U.S. patent number PP12,791 [Application Number 09/537,508] was granted by the patent office on 2002-07-23 for novel, high yielding stable mentha arvensis plant named `damroo`.
This patent grant is currently assigned to Council of Scientific & Industrial Research. Invention is credited to Alok Kalra, Suman Preet Singh Khanuja, Birendra Kumar, Sushil Kumar, Vijay Kumar, Nareshwar Mengi, Mahendra Singh Negi, Nirmal Kumar Patra, Dharmendra Kumar Rajput, Paltoo Ram, Raja Ram, Shiv Ram Sharma, Ajit Kumar Shasney, Ram Sajeevan Shukla, Hemendra Pratap Singh, Herikesh Bahadur Singh, Jitendra Pratap Singh, Ved Ram Singh, Vijay Pal Singh, Hasan Tanveer, Neeraj Kumar Tyagi.
United States Patent |
PP12,791 |
Patra , et al. |
July 23, 2002 |
Novel, high yielding stable Mentha arvensis plant named
`Damroo`
Abstract
A novel Mentha arvensis mint population-variety `Damroo` capable
of producing viable seeds and phenotypically homogeneous
seed-derived plant population when cross pollinated within its own
population and capable of high yield of mint oil.
Inventors: |
Patra; Nirmal Kumar (Lucknow,
IN), Kumar; Sushil (Lucknow, IN), Khanuja;
Suman Preet Singh (Lucknow, IN), Shasney; Ajit
Kumar (Lucknow, IN), Kalra; Alok (Lucknow,
IN), Singh; Herikesh Bahadur (Lucknow, IN),
Singh; Hemendra Pratap (Lucknow, IN), Singh; Ved
Ram (Lucknow, IN), Tanveer; Hasan (Lucknow,
IN), Mengi; Nareshwar (Lucknow, IN),
Rajput; Dharmendra Kumar (Lucknow, IN), Negi;
Mahendra Singh (Lucknow, IN), Tyagi; Neeraj Kumar
(Lucknow, IN), Ram; Paltoo (Lucknow, IN),
Singh; Vijay Pal (Lucknow, IN), Shukla; Ram
Sajeevan (Lucknow, IN), Kumar; Birendra (Lucknow,
IN), Singh; Jitendra Pratap (Lucknow, IN),
Ram; Raja (Lucknow, IN), Kumar; Vijay (Lucknow,
IN), Sharma; Shiv Ram (Lucknow, IN) |
Assignee: |
Council of Scientific &
Industrial Research (New Delhi, IN)
|
Family
ID: |
24142939 |
Appl.
No.: |
09/537,508 |
Filed: |
March 29, 2000 |
Current U.S.
Class: |
PLT/259 |
Current CPC
Class: |
A01H
5/12 (20130101) |
Current International
Class: |
A01H 005/00 () |
Field of
Search: |
;PLT/259 |
Primary Examiner: Campell; Bruce R.
Assistant Examiner: Hwu; June
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
Claims
We claim:
1. A new and distinct cultivar of Mentha arvensis plant named
`Damroo,` substantially as herein illustrated and described, having
the following characteristics: (a) dark greenish leaves (137A),
white to whitish purple (76D) petals, and branching providing a
pyramidal habit; (b) tolerance to leaf spot, rust, and powdery
mildew; (c) essential oil containing 78-80% menthol and 12-17%
isomenthone; (d) seed yields in the range of about 90-96kg/hectare;
and, (e) the capacity to retain homogeneity of plant traits,
despite out-crossing within the population.
Description
FIELD OF INVENTION
The present invention is related to the development of a stable and
high yield mint plant called `Damroo` capable of producing viable
seeds and phenotypically homogeneous seed derived population. More
particularly, the invention relates to a high essential oil
yielding variety `Damroo` capable of producing viable seeds and
therefore useful as a regular seed-source for raising homogenous
seedling populations, an essential prelude to raising an ideal
transplanted mint crop. The mint crop can be grown by
transplantation after wheat cultivation, instead of cultivating it
as main crop in place of wheat, a long sought wise option for
cultivating mint without affecting the cultivation of the staple
cereal wheat. `Damroo` owing to its stability in seed-grown
population for all morpho-physiological attributes, advances the
development of sustained yields.
BACKGROUND OF THE INVENTION
Menthol mint is grown in tropical and sub-tropical agro-climates
for its essential oil. The oil, besides being widely used for
producing menthol and the by-product dementholised oil (DMO), also
finds uses in pharmaceutical and cosmetic industries. Menthol has a
cooling, refreshing aroma and antiseptic properties. The menthol
derivatives are also used in flavouring confectionery and
cigarettes. Indeed, profitability in menthol mint is motivating the
crop growers to grow it widely, even at the expense of conventional
crops like wheat, sugarcane, and vegetables. This has been a metter
of concern, especially regarding the fate of wheat crop in the
Indogangetic plains of India. Wheat being a major staple food,
significant reduction in wheat cultivation in exchange for
cultivation of menthol mint may lead to the eventual wheat
shortages. One pragmatic solution lies in the development of more
efficient agrotechnologies for mint crops, so that crop growers
would need only 50% of the area used presently and be able to
cultivate both the crops. To the plant breeder, it means that he
should put efforts to evolve varieties having doubled productivity.
The Central Institute of Medicinal and Aromatic Plants (CIMAP),
Lucknow, India, having made large efforts in this regard, has
witnessed fascinating success in developing high yielding varieties
with much impressive yield improvement, of which the variety
`Kosti` (U.S. Ser. No. 09/145,546) having double oil productivity
over earlier widely grown familiar variety `Shivalik` (unpatented),
is now enjoying the highest adorations of the crop growers.
Besides evolving the productive varieties, another wise option,
which has long been proposed and initiated, but is yet to be much
improved for its wide acceptance, is to resort to cultivating
menthol mint as a late transplanted crop from April to July after
wheat cultivation instead of cultivating it as major crop during
February to June, when wheat is grown. In cultivating menthol mint
as a transplanted crop, to depend upon the late planted
sucker-grown nursery (but not seed-grown nursery) during the advent
of summer (or spring) has been a general practice in raising
transplanted mint crops during summer. However, with such a
sucker-grown nursery exclusively providing the over matured hardy
plants for transplanting, the plant growth as well as productivity
in the transplanted mint crop, with very rare exceptions, are
always very low. Seed-progeny research over the last five years has
given an a priori clue that seeds can be grown in a nursery during
winter months and young seedlings can be made available during
summer months (April-May) for raising the transplanted mint crop.
Keeping this in mind, attempts were made during 1994-1996 to
extensively research into the open pollinated seed progenies of the
familiar variety `Shivalik` (unpatented) to explore the possibility
of inventing a stable producing genotype.
OBJECTIVES
The main object of the invention is to develop a stable and high
yielding mint plant capable of producing viable seeds and
phenotypically homogeneous seed derived plant population.
Another object of the invention is to identify and develop a stable
seed-producing population variety of M. arvensis plant which, as
generally known, does not set seeds under selfing conditions
(except in very rare cases).
Yet another object of the invention is to develop plants that can
provide homogeneous seeds even under cross pollination conditions
within its own plant population.
Still another object is to develop mint plants capable of high
yield of mint oil.
Another object of the invention is to develop a stable seed
producing mint variety with high mint oil yield and menthol
content.
Yet another object of the invention is to develop a novel mint
variety that has improved disease resistance, higher biomass, high
oil yield, and high seed yield.
SUMMARY OF THE INVENTION
To meet the above objectives, the present invention provides a
novel Mentha arvensis mint population-variety `Damroo` capable of
producing viable seeds and phenotypically homogeneous seed-derived
plant population when cross pollinated within its own population
and capable of high yield of mint oil.
DETAILED DESCRIPTION
Accordingly, the invention provides a new and distinct variety
`Damroo` having the following new combination of characteristics as
compared to conventional known varieties of M. arvensis, said plant
having the following combination of characteristics: (a) a plant
height of about 100-110 cm; (b) dark greenish leaves, whitish to
whitish-purple flowers, and branching providing pyramidal habit;
(c) a high seed yield, compared to all other existing varieties of
menthol mint; (d) better tolerance to leaf spot, rust, and powdery
mildew; (e) a yield of essential oil containing 78-80% menthol and
12-17% isomenthone; (f) a yield of seeds in the range of about
90-96 kg/hectare against 30 kg/hectare in `Shivalik` (unpatented);
and (g) capable of retaining homogeneity in population for plant
traits, despite out-crossing within the population.
In an embodiment, the invention also provides seeds produced by the
novel plant `Damroo.`
In yet another embodiment, the invention provides progenies
produced by the novel plant `Damroo.`
The seed producing variety `Damroo` is the selection from the
existing variety of mint plant called `Shivalik` (unpatented).
The invention is described in detail herein below.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings that accompany:
FIG. 1 represents the seedlings of the variety `Damroo` (Mentha
arvensis).
FIG. 2 represents a seed nursery of the variety `Damroo,` showing
the profuse growth of seedlings.
FIG. 3 represents a single `Damroo` plant during flowering.
FIG. 4 represents pyramidal plant habit of `Damroo`.
BREEDING HISTORY
The seed producing variety `Damroo` developed in this invention is
an outcome of a strategic approach of raising a large population of
open pollinated seed progenies to serve as an original gene pool of
a specific menthol mint variety, identifying the variant
(spontaneous recombinant) with the desirable traits (higher oil
seed yield and high oil productivity), progeny-testing of the
variant for phenotypic segregation, creating homogeneous progeny of
the variant via repeated, intentional, natural out-crossing between
the phenotypically identical progenies, selections in the progeny
generations only for the "likes" and appraisals of the homogeneous
progeny population (i.e. population variety `Damroo`) against
existing standard cultivars (controls) for the desirable plant
traits. `Damroo` cultivar development, propagation, and testing
were performed in field plots in Lucknow, India, and at Field
Station Pantnagar, in Pantnagar, India. Among the existing menthol
mint cultivars, `Shivalik` (unpatented) was the best genotype for
setting viable seeds under out-crossing, and was identified as the
starting genetic material for raising the open pollinated seed
progenies for the genetical selections. The Applicants collected
about 10 gms of open pollinated minute seeds in bulk from a total
of randomly selected 15 morphologically elite plants of `Shivalik`
(unpatented) grown in a large commercial field measuring a total
cropping area of five hectares during first week of July 1994. The
bulked seeds from the 15 plants were grown in a well prepared
raised nursery bed during November 1994. Of the total 250 seedlings
obtained from the nursery and subsequently transplanted in a
separate field during April 1995, 222 survived to provide as
original gene pool for exercising the genetical selections. Among
the 222 plants, a total of only 14 plants showing profuse
flowering, was selected and their seeds were separately collected
during June 1995. The seed weight in the selected plants ranged
from 0.50 to 2.50 gms, the highest seed weight (2.50 gms) being
recorded in the Sel.4-6-125 which was alike with its mother plant
for deep green leaf colour, but excelled the latter as well as the
rest 13 selected plants for growth habit and flowering branches. In
order to avoid the possible chances of losing the material through
natural mortality, all the 14 selected plants were separately
vegetatively multiplied by their underground suckers and maintained
mainly as buffer clonal stocks marking them as the "fixed first
(S.sub.0) generation-hybrid" progenies (fixed for all plant traits
by vegetative propagation). The open pollinated seeds of June 1995
were grown in nursery beds during November 1995. The seedlings were
maintained in nursery beds with proper care till the 6.sup.th
April, 1996--i.e. until the time when they attained the fifth
leaf-stage and the average height of 15 cm (as against the
sucker-grown mature plants of at least 30 cm which are generally
used for raising the transplanted mint crop). The number of
seedlings in the 14 selections greatly varied with the range: 35
(in the Sel.8-4-125) to as high as 762 (in Sel.4-6-125). FIG. 1
represents of the seedling of the variety `Damroo` (Mentha
arvensis). It represents seed-nursery of the mother variety
`Shivalik` (unpatented), showing sparsely grown seedling.
A point of much interest arose with our study of segregation
(heterogeneity). The plant traits in the seedling population of the
14 selected plants are supposed to show heterogeneity in the
seed-progeny, under the assumption of the generally accepted view
of invariable genetic segregation in an open pollinated seed
progeny of heterozygous perennial plants (M. arvensis, though grown
as annual, is indeed perennial because it is grown vegetatively by
suckers). However, none of the 14 selections revealed any
segregation, with the very rare exceptions of 1 to 6 variant plants
exhibiting weak growth habit and somewhat different leaf colour
(light green against dark green of the progenitor and shape
(globalur/bushy against pyramidal of the progenitor), revealed any
segregation. Unexpectedly, all the open pollinated
seed-progeny-populations (S.sub.1 populations) of the selections,
including that of the Sel.4-6-125, which had supremacy over others
for growth performance, were identical to their progenitors for
morphology. The grown-up seedling of all the selections were
separately transplanted in isolated blocks on 7.sup.th April, 1996,
leaving their off-type variants to facilitate the natural
out-crossings between the "likes" within each selection (the open
pollinated seed-progeny population).
Attempts were made to collect selfed and out-crossed seeds of all
the selections. It is worth while to record that none of them
except Sel.4-6-125, set seeds under controlled selfing, despite all
of them nevertheless setting seeds under out-crossings between the
"likes." The seeds were separately collected during July-August
1996 and subsequently grown in nursery as the third generation
populations (S.sub.2 populations). The number of raised seedlings
in S.sub.2 populations ranged from 68 (in Sel.8-12-125) to 688 (in
Sel.4-6-125). Thus, once again the selection 4-6-125, came out as
the best among 14 selections for viable seed productivity as
axiomatic to its ascertained ability to give the maximum seedlings.
The seedlings of S.sub.2 populations were transplanted in the
similar way as done for S.sub.1 generation, during first week of
April 1997. The comparative results of morpho-physiological
fitnesses of the S.sub.2 populations were completely consistent
with those of S.sub.0 and S.sub.1 populations. Despite the "within
the population" out-crossings in S.sub.1 populations, none of the
derived S.sub.2 populations including that of Sel.4-6-125 revealed
segregation for plant traits except each being identical with its
progenitor population (S.sub.1). Interestingly, both the selfed and
out-crossed S.sub.2 populations of Sel.4-6-125, besides retaining
their morphological similarity with their progenitor population
(S.sub.1), did not differ from each other for morphology.
From the results of the S.sub.0, S.sub.1, and S.sub.2 populations,
it was evident that Sel.4-6-125, unlike the other 13 selections,
has both selfing, and out-crossing systems, coupled with the
additional genetic mechanism for retaining its maternal traits,
perhaps through apomixis over generations, provided its population
in different generations comprises morpho-physiologically identical
individuals. It appeared likely that all our developed selections
except Sel.4-6-125 are perhaps obligate apomicts which, apart from
having only cross fertility, do not have self compatibility leading
to no seed settling in their selfing. Sel.4-6-125, later named as
the population-variety `Damroo`, owing to its superiority over the
others for seed yield and population stability for all
morpho-physiological fitnesses, was attempted for its further
assessment against all standard varieties for productivity. In
fact, the consistent results of S.sub.0 and S.sub.1 seedling
populations of `Damroo` regarding its morpho-physiological
stability, led us to conduct its preliminary yield trial (PYT)
during 1997-1998. Its pilot scale yield trial was conducted during
1998-1999, on the basis of the consistent stability results of the
S.sub.0, S.sub.1, and S.sub.2 populations. FIG. 2 represents a seed
nursery of the variety `Damroo` showing profuse growth of
seedlings. Similarly, FIG. 3 represents a field of `Damroo` showing
its synchronous flowering. FIG. 4 represents the canopy of
`Damroo`. Tables 1 and 2 represent the performance of `Damroo` in
comparison with the mint varieties `Shivalik` (unpatented), `Kosi`
(U.S. Ser. No. 09/145,546) and `Himalaya` (U.S. Plant Pat. No.
10,935).
TABLE 1 Comparative performances of menthol mint strain `Damroo`
and three existing standard cultivars in Pilot Scale Trial
conducted at Field Station Pantnagar (Plot Size: 16 m .times. 5 m).
Varieties/Strain Characters Shivalik Himalaya Kosi Damroo C.D. (5%)
Plant height 95.5 122.1 122.7 104.2 4.13 (cm) Length of leaf 7.3
7.6 7.4 7.5 0.25 lamina (cm) Leaf width 4.5 4.2 3.3 4.6 0.32 (cm)
No. of leaves/ 147.3 156.4 165.5 161.2 7.61 3 aerial shoots Leaf:
Stem 0.75 0.94 1.31 0.90 0.065 ratio Days to 120-130 110-120 90-100
120-130 -- maturity Oil content (%) 0.55 0.65 0.85 0.75 0.13
Herbage 39.50 60.19 66.17 70.92 6.72 yield/plot (kg) (6 m .times. 4
m) Herbage 164.6 250.8 275.7 295.5 3.10 yield/ha (g) Oil yield/ha
90.5 163.0 234.3 221.6 4.12 (kg) Menthol 70-75 75-78 78-80 75-78 --
content (%) Seed 1.0-2.0 0.7-1.2 1.0-1.5 1.0-3.0 -- yield/plant
(g)
TABLE 2 Comparative seed yield performances of `Damroo,` and other
16 genotypes (13 selections + three controls) during 1998-99 at
Pantnagar Plant height Seed yield/ha Genetic Stocks DP DH (cm) (kg)
Sel. Feb., 7 June, 10 102.0 94.7 4-6-125 (Damroo) Sel. Feb., 7
June, 10 104.3 37.5 8-12-125 Sel. Feb., 7 June, 10 102.8 48.3
4-3-125 Sel. Feb., 7 June, 10 96.5 71.0 1-3-325 Sel. Feb., 7 June,
10 103.6 40.0 11-7-125 Sel. Feb., 7 June, 10 94.3 72.2 4-4-125 Sel.
Feb., 7 June, 10 110.5 29.1 8-4-125 Sel. Feb., 7 June, 10 95.8 60.5
1-1-123 Sel. Feb., 7 June, 10 103.5 71.5 7-4-125 Sel. Feb., 7 June,
10 102.6 30.4 11-5-125 Sel. Feb., 7 June, 10 115.4 63.5 10-125 Sel.
Feb., 7 June, 10 112.08 37.5 7-7-125 Sel. Feb., 7 June, 10 92.1
60.8 8-9-125 Sel. Feb., 7 June, 10 96.3 63.8 13-2-125 Shivalik
Feb., 7 June, 10 90.4 30.6 Himalaya Feb., 7 June, 10 116.6 18.4
Kosi Feb., 7 June, 10 118.3 29.5 C.D. (5%) -- -- 3.44 2.79
`Damroo` was vegetatively multiplied on a large scale during
1997-1998, to assess its productivity in PYT and PST. The PYT
results clearly showed that the per hectare oil yield in `Damroo,`
besides being almost at par with that of `Kosi` (U.S. Ser. No.
09/145,546) (221.6 kg against 234.3 kg of `Kosi`), was much high
over that of `Himalaya` (U.S. Plant Pat. No. 10,935) (163.0 kg) and
`Shivalik` (unpatented) (90.5 kg). The PST results of assessment of
`Damroo` against the mentioned three standard varieties as well as
the rest 13 seed producing selections for seed productivity are
shown in Table 2. Per hectare seed yield in `Damroo` was 94.7 kg as
against 18.4 kg to 72.2 kg in the others. In order to have an
understanding the potentiality of `Damroo`, as compared to the
other varieties at both the crop levels: Main crop when grown
during February-June and transplanted crops based on mature plants
and seedlings and grown during April-July, we conducted another
PST. It was evident that `Damroo`, besides registering per hectare
oil yield, comparable with that of `Kosi` (U.S. Ser. No.
09/145,546) in main cropping season (206.7 kg against 220.5 kg of
`Kosi`), retains its oil yield potential, even when grown as
seedling-based transplanted crop. It came out as the best variety
for exhibiting the maximum oil yield (200.1 kg against 70.5 kg to
150.3 kg of the others) in transplanted cropping season (Table
3).
TABLE 3 Comparative performances of menthol mint strain `Damroo`
and three exist standard cultivars in Pilot Scale Trial conducted
at Field Station Pantnagar (Plot Size: 16 m .times. 5 m). Oil
production ration of transplanted Plant Herbage Oil Oil crop and
main Varieties/ height yield/ha content yield/ha crop Strain (cm)
(q) (%) (kg) (TC:MC) Shivalik: MC 94.3 164.00 0.55 90.2 0.78 (Feb.)
: TC (April) 92.5 156.67 0.45 70.5 Himalaya: MC 121.5 250.67 0.60
150.4 0.67 (Feb.) : TC (April) 120.7 201.2 0.50 100.6 (Mature
plant) Kosi: MC 122.1 275.62 0.80 220.5 0.68 (Feb.) : TC (April)
120.5 231.23 0.65 150.3 (Mature plant) Damroo: MC 102.5 295.28 0.70
206.7 0.97 (Feb.) (TC raised by : TC (April) 102.3 333.50 0.60
200.1 seedlings (Seedling) 0.39 : TC (April) 101.6 160.60 0.50 80.3
(Mature plant) C.D. (5%) for 4.24 3.12 0.12 4.10 MC C.D. (5%) for
4.18 3.08 0.11 5.21 TC MC (Feb.): Main crop planted in February. TC
(April): Transplanted crop raised by mature plants (Mature plant)
in the month of April. TC (April): Transplanted crop raised by
seedlings in the (seedling) month of April.
Essential oil samples, prepared from `Damroo,` and the mentioned
three control genotypes were examined by gas liquid chromatography
(GLC). The oil content in `Damroo` is higher (78 to 80%) in
comparison to that in `Shivalik` (unpatented) (70-75%) and
`Himalaya` (U.S. Plant Pat. No. 10,935) (75-78%) but is equal to
that in `Kosi` (U.S. Ser. No. 09/145,546) (78-80%).
Studies on disease resistance were conducted and the reactions of
the new variety `Damroo` as well as three control varieties:
`Shivalik` (unpatented), `Himalaya` (U.S. Plant Pat. No. 10,935)
and `Kosi` (U.S. Ser. No. 09/145,546), to leaf spot, rust, powdery
mildew, wilt, and root rot diseases under field conditions were
scored during 1998-1999 (Planting date: 20th January) in CIMAP
field Station Pantnagar. Leaf spot and rust scored on modified 9
point disease scale, where 1=0%, 2=1 to 5%, 3=6 to 10%, 4=11 to
20%, 5=21 to 30%, 6=31 to 40%, 7=41 to 60%, 8=61 to 80%, 9=81 to
100% foliage destroyed. Any variety was considered resistant, when
it showed resistance on 1 to 3 in the scale. Powdery mildew scored
a 1 to 5 on the scale and the variety scoring 0 to 1 was considered
resistant. As to scoring in respect to wilt and root rot disease,
reactions were found out on the basis of percent infected plants.
Table 4 shows the results convincingly indicating relative
resistance of the new variety `Damroo` and the control `Kosi` (U.S.
Ser. No. 09/145,546).
TABLE 4 Comparative reaction of `Damroo` and other three cultivars
to, wilt and root rot disease, leaf spot rust, and powdery mildew
disease. Per cent wilted Disease score (days after sowing) Name of
the plants after Leaf spot Rust Powdery mildew variety/genotype 80
days 40 60 80 40 60 80 40 60 80 Shivalik 10 1.7 4.2 5.8 2.0 4.1 5.9
00 0.1 0.7 Himalaya 02 1.0 1.2 1.8 1.0 1.0 1.0 00 0.4 0.7 Kosi Nil
1.0 1.4 1.7 1.0 1.0 1.0 00 00 0.3 Damroo Nil 1.0 1.0 1.2 1.0 1.0
1.0 00 00 0.3 C.D. (5%) -- 0.16 0.60 0.72 0.22 0.30 0.31 00 0.10
0.34
`Damroo` was further examined for its detailed
cyto-chemo-taxonomical specificities. The corresponding results are
as given below: 1. Genus: Mentha. 2. Sub-genus: Menthastnim. 3.
Species: arvensis L. 4. Family: Lamiaceae. 5. Common name: Japanese
mint/corn mint/menthol mint. 6. Plant: Height.--104.2.+-.1.3 cm.
Width.--47.+-.20 cm. 7. Growth habit: Erect, vigorous with
Pyramidal habit. 8. Stem: Round to quadrangular hard, woody,
pubescent, yellowish green (144C), 7-9 mm thick at the internode.
9. Number of internodes: 28 to 35. 10. Length of internodes: 3.0 to
3.5 cm. 11. Leaf colour: Dark green (137 A) on upper surface. Dark
green (137 A) to Green (137 C) on lower surface.
Texture.--Moderately thick and rigid. Surface.--Slightly raised
inbetween the veins, moderately hairy with glandular trichomes --
on both sides-- the ventral surface containing more trichomes.
Shape.--Ovate at the beginning (until about 45 days after planting)
and elliptic thereafter, compared to sustained elliptic growth in
`Himalaya,` `Shivalik,` and `Kosi`. Margin.--Shallow serration
(38-64 number). Tip.--Acute. Base.--Attenuate. Size.--Moderately
broad and long. Petiole length.--1.0-1.5 cm. Area.--14.0 cm.sup.2.
Length.--7.5 cm. Width.--4.6 cm, compared to 3.3 to 4.5 cm in
`Himalaya,` `Shivalik,` and `Kosi`. 12. Leaf: Stem ratio (w/w):
0.90. 13. Inflorescence: Verticillate (cymes). Each cyme comprises
26-28 as against 15 to 30 in `Shivalik,` `Himalaya,` and `Kosi`;
cymes occur in the leaf axils and form a whorl of florets around
the stem. 14. Flowers (florets): Very small in size, perfect,
hermaphrodite, nearly actinomorphic, and hypogynous. Pedicel.--1.5
to 2.5 mm in length, yellow green (154 C). Calyx.--Four sepals,
persistent 2 to 3 mm in length, narrowly deltoid and acuminate,
yellow green (145 B). Corolla.--White to Whitish-purple (76 D), 4.0
to 5.5 mm in length, composed of 4 petals, differentiated into tube
and limb (tube due to fusion of the petals at their base).
Anthers.--Four, ocidimetary, white, remain inside the corolla tube.
Stigma.--Bifid, bicarpellary syncarpous; ovary superior, deeply
fourlobed, bilocular, placentation exile, style gynobasic arising
between the lobes of the ovary. Fruit and seed.--The fruit is of
four one-seeded nutlets enclosed by the persistent calyx, the seed
with a scanty endosperm and striate embryo. The seeds are brown,
minute in size. 15. Underground: Profuse in number, faint purplish
red (69 A) at the sucker apical Part. 16. Oil content in the fresh
herb (%): 0.75 against 0.55, 0.65 and 0.85 of `Shivalik,`
`Himalaya,` and `Kosi,` respectively. 17. Oil quality: Menthol
content.--78 to 80%. Isomenthone content.--12 to 17%. Congealing
point.--2 to 21.degree. C.
The new variety `Damroo` is a herbaceous perennial with upright
aerial shoots coming out of the underground suckers (rhizomes)
growing laterally. The shoots grow erect, having branching with a
special arrangement of branches giving a pyramidal look. The
flowers are arranged in whorls and the inflorescence grows from the
nodes at the leaf axil (FIG. 1). The chromosome number is 2n=12x=96
(octopliod). (The colour codes referred here are in accordance with
The "R.H.S. colour chart" published by The Royal Horticultural
Society, 80 Vincent Square, London SWIP 2PE, 1995).
Stability
`Damroo,` besides producing profuse homogenous seeds to facilitate
the cultivation of mint as a transplanted crop, gives a high oil
yield over all standard varieties in both a transplanted crop
(April-July), as well as a main crop (February-June).
The plant has been cultivated and assessed for five years
(1994-1999) and is found to be stable in producing homogenous
seeds. Further, the plant has been tested continuously for two
years and found that its essential oil yield is also consistent in
two consecutive years (1997-1999) in various yield trails.
Statement of distinction
As evident from the morpho-physiology, new variety `Damroo` is
distinct from its mother variety as well as other existing
varieties by having a new combination of plant traits. The
pyramidal vigorous plant habit with dark green leaves, high yield,
high oil yield, coupled with high methol content and capability in
retaining homogeneity in population for plant traits, despite
out-crossing within population in `Damroo,` lead it to be a novel
population-variety. High seed yielding ability is the major
physiological "marker" for identifying `Damroo,` from all the
existing menthol mint varieties. The novelty of the invention is
that `Damroo`, besides distinguishing it from the other varieties
like `Himalaya` (U.S. Plant Pat. No. 10,935) and `Shivalik`
(unpatented) in main cropping season by having oil productivity,
distinctly out-classes all the standard varieties by possessing
high oil productivity in transplanted mint cropping season. High
seed productivity in `Damroo` in particular, leads it to be the
best variety for its meaningful uses as a potent seed source for
raising much productive transplanted mint crop. To evolve a
genotype having potentiality in giving profuse homogenous seeds
even under cross pollination within its own plant population is a
new finding in the world, where till date it is known that cross
pollinated genotype gives only heterogeneous seeds.
`Damroo` gives about 94.7 kd seeds/hectare against only 30.5 kg of
the familiar variety `Shivalik` (unpatented). `Damroo,` when grown
as transplanted mint through its homogenous seed, gives about 200
kg essential oil/hectare against about 70.5 kg of oil/hectare in
the widely cultivated variety `Shivalik` (unpatented).
In short, the present invention provides a novel Mentha arvensis
mint population variety `Damroo` characterized for its sustained
high potentiality of reproducing viable seeds and phenotypically
homogenous seed-derived plant population under out-crossing, and
facilitating for economically viable transplanted menthol mint
cropping to avoid the cultivation of menthol mint in place of
staple cereal wheat.
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