Gametocides, also known as chemical hybridizing agents, induce male sterility in plants by disrupting pollen development. This document discusses the various chemicals used as gametocides in different crops, how they work to inhibit pollen development, optimal application times, and advantages of using gametocides for hybrid seed production over male-sterile cytoplasmic methods. Gametocides are applied at specific plant development stages to disrupt meiosis or exine formation, resulting in non-viable pollen. Their use allows for hybrid seed production without maintaining A, B, and R lines.

2.  The chemicals that induce the male sterility in
plants are called Gametocides.
 This terminology was introduced by Eaton, who
demonstrated the potential of producing Gossypium
hirsutum hybrids using FW-450.
 Also termed as Chemical Hybridizing Agents, Male
sterilants, Pollen suppressants, Pollenicides,
Androcides,etc.,

3.  Induction of male but not female sterility
 Complete inhibition of pollen development
 Independent from environmental conditions
 Independent from genotypic differences
 Wide flexibility of rate and time of application

4.  Absence of phyto-toxicity/ adverse effects
 Non mutagenic
 Environmental safety
 Minimum side effects
 Cost effectiveness

5.  Disruption of meiosis lending of arrest of anther
development and degeneration of pollen mother
cells or curly microspores.
 Disruption of exine formation resulting in thin
walled, irregular and non viable microspores.
 Decrese of starch deposition and appearance of
abnormal vacuoles in the micospores making
them non-viable.

6.  Persistence and abnormal growth of tapetal
layers.
 Indehiscence or delayed dehiscence of
normally developed anthers with viable pollen.
 Non-germination of pollen on stigma or
cessation of elongation of pollen tube resulting
in non-fertilization.

7.  Treatment at panicle initiation stage (pre
meiotic) affects normal development of anthers
and PMCs.
 Treatment at bolting stage (meiotic phase ) and
flowering stage (post-meiotic ) disturbs normal
development and functioning of microspores.

8. CHA Chemical formulation Crops
Arsenicals Zinc methyl arsenate,Sodium methyl
arsenate
Rice, ( 5 days before
heading ),Oilseed rape
Dalapon Sodium 2,2- dichloro propionate Cotton,Pearl millet, Wheat,
Linseed,Sesame,Onion,
Capsicum
DPX 3778 3-(p-chlorophenyl)-6-methoxy -3-
triazine-2,4(1H,3H) dione
Maize, Wheat &
Triticale(late tillering+late
boot stages)
Ethepon 2-chloroethyl phosphonic acid, Wheat, Barley , Rice, Oats,
Triticale, Cucumber
FW 450(Mendok) Sodium α,β-dichloro isobutyrate Capsium, Cotton, Pearl
millet, Sesame, Sunflower,
Tomato

9. CHA Chemical formulation Crops
OMT L-O-Methyl threonine Cotton
MH 1,2-dichloropyridazine-3,6-dione Maize,Wheat,Capsicum,Cotton,
Oats,Sorghum,Onion,Okra – Early
microsporogenesis
GA Gibberellic acid Maize, Barley,Wheat,Rice – 1 to 3
days prior to onset of meiosis.
Onion, Oats, Sunflower.,Okra,
6 BAP Benzyl amino purine Onion

10. Proper environmental conditions:
 No rain during CHA application
 Adequate sunshine and absence of strong winds
 Rice – ideal condition : 26-28˚C, 80% RH

11. Synchronisation:
 Flowering of male and female parents
 Achieved by varied sowing dates

12.  Application of CHA at precise stage
 GA3 spray to promote stigma exertion.
 Supplementary pollination to maximise seed set
 2 sprays of CHA @ lower concentration is better
than single application of same dose, as the former
induces more uniform male sterility
 Care not to spray the pollinator rows

13.  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
 Maintanence 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.

14.  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
 Affect human health

15.  Singhal.N.C., Hybrid Seed Production in Field
Crops Principles and Practices,second edition,
Kalyani publishers,New Delhi
 http://www.arccjournals.com/uploads/articles/ar262
004.pdf
 https://link.springer.com/chapter/10.1007/978-3-
642-83139-3_4