Thermosensitive genic male sterile (TGMS) lines are suitable for developing two-line hybrids in the tropics because temperature variations are found in different seasons and/or locations for maintaining effective sterility and fertility. Research efforts by IRRI and national agricultural research systems (NARS) have resulted in identifying many TGMS lines from four to five sources that can be deployed for developing two-line hybrids. Production of good-quality pure seed of TGMS lines is a prerequisite for successful use of these lines.
Experience in China has indicated that TGMS lines multiplied conventionally by bulking their seeds at a fertility-inducing temperature may tend to segregate for their critical sterility /fertility points. Seed obtained from such lines may not be pure. These lines, when used to produce two-line hybrid seeds, could be a mixture of selfed and hybrid seeds, resulting in unstable hybrids. Nucleus and breeder seed production strategies should, therefore, aim to meet the dual objectives of maintaining complete male sterility during hybrid seed production and higher seed set during TGMS multiplication. We describe here a simple method of producing nucleus and breeder seed of TGMS lines under field conditions.