Author : Sawatdee Liangsuthisakon

Summary : The study was conducted to determine the effect of Xanthomonas oryzae (Uyeda et Ishiyama) Dowson on grain yield of three non-seasonal rice varieties, IR-8, C4-63 (G) and IR-20 susceptible, intermediate and resistant varieties, respectively, during 1972 dry and 1973 wet seasons. The experimental plants were inoculated at 60, 75, and 90 days after sowing at three disease-intensity levels, 25, 50, and 75 per cent. Results of the study indicated that the disease can decrease the yield potential of the three varieties. The average yield losses in IR-8 were 10.77% and 25.87% for the dry and wet seasons, respectively. The average yield losses in C4-63 (G) were 8.01 and 18.76%, in IR-20 they were 3.31 and 13.82% for the dry and wet seasons, respectively.