The genic male sterile rice (GMS) sensitive to temperature during the panicle development period is a novel type of germplasm in rice, which is sterile under high temperature condition but fertile in low temperature condition. A number of TGMS lines have been popularly used in commercial seed production of hybrid rice in China and India. To fix the duration of critical sterility temperature expression of TGMS lines for hybrid seed production, eight TGMS lines developed by Department of Rice, Tamil Nadu Agricultural University were sown in weekly intervals from December 16, 2015 to January 27, 2016. Heading date and pollen sterility were observed on each line during every planting interval. The data showed that the critical stage for most of the TGMS lines occurred during panicle development stages and approximately 26 to 5 days before heading. The pollen sterility recorded on the plants raised at weekly interval revealed that all lines had stable sterile phase with 100% pollen sterility for more than 40 consecutive days during high temperature conditions. TGMS lines TNAU45S, TNAU60S, TNAU95S, GDR 61S and GDR 70S were identified to have critical sterility point (CSP) at a mean temperature of above 29ËšC. The TGMS lines viz., TNAU45S, TNAU60S, TNAU 95S and GDR61S were performing stable even during mild changes in temperature and these lines are considered as stable lines and can be recommended for hybrid seed production. Evaluating TGMS lines using this new strategy was found to be more stable in terms of sterility expression and these lines can efficiently used for Two line hybrid production.

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