Screen of antagonistic bacteria against Ralstonia solanacearum. Q. XUE (1), J. Guo (1)
(1) Plant Protection, Nanjing, Jiangsu, China
Phytopathology 98:S175

Abstract: Bacterial wilt caused by Ralstonia solanacearum is a serious threat for agricultural production in many provinces in China. In this study bacterial strains isolated from different environment were screened as potential biocontrol agents according to antagonistic tests on plates and experiments in greenhouse and field. Beforetime several bacterial isolates, such as ZAg, ZBts, and AR156 and so on, were chosen because of their in vitro antagonistic activity to only one R. solanacearum strain. However, based on the diversity analysis of R. solanacearum isolates from China, we found that even the same antagonist can show different antagonistic activity to diverse R. solanacearum strains. Strain Zs36 identified as Serratia spp. was selected because of its different inhibition to various 29 R. solanacearum strains. When 8 pathogen strains were chosen to do greenhouse experiments, the results indicated that the biocontrol efficacy of Zs36 to these R. solanacearum strains were between 19% and 70%. When it was applied together with other bacteria strains, the biocontrol efficacy against bacterial wilt of the mixture can reach 100%. This mixture controlled Phytophthora blight and root-knot nematode disease in a good efficiency as well. Furthermore, they can promote growth of tomato, pepper and cucumber and other plants. Besides, Zs36 colonized rhizosphere of plant perfectly. On the 14th day after seed inoculation, strain Zs36 colonized with the concentration of 5.05 × 107 cfu per gram rhizosphere soil when the concentration of the inoculum was around 2 × 109 cfu/ml. DGGE analysis for bacterial community of rhizosphere of plant treated with Zs36 showed that it had lesser effect on indigenous bacteria community. These work showed that Zs36 has a good commercial potential.