Genetic Histological Biochemical and Molecular Basis of Thermosensitive Genetic Male Sterility TGMS and Exploitation of Heterosis in Cotton Gossypium arboreum L

Abstract

Cotton (Gossypium sp.) is a major crop of global importance and has high newlinecommercial value. The present investigation in TGMS lines confirmed that minimum of 180C newlineweekly mean minimum temperature is enough to maintain high fertility levels under field newlinecondition. Under controlled conditions (8 hrs of 180C) for 7 days was required to induce 100 newlineper cent fertility levels to ensure 100 per cent selfed seeds in G. arboreum TGMS lines. newlineGenetics of TGMS was studied in Ga TGMS-3 line × ARBHA-35 F2 population, with newline145 fertile and 40 sterile plants. Chi square test revealed that the thermo sensitive genetic newlinemale sterility in the Ga TGMS-3 line was conditioned by single recessive gene. Three ESTSSR newlinemarkers were identified viz., NAU2176, BNL1227 and BNL1227b which can be used as newlinetightly linked markers to the TGMS trait as evident from their differential expression in fertile newlineand sterile anthers by q-PCR. newlineIn TGMS anthers abnormal development and vacoulation of microspores associated newlinewith early disintegration of tapetum. The sterile pollen grains had thicker intine as compared newlinewith fertile anther. Higher callase enzyme activity was noticed during late tetrad stage of fertile newlineflower anther, whereas in the TGMS lines had poor callase enzyme activity, which indicated newlinethat in sterile anthers the release of microspores was affected when compared to fertile newlineanthers. newlineAs far as heterosis for seed cotton yield (kg/ha) is concerned, two crosses newlineGa TGMS-7 line × A-2 (2800 kg/ha) and Ga TGMS-7 line × QT-14 (2723.62 kg/ha) had newlinesignificantly higher positive heterosis over the mid-parent, better parent, varietal check DLSa- newline17 and hybrid check G. Cot MDH-11.