SCREENING OF SALT TOLERANT BACTERIA FOR PLANT GROWTH PROMOTION ACTIVITIES AND BIOLOGICAL CONTROL OF RICE BLAST AND SHEATH BLIGHT DISEASE ON MANGROVE RICE

Abstract

From 22 rice, soil and water samples collected in the field of Long An and Tien Giang provinces, we isolated and screened 87 strains of bacteria around the root zone and endophytic bacteria. Through testing the ability of plant growth stimulation, the result showed 16 strains were capable of nitrogen fixation, 13 strains were capable of phosphate solubilization, 27 strains were capable of IAA production and 2 strains had all 3 activities. By the dual testing method and the percentage of inhibition method between bacterial and fungal pathogen, LD5 and LS6 strains had the highest antifungal activity against Rhizotocnia sp. CR1 at 94.02 %. TS3 and TĐ13 strains had the highest antifungal activity against Magnaporthe sp. BP3 at 81.74 ± 0.88 % and 80 ± 0.60 %, respectively. Furthermore, there were 6 strains inhibiting both Rhizotocnia sp. CR1 and Magnaporthe sp. BP3 (LĐ5, LS4, LS6, LN1, LN6, TS3). The strains were identified by biochemical methods. The results showed that LD5, LS6 and TS3 were 70.37 % similar to Bacillus thurigiensis, TD13 strain was 70.37 % similar to Bacillus pantothenticus, TD9 strain was 72.72 % similar to Azotobacter vinelandii and TD6 strain was 70.37 % similar to Bacillus subtilis. Regarding the test of activity to stimulate growth in net house model, combination of 4-strain (TD6, TD9, TD13, TS3) had the effect of increasing the length of roots, trunk and weight of rice compared with control treatment. For evaluation of biocontrol of fungal pathogen in net house model, the abilities to control sheath blight in N-2C1 and N-LĐ5 treatment were the highest (40.59 % and 39.06 %, respectively). The ability to control rice blast in N-2C2 treatment was the highest (41.26 %). The ability to biocontrol both sheath blight and rice blast in N-4C treatment was 37.89 %.