Cultivar improvement for rainfed lowland rice in Thailand

The rainfed lowland rice ecosystem occupies approximately 75% of the total rice area in Thailand. Attempts to improve rice cultivars in the country started in 1910 during the reign of King Rama V, who established the first rice experimental station in 1916. The breeding objective in the early years was grain quality improvement and increasing the yield potential of local cultivars. Through evaluation and selection among collected local variations, a batch of traditional improved cuitivars was first recommended in 1935. Currently, the yield constraints for rainfed lowland rice include frequent drought and flood in all regions, the inland saline and sandy soils in the northeast, acid sulfate soils in the Central Plain and coastal acid-saline soils in the south. Rice diseases such as blast and bacterial blight, and insect pests like gallmidge and stem borers, are also major problems. The current breeding objectives are to develop cultivars that are tolerant to adverse environmental conditions and resistant to disease and insects, while maintaining the superior grain characteristics of the traditional cultivars and their appropriate maturity characteristics. Breeding mainly involves hybridisation and selection. Biotechnology is used in an attempt to improve breeding techniques. Past breeding efforts have led to the development of a number of improved cultivars and today 25 cultivars are recommended for farmers in rainfed lowland regions.