Isolation and characterization of bacterial isolates for biological control of clubroot on Chinese cabbage

Abstract

Clubroot caused by Plasmodiophora brassicae is becoming an emerging threat to the production of crucifer vegetable crops in China. The aim of this study was to develop an effective biocontrol strategy against clubroot of Chinese cabbage. Results indicated that six out of fourteen bacterial strains that were isolated from vegetable rhizosphere soil reduced disease severity of Chinese cabbage by more than 50.% under greenhouse conditions.In greenhouse experiments, a soil-drench application of strain YFY 02, 13-1 and HY cell-free culture filtrate reduced the clubroot by 37.7-74.6 % relative to pathogen post-inoculation control on the highly susceptible Chinese cabbage cultivar. Seed treatment of strain YFY 02, 13-1 and HY cell-free culture filtrate reduced clubroot by 23.8-56.0 % in greenhouse experiments. In two field trials conducted at Tonghai and Lufeng sites, cell-free culture filtrates of three isolates reduced clubroot severity on Chinese cabbage by 62.4-76.8 % and 79.4 % -85.1 %, respectively. This efficacy was similar to fungicide Cyazofamid. Based on the sequence analysis of the 16S rDNA gene and identification of biochemical and physiologica criteria l(Biolog carbon source utilization analysis), the strains YFY 02 and HY were identified as Lysobacter antibioticus. To our knowledge, this is the first report of L. antibioticus strains being a promising candidate as a biological control agent against clubroot.