Abstract: The experiment was carried out to screening Bacillus to control rice blast, in order to provide the germplasm resources for the prevention of rice blast in sustainable development. In this study, the antagonistic activities of all the bacterial isolates were screened against the pathogens by dual inoculation technique and leaf blade in vitro. To determine its classification status, identification experiments were carried out through morphological characteristic observation, biolog determination and 16S rDNA sequences assay. It had been carried out for 2 years field experiments to confirm the inhibition efficacy of test strains against rice blast and its growth-promoting effect. A total of 280 bacteria were isolated from rice leaves of cultivar Rejingyou NO. 35. Only three isolates, SYX04, SYX20 and S-22 strongly inhibited the growth of M. oryzae in dual culture technique and leaf blade in vitro. The highest inhibition rate of growth for M. oryzae on oat-tomato medium plate cultured after 2 d were 95.6%, 97.5% and 75%, respectively. The control effect of strain SYX04, SYX20 and S-22 in leaf blades were 89.6%, 91.9% and 80.1%, respectively. The results of strain SYX04 and SYX20 had no evident difference from the bacteriostatic efficacy of 20% tricyclazole solution. Strain SYX04 and SYX20 had the nearest evolutionary distance with B. subtilis sp. by the comparing of 16S rDNA sequences, combining with its results of morphological characteristic, biolog analysis, they were identified as B. subtilis. Strain S-22 had the nearest evolutionary distance with S. multivorum and was identified as S. multivorum. The experimental results showed that strain SYX04 and SYX20 played a good role in rice growth, could promote rice root length by 6.7% and 13.2%, increase plant height by 7.8% and 8.2%, panicle weight by 23.1%, thousand seed weight by 10.7% and 11.1%, respectively. In field experiments, the control effect of B. subtilis SYX20 against leaf blast by 73.5%―83.5% and panicle blast by 64.0%―85.6%. There were no significant differences between strain SYX20 and 75% tricyclazole wettable powder. The control effect of B. subtilis SYX04 against leaf blast by 71.5%―82.6% and panicle blast by 63.5%―83.8%. There were no significant difference between strain SYX04 and Lüdikang, but different from tricyclazole. The control effect of S. multivorum strain S-22 against rice leaf blast by 69.2%―73.3% and panicle blast by 61.6%―77.9%. The results were different from Lüdikang and tricyclazole.

Key words: rice blast, Bacillus, screen, bio-control, identification