Biocontrol potential of Myxococcus sp strain BS against bacterial soft rot of calla lily caused by Pectobacterium carotovorum

Bacterial soft rot caused by Pectobacterium carotovorum subsp. carotovorum is a devastating plant disease in calla lily (Zantedeschia spp.). Considering the economic value of calla lily in the cut flower industry, effective means for controlling this disease are urgently needed. A screening of 12 isolates yielded strain BS as the best antagonist against P. carotovorum. The isolate with excellent antibacterial activity was identified as belonging to Myxococcus sp. Further research indicated that predator-prey interactions involving extracellular vesicles are involved in the antibacterial behavior, and that efficient predation followed by fruiting body formation was responsible for the adaption and colonization ability of BS in soil. Pot experiments showed that strain BS significantly decreased the incidence of soft rot of calla lily to 19.8% from 75.0%, and the disease index was lowered to 6.3% from 62.5%. When the strain BS was applied to the soil, the pre-treated calla lily plants displayed significantly higher levels of growth and greater number of progeny tubers than untreated controls. Due to its multiple beneficial traits, strain BS has the potential to be developed into a plant growth promoting and biocontrol agent for integrated disease and health management strategies.