Suppression of Rice Blast by Bacterial Strains Isolated from Cultivated Soda Saline-Sodic Soils

Rice blast caused by Magnaporthe oryzae is one of the most serious rice diseases worldwide. Biological control is gaining popularity as a promising method for the control of this disease; however, more effective microbial strains with strong adaptability in rice fields need to be identified. Here, we report for the first time the successful identification of biocontrol bacterial strains from frozen soils of the soda saline-sodic land. We isolated 82 bacterial strains from rice fields in the western Songnen Plain of China, one of the three major soda saline soils in the world. Five of the isolated strains exhibited strong inhibition to M. oryzae growth. The potential strains were identified as Bacillus safensis JLS5, Pseudomonas koreensis JLS8, Pseudomonas saponiphila JLS10, Stenotrophomonas rhizophila JLS11 and Bacillus tequilensis JLS12, respectively, by 16s RNA gene sequence analysis. The antagonistic assay and the artificial inoculation tests showed that JLS5 and JLS12 could effectively inhibit conidial germination and pathogenicity of the rice blast fungus, both preventively and curatively. The suppression of pathogenicity was further confirmed by greenhouse experiments, showing the effectiveness of JLS5 and JLS12 as a potential biological control agents of M. oryzae. The potential application of these cold-tolerant strains for rice blast control in cold regions is discussed. Our data suggest that soda saline-sodic soils are a rich source for biocontrol strain isolation.