male sterility system and its exploitation in monocot and Dicot plant

1. PRESENTED BY-
S.V YAMGAR
Reg. NO. 2016/07
PhD-1 year GENETICS & PLANT
BREEDING
PRESENTED TO-
Dr. N. S. KUTE
ASSOCIATE PROFESSOR
GENETICS & PLANT BREEDING
MPKV, Rahuri.

2. Male Sterility
 Male sterility is characterized by nonfunctional pollen grains,
while female gametes function normally.
 Inability to produce or to release viable or functional pollen as
a result of failure of formation or development of functional
stamens, microspores or gametes.
 Main reason is mutation.
Sterile SterileFertile Fertile

3. Manifestations of Male Sterility
 Absence or malformation of male organs.
 Failure to develop normal microsporogenous tissue- anther
 Abnormal microsporogenesis (deformed or inviable pollen)
 Abnormal pollen maturation
 Non dehiscent anthers but viable pollen,

4. History of Male Sterility
 J.K. Koelreuter (1763) observed anther abortion within species
& species hybrids.
 Genic male sterility has been reported in cabbage (Rundfeldt
1960), cauliflower (Nieuwhof 1961)
 Male sterility systems have been also developed through genetic
engineering (Williams et al. 1997) and protoplast fusion
(Pelletier et al. 1995)
 Male sterility were artificially induced through mutagenesis
(Kaul 1988)

5. Why Male Sterility ???
 Reduced the cost of hybrid seed production.
 Production of large scale of F1 seeds.
 Avoids enormous manual work of emasculation
and pollination.
 Speed up the hybridization programme.
 Commercial exploitation of hybrid vigour.

6. Creation of Male Sterility
 Spontaneous mutations
 Interspecific hybridization
 Mutation induction (EtBr)
 Genetic Engineering
 Chemically induced male sterility (CHAs)

7. Detection of Male Sterility system
Whether a particular sterile genotype belongs to which MS
system can be detected by its progeny performance on crossing
with a few normal genotypes.
 Trend-I- All progenies in all the rows may be sterile- CMS
 Trend-II- Some rows may consist all fertile
Some rows sterile and fertile in 1:1 ratio- GMS
 Trend-III- sterile plant produces all fertile progeny when
crossed with restorer - CGMS

8. Classification of Male Sterility
Kaul (1988) Classified Male Sterility in three major groups
1. Phenotypic Male Sterility (Morphological)
 Structural or Staminal Male Sterility
 Pollen Male Sterility
 Functional Male Sterility
2. Genotypic Male Sterility
 Genetic Male Sterility (GMS)
 Environmental Sensitive (EGMS)
a) Thermo sensitive genetic male sterility (TGMS)
b) Photoperiod sensitive genetic male sterility (PGMS)
 Environmental non-sensitive
 Cytoplasmic Male Sterility (CMS)
 Cytoplasmic Genetic Male Sterility (CGMS)
 Transgenic Male Sterility (TMS)
3. Chemically Induced Male Sterility (CHA)

9.  Pollen sterility: in which male sterile individuals differ from
normal only in the absence or extreme scarcity of functional
pollen grains (the most common and the only one that has played
a major role in plant breeding).
 Structural or staminal male sterility: in which male flowers or
stamen are malformed and non functional or completely absent.
 Functional male sterility: in which perfectly good and viable
pollen is trapped in indehiscent anther and thus prevented from
functioning
Phenotypic Male Sterility

10. Cytoplasmic Male Sterility (CMS)
 Determined by the cytoplasm (mitochondrial or chloroplast genes).
 It was first reported by welch and Grimball in1947
 Result of mutation in mitochondrial genome (mtDNA)- Mitochondrial
disfunction.
 Progenies would always be male sterile since the cytoplasm comes
primarily from female gamete only.
 Nuclear genotype of male sterile line is almost identical to that of the
non -recurrent pollinator strain.
 Male fertile line (maintainer line or B line) is used to maintain the
male sterile line (A line).
 CMS is not influenced by environmental factors (temperature) so is
stable.

11.  CMS can used in hybrid seed production of certain ornamental
species or in species where a vegetative part is of economic value.
 But not for crop plants where seed is the economic part because the
hybrid progeny would be male sterile.
 This type of male sterility found in onion, fodder jowar, cabbage etc.
Utilization of CMS in Plant Breeding

12. Genetic Male Sterility (GMS)
 Also called as nuclear male sterility.
 Mostly governed by single recessive gene (ms) but dominant gene
governing male sterility (safflower).
 Origin: Spontaneous mutation or artificial mutations (Gamma rays,
EMS) are common.
 ‘ms’alleles may affect staminal initiation, stamen or anther sac
development, PMC formation, meiosis, pollen formation, maturation
and dehiscence.
S.No. Mutagens Crops
1 Colchicine Jowar
2 Ethidium Bromide Groundnut, Maize, wheat
3 Acetone Barley

13. Types of GMS
 Environment insensitive GMS: ms gene expression is much less affected
by the environment.
 Environment sensitive GMS: ms gene expression occurs within a
specified range of temperature and /or photoperiod regimes (Rice, Tomato,
Wheat etc.).
1. TGMS: sterility is at particular temperature e.g. In rice TGMS line
(Pei- Ai645) at 23.30C (China).
 TGMS at high temperature is due to failure of pairing of two
chromosomes at metaphase was evident.
 This abnormality led to abnormal meiosis, abnormal or sterile pollens.
 Anthers were shriveled and non-dehiscence-Male sterile.
 However, these lines produced normal fertile pollen at low temp.
Sensitive period : PMC formation to Meiosis

14. 2. PGMS: Governed by 2 recessive genes.
 Sterility is obtained in long day conditions while in short days,
normal fertile plant.
 Rice:- Sterile under Long day conditions (13 hr. 45 min + Temp. 23-
290 C) but fertile under short day conditions.
 Sensitive period: Differentiation of secondary rachis branches to
PMC formation

15. Cytoplasmic Genetic Male Sterility (CGMS)
 CGMS is also known as nucleoplasmic male sterility.
 It is first reported by Jones and Davis (1944) in onion
 Case of CMS, where a nuclear gene (R) for restoring fertility in
male sterile line is known.
 R (restorer gene) is generally dominant can be transferred from
related strains or species.
 This system is known in cotton, maize, jowar, bajra, sunflower,
cotton, rice and wheat etc.

16. Hybrid seed production using CGMS system

17. S.No. Crop Hybrid Variety Seed Production
1. Maize Ganga 101, Ganga 1,
Deccan, Ranjit,
Trishulatha, DHM-107,
DHM-109
CMS
2. Sorgum CSH1 CMS
3. Bajra HB1 CMS
4. Sunflower BSH1 CMS
5. Rapeseed PGSH51 CMS
6. Red Gram ICPH-8 GMS
7. Rice PRH1 CMS
Male Sterility based Hybrids in Important Crops

18.  Undesirable effects of the cytoplasm
 Unsatisfactory fertility restoration
 Unsatisfactory pollination
 Spontaneous reversion
 Modifying genes
 Contribution of cytoplasm by male gamete
 Environmental effects
 Non availability of a suitable restorer line
Limitations of Cytoplasmic-Genetic Male Sterility

19.  Transgenic male sterility in plant is induced by using recombinant
DNA techniques for disturbing any or number of developmental
steps required for the production of functional pollen within the
microspore or for the development of any somatic tissues
supporting the microspores.
 Transgenes for male sterility are dominant to fertility.
 Also to develop effective fertility restoration system for hybrid
seed production.
 Example: Barnase/Barstar system
Transgenic Male Sterility

20.  Barnase is extracellular RNase; barstar is inhibitor of barnase
(Bacillus amyloliquefaciens)
 Plants with TA29 promoter-Barnase construct are male sterile
 Those with TA29-Barstar are not affected by the transgene barnase.
 Barstar is dominant over the Barnase
 Fuse the barnase and barstar genes to TA29 promoter–TA29 is a plant
gene that has tapetum specific expression.
 Cross male sterile (barnase) with male fertile (barstar) to get hybrid
seed, which now has both barnase and barstar expressed in tapetum
and, hence, is fully fertile
Barnase/Barstar system

22. Hybrid seed production using Barnase/Barstar system

23.  CHA is a chemical that induces artificial, non-genetic male
sterility in plants so that they can be effectively used as female
parent in hybrid seed production.
 Also called as Male gametocides, male sterilants, selective male
sterilants, pollen suppressants, pollenocide, androcide etc.
 The first report was given by Moore and Naylor (1950), they
induced male sterility in Maize using maleic hydrazide (MH).
Chemical Induced Male Sterility

24. Properties of an Ideal CHA
 Must be highly male or female selective.
 Should be easily applicable and economic in use.
 Time of application should be flexible.
 Must not be mutagenic.
 Must not be carried over in F1 seeds.
 Must consistently produce >95% male sterility.
 Must cause minimum reduction in seed set.
 Should not affect out crossing.
 Should not be hazardous to the environment.

25. S.No. CHAs Critical stage Crop species
1. Zink Methyl Arsenate
Sodium Methyl Arsenate
5 days before heading Rice
2. Ethephon/ Ethrel Depends on crop Barley , oat, bajra,
rice
3. Mendok Depends on crop Cotton, sugarbeet
4. Gibberellic acid 1-3 days before meiosis Maize, Barley,
Wheat, Rice,
Sunflower
5. Maleic Hydrazide Early microsporogenesis Maize, wheat,
cotton, onion
Some important CHAs

26. Hybrid Seed Production based on CHAs
 Proper environmental conditions (Rain, Sunshine, temp, RH etc.)
 Synchronisation of flowering of Male & Female parents.
 Effective chemical emasculation and cross pollination
 CHA at precise stage and with recommended dose
 GA3 spray to promote stigma exertion.
 Supplementary pollination to maximise seed set
 Avoid CHA spray on pollinator row.
Conditions required:-

27. Advantages of CHAs
 Any line can be used as female parent.
 Choice of parents is flexible.
 Rapid method of developing male sterile line.
 No need of maintaining A,B&R lines.
 Hybrid seed production is based on only 2 line system.
 Maintenance of parental line is possible by self pollination.
 CHA based F2 hybrids are fully fertile as compared to few sterile
hybrids in case of CMS or GMS.

28. Limitations of CHAs
 Expression and duration of CHA is stage specific.
 Sensitive to environmental conditions.
 Incomplete male sterility produce selfed seeds.
 Many CHAs are toxic to plants and animals.
 Possess carryover residual effects in F1 seeds.
 Interfere with cell division.
 Affect human health.
 Genotype, dose application stage specific.

29. Exploitation
of Male
Sterility in
Monocots
and Dicots

30. Male sterility system in Rice hybrid seed production
 Male sterility: a condition in which the pollen grain is unviable or
cannot germinate and fertilize normally to set seeds.
 Male Sterility Systems (genetic and non-genetic):
Cytoplasmic genetic male sterility (CMS)
Male sterility is controlled by the interaction of a genetic factor
(S) present in the cytoplasm and nuclear gene (s).
Environment-sensitive genic male sterility (EGMS)
Male sterility system is controlled by nuclear gene expression,
which is influenced by environmental factors such as temperature
(TGMS), daylength (PGMS), or both (TPGMS).
Chemically induced male sterility
Male sterility is induced by some chemicals (gametocides)

32. Two Commercial MS Systems for Hybrid Rice

33. Procedure of utilization of TGMS/PGMS line
in Seed production

34. Advantage & Disadvantage of 2-line hybrid rice system
 Advantages
Simplified procedure of hybrid seed production
Multiple and diverse germplasm available as parents
Any line could be bred as female
97% (2-line) vs 5% (3-line) of germplasm as male
Increased chance of developing desirable & heterotic hybrids
Multiple cytoplasm courses as female parents
 Disadvantages
Environmental effect on sterility could cause seed purity
problem

35. List of TGMS lines in Rice
Genetic Control lines Origin Expression of MS
Controlled by single
recessive gene
Annong- 1s Spontaneous mutation Temperature of 27 ᵒC
Hennong S Hybridization Temperature < 29ᵒC
5460S Irradiation Temperature >30ᵒC
SM-38 Spontaneous mutation Temperature < 22ᵒC
SM-5 Spontaneous mutation Temperature < 22ᵒC
JP-2 Spontaneous mutation Temperature < 26ᵒC
JP-38S Spontaneous mutation Temperature > 30ᵒC
Source: Singh, B, D.(2012). Plant Breeding , Principles and Methods. Chapter 6,90.

36. List of PGMS lines in Rice
Genetic Control lines Origin Expression of
MS
Controlled by two
recessive genes
PGMS lines
Nongken 58S Spontaneous
mutation
Day length shorter
than 13.75hr
X88 Hybridization Day length shorter
than 13hr
MG 201 EMS Mutagenesis Day length 12hr
Source: Singh, B, D.(2012). Plant Breeding , Principles and Methods. Chapter 6,90.

37. Requirements for 3 Lines in CMS System
 A-line
Stable Sterility
Well developed floral traits for outcrossing
Easily, wide-spectum, & strongly to be restored
 B-line
Well developed floral traits with large pollen load
Good combining ability
 R-line
Strong restore ability
Good combining ability
Taller than A-line
Large pollen load, normal flowering traits and timing

38. Advantage & Disadvantage of 3-line hybrid rice system
 Advantages
 Stable male sterility.
 Disadvantages
 Limit germplasm source (CMS, Restorer)
 Dominant CMS cytoplasm in large area (WA)
 One more step for parental seed production
 Time consuming of CMS breeding

39. CHA’s in Hybrid seed Production in
Rice
• Male sterility is artificially induced by spraying
gametocides to cause stamen sterility without
harming the pistil.
• The chemical which makes sterile the stamen, plant
can be used as female parent for producing hybrid
seed.
• Two selected lines are planted in alternate strips and
one is utilized as female (chemically sterilized) and is
pollinated by the other line, for production of hybrid
seed.

40. Exploitation of Male Sterility by
CHA’s in Rice
 Application of chemicals at specific growth
stage of crop results in chemically induced
male sterility and chemical components used
are called as Chemical Hybridizing agents.
 Two arsenical CHA’s are used in Rice
MG1( based on zinc methyl arsenate)
MG2 (based on sodium methyl arsenate)

41. Male sterility system in Maize hybrid seed production
Different ways of inducing male sterility in maize
I. Manual/mechanical emasculation (detasselling)
II. Genic male sterility
III. Cytoplasmic genetic male sterility
IV. Gametocides
1. Genetic Male sterility
Male sterility determined by single recessive gene
40 loci involved have been identified (ms1 to ms52)
ms5 –cloned
Problem : impossible to maintain male sterile inbred
detasselling required

42. 2. Cytoplasmic Male sterility
1. CMS-T (Texas) (Rogers and Edwardson, 1952)
 Highly stable under all environmental conditions
 Characterized by failure of anther exertion and pollen abortion
 Susceptible to race T of the southern corn leaf blight - (Cochliobolus
heterostrophus = Bipolaris maydis)
 Widespread use of T-cytoplasm for hybrid corn production led to
epidemic in 1970 with the widespread rise of Race T.
 Toxin produced by C. heterostrophus = T-toxin.
 Fertility restoration is sporophytic
 Rf1 (chr. 3) & Rf2 (chr.9) are responsible for fertility restoration

43. 2. CMS-C (Charrua) (Beckett, 1971)
 Mutations in three genes viz atp6, atp 9 and cosII- confer CMS
phenotype
 Fertility restoration is Sporophytic
 Rf4, Rf5, Rf6 are responsible for fertility restoration
3. CMS-S (USDA) (Jones,1957)
 Sterility associated with orf355-orf77 chimeric mt gene
 Fertility restoration is Gametophytic
 Rf3 (chr. 2) are responsible for fertility restoration
 Plasmid like element S1 & S2
T-urf13 gene in T cytoplasm maize
 Mitochondrial gene T-urf13 is a unique chimeric sequence
Effect of URF13 protein-
 Degeneration of the tapetum during microsporogenesis
 Disruption of pollen development leading to male cell abortion

44. A X B
(frfr) (frfr)
ms mf
AB
(frfr)
ms
X C
(FrFr)
mf
ABC
(Frfr)
mf
Triple Cross Hybrid
C X D
(frfr) (FrFr)
ms mf
CD
(Frfr)
mf
A X B
(frfr) (frfr)
ms mf
AB
(frfr)
ms
X
ABCD
1
(Frfr)
mf
1
(frfr)
ms
:
:
:
Double Cross Hybrid

45. Types of Hybrids
 Single cross hybrid (A×B)
 Double cross hybrid (A×B)×(C×D)
 Three way cross Hybrid (A×B)×C
 Top cross (C×OPV)
Male sterility system in Bajra hybrid seed production

46. Exploitation of Male sterility in Bajra
• The discovery of cytoplasmic-genic male-sterility
often called cytoplasmic male-sterility and the
development of male-sterile line Tift 23A1 (Burton
1958, 1965) laid the foundation of the pearl millet
(Penniseturn americanum) hybrid seed industry in
India.
• The first commercial hybrid was HB 1.
• It was bred on Tift 23A1 at the Punjab Agricultural
University (PAU), Ludhiana, India, and it showed a
100% yield average over the open-pollinated check
varieties (Athwal 1966).

47. Source of Cytoplasmic Male sterility in
Bajra
Cytoplasm Source CMS line Remarks
A1(Tifton) Mutation Tift 23 A, Tift 23 D2 A Used for
commercial
cultivation
A2 (Ludhiana) Mutation L66A Incomplete
expression of
MS
A3 P. Violaceum L67A Extremely stable
for male sterility
,very promising
restores in bajra
A4 Half sib pool of
the early gene
pool
ICMA-90111 Developed at
ICRISAT

48. Hybrid seed production using CGMS
 Depends on the cytoplasm that produce male sterility and gene that
restores the fertility.
 Steps:
 Multiplication of CMS (A) line
 Multiplication of Maintainer (B) line and Restorer (R) line
 Production of Hybrid seed (A×R)
 Maintenace of A & B lines:
 Grow A line and its corresponding B line together in an isolated
plots.
 Isolation distance for A×B production fields is at least 1000m.
 A ratio of 1A:1B row is maintained.
 Pollens produced by the B line fertilize the male sterile plant (A)
and seeds produced thus
 Give rise to A line again.

49.  Maintenance of R line:
 Pearl millet R line could be either an inbred line or an Open
pollinated variety which can be multiplied as variety.
 Seeds of R lines are produced by multiplying seeds in isolated
plots having distance 1000m.
 Any plant in the R line plot appearing different from true R
type should be uprooted or rogued out before anthesis.
 Purity of the parental seed is very important because it affects
the quality of the hybrid seeds that is generated.

50. Scheme of hybrid seed
production in pearl millet
Layout of hybrid seed
production plot

51. Identification of potential hybrid parents (A,B and R lines)
 Potential male and female parents for hybrid seed production are
identified by crossing male fertile parent (Inbreds, variety,
germplasm, breeding stocks in advanced generations) to a male sterile
line (A line) and observing their corresponding hybrids in small plots
of an observation nursery.
 A few plants of each cross are subjected to the bagging test i.e.
covering the few panicles with the paper bags before anthesis and
observing the seed set under the bag after few weeks.

52. Male sterility system in Brassica hybrid seed production
Cytoplasmic male-sterile
 Stamen (anther and filament) and pollen grains are affected
 It is divided into:
a. Autoplasmic
 Arisen within a species as a result of spontaneous
mutational changes in the cytoplasm, most likely in the
mitochondrial genome
b. Alloplasmic
 Arisen from intergeneric, interpecific or occasionally
intraspecific crosses and where the male sterility can be
interpreted as being due to incompatibility or poor co-operation
between nuclear genome of one species and the organellar
genome.
 Another CMS can be a result of interspecific protoplast fusion

53. Genetic Male Sterility
 GMS is governed by two genes either recessive or dominant
genes(Kaul,1988)
 One more dominant gene is associated with development of male
sterility in B.napus type by means of transgenic male sterility
Chemical Male sterility
 Enthrel – Brassica juncea
 Zinc methy arsenate- B.napus
 GA- B.oleracea var capitata

54. Presently genetic male sterility (GMS), cytoplasmic male sterility
(CMS) and thermo sensitive genetic male sterility (TGMS) lines are
available in India.
Development of agronomically superior genetic male-sterile lines in
safflower in India have resulted in the development and release of
spiny safflower hybrids DSH-129 and MKH-11 in 1997 and NARI-
H-15 in 2005, the first non-spiny hybrid safflower NARI-NH-1 in
2001.
Male sterility system in Safflower hybrid seed production

55. Exploitation of Male sterility in
Sunflower
• MS system used is Cytoplasmic Genetic Male
sterility system.
• Here both cytoplasmic genes and nuclear
genes govern the Male sterility.
• Source of male sterility in sunflower is CMS-
PET1 cytoplasm.
• CMS-PET1 cytoplasm of sunflower arose
from an interspecific cross between Helianthus
petiolaris and H. annuus.

56. Utilization of CMS PET Cytoplasm in
seed production

57. Exploitation of Male sterility in
Pigeon Pea
• MS system used is GMS and CMS.

58. CMS cytoplasm in Pegion Pea
Cytoplasm Source
A1 Cajanus scarabaeoides
A2 Cajanus sericeus
A3 Cajanus volubilis
A4 Cajanus cajanifolius
A5 Cultivated Pegion pea

59. Exploitation of in CMS Pigeon Pea
a) A1 Cytoplasm:
Cajanus scarabaeoides x cultivated Pigeon pea
Hybrid
Draw back: male sterile plant derived from this
cross found to have female sterility.

60. b) A2 cytoplasm:
Cajanus sericeus x short duration advanced
breeding line
Hybrid
Draw back:
• F1 was partially male sterile
• Backcross population were found segregating
for male sterility.

61. A4 Cytoplasm is a boon for hybrid
breeding in Pegion Pea.
• Closely related to cultivated type.
• No morphological defects
• Produce plenty of pollen with restorer lines in
hybrid combination.
• Stable male sterile source
• Capable of producing high yielding hybrids.
Source: Saxena, K, B. et.al(2006).. Commercial pigeon pea hybrids are just a few
steps away. Indian Journal of Pulse Research. Vol 19:1, 7-16.

62. • In cotton, GMS has been reported in upland, Egyptian
and arboreum cottons.
• Gregg 399 is important source of genetic male sterility.
• In tetraploid cotton, male sterility is governed by both
recessive and dominant genes. However, male sterility
governed by recessive genes is used in practical plant
Breeding.
• Sixteen different genes in tetraploid cottons (13 in G.
hirsutum and 3 in G.barbadense) and two in G.
arboreum have been identified for genetic male
sterility.
Exploitation of in MS Cotton

63. • Sterility is conditioned by dominant alleles at five loci
viz, MS4, MS7, MS10, MS11 and MS12
• By recessive allele at other loci viz. msl, ms2, ms3,
msl3, msl4 (Dong A), msl5 (Lang A) and msl6 (81
A).
• Two male sterile phenotypes viz. m5ms6 and ms8ms9
are conditioned by duplicate recessive factors.
• The expression of male sterility varies greatly in
extent and stability among the loci.

64. • In diploid cotton, two genes have been identified for
GMS from Akola and HAU, Hisar.
• At Akola, the male sterility was obtained from
anomalum x arboreum crosses while at Hisar it was
identified as a spontaneous mutant in arboreum
variety DS 5.
• G. hirsutum line Gregg (MS 399) from USA is the
basic source of GMS possessing ms5ms6 gene for
male sterility.

65. • G. harknessii was the only available source of CMS until 1997.
• After concerted efforts, the cytoplasmic lines with G. aridum .
(D4) has been developed by the Cotton Research Unit, PDKV,
Akola.
• A new system of CMS has also been developed at the University
of Arkansas, USA wherein G. trilobum cytoplasm was utilized.
• The new system of cytoplasm called CMS 8 (D-8) has undergone
extensive testing to eliminate undesirable effects (eg. Low fibre
maturity) of the G. hirsutum nucleus interaction with the G.
trilobum cytoplasm.
• Another different source of CMS i.e CMS-C1 has been recently
developed by using G. sturtianum.
Exploitation of in CMS Cotton

66.  Male sterility a primary tool to avoid emasculation in hybridization.
 Hybrid production requires a female plant in which no viable
pollens are borne. Inefficient emasculation may produce some self
fertile progenies.
 GMS is being exploited (Eg.USA-Castor, India-Arhar).
 CMS/ CGMS are routinely used in Hybrid seed production in corn,
sorghum, sunflower and sugarbeet, ornamental plants.
 Saves lot of time, money and labour.
Significance of male Sterility in Plant Breeding

67.  Existence and maintenance of A, B & R Lines is laborious and
difficult.
 If exotic lines are not suitable to our conditions, the native/adaptive
lines have to be converted into MS lines.
 Adequate cross pollination should be there between A and R lines for
good seed set.
 Synchronization of flowering should be there between A & R lines.
 Fertility restoration should be complete otherwise the F1 seed will be
sterile Isolation is needed for maintenance of parental lines and for
producing hybrid seed.
Limitations in using Male Sterile line

68. Thank You