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.
Highlights
Clubroot, caused by the obligate parasite Plasmodiophora brassicae, is an economically important disease affecting plants in the family Brassicaceae worldwide (Howard et al 2010; Dixon 1998)
The bacterial strains YFY 02, HY, 13-1 isolated in the present study were identified as L. antibioticus based on biochemical and physiological identification (Biolog carbon source utilization analysis) and 16S ribosomal DNA (rDNA) sequences analysis
The inhibitory effect depended on bacterial isolate, and bacterial components as well as the bacterial application method
Summary
Clubroot, caused by the obligate parasite Plasmodiophora brassicae, is an economically important disease affecting plants in the family Brassicaceae worldwide (Howard et al 2010; Dixon 1998). The disease has become the main limiting factor for the production of cruciferous crops in almost all provinces, in particular, Liaoning, Zhejiang, Jiangxi, Sichuan and Yunnan provinces (Huang 2010; Wang et al 2011). This may be due toChinese cabbage being one of the major crops in these provinces, one-third of which is traditionally planted in acidic soils that favour disease development (Howard et al 2010). Crop rotation is the simplest and most effective approach for the management of clubroot, but may not be practical due to the longevity of the pathogen in infested soils (Haiyan, Xu 2011)
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