KHẢ NĂNG CHỊU HẠN CỦA CÁC GIỐNG LÚA NGẮN NGÀY, NĂNG SUẤT CAO CHO VÙNG ĐẤT CẠN VÀ VÙNG ĐẤTKHÓ KHĂN VỀ NƯỚC

Evaluating drought tolerance by the characteristic morphology method is simple, easy to implement with low cost and high efficiency and at the same time, it is the scientific basis for selecting and developing new drought-resistant rice varieties produce for adversed areas of dry and water-defecit lands which are totally dependant on the rainfall (rainfed cultivation). The tolerance limit of 10 rice lines/varieties were evaluated, and they were grouped according to the type of land cultivated. Group I consists of drought-tolerant rice varieties and sowing in water-defecit areas. Group II consists of upland rice varieties and sown by direct seedling method in upland areas which are completely dependant on rainfall. In artificial conditions, the evaluation of drought tolerance of rice is determined by the seed germination rate, percentage of black sprout root in KClO3 3% solution or 1% saccharin solution. The higher rate of seed germination and the lower rate of black sprout roots are, the higher drought tolerance ability it has and vice versa. In Group I, the germination rate was higher than 45% in 1% saccharin solution or proportion of black sprout roots of about 18 to 25% in KClO3 3%. The germination rate of Group II was higher than 58% in 1% saccharin or proportion of black sprout roots of about 11-13% in KClO3 3% solution In field conditions, the evaluation of drought tolerance of rice varieties were identified by morphological features such as the rolling of the leaves, the ability to recover after drought, the canopy, humidity of wilting plants, booting ability, the productivity of the seeds/ear and yield. Varieties CH16, LCH37 have been identified as pretty drought tolerant, high yield and wide adaptation in arid and water defecit areas. CH10 and CH12 rice varieties are of good drought tolerance, rather good yield (4.43-4.57 tons/ha) and high adaptability for completely rainfed-arid soils.