GP 605 Environment sensitive genetic male sterility Speaker Nimit Kumar. 1

 Male sterility:- Male sterility is defined as the deviant condition in normally bisexual plants (monoecious as well as hermaphrodite) when no viable pollen is formed Kaul (1988) classified male sterility in three major groups Genetic male sterility Morphological male sterility:- Environmental genetic male sterility (EGMS)  TGMS- Thermo sensitive genetic male sterility  PGMS- Photoperiod sensitive genetic male sterility 2

 Genetic 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) 3

 Phenotypic male sterility Structural male sterility: Abnormalities in male sex organs occur Tomato (positional sterility (Atanassova 1999) etc. Sporogenous male sterility: Stamens are normally formed, but pollen is absent Functional male sterility: Viable pollen form, but barrier prevents fertilization 4

 Genotypic male sterility Genetic male sterility: Mendelian inheritance due to nuclear gene (Tomato, Capsicum, cabbage, cauliflower, Watermelon, Lima bean, Lettuce, Muskmelon etc.) Cytoplasmic male sterility: Non-Mendelian inheritance – cytoplasmic (Tomato, Pepper, Cole vegetables, Onion, Carrot, Radish) Cytoplasmic- genetic male sterility: Both nuclear and cytoplasmic genes (Onion, Carrot, Sugarbeet, Capsicum, Radish etc. ) 5

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, sporophytic control Barriers other than incompatibility preventing pollen from reaching ovule 6 Mehdi and Anwar 2009

Environmental- genetic male sterility TGMS – Expression of male sterility is influenced by temperature PGMS – Expression of male sterility is influenced by photoperiod, i.e. relative day length 7

TGMS in rice ms genes are expressed above 23.3 o C temperature Hence plants will be male sterile Below 23.3 o C and above 29 o C, plants are fertile e.g., Line Pei-Ai645 Period of development sensitive to temperature lasts from – Formation of PMC’s to meiosis in rice 8

PGMS in rice ms genes are expressed under long day conditions (Day length= 13 hr and 45 min) provided: – Temperature lies within the critical range (23.3 to 29 o C) Period of development sensitive to photoperiod lasts from – Differentiation of secondary rachis branches to formation of PMC’s in rice 9

An ideal PGMS line A low critical temperature for fertility induction A high critical temperature for induction of sterility A wide temperature range for photoperiod sensitivity A strong interaction between photoperiod and temperature 10

EGMS in other crops VegetableMutantTemperatureReference CabbageTGMS, PGMS<10 0 CRundfeldt 1961 Brussels sproutsTGMS<10 0 CNieuwhof 1968 BroccoliTGMS, PGMS CRick 1948; Sawhney

EGMS is more popularly termed as “Two line Hybrid Breeding” 12

Criteria of EGMS for hybrid seed production Plants of male sterile line should exhibit 100% male sterility & uniformity on morphological basis The environmental conditions should be such that the male sterility period lasts for at least 30 consecutive days 13

 Expression of male sterility trait is associated with Morphological changes Histological changes Cytological changes Biochemical changes and Molecular changes 14

Variable (complete absence of male reproductive organs) Male sterile flowers are commonly smaller in size in comparison to the fertile The size of stamens is generally reduced 15

 Role of tapetum Premature breakdown of tapetum Abnormal development of tapetum in male sterile plant first report by (Monosmith 1926)  Role of callase Early or delayed callase activities have been found to be associated with male sterility  Role of esterase Decreased activity of esterase in male sterile plants has been observed in tomato (Bhadula and Sawhney 1987) & in radish (Zhou and Zhang 1994)  Role of PGR’s Reduced level of cytokinins and increased level of abscisic acid associated with GMS and CMS plants 16 Mehdi and Anwar 2009

In both GMS and CMS systems, male sterility is the consequence of breakdown of tightly regulated pollen development and fertilization processes at any of the pre- or post-meiotic stages i.e.  During the formation of tetrad  During the release of the tetrad  At the vacuolated microspore stage or at pollen dehiscence stage 17 Wu and Yang 2008

 Amino acids Reduced the level of proline, leucine, isoleucine, phenylalanine and valine Increased the level of asparagine, glycine, arginine, aspartic acids  Soluble proteins Male sterile anthers contain lower protein content and fewer polypeptide bands  Enzymes Mistiming of callase activity Decreased the activity of esterase and amylases 18

Reduces the cost of hybrid seed production Production of large scale of F 1 seeds Avoids enormous manual work of emasculation and pollination Speeds up the hybridization programmes 19

Thank you 20