Two New Biocontrol Agents Against Clubroot Caused by .

Clubroot disease caused by can lead to serious yield losses in crucifers such as . In this study, 323 bacterial strains were isolated from the rhizosphere of severely diseased in Dangyang county, Hubei province, China. Antagonistic strains were first identified based on dual culture inhibition zones with and . These were then further screened in germination inhibition and viability assays of resting spores of . Finally, eight of the antagonistic strains were found to significantly reduce the disease severity of clubroot by more than 40% under greenhouse conditions, and two strains, F85 and T113, were found to have efficacy of more than 80%. Root hair infection experiments showed that F85 and T113 can inhibit early infection of root hairs, reduce the differentiation of primary plasmodia of , and inhibit formation of secondary zoosporangia. Based on sequence analysis of 16S rDNA gene, gene and 22 housekeeping genes as well as carbon source utilization analysis, the F85 was identified as and T113 as . Genome analysis, PCR and RT-PCR detection revealed that both F85 and T113 harbor various antibiotic biosynthesis gene clusters required to form peptides with antimicrobial activity. To our knowledge, this is the first report of as a biocontrol agent against clubroot disease.