Study On Biocontrol Of Rice Bacterial Leaf Streak With Antagonistic Bacteria

One hundred and forty-eight bacterial strains were isolated from air, soil, ricepaddy water, exteriors of rice and inside of rice collected from various areas in Guangxi.Fifty-seven strains with antagonistic activity against Xanthomonas oryzae pv. oryzicola,were obtained using inhibition zone as screening indicator. Of the antagonistic strains,Ja2 was identified as Burkhoideria vietnamiensis Yabuuchi et al. based on itsmorphological, physiological and biochemical characteristics as well as 16S rDNAsequence, and strain Dc3 as Pseudomonas sp. based on its morphological, physiologicaland biochemical characteristics. For the growth of strain Ja2, the optimum pH andtemperature were 7.5～8.0 and 34℃, respectively. For the growth of strain Dc3, theoptimum pH and temperature were 7.0 and 34℃, respectively. It could use manysubstances as carbon and nitrogen sources.Their fungistatic actions were influenced by temperatures, pHs and media. Thebioassay results of genetic stability in the inhibition activity of Ja2 and Dc3 indicatedthat strains Ja2 and Dc3 had stable antagonistic activities against Xanthomonas oryzaepv. oryzicola. During eight generations transferred, the diameters of inhibition zonescarcely varied. The tests on the ability of promoting rice growth showed that, therewere eleven strains with the ability of promoting growth of rice among the fifty-sevenantagonistic strains. In greenhouse tests, strains Ja2 and Dc3 showed 51.7% and 38.1%of efficacies in reducing lesion formation of rice bacterial leaf streak, respectively. StainsJa2 and Dc3 showed widespread antimicrobial spectrum. They could inhibit not onlygrowth of bacteria, but also fungi causing plant diseases.