Breeding and varietal improvement in Thailand

In Thailand cassava breeding is the responsibility of the Rayong Field Crops Research Center of the Department of Agriculture (DOA), and of Kasetsart University (KU). From 1975 to 1992, six cultivars have been released for industrial use, i.e. Rayong 1, Rayong 3, Rayong 60, Rayong 90, Sri Racha 1 and Kasetsart 50. All these recommended cultivars are widely adopted by farmers, but the area planted with improved cultivars was increasing only slowly due to the low multiplication rate of cassava. Therefore, in 1992 the Government approved the allocation of 1 1 million US dollars for the DOA and the Department of Agricultural Extension (DOAE) to rapidly multiply stakes of those cultivars and distribute those to the farmers, in order to replace about 240,000 ha of Rayong 1 with new high-yielding cultivars by the year 1996. According to the most recent survey by DOAE, this target has been well accomplished before the end of the project period. During the past three years, the cassava breeding program in Thailand continued to emphasize selection for high yield and high dry matter content, as well as some other desirable traits, especially high total plant weight and harvest index, and good plant type, germination and survival under stressful conditions. One of our successes has been the release of another industrial cultivar, Rayong 5, in October 1994. Rayong 5 is superior to Rayong 1 in many aspects. It has been well adopted and is spreading rapidly in many parts of the country. For Thai cassava breeders it seems to be increasingly more difficult to produce new clones that can surpass the exellent cultivars KU 50 and Rayong 5; however, some of our new clones, such as CMR33-57-81 and CMR33-53-181 appear quite promising, and CMR33-57-81 may be released as Rayong 7 in the next 2-3 years.