Identification and characterization of temperature sensitive genic male sterile sources in rice (Oryza Sativa L.)

Identification and isolation of the usable sources of temperature sensitive genic male sterility-fertility system for developing two-line hybrid technology in rice were the objectives of the study. Among the several male sterile plants isolated from stagger/late planted germplasm, breeding lines at different stages of development, and mutagen-treated populations, six strains namely, SM 3, SM 5, F61, JP 2, JP 8–1 A-12 and SA 2 (F 43), remained sterile at high temperatureand turned fertile at low temperature. The six lines were studied in growth chambers maintained at specific temperature ranges, decided on the basis of sensitive stage which was determined by a newly developed ‘tracking technique’ to identify the critical sterility point (CSP), i.e. the temperature at which a plant is completely male sterile, and the critical fertility point (CFP), i.e. the temperature at which the plant turns completely male fertile. The lines were categorized into high CSP-low CFP, high CSP-high CFP, and low CSP-low CFP types. Among them, JP- 8-1-A-12, F-61 and SA 2 (F 43) belonging to the low CSP-low CFP group were found to be the most promising sources of stable sterility. Transfer of temperature sensitivity from them to other productive agronomic backgrounds and identification of appropriate locations for optimization of seed production would make the two-line approach a commercial reality.