Chapter 4 Male Sterility Male sterility,that is,the incapacity of a plant or plants to produce or to release functional pollen may be true sterility,functional male sterility or sterility induced by a chemical gametocide 1)True male sterility:This type of male sterility is either due to unisexual flowers,that is,absence of male sex organs in female flowers,as in dioecious species and monoecious species,or due to pollen sterility because of irregularities in the development of microspores,causing abortion of the pollen grain in bisexual flowers(hermaphrodite species) 2)Functional male sterility:This type of male sterility results from a defect in the dehiscence mechanism of the anther duo to which pollen are not released and thus fail to fertilize,even though they are fertile. 3)Induced male sterility:This type of male sterility results when certain chemicals (gametocides)are used at a particular stage of crop growth in appropriate doses which interfere with the development of male gametophyte leading to aborted anthers. 1.True Male Sterility 1)Dioecious Species In dioecious species(for example asparagus,hemp,spinach,papaya,date palms)male and female flowers or inflorescences are borne on different plants.Sex determination is under the control of one major gene pair,mm female and Mm male. In all such cases,in which specific sex chromosomes have been identified,the female and male plants are designated as xx(female)and xy(male) 2)Monoecious Species In monoecious species,for example corn,male and female flowers or inflorescences are borne on the same plant but at different places.In some crops,for example cucurbits,the male and female flowers develop successively. 3)Pollen Sterility (Pollen Abortion) Pollen sterility,that is,the failure of the stamens to produce viable pollen may be due to chromosomal factors,extrachromosomal hereditary particles(cytoplasm),or could be due to both the cytoplasmic and chromosomal factors(genetic factors). Non-functional or abortive pollens may be formed in varying degree.Three are generally recognized 010 Chapter 4 Male Sterility Male sterility, that is, the incapacity of a plant or plants to produce or to release functional pollen may be true sterility,functional male sterility or sterility induced by a chemical gametocide. 1) True male sterility: This type of male sterility is either due to unisexual flowers, that is, absence of male sex organs in female flowers, as in dioecious species and monoecious species, or due to pollen sterility because of irregularities in the development of microspores, causing abortion of the pollen grain in bisexual flowers(hermaphrodite species) 2) Functional male sterility: This type of male sterility results from a defect in the dehiscence mechanism of the anther duo to which pollen are not released and thus fail to fertilize, even though they are fertile. 3) Induced male sterility: This type of male sterility results when certain chemicals (gametocides)are used at a particular stage of crop growth in appropriate doses which interfere with the development of male gametophyte leading to aborted anthers. 1. True Male Sterility 1) Dioecious Species In dioecious species( for example asparagus, hemp, spinach, papaya, date palms)male and female flowers or inflorescences are borne on different plants. Sex determination is under the control of one major gene pair, mm female and Mm male. In all such cases, in which specific sex chromosomes have been identified, the female and male plants are designated as xx(female) and xy(male). 2) Monoecious Species In monoecious species, for example corn, male and female flowers or inflorescences are borne on the same plant but at different places. In some crops, for example cucurbits, the male and female flowers develop successively. 3) Pollen Sterility (Pollen Abortion) Pollen sterility,that is, the failure of the stamens to produce viable pollen may be due to chromosomal factors, extrachromosomal hereditary particles(cytoplasm),or could be due to both the cytoplasmic and chromosomal factors(genetic factors). Non-functional or abortive pollens may be formed in varying degree. Three are generally recognized