Abstract

                                Thermosensitive genic male sterility (TGMS) is a type of genetic male sterility expression regulated by certain temperature conditions. The knowledge of the critical sterility temperature and the critical thermosensitive stage for fertility alteration of TGMS lines is useful to determine most suitable time of their planting for multiplication or hybrid seed production. The experiment was conducted in mini phytotron. The critical sterility temperature of three TGMS lines viz. TGMS 6, TGMS 16 and TGMS 29 was assessed by subjecting them to different temperatures during reproductive stage. The pollen sterility percentage increased as the daily mean temperature increased and the genotypes behaved differently before they attain complete pollen sterility. The results that the CST of TGMS 6 was 28.0°C, TGMS 16 was 27.0°C and TGMS 29 was 27.5°C with 34.0, 33.0°C and 34.0°C the maximum temperatures respectively. Three TGMS lines were exposed to CST for different durations coinciding the various stages of panicle development to understand the critical stage of thermosensitivity for fertility alteration. In this study, 10-25 DBH was identified as critical thermosensitive stage for fertility alteration, which corresponds to differentiation of secondary branch primordiam, differentiation of pistil and stamen, formation of PMC and early meiosis stages (Stage 111 to IV).

Key words : Rice, TGMS lines, CST, Critical stage of Thermosensitivity.