**10.2 Seed multiplication of TGMS Lines**

Seed production potential in the TGMS lines were studied at Tamil Nadu. During fertility reversion phase can be enhanced by growing them under medium hill regions of Gudalur (1500 m MSL) in Nilgiris district, vTamil Nadu [83]. At Gudalur, the temperature range during the month of July and August was less than 20°C. The appropriate sowing date of TGMS lines was fixed during June–July in such a way that the critical stages of panicle development would be exposed to the required temperature. The individual lines were maintained under isolation and genetically pure seeds were produced at Gudalur. The TGMS line TNAU 60S was evaluated at different locations for their stability in sterility and it was proved that under high temperature (Coimbatore) it expressed 100% sterility and at low temperature it produced more than 90% seed set at Gudalur [74]. This line with wider pollen sterility period under plains can be very well exploited for developing two line rice hybrids during the period of December to April. The same lines can be easily seed multiplied at Gudalur during July to November.

Alternate to hilly areas fertility reversion was studied at plains also in the cooler months by [84]. They evaluated 255 TGMS derivatives generated at IARI-RBGRC, Aduthurai, for fertility phase changes during kharif season. The lines were grown during Apr – Aug at Aduthurai (elevation 19.5 m) conditions when ambient temperature was above 27°c (Season 1). Fully sterile plants identified were stubble planted during Aug – Dec at Gudalur (elevation 416 m) for testing the reversion phase (Season 2). Concurrently, a subset of 43 random fully sterile stubbles were retained at Aduthurai during the same period (Aug-Dec) and their fertility behavior was also observed. There was 69% of the lines showing SF of >45%, since 45% seed set or more is desirable for commercial seed production. In Season 2, the lines stubble planted at Aduthurai also showed fertility reversion between 12 and 65% with 35.6% of the population showing >45% seed set. Temperature of Gudalur ranged between 19 and 33°c during flowering (Nov), while at Aduthurai, it was between 21 and 34°c in the same season. Results indicate that minimum temperature is more crucial than the maximum temperature in fertility reversion behavior.
