Abstract: This paper reports radiant effect of 60Co-gamma rays on screening rice resistant mutants in vitro with seed-somato-derived and microspore -derived callus clone. The tested materials included 4 Hsien (Indica)rice varieties such as Ce 49 and Zhen-you No.l1, and 1 Keng (Japonica) rice variety (Li-jiang-xin-tuan-hei-gu). The radiant dose was 0-12 Kr for seed-somato-derived-calli, 0-10 Kr for microspore derived calli,0-2 Kr for placed anthers. The raw toxin extract of the race ZA1 or ZB15 of piricularia oryzae (0.1ml/tube) was applied to the surface of N6 medium with 2,4-D 2,NAA 2,KT 1 mg/1,The treated medium was used for selection medium.And the treated medium supplemented with sterile water was taken for control group. Three pieces of calli (about 1.5 mm in diameter) or 65-75 anthers (late-monokaryotic stage) were placed in each test tube.After screening for 30 days in vitro at 28±1℃, anther culture in dark condition and callus culture in 2500-3000 lx for 8-10 h/day, the growth of callus or the rate of pollen-callus induction was investigated. After regenerating for 30 days, the rate of green plant regeneration was investigated.The result showed that the induction of pollen-callus, growth of seed-somato-derived and microspore-derived calli and plant regeneration were retarded to a certain degree by 60Co-gamma rays, when the raw toxin extract of P. oryzae was taken for stress factor.There was negative relation between the growth of calli and radiant dose, particularly in the first in vitro screening.The retarded effect of raw toxin extract of the race ZA1 on pollen-callus induction in anther culture was more obvious than that of ZB15.The somato-clone was more suscepfive to 60Co-gamma rays than microspore-clone within 4-8 Kr. This study shows the possible potential of the induced variation by 60Co-gamma rays together with the raw toxin extract of P. oryzae being applied to screening rice resistant mutants in vitro.