Author : Do Khac Thinh; Hung Phi Oanh; Nguyen Thi Cuc; Nguyen Ngoc Quynh

Summary : From past years, rice varieties which have been cultivated in South Vietnam originated from domestic hybridization or introduction from IRRI, the rice induced mutation breeding has been initiated. With 60 Co gamma - rays, dose 20 Krad, dose rate of 280 Krad/h, dry and germinated seeds of introduced rice varieties: IR 64, IR9729, IR50404, IR 59606, IR 59656 were irradiated in 1993. The irradiated seeds were immediately sown within 24 and 94 hours for wet seeds and dry seeds after treated radiation respectively. Population of 10,000 - 15,000 plants were established and evaluated by IRRI's evaluation standard from M2 - M7 generations. Promising lines and varieties have been identified and evaluated through observational nurseries and yield trials. The best lines and varieties were tested and demonstrated in different agro-ecological areas of South Vietnam. During 1997-1999m two mutant varieties had been approved as national varieties by IAS and Ministry of Agriculture and Rural Development of Vietnam (MARD).