KẾT QUẢ PHÂN LẬP, TUYỂN CHỌN VI KHUẨN ĐỐI KHÁNG PHỤC VỤ SẢN XUẤT CHẾ PHẨM SINH HỌC PHÒNG TRỪ NẤM GÂY BỆNH PHẤN TRẮNG TRÊN MỘT SỐ CÂY TRỒNG

Using PCR technique for cloning 16S rRNA by two universal primers 27 F and 1527R (Lane, 1991) and analysing phylogeny tree NJ by MEGA 5.2 with 2000 replications for bootstrap test, the endobacteria from rubber tree leave, Bacillus amyloliquefacien, isolate 2.3, 1127bps and soil bacteria, B. amyloliquefacien, isolate 1, 1469bps and B. thuringiensis (belonging to B. cereus), isolate 12, 1541bps were identified with 100% bootstrap value supports. In vitro tests indicated that endobacteria isolate No. 2.3, B. Amyloliquefacien, has the highest ability in decreasing the rate of powdery mildew conidial germination on mandarine and soybean leaves (6.2±0.4%), (3.9±0.3%) respectively in comparison with the control, over 40%. This bacterial was chosen as bioagent to produce bioproduct (BA1). In glass-house trial, BA1 with 108 cfu/ml at 5% concentration had reduced more than 80% of diseased incidence when compared with the control and the efficacy was stable up to 30 days after application. For prevention, spraying on soybean leaves 1 month earlier before the disease occurrence, BA1 also provided good efficacy with concentration from 3-4%.