Hybrid Rice in Thailand

Abstract

Hybrid rice research in Thailand ws intiated in 1980. The initial objective was to test the possibility of using the three component lines and popular hybrids from the people's Republic of china (PROC) and the International Rice Research Institute (IRRI), under Thai conditions. It was also aimed to develope lines and combinations for hybrid seed production in Thailand.
Most male-sterile lines and their maintainers from PROC and IRRI had a maturity time of about 100 days and were 80 - 100 cm in height. The restoreres (IR var.) were 10 - 20 days longer maturing than the male-sterile lines. All lines from PROC and IRRI had short and chalky grain. The performance of popular hybrids from both sources was inferior to varieties already recommended in Thailand. Their yield was no better and, in some instances inferior to varieties already recommended in Thailand. Yield and maturity time of the hybrids were about the same as for RD 25; they were lower yielding and shorter maturing than either RD 21 or RD 23. Grain characteristics were also no better than for the Thai varieties.
Transfer of the 'WA' cyto-sterility system into Thai varieties was commenced in 1981. Subsequently in 1984 the lines RD21A -23 and RD21A-1 were identified as Thai male-sterile lines. An evaluation of the Thai hybrid RD21A - 23/Rd7 -4 in 1987 showed promise in both the wet and dry seasons; it matured in about 120 days and was about 130 cm in height. The grain of this hybrid was long, slender and clear. It will be further tested before being considered for release to farmers.