cis riboswitches may control gene
expression by harnessing allosteric structural changes caused by
ligand binding, whereas trans riboswitches control expression not
operably linked to the riboswitch itself. For example, a riboswitch
defaults to "on" position during gene expression, and the
riboswitch is turned to the "off" position when an increased
concentration of the ligand is bound by the aptamer domain of the
riboswitch and the riboswitch terminates transcription or
translation of the gene under its control. Thus, in certain
embodiments described herein, plant cells are modified and may
result in stable transgenic plants as determined by the ligand
being bound to an aptamer and the resulting expression or
suppression of a target sequence.
[0082] Another class of RNA apatamers useful with an embodiment
disclosed herein include "thermoswitches" which do not bind a
ligand but that determine the aptamer's conformation by
temperature, so as to be thermally responsive.
[0083] In an embodiment, modifying plant cells to reduce damage
caused by disease or pest includes a transgene that transcribes to
an RNA aptamer capable of binding to a ligand that is at least part
of a molecule endogenous to the pest or pathogen source of the
disease or destruction. In this way, binding to the ligand reduces
damage to the plant relative to a plant without the transgene. In
an embodiment, the transgene includes at least partial sequence of
a gene found in a pathogen or in the gut of a pest.
[0084] In an embodiment, a target sequence includes a gene native
to the particular plant utilized in various embodiments disclosed
herein, a transgene in a transgenic plant, a gene native to a pest
or pathogen, etc. For example, plant cells modified as described
herein may be modified to provide resistance to a particular
disease or pest. In order to convey such resistance, a gene native
to the particular causal agent may be incorporated into the plant
when modified as disclosed in various embodiments herein.
Alternatively, in another example, multiple copies of a native gene
to the plant may be incorporated, for example, to increase yield or
nutritional content. A target sequence includes a sequence that
expresses a specific gene or a sequence that suppresses a specific
gene. Moreover, the target sequence includes a translatable
sequence (coding sequence) or a non-coding sequence (non-coding
regulatory sequence), or both. The target sequence includes
sequences from the plant itself, its species, or another species
including any eukaryote or prokaryote, depending on the desired
characteristic.
[0085] In an embodiment, regulatory RNA is utilized to modify plant
cells as described herein, and include ribozymes (self-cleaving
ribozymes, hammerhead ribozymes, hairpin ribozymes, etc.) and may
include sense or anti-sense segments capable of hybridizing to form
an intramolecular double-stranded RNA.
[0086] In an embodiment, clustered regularly interspersed short
palindromic repeats (CRISPR) is utilized for the one or more
modifications of plant cells for Rapid-breeding of plants as
described. See van der Oost, Science, (2013) pp. 768-770, vol. 339;
and Mali et al., Science (2013), pp. 823-826, vol. 339; and Cong et
al., Science (2013), pp. 819-823, vol. 339; each of which is hereby
incorporated by reference. For example, CRISPR utilizes RNA-guided
DNA nuclease for highly specific gene targeting (e.g. for
modification of genes). Id. For example, precise genome engineering
may be conducted based on the RNA-guided Cas9 nuclease, and can be
utilized for multiple gene recognition sites. Id.
[0087] For example, in an embodiment CRISPR is utilized for
targeting based on Watson-Crick complementarity, and in an
embodiment CRISPR machinery can be reprogrammed to target a
different DNA sequence through the use of a different crRNA. In an
embodiment, CRISPR is utilized for targeting a complementary 24-48
RNA sequence, with little to no mismatches.
[0088] As described herein, plant stem cells are utilized in
various embodiments disclosed. However, various other plant cells
may be utilized from the resulting plant generated by methods
disclosed herein, or in the process of generating the resulting
plant. In this regard, plants may be crossed by modifying one
gamete or nucleus and not the second gamete or nucleus utilized in
sexual fertilization of the new progeny. In certain aspects,
markers associated with one gamete, nucleus, or modification (e.g.,
gene modification) are utilized with various embodiments disclosed
herein. For example, a selectable marker may be linked to a DNA
construct, a marker for herbicide tolerance may be tested by
application of the herbicide to the progeny plant, or antibiotic
resistance may serve as a marker for stable integration of a
construct in the plant cell.
[0089] Transformation of DNA constructs into plant cells is likely
to result in a percentage of target plant cells that do not receive
the construct or achieve expression of the construct. Common
selective marker genes include those that confer resistance to
antibiotics such as kanamycin and paromomycin, hygromycin B,
spectinomycin, gentamycin, for example, or resistance to herbicides
such as glufosinate, dicamba, or glyphosate. As with animal cells,
markers such as green fluorescent protein or luciferase may be
employed to indicate that gene expression from the construct is
occurring, or for example, a gene expressing beta-glucuronidase or
uidA gene may be utilized, in conjunction with chromogenic
substrates to visually screen modified plant cells.
[0090] As described herein, if plant cells are modified as part of
various embodiments disclosed, subsequent to fertilization occurs
and the resulting progeny plant seed is obtained, the seed may be
tested or optionally cultured to a plantlet stage and then tested.
In the case where the fertilized seed is tested, in an embodiment a
portion of the endosperm is removed for analysis without disrupting
the embryo of the seed. In an embodiment, a portion of the embryo
is analyzed without disrupting the viability of the embryo. In an
embodiment, a small portion of the fertilized seed is analyzed
without disrupting the viability of the embryo.
[0091] As described herein, an optional step in various embodiments
disclosed include culturing the progeny seed under conditions that
allow for the seed to grow to multiple cells, to a plantlet stage,
or to a mature plant. Plant seeds that have been modified, in
certain embodiments, grow to plants that have an improved
characteristic as compared with a control plant. As described
herein, modified seeds or plants with improved characteristics are
selected by evaluating the seeds or plants at a microscopic,
molecular, genotype, or phenotype level.
[0092] In other embodiments, the seed and or plant generated by
various embodiments disclosed herein harbor naturally occurring
improvements over control plants, and such improved seeds or plants
are derived by the Rapid-breeding processes disclosed. Improvements
include, for example, higher seed quality, better water efficiency,
better nutrient efficiency, greater temperature tolerance, higher
yield, increased seed protein, or increased seed oil, level of
fermentable starch, increased metabolite, level of fatty acids,
level of amino acids or proteins, as well as other characteristics
described herein.
[0093] As described herein, the progeny of various embodiments
disclosed herein may be analyzed by various means, including, for
example, microscopic or molecular analysis. In addition to the
molecular or microscopic analysis of the progeny seeds or plants,
in certain aspects where the seeds are grown to plantet or mature
plant stage, several screening assays may be utilized, depending on
the characteristic desired to be analyzed. For example, plantlets
or mature plants may be screened in greenhouses or field trial or
research centers, and may include detecting changes in morphology
of the plant, physiological characteristics, biomass, or chemical
composition. For example, chemical composition of the progeny seeds
or plants may be analyzed by evaluating seed composition for
protein, free amino acids, oil, free fatty acids, starch,
tocopherols, and other components. For example, biomass may be
measured by evaluating plant height, stem diameter, root and shoot
weights, leaf or shoot lengths or diameters, etc., whereas plant
morphology may be evaluated by screening for days to pollen shed,
days to silking, leaf extension rate, chlorophyll content, leaf
temperature, stand, seedling vigor, internode length, plant height,
leaf number, leaf area, tillering, brace roots, stay green, stalk
lodging, root lodging, plant health, barreness or prolificacy,
green snap, pest resistance, kernals per row, number of rows of
kernals on an ear, kernel abortion, kernel weight, kernel size,
kernel density, physical grain quality, bushiness, height, thicker
or narrower leaves, striped leaves, knotted trait, chlorosis,
albino, anthocyanin production, altered tassels, altered ears,
altered roots, or similar characteristics. As described herein, in
addition to molecular or microscopic/cellular analysis, seeds or
plants can be analyzed by testing against stress conditions, such
as water use efficiency, enhanced cold tolerance, shade tolerance,
herbicide resistance, etc., by growing plants/plantlets under the
stress condition to be analyzed and evaluating the response against
control plants/plantlets.
[0094] For example, marker-assisted selection (MAS) relies on
quantitative trait loci (QTL) studies derived from the analysis of
a few segregating populations and may be employed for the analysis
as described herein with regard to several claimed embodiments.
Likewise, genomic selection relies on phenotyping and high-density
genotyping of a sufficiently large and representative sample of the
population, with the majority of loci regulating a quantitative
trait in linkage disequilibrium with one or more molecular markers.
See, for example, Resende, et al., New Phytologist (2012) 193:
617-624, which is incorporated herein by reference. In certain
embodiments, the MAS or genomic selection is utilized on a very
early plant (zygote, blastocyst, embryo, etc.), while in certain
other embodiments the MAS or genomic selection is utilized at a
plantlet or mature plant stage. For example, age and
genotype.times.environment interaction affect expression of certain
complex genetic characteristics, and need a more mature plant in
order to accurately measure such characteristics. Likewise, for
certain characteristics that are expressed in the early plant,
simple molecular testing of particular markers at the early plant
stage are sufficient for establishing presence or absence of the
trait. As described herein, in certain plants the time-frame
between the beginning of breeding and the production of improved
seeds can span multiple decades. Id. Thus, in an embodiment, the
techniques of MAS and genomic selection may be employed with
certain embodiments disclosed herein for Rapid-breeding
methods.
[0095] In an embodiment, one or more QTLs are linked with at least
one of herbicide tolerance, disease resistance, insect or pest
resistance, altered fatty acid, protein or carbohydrate metabolism,
increased grain yield, increased oil, increased nutritional
content, increased growth rates, enhanced stress tolerance,
preferred maturity, enhanced organoleptic properties, altered
morphological characteristics, increased consumer appeal,
industrial use characteristics, or other characteristics as
described herein. In an embodiment, one or more progeny are
selected based on at least one characteristic indicative of a
recurrent parent that assists in selection for marker-assisted
backcrossing.
[0096] In an embodiment, additional transcription factors for use
in various embodiments disclosed, or additional genes of interest
associated with desired characteristics may be derived by
techniques, such as differential screening using, for example,
subtractive hybridization of a cDNA library, PCR, RT-PCR, Northern
blot, Reverse Northern blot, Southern blot, Western blot, DNA
fingerprinting, dot-blots, new generation sequencing, gene cloning
or Random Primed RT-PCR, etc. readily assists in identification of
genes or proteins of interest in eukaryotic cells, including
plants.
[0097] For example, the genomes of many different plant varieties
have been sequenced in full or in large part, thus enabling ready
identification of particular genes or proteins as determined by
differential screening related to various cell types, for example.
In an embodiment, a differential screening for a particular plant
is conducted with at least two or more of a gametophyte, gamete,
spore, or sporophyte. In an embodiment, a differential screening is
conducted between a male gamete and a female gamete of the same
species. In an embodiment, the differential screening is conducted
between related but different species, or related but different
cultivars, in order to more readily identify the genes or proteins
more intricately involved in differentiation of different cell
types. In an embodiment, identification of a homolog is sufficient
for utilization in differentiation of a cell type or development of
a sufficient factor therefor.
[0098] For example, genomic sequence information for rice, maize,
cucumber, oilseed, legumes, cocoa, eucalyptus, wild strawberry,
apple, grape, tomato, potato, wheat, barley, banana, cannabis,
grasses, and other crops and trees have been obtained in whole or
in large part. With new generation sequencing, the relevant
sequence information of other plants is readily identifiable.
[0099] As illustrated in FIG. 1, an embodiment includes a method
100 for Rapid-breeding of plants. As illustrated, cells (stem
cells, gametophytes, sporophytes, somatic cells, etc.) are
extracted 105 from Parent 1 and Parent 2 and induced to
differentiate in vitro tissue culture 110, deriving gametes or
transferable nuclei 115 that when combined 120, give rise to one or
more zygote progeny 185. Next, the progeny are analyzed 130 as
described herein utilizing cell, molecular, or microscopic methods,
for example, or optionally cultured 125 to give rise to more than
one cell. As illustrated, if the progeny are optionally cultured
125, they may be subsequently analyzed 130 for example, by removing
a small portion of plant tissue or clonal cells to evaluate the
genotype as described herein. Following analysis of the progeny
130, the progeny are selected 135 based on the analysis.
Optionally, the selected progeny may be cultured 125, or cultivated
140 to plantlet stage or optionally to mature plant stage 150.
Alternatively, following selection 135 of the progeny based on the
analysis, the progeny cells (which include multipotent,
pluripotent, and/or totipotent cells) are utilized to repeat 195
the Rapid-breeding process. Optionally, cultured plant cells 125,
cultivated plantlets 140 or cultivated mature plants 150 may be
optionally validated through a second analysis 145 following the
growth in culture or through cultivation. Cells may be obtained
from progeny at any step following analysis for one or more desired
characteristics, as illustrated in FIG. 1. For example, in an
embodiment, culturing plant cells or plant progeny includes growing
them in a tissue culture plate. In an embodiment, cultivating a
plant includes growing the progeny or other plants in a greenhouse,
field, test plot, or small plant containers located indoors or
outdoors.
[0100] As illustrated in FIG. 2, in an embodiment, a portion of the
plant tissue (such as a seed) is removed for analysis as described
herein. In an embodiment, a portion of the endosperm is removed for
analysis, leaving the embryo intact and maintaining the germination
viability of the seed. In an embodiment, the endosperm and embryo
are derived from sperm that share the same genotype, thus
eliminating possible variation in inheritance from the sperm
fertilizing the polar body that gives rise to the endosperm and the
sperm fertilizing the egg that gives rise to the embryo.
[0101] As illustrated in FIG. 3, in an embodiment, the progeny
generated from the rapid-breeding disclosed herein are analyzed
genetically (including genotypically, for example) or
epigenetically, as described herein, and further analyzed
phenotypically in tissue culture plates, or as plantlets/plants in
a greenhouse or field. As illustrated in FIG. 3, one or more
cameras 300 are utilized to survey a plot, a row, or a specific
plant/dish, while a location marker (e.g., global positioning
system indicator, etc.) 370 is placed at various positions around
or near the growing plants/plant cells. As described herein, the
cameras include one or more of infrared cameras, visual cameras,
x-ray cameras, or similar. Information detected from these or other
sensors are transmitted (optionally wirelessly) to a central
database, as indicated by "1," "2," or "3," and the data collected
397 is evaluated by a user that is a person 395, or computer 380,
for example. The user evaluates the data and optionally enters
additional observed data via an input/output device 390. Based on
the data evaluation, a Desired Characteristic Value from one or
more samples is assigned, and any experimental progeny (310, 330,
350, etc.) that include desired characteristics may be assessed
further. Likewise, any experimental progeny that lack the desired
characteristics, or that bear a phenotype no better than the
control progeny (320, 340, 360, etc.) may be culled from further
research. In an embodiment, a locator indicator 398 is utilized to
locate a particular progeny for further assessment or for culling
based at least in part on the location marker 370 in the field or
greenhouse. In an embodiment, for example, the location marker 370
includes a transmitter, and the location indicator 398 includes a
receiver. In an embodiment, for example, the location marker 370
includes a receiver, and the location indicator 398 includes a
transmitter. In an embodiment, one or more components described in
FIG. 7 are implemented in FIG. 3. In an embodiment, an integrated
sensor-to-database collection may be utilized, such as a wireless
sensor network, for example that integrates collected information,
optionally encrypts information shared wirelessly and optionally
through an internet interface. See Bencini et al., intechopen pp.
1-18, which is incorporated herein by reference. In an embodiment,
the information contributes to and/or compares the information with
a database. In an embodiment, the database includes genomic
sequence information for the particular
[0102] As illustrated in FIG. 4, included in the analysis of the
progeny of the rapid-breeding disclosed herein, the phenotype may
be assessed by utilizing one or more sensors, for example, that
contact the plant or plant cells, or are in the vicinity of the
plant or plant cells. In an embodiment, the one or more sensors
include at least one of a receiver or transmitter. In an example,
the sensors detect particular environmental conditions or
plant/plant cell conditions and transmit the information to a user
(as shown in FIG. 3) where the information is collected and/or
evaluated. In an embodiment, as described in FIG. 3, one or more
progeny are culled or further assessed depending on the information
collected or evaluated from the one or more sensors.
[0103] For example, a collar 400 includes a flexible band with a
force sensor or strain sensor incorporated that senses stalk
diameter may be utilized for sensing plant growth. In an
embodiment, the collar 400, is in a fixed state and erupts or
breaks apart as the plant reaches a threshold size, wherein the
breaking of the collar sends a signal. In an embodiment, a sensor
in the form of a patch 410 is attached to a leaf and is capable of
measuring leaf morphology or growth. In an embodiment, a capture
strip 420A or B is utilized for detecting emitted plant chemicals,
such as carbon dioxide, oxygen, pheromones, stress hormones,
reactive oxygen species, and others. In an embodiment, the capture
strip 420A is located on the plant or plant cells. In an
embodiment, the capture strip is located in the vicinity of the
plant or plant cells, and may include, for example, the cover 420B
to a tissue culture dish or 420C the floor of the tissue culture
plate. For example, a colorimetric oxygen sensor, or other gas
sensor may be employed with the tissue culture dishes. In another
example, a pH indicator or nutrient indicator is employed that
includes a transmitter or receiver in order to share information
relating to the tissue culture plates. In another embodiment (not
shown), remote spectral sensing is employed that includes sharing
of information or evaluating the information against a data base,
as described herein. For example, remote spectral sensing of crops
has been utilized through imagery of a field or plot, where the
incident electromagnetic radiation is generally sunlight. See Li et
al., Electrochem. Soc. Winter 2010, pp. 41-46, which is
incorporated herein by reference. For example, measuring sunlight
of the crop and soil that is reflected, absorbed, and/or
transmitted depending on the wavelength and the surface it strikes,
indicates differences in physical or chemical properties of the
crops, e.g., leaf color, texture, shape, etc. In an embodiment, the
spectral reflectance measurements are utilized for analysis,
including the ratio of reflected energy to incident energy as a
function of wavelength, and can be evaluated based on spatial or
temporal resolution. In an embodiment, one or more of a
spectrometer, radiometer, or digital camera may be mounted on a
variety of platforms either on the ground, aerial, or space to
gather data. Id.
[0104] In an embodiment, one or more sensors include soil and/or
air sensors 470 that detect environmental conditions. In an
embodiment, one or more root sensors 480 are banded on the plant
roots with a strain sensor or threshold sensor as described for the
plant stalk, or set at a goal distance for root growth to approach
and provide a signal. In an embodiment, one or more cameras 300 are
placed on or near the vicinity of the plants or plant cells in
order to gather visual information about the plants or plant cells.
As described in FIG. 3, the cameras include one or more of infrared
cameras, visual cameras, x-ray cameras, or similar.
[0105] In an embodiment, one or more sensors including Raman and
Fourier Transform Infrared spectroscopy, capacitance probes,
reflectometers, ultrasonic ranging sensors, pH soil-based sensors,
Eddy covariance sensors, fluorescence-based optical sensor, optical
or microwave sensors, or other sensors may be employed in certain
embodiments. See Pajares, Sensors (2011) 11:8930-8932, which is
incorporated herein by reference.
[0106] In an embodiment, one or more "smart transducers" are
utilized with certain embodiments disclosed. Specifically, "smart
transducers" include sensors or actuators equipped with
microcontrollers to provide local "intelligence" and network
capability and can combine sensing, computing, and communication.
See Wang et al., Comp. and Elect. In Ag. (2006) 50: 1-14, which is
incorporated herein by reference.
[0107] In an embodiment, a system disclosed herein includes a
network of research stations or plant testing stations that are
configured to share information regarding the one or more measured
characteristics of the plantlet or mature plant developed according
to methods described herein. In an embodiment, the network of
stations includes means to transmit and/or receive information
regarding the one or more measured characteristics of the plantlet
or mature plant developed according to methods described
herein.
[0108] As described in FIG. 5, a system or method 500 includes
culturing or cultivating the progeny 501 of the rapid-breeding
process, and analyzing the progeny 515. In an embodiment, genotype
information is obtained from the progeny and input 510 into the
system. In an embodiment, sensed information as described herein,
relating to phenotype 505 is input into the system. Utilizing the
input information, next a comparator for the genotype and/or
phenotype input is employed with a Desired Characteristic Value
dataset 520. In an embodiment, the comparator is operably coupled
to a database related to one or more of at least one parent plant
of the progeny tested, or other progeny of a breeding cycle with at
least one parent in common as the progeny tested. In an embodiment,
the database is related to progeny of an earlier breeding cycle as
the progeny tested. In an embodiment, the database is related to
progeny of a later breeding cycle as the progeny tested (for
example, when the progeny tested was allowed to grow for a length
of time that surpassed the amount of time needed for at least one
additional breeding cycle). In an embodiment, a generator for the
Desired Characteristic Value 525 is employed based on the
comparison. From the generated Desired Characteristic Value, in an
embodiment, the Desired Characteristic Value exceeds a (optionally
predetermined) threshold value 530 and an output is generated
indicating that the progeny should be continued to be used in the
process 535 (e.g., allowed to grow further or be subjected to
further analysis). In an embodiment, the Desired Characteristic
Value does not exceed a (optionally predetermined) threshold 540
such that an output is generated indicating that the progeny should
be discontinued from the process (e.g., culled from the group). See
for example, FIG. 1. In an embodiment, one round of fertilization
are performed, and the progeny are from that first round of
fertilization. In an embodiment, multiple rounds of fertilization
are performed, and the progeny from one or more of the second,
third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, or more
round.
[0109] For example, a sensed response for a particular progeny
being tested generates a Desired Characteristic Value dataset (or a
starting dataset is derived from "ideal" Desired Characteristic
Values based on quantification of genotype and phenotype
characteristics). Based on the queries of the database from further
sensors reporting additional information regarding the progeny, the
Desired Characteristic Value may increase or decrease as time goes
on. Further as described, such database generation or inquiry may
occur in real-time, and may provide feedback in the form of an
output or other information. For example, as described, once a
progeny exceeds a particular threshold, an alert is generated in
the form of an output (e.g., visual, audio, tactile, etc.)
indicating that the threshold has been exceeded and the progeny
should continue to be used in the process. Additionally, any change
itself in the Desired Characteristic Value may be alerted as to
whether the change has exceeded a threshold (optionally
predetermined) for a particularly exuberant progeny. As indicated,
in an embodiment, the Desired Characteristic Value (DCV) dataset
may be derived from various sources, and may evolve with additional
queries or inputs. See for example, FIGS. 5 and 6. In this way, the
progeny may be evaluated phenotypically, as well as genotypically
or epigenetically, over time. As described, the first analysis of
progeny is conducted very early following fertilization, and
optionally progeny are selected for culturing in the lab or
cultivating in a greenhouse or field. Thus, in an embodiment the
DCV is dynamic, and the first input related to the DCV may include
the first genotyping or other analysis of the progeny very early
following fertilization, and this information may be maintained
over time either as stored information or for use with comparison
for other progeny being tested. As indicated herein, any number of
steps in the various disclosed rapid-breeding embodiments may be
automated. For example, shortly after fertilization when the first
analysis is conducted on the progeny, several progeny show positive
genotypes for a particular desired characteristic and may start out
with a high Desired Characteristic Value. Next, the positive
genotype progeny are selected for further culturing and over time
additional positive or negative phenotypic or epigenetic changes
occur that increase or decrease the progeny's Desired
Characteristic Value depending on the "ideal" desired
characteristic. Thus, the various characteristics of the progeny
may be quantified and compared in order to determine the Desired
Characteristic Value over time.
[0110] As illustrated in FIG. 6, sexual reproduction in plants
involves meiosis and mitosis, for example, when gametophytes give
rise to sperm (haploid) or egg (haploid) cells. When fertilization
occurs, and the male sperm and female egg cells are combined, the
resulting zygote (diploid) undergoes mitosis, producing a
sporophyte, which in turn undergoes meiosis to produce spores
(haploid) that undergo mitosis to produce the gametophyte. As
described herein, certain rapid-breeding embodiments bypasses
various portions of this process and as a result, increases the
efficiency and effectiveness of plant breeding.
[0111] As described herein, FIG. 7 illustrates an input/output
device 700 operably coupled with a computing device 720 that
includes a processing unit 721, a system memory 722, and a system
bus 723 that couples various system components including the system
memory 722 to the processing unit 721. The system bus 723 may be
any of several types of bus structures including a memory bus or
memory controller, a peripheral bus, and a local bus using any of a
variety of bus architectures. The system bus 723 may be any of
several types of bus structures including a memory bus or memory
controller, a peripheral bus, and a local bus using any of a
variety of bus architectures. By way of example, and not
limitation, such architectures include Industry Standard
Architecture (ISA) bus, Micro Channel Architecture (MCA) bus,
Enhanced ISA (EISA) bus, Video Electronics Standards Association
(VESA) local bus, and Peripheral Component Interconnect (PCI) bus,
also known as Mezzanine bus.
[0112] The system memory includes read-only memory (ROM) 724 and
random access memory (RAM) 725. A basic input/output system (BIOS)
726, containing the basic routines that help to transfer
information between sub-components within the thin computing device
720, such as during start-up, is stored in the ROM 724. A number of
program modules may be stored in the ROM 724 or RAM 725, including
an operating system 728, one or more application programs 729,
other program modules 730 and program data 731.
[0113] A user may enter commands and information into the computing
device 720 through input devices, such as a number of switches and
buttons, illustrated as hardware buttons 744, connected to the
system via a suitable interface 745. Input devices may further
include a touch-sensitive display with suitable input detection
circuitry, illustrated as a display 732 and screen input detector
733. The output circuitry of the touch-sensitive display 732 is
connected to the system bus 723 via a video driver 737. Other input
devices may include a microphone 734 connected through a suitable
audio interface 735, and a physical hardware keyboard (not shown).
Output devices may include at least one the display 732, or a
projector display 736.
[0114] In addition to the display 732, the computing device 720 may
include other peripheral output devices, such as at least one
speaker 738. Other external input or output devices 739, such as a
joystick, game pad, satellite dish, scanner or the like may be
connected to the processing unit 721 through a USB port 740 and USB
port interface 741, to the system bus 723. Alternatively, the other
external input and output devices 739 may be connected by other
interfaces, such as a parallel port, game port or other port. The
computing device 720 may further include or be capable of
connecting to a flash card memory (not shown) through an
appropriate connection port (not shown). The computing device 720
may further include or be capable of connecting with a network
through a network port 742 and network interface 743, and through
wireless port 746 and corresponding wireless interface 747 may be
provided to facilitate communication with other peripheral devices,
including other computers, printers, and so on (not shown). It will
be appreciated that the various components and connections shown
are examples and other components and means of establishing
communication links may be used.
[0115] The computing device 720 may be designed to include a user
interface. The user interface may include a character, a key-based,
or another user data input via the touch sensitive display 732. The
user interface may include using a stylus (not shown). Moreover,
the user interface is not limited to an actual touch-sensitive
panel arranged for directly receiving input, but may alternatively
or in addition respond to another input device such as the
microphone 734. For example, spoken words may be received at the
microphone 734 and recognized. Alternatively, the computing device
720 may be designed to include a user interface having a physical
keyboard (not shown).
[0116] In certain instances, one or more components of the
computing device 720 may be deemed not necessary and omitted. In
other instances, one or more other components may be deemed
necessary and added to the computing device.
[0117] In certain instances, the computing system typically
includes a variety of computer-readable media products.
Computer-readable media may include any media that can be accessed
by the computing device 720 and include both volatile and
nonvolatile media, removable and non-removable media. By way of
example, and not of limitation, computer-readable media may include
computer storage media. By way of further example, and not of
limitation, computer-readable media may include a communication
media.
[0118] Computer storage media includes volatile and nonvolatile,
removable and non-removable media implemented in any method or
technology for storage of information such as computer-readable
instructions, data structures, program modules, or other data.
Computer storage media includes, but is not limited to,
random-access memory (RAM), read-only memory (ROM), electrically
erasable programmable read-only memory (EEPROM), flash memory, or
other memory technology, CD-ROM, digital versatile disks (DVD), or
other optical disk storage, magnetic cassettes, magnetic tape,
magnetic disk storage, or other magnetic storage devices, or any
other medium which can be used to store the desired information and
which can be accessed by the computing device 720. In a further
embodiment, a computer storage media may include a group of
computer storage media devices. In another embodiment, a computer
storage media may include an information store. In another
embodiment, an information store may include a quantum memory, a
photonic quantum memory, or atomic quantum memory. Combinations of
any of the above may also be included within the scope of
computer-readable media.
[0119] Communication media may typically embody computer-readable
instructions, data structures, program modules, or other data in a
modulated data signal such as a carrier wave or other transport
mechanism and include any information delivery media. The term
"modulated data signal" means a signal that has one or more of its
characteristics set or changed in such a manner as to encode
information in the signal. By way of example, and not limitation,
communication media include wired media, such as a wired network
and a direct-wired connection, and wireless media such as acoustic,
RF, optical, and infrared media.
[0120] The computing device 720 may also include other
removable/non-removable, volatile/nonvolatile computer storage
media products. For example, such media includes a non-removable
non-volatile memory interface (hard disk interface) 745 reads from
and writes for example to non-removable, non-volatile magnetic
media, or a removable non-volatile memory interface 750 that, for
example, is coupled to a magnetic disk drive 751 that reads from
and writes to a removable, non-volatile magnetic disk 752, or is
coupled to an optical disk drive 755 that reads from and writes to
a removable, non-volatile optical disk 756, such as a CD ROM. Other
removable/nonremovable, volatile/non-volatile computer storage
media that can be used in the example operating environment
include, but are not limited to, magnetic tape cassettes, memory
cards, flash memory cards, DVDs, digital video tape, solid state
RAM, and solid state ROM. The hard disk drive 757 is typically
connected to the system bus 723 through a non-removable memory
interface, such as the interface 745, and magnetic disk drive 751
and optical disk drive 755 are typically connected to the system
bus 723 by a removable non-volatile memory interface, such as
interface 750.
[0121] The drives and their associated computer storage media
discussed above provide storage of computer-readable instructions,
data structures, program modules, and other data for the computing
device 720.
[0122] A user may enter commands and information into the computing
device 720 through input devices such as a microphone, keyboard, or
pointing device, commonly referred to as a mouse, trackball, or
touch pad. Other input devices (not shown) may include at least one
of a touch sensitive display, joystick, game pad, satellite dish,
and scanner. These and other input devices are often connected to
the processing unit through a user input interface that is coupled
to the system bus, but may be connected by other interface and bus
structures, such as a parallel port, game port, or a universal
serial bus (USB).
[0123] The computing system may operate in a networked environment
using logical connections to one or more remote computers, such as
a remote computer 780. The remote computer 780 may be a personal
computer, a server, a router, a network PC, a peer device, or other
common network node, and typically includes many or all of the
elements described above relative to the computing device 720,
although only a memory storage device. The network logical
connections include a local area network (LAN) and a wide area
network (WAN), and may also include other networks such as a
personal area network (PAN) (not shown). Such networking
environments are commonplace in offices, enterprise-wide computer
networks, intranets, and the Internet. Included herein is a network
for field research station(s).
[0124] When used in a networking environment, the computing system
is connected to the network 771 through a network interface, such
as the network interface 770, the modem 772, or the wireless
interface 793. The network may include a LAN network environment,
or a WAN network environment, such as the Internet. In a networked
environment, program modules depicted relative to the computing
device 720, or portions thereof, may be stored in a remote memory
storage device. By way of example, and not limitation, remote
application programs 785 as residing on computer medium 781. It
will be appreciated that the network connections shown are examples
and other means of establishing communication link between the
computers may be used.
[0125] In certain instances, one or more elements of the computing
device 720 may be deemed not necessary and omitted. In other
instances, one or more other components may be deemed necessary and
added to the computing device 720.
[0126] The signal generator 790 includes a signal generator
configured to generate a signal indicative of the desired
characteristic of the plant or plant tissue. In one embodiment, the
signal may include a raw data signal, i.e., a capacitance
measurement, a change in one or more measurements of a phenotypic
characteristic, or an indicator that a desired characteristic has
exceeded a (predetermined) threshold. In one embodiment, the signal
generator may include a processor circuit 792, a threshold circuit
794, an output circuit 796, or a communications circuit 798. In one
embodiment, the communications circuit may be operable to
communicate using an electrical conductor or using a wireless
transmission. In one embodiment, the signal generator may include
an instance of the thin computing device 720 and the processor
circuit may be the processing unit 721.
[0127] In one embodiment, the system actively monitors (e.g.,
detects, tracks, etc.) a plant or plant tissue located by using at
least one of computerized axial tomography, fiber optic
thermometry, infrared thermography, magnetic resonance imaging,
magnetic resonance spectroscopy, microwave thermography, microwave
dielectric spectroscopy, positron emission tomography, ultrasound
reflectometry, spectroscopic imaging, visual imaging, infrared
imaging, single photon emission computed tomography, global
positioning system, satellite imaging, or the like.
PROPHETIC EXAMPLES
Example 1: Cycling of Gametes In Vitro (CoGiV)
[0128] 1. Producing Pluripotent Plant Stem Cells In Vitro.
[0129] Plant cell explants are cultured in vitro (dedifferentiated)
to generate callus cells which contain pluripotent plant stem
cells. Plant pluripotent stem cells may be obtained from in vitro
plant tissue cell cultures which are initiated from somatic or
embryonic tissues. For example, a leaf tissue explant, of
approximately 1 cm2, is cultured on solid media (containing agar)
which contains essential salts, vitamins and hormones. The media
contain plant hormones, auxins (e.g., 2,4 dichlorophenoxyacetic
acid (2,4-D)) and cytokinins known to induce growth of a callus
which is comprised of pluripotent stem cells (see e.g., He et al.,
PLoS Genetics 8: e1002911. doi:10.1371/journal.pgen.1002911 and
Plant Cell and Tissue Culture, p. 3-15, Indra K. Vasil, Trevor A.
Thorpe (eds.), 1994 Kluwer Acad. Publ., Dordrecht, The Netherlands,
each of which is incorporated herein by reference). Callus cells
which arise in culture are propagated in suspension culture and
used to generate gametes for in vitro fertilization.
[0130] 2. Inducing Differentiation of Plant Stem Cells to Gametes
In Vitro.
[0131] Pluripotent callus cells are differentiated in vitro to
undergo meiosis and generate haploid gametes. The stem cells are
cocultured in vitro with plant tissues and media which promote
gametogenesis. For example, male gametes may be derived by
coculture with anther-derived tissues and culture media which
promote meiosis and gamete differentiation. For example, anther
tissues from Arabidopsis thaliana including the endothecium, middle
cell layer and tapetum, are cocultured with the pluripotent stem
cells to initiate and support gamete formation (see e.g., Wilson et
al., Reproduction 128: 483-492, 2004 which is incorporated herein
by reference). Media and methods to promote meiosis and microspore
culture may be optimized from similar described (see e.g.,
International Publication No. WO 03/017753 by Dirks et al.,
published on Mar. 6, 2003 and Wang et al., Plant Physiol. 124:
523-530, 2000 each of which is incorporated herein by reference).
To induce female gamete differentiation in pluripotent cells
tissues from the ovule, including the nucellus and integument, the
tissues are cocultured with the stem cells. Methods to induce
meiosis and megaspore differentiation may be optimized from similar
described (see e.g., Wilson et al., Ibid. and Wang et al., 2000,
Ibid.). Gametes obtained by in vitro culture and differentiation of
pluripotent stem cells are "bred" by electrofusion in vitro.
[0132] 3. Breeding of Haploid Gametes to Generate Hundreds of
Diploid Plant Zygotes which are Sorted and Cultured In Vitro.
[0133] Gametes derived from pluripotent stem cells are "bred" by
fusing pairs of gametes and culturing the diploid hybrids (i.e.,
zygotes) in vitro to generate cell lines and/or plant embryos.
Gamete pairs are fused by applying a brief electric charge (50
msec, 1 kV/cm) to the gametes which are aligned by
dielectrophoresis. Electrofusion and culture of gamete pairs in
vitro may yield hundreds of plant embryos. For example,
electrofusion of egg cells and sperm from maize may be done on
microscope coverslips with approximately 2000 gamete pairs and
yield fusion products, i.e., zygotes, which are capable of growing
to become plant embryos (see e.g., Kranz et al., The Plant Cell 5:
739-746, 1993 which is incorporated herein by reference). Zygotes
obtained by electrofusion are propagated in vitro and sorted using
a fluorescence activated cell sorter (FACS). For example,
multicellular structures obtained approximately 5 days after
electrofusion of maize gametes are stained with fluorescent DNA
stains and fluorescently labeled antibodies, and sorted into
individual wells of a microtiter plate. Zygotes may be stained with
propidium iodide to determine DNA content, (e.g., diploid, haploid,
tetraploid, or aneuploid) and antibodies which detect cell wall
components or plasma membrane components. Methods and
instrumentation for flow cytometry sorting of plant cells and plant
cell protoplasts are described (see e.g., Gaurav, Vishal, "Flow
Cytometry of Cultured Plant Cells for Characterization of Culture
Heterogeneity and Cell Sorting Applications" (2011). Open Access
Dissertations. Paper 370 available online at:
scholarworks.umass.edu/open_access_dissertations/370/ which is
incorporated herein by reference). Zygotes with the appropriate
number of chromosomes, e.g., 2n, and expressing desired cell wall
or cell membrane components are cultured in vitro to generate cells
for genomic selection.
[0134] 4. Genomic Selection of Zygotes
[0135] Zygotes selected by cell sorting are propagated in vitro and
then selected by genomic selection. Genomic selection of zygotes is
done by determining the DNA sequence of single nucleotide
polymorphisms (SNPs) which mark specific chromosomal loci,
haplotypes and alleles. For example, SNPs may be determined by
whole genome sequencing (see e.g., Resende Jr. et al., New
Phytologist 193: 617-624, 2012 which is incorporated herein by
reference). SNPs may provide markers for specific haplotypes,
quantitative trait loci and individual alleles that are present in
the zygotes. Next generation sequencing technology combined with
other technologies is used to determine SNPs present in the
individual zygote DNAs. (See e.g., Siva P. Kumpatla et al., (2012)
Genomics-Assisted Plant Breeding in the 21st Century: Technological
Advances and Progress, Plant Breeding, pp. 131-184, Abdurakhmonov
(Ed.) InTech Publ., Rijeka, Croatia, which is included herein by
reference.) For example Illumina's BeadArray platform (available
from Illumina, San Diego, Calif.) uses beads with oligonucleotides
attached to determine 3072 SNPs in a single reaction. Zygotes with
combinations of preferred chromosomes are selected for another
round of breeding and/or embryogenesis and optionally, plantlet
development.
[0136] 5. Cell Culture of Selected Zygotes to Obtain Stem Cells and
Plantlets
[0137] Selected zygotes are cultured in vitro to obtain stem cells
and/or plantlets. The zygotes resulting from electrofusion are
pluripotent and give rise to flowering plants if cultured in vitro.
Media and methods to propagate the zygotes in vitro may be
optimized from similar described (e.g., see Kranz et al., Ibid).
Alternatively to start another round of breeding the selected
zygotes are differentiated in vitro to gametes (see Step 2 above)
and enter another cycle of breeding, and genomic selection followed
by in vitro culture to generate zygotes with improved traits.
Repeated rounds of gamete cycling combined with genomic selection
will reduce the time required to create highly selected plants with
optimal traits.
Example 2: Rapid Breeding of Apple Trees Using Gamete Cycling In
Vitro
[0138] A rapid breeding method is used to create apple trees that
produce apples with desired traits in a short time frame. The rapid
breeding method is used in combination with genetic marker
selection to rapidly produce and select apple trees bearing
multiple genetic markers that determine desired apple traits. Stem
cells (apical meristem cells) are cultured in vitro and
differentiated to generate gametes which are mated to produce
embryos which serve as a source of stem cells for another round of
breeding. Multiple embryos produced at each round of breeding are
genotyped using next generation DNA sequencing technology to
identify DNA markers associated with the desired apple traits.
[0139] The rapid breeding method may be initiated by in vitro
fertilization using gametes from elite strains of apple trees with
desired apple fruit traits. For example male gametes from a
semi-sweet apple, e.g., Granny Smith, may be electrofused with egg
cells from a sweet apple, e.g., Golden Delicious. Electrofusion and
culture of gamete pairs in vitro may yield hundreds of plant
embryos (see e.g., Kranz et al., The Plant Cell 5: 739-746, 1993
which is incorporated herein by reference). The resulting "Granny
Smith".times."Golden Delicious" embryos are genotyped to identify
embryos with a desired combination of genes from Granny Smith and
Golden Delicious apple trees. For example, if a Granny Smith apple
with the sweetness of a Golden Delicious apple is desired, then an
embryo with a set of "sweetness genes" derived from Golden
Delicious apples is selected. DNA sequencing of the apple genome
has identified a set of genes associated with carbohydrate
metabolism in Golden Delicious. For example, multiple copies are
found of the gene encoding sorbitol-dehydrogenase which converts
sorbitol to fructose in the fruit. Moreover there are 71 sorbitol
metabolism and transport genes in the apple genome which may be
candidates for "sweetness genes". See e.g., Velasco et al., Nature
Genetics, 42: 833-839, 2010 which is incorporated by reference
herein. Genotyping of the embryos may be done by using next
generation sequencing technology to sequence specific loci, e.g.,
the sorbitol metabolism genes, or to survey DNA markers (e.g.,
single nucleotide polymorphisms (SNPs)) genome-wide. Genetic
markers may be associated with desired traits in plants by whole
genome sequencing or exome sequencing (see e.g., Resende Jr. et
al., New Phytologist 193: 617-624, 2012 which is incorporated
herein by reference). Genomic selection of apple tree embryos may
be done approximately 10-14 days after electrofusion of gametes
when a meristem part of the embryo enlarges and cells for DNA
isolation and sequencing may be obtained as well as cells for
induction of gametes.
[0140] Preferred embryos are selected by genomic selection and the
corresponding stem cells are isolated for induction of gametes and
a second round of breeding. Apple stem cells are isolated from
apical meristem cells by dissection of apple embryos thus
eliminating the time required for sexual maturation of trees (apple
trees require approximately 10 years to mature sexually). The
isolation and propagation of meristem cells are described (see
e.g., U.S. Patent Appl. No. 2004/0016015 by Nguyen et al.,
published on Jan. 22, 2004 which is incorporated herein by
reference). For example, embryo meristem cells may be obtained 8-10
days following electrofusion of gametes (see Kranz et al., Ibid.).
To induce gametogenesis in plant stem cells, in vitro cultures are
established in conjunction with gene expression vectors encoding
transcription factors essential to gametogenesis. Methods to induce
gamete production from embryonic stem cells in mice are described
(see e.g., Hayashi et al., Science 338: 971-975, 2012 and Nayernia
et al., Developmental Cell 11: 125-132, 2006 which are incorporated
herein by reference). To generate apple male gametes, an in vitro
culture system for apple apical meristem cells is established with
plant hormones and nutrients. Methods to culture meristem cells in
vitro are known (see e.g., U.S. Patent Appl. No. 2004/0016015,
Ibid.). To promote differentiation of the stem cells to gametes,
vectors encoding transcription factors essential for male gamete
production are transfected into the stem cells. For example,
MADS-box genes encoding essential transcription factors include:
SPOROCYTELESS (SPL)/NOZZLE (NZZ), AGAMOUS-LIKE 66 (AGL66) and
AGL104 (see e.g., Gramzow et al., Genome Biology 11: 214, 2010
available online at: http://genomebiology.com/2010/11/6/214 which
is included herein by reference). Plasmid expression vectors
containing MADS-box genes may be derived from Agrobacterium
tumefaciens Ti plasmids (see e.g., U.S. Pat. No. 7,612,258 issued
to He et al. on Nov. 3, 2009 which is incorporated herein by
reference). Expression vectors with promoter sequences, MADS-box
genes, selectable markers (e.g. Hygromycin resistance gene) and
regulatory sequences may be transferred into stem cells by
microprojectile bombardment or electroporation (see e.g., U.S.
Patent Appl. 2004/0016015, Ibid.) Similarily a vector encoding
AGL23, may be used to promote female gamete (i.e., egg cell)
differentiation in apple stem cells. MADS-box genes essential to
gametogenesis are described (see e.g., Gramzow et al., Ibid.)
[0141] Gametes derived from the meristem cells of genetically
selected apple tree embryos are bred again to improve the apple
tree genotype. For example, zygotes bearing "sweetness genes",
e.g., the Golden Delicious alleles for sorbitol metabolism and
transport may be crossed with Golden Delicious gametes to capture
both alleles at each "sweetness gene" locus. Domesticated apple
trees such as Golden Delicious are highly heterozygous, and in
addition multiple genes may be required to control a single trait
such as sweetness (see e.g., Velasco et al., Ibid.). A second round
of electrofusion generates hundreds of zygotes which are cultured
in vitro for 10-14 days and then genetically selected by DNA
sequencing of sorbitol metabolism and transport genes or associated
SNP's (as described above). Progeny are selected that contain
Golden Delicious alleles at the sorbitol gene loci and Granny Smith
alleles at other loci. Meristem cells may be isolated and induced
to generate male and female gametes for another round of
breeding.
[0142] Repeated breeding cycles coupled with genetic selection
using next generation sequencing technology allows rapid
development of apple trees with traits such as sweetness which are
controlled by multiple heterozygous genes. For example, apple tree
embryos with multiple sorbitol metabolism genes derived from Golden
Delicious on a background of Granny Smith genes may be selected in
multiple crosses which require approximately 11-15 days each. In
vitro culture and plant outgrowth of multiple preferred apple tree
embryos may be done by optimizing similarly described methods (see
e.g., U.S. Pat. No. 7,612,258, Ibid.) and optimized apple trees
bearing fruit may be obtained in less than one year using grafting
techniques.
Example 3: Rapid Breeding of Cotton by In Vitro Gamete Cycling
[0143] To develop improved cotton cultivars a rapid breeding method
is employed that induces stem cells to differentiate directly to
gametes which are mated and propagated in vitro. An elite cotton
cultivar is crossed with a second elite cultivar to select for a
desired trait, for example, drought resistance. Rapid breeding is
combined with genomic selection to identify preferred progeny
emanating from an initial cross and multiple backcrosses.
[0144] The rapid breeding method may be initiated by in vitro
fertilization using gametes from elite cotton cultivars, e.g.,
Gossypium hirsutum, cv. Siv'on (GH) and Gossypium barbadense, cv.
F-177 (GB) which carry quantitative trait loci (QTL) conferring
drought resistance (see e.g., Levi et al. Mol. Breeding 23:
179-195, 2009 which is incorporated herein by reference). For
example male gametes from GH may be electrofused with gametes from
GB. Electrofusion and culture of gamete pairs in vitro may yield
hundreds of plant embryos (see e.g., Kranz et al., The Plant Cell
5: 739-746, 1993 which is incorporated herein by reference). The
resulting "GH.times.GB" embryos are genotyped to identify embryos
bearing chromosomal loci conferring draught resistance: For example
QTL on chromosome 6 and chromosome 2 of GB are associated with
drought resistance, and QTL on chromosome 25 and chromosome 22 of
GH were also linked to drought resistance (see Levi et al., Ibid.).
Genotyping of the embryos may be done by using next generation
sequencing technology to sequence specific loci, e.g., QTL, or to
survey DNA markers (e.g., single nucleotide polymorphisms (SNPs))
genome-wide. For example SNPs identifying GH chromosomes versus GB
chromosomes may be used for genomic selection (see e.g., Yu et al.,
G3, Genes; Genomes; Genetics 2: 43-58, 2012 and Resende Jr. et al.,
New Phytologist 193: 617-624, 2012 which are incorporated herein by
reference). Genotyping of cotton embryos is done using next
generation sequencing technology. For example the Illumina Infinium
assay (available from Illumina, San Diego, Calif.) is used to
determine cotton SNPs using software also available from Illumina.
Genomic selection of cotton embryos may be done approximately 10-14
days after electrofusion of gametes when a meristem part of the
embryo enlarges and cells for DNA isolation and sequencing may be
obtained as well as cells for induction of gametes (see Kranz et
al., Ibid.). Alternatively polymerase chain reaction (PCR) and
agarose gels may be used to identify embryos containing a specific
gene (see e.g., Wang et al., Plant Breeding 130: 569-573, 2011
which is incorporated herein by reference).
[0145] Cotton embryo hybrids bearing GH chromosomes conferring
drought resistance are backcrossed to the elite cotton cultivar,
GB, to restore the GB genetic background. Gamete cycling and
genomic selection are used to expedite the breeding process and
eliminate the time needed for sexual maturation of the cotton
embryos. For example the generation time for cotton plants in the
field is approximately 130-140 days (e.g., see Wang et al., 2011,
Ibid.) versus a generation time of approximately 11-15 days using
gamete cycling in vitro.
[0146] Hybrid embryos (GH.times.GB) bearing the drought-resistance
loci are dissected to obtain pluripotent meristem cells which are
cultured in vitro to induce gamete formation. Meristem cells that
are pluripotent stem cells are isolated from the hybrid embryos,
where they appear 8-10 days after electrofusion of gametes (see
e.g., Kranz et al., Ibid.). The stem cells are cocultured in vitro
with plant tissues and media which promote gametogenesis. For
example, male gametes may be derived by coculture with
anther-derived tissues and culture media which promote meiosis and
gamete differentiation. For example, anther tissues from GH
including the endothecium, middle cell layer and tapetum are
cocultured with the hybrid stem cells to support gamete formation
(see e.g., Wilson et al., Reproduction 128: 483-492, 2004 which is
incorporated herein by reference). Media and methods to promote
meiosis and microspore culture have been described (see e.g.,
International Publication No. WO 03/017753 by Dirks et al.,
published on Mar. 6, 2003 and Wang et al., Plant Physiol. 124:
523-530, 2000 which are incorporated herein by reference). For
example media for cotton anther and ovule culture in vitro are
described (see e.g., Memon et al., World Applied Sciences Journal
8: 76-79, 2010 which is incorporated herein by reference).
Murashige and Skoog media with 2,4 dichlorophenoxyacetic acid
(2,4-D), indole-3-acetic acid (IAA), indole-3-butyric acid (IBA),
and kinetin (6-furfuryl-aminopurine) (all available from
Sigma-Aldrich Corp., St. Louis, Mo.) may be used to culture ovule
and anther tissues. The plant hormone abscisic acid may be added to
promote androgenesis (see e.g., Wang et al., 2000, Ibid.). Gametes
derived from the stem cells of genetically selected embryos are
bred again to improve the cotton cultivar. For example the
preferred hybrid embryos (GH.times.GB) may be backcrossed with GB
to create an improved drought-resistant strain with all the
positive traits of GB.
[0147] Gametes derived from genomically selected GH.times.GB
embryo's meristem cells are bred with GB gametes to obtain cotton
with predominantly GB genes and multiple GH genes conferring
drought-resistance. Multiple chromosomal loci may be required to
confer a single trait such as drought resistance (see e.g., Levi et
al., Ibid.). A second round of electrofusion generates hundreds of
zygotes which are cultured in vitro for 10-14 days and then
genetically selected by DNA sequencing of specific loci or the
corresponding SNP's (as described above). Progeny are selected that
retain GH drought-resistance loci and carry predominately GB
chromosomes otherwise. The selected embryos may be used as a source
of stem cells and gametes for another round of breeding. For
example, a breeding program may include four backcross generations
to select an optimal cultivar with an improved trait. The rapid
cycling of gametes method requires approximately 60 days to
complete four backcrosses versus approximately 360 days for four
generations using alternative methods (see e.g., Wang et al., 2011,
Ibid.).
[0148] While various aspects and embodiments have been disclosed
herein, other aspects and embodiments will be apparent to those
skilled in the art. The various aspects and embodiments disclosed
herein are for purposes of illustration and are not intended to be
limiting, with the true scope and spirit being indicated by the
following claims.
* * * * *
References