Suppressive Effects of Volatile Compounds from Bacillus spp. on Magnaporthe oryzae Triticum (MoT) Pathotype, Causal Agent of Wheat Blast.

The (MoT) pathotype is the causal agent of wheat blast, which has caused significant economic losses and threatens wheat production in South America, Asia, and Africa. Three bacterial strains from rice and wheat seeds ( BTS-3, BTS-4, and BTLK6A) were used to explore the antifungal effects of volatile organic compounds (VOCs) of spp. as a potential biocontrol mechanism against MoT. All bacterial treatments significantly inhibited both the mycelial growth and sporulation of MoT in vitro. We found that this inhibition was caused by VOCs in a dose-dependent manner. In addition, biocontrol assays using detached wheat leaves infected with MoT showed reduced leaf lesions and sporulation compared to the untreated control. VOCs from BTS-4 alone or a consortium (mixture of BTS-3, BTS-4, and BTLK6A) of treatments consistently suppressed MoT in vitro and in vivo. Compared to the untreated control, VOCs from BTS-4 and the consortium reduced MoT lesions in vivo by 85% and 81.25%, respectively. A total of thirty-nine VOCs (from nine different VOC groups) from four treatments were identified by gas chromatography-mass spectrometry (GC-MS), of which 11 were produced in all treatments. Alcohols, fatty acids, ketones, aldehydes, and S-containing compounds were detected in all four bacterial treatments. In vitro assays using pure VOCs revealed that hexanoic acid, 2-methylbutanoic acid, and phenylethyl alcohol are potential VOCs emitted by spp. that are suppressive for MoT. The minimum inhibitory concentrations for MoT sporulation were 250 mM for phenylethyl alcohol and 500 mM for 2-methylbutanoic acid and hexanoic acid. Therefore, our results indicate that VOCs from spp. are effective compounds to suppress the growth and sporulation of MoT. Understanding the MoT sporulation reduction mechanisms exerted by VOCs may provide novel options to manage the further spread of wheat blast by spores.