To develop an effective biological agent to control S. sclerotiorum， three endophytic Bacillus spp. strains with high antagonistic activity were isolated from maize seeds and characterized. In vitro assays revealed that the Bacillus endophytes could produce volatile organic compounds (VOCs) that reduced sclerotial production， and inhibited mycelial growth of S. sclerotiorum. Gas chromatography-Mass spectrometry (GC-MS) revealed that the selected strains produced sixteen detectable VOCs. Eight of the produced VOCs exhibited negative effects on S. sclerotiorum， while a further four induced accumulation of reactive oxygen species (ROS) in mycelial cells. Mixture of VOCs produced by Bacillus strain VM11 cause... More
To develop an effective biological agent to control S. sclerotiorum， three endophytic Bacillus spp. strains with high antagonistic activity were isolated from maize seeds and characterized. In vitro assays revealed that the Bacillus endophytes could produce volatile organic compounds (VOCs) that reduced sclerotial production， and inhibited mycelial growth of S. sclerotiorum. Gas chromatography-Mass spectrometry (GC-MS) revealed that the selected strains produced sixteen detectable VOCs. Eight of the produced VOCs exhibited negative effects on S. sclerotiorum， while a further four induced accumulation of reactive oxygen species (ROS) in mycelial cells. Mixture of VOCs produced by Bacillus strain VM11 caused morphological changes in the ultra structure and organelle membranes of S. sclerotiorum mycelial cells. The bromophenol blue assay revealed yellow color of untreated fungal mycelium， which grew fast and deeper from 24 to 72 hours post inoculation (hpi)， as an indication of reduced pH. The potasium permanganate (KMnO) titration assay showed that， the rate of oxalic acid (OA) accumulation was higher in the MS liquid medium culture inoculated with untreated fungal plugs compared with Bacillus VOC-treated ones. Interestingly， biological control assays using host-plant leaves challenged with VOC-treated fungal mycelial plugs produced reduced lesions compared to the control. These findings provide new viable possibilities of controlling diseases caused by S. sclerotiorum using VOCs produced by Bacillus endophytes.
