Effects of Lysobacter antibioticus HS124, an effective biocontrol agent against Fusarium graminearum, on crown rot disease and growth promotion of wheat.

Lysobacter antibioticus HS124 inhibited mycelial growth of Fusarium graminearum (74.66%) under the dual culture method. Microscopic investigation clearly showed that amendment with different concentrations (10%, 30%, and 50%) of HS124 bacterial culture filtrate on potato dextrose agar plates caused abnormal hyphal structures, including swelling and distortion. Its inhibition toward mycelial growth of F. graminearum was increased with increasing concentration of n-butanol crude extract of HS124. The highest inhibition (43.14%) was detected at a crude concentration of 10 mg/disc, whereas the lowest inhibition (21.57%) was observed at 2 mg/disc. Although mycelial growth of F. graminearum was promoted by volatile organic compounds (VOCs) produced by HS124 as compared with the control, these VOCs clearly decreased fungal pigmentation resulting in a reduction of fungal sporulation. Microscopic investigation revealed hyphal deformation of F. graminearum due to VOCs. These compounds also had a negative effect on spore germination of F. graminearum. In vivo evaluations demonstrated that HS124 inoculation of wheat plants reduced crown rot disease incidence by 73.70% as compared with the control. HS124 inoculation of wheat plants also promoted most of the growth characteristics compared with the control or fungicide-treated plants. Our results provide strong evidence that HS124 could control F. graminearum infections and promote growth of wheat plants as part of management strategies for crown rot disease.