Effects of two different soil amendments on the biocontrol efficacy of biological control agents (BCA) against Ralstonia wilt on ginger

Abstract

In this research, we developed an integrated approach to control Ralstonia wilt on ginger. Two organic composts (maize powder and soybean residue) were combined with one combination (the aqueous solution of Bacillus subtilis and Bacillus cereus) and two single (B. subtilis 1JN2 and Bacillus megaterium B1301) biological control agents (BCA) which together showed significant biocontrol efficacies in our previous study. Biocontrol efficacy of each treatment was measured. According to the results, a 3 - 30% biocontrol efficacy improvement was obtained by addition of the two organic composts compared to the BCA treatment. The best biocontrol activity (73.7%) was obtained from the combination of B. megaterium B1301 and maize powder. Colonization ability and the impacts on the bacterial community structure of each BCA were determined by denaturing gradient gel electrophoresis (DGGE). The DGGE fingerprints gave us an insight into the rhizosphere of the plant. And there is no noticeable bacterial structure shift, which means the exotic BCAs by artificial inoculation have little impacts on the local organism community. Additionally, the colonization ability of the tested BCAs was excellent and they could be detected at 120 days post inoculation. Furthermore, the available N, P, K and organic matter of rhizosphere soil from each treatment was measured. The organic matter did not show significant change among each treatment, while maize powder, soybean residue and BCA 1JN2 enhanced the available N, P and K significantly ranging from 79 - 133%, 166 - 251% and 252 - 368%, respectively compared to the blank control.

Key words: Integrated management, biological control agents (BCA), organic compost, ginger wilt.