Antagonistic Activity of <i>Bacillus velezensis</i> SDTB038 against <i>Phytophthora infestans</i> in Potato

Abstract

Potato late blight is a severe and highly epidemic disease caused by <i>Phytophthora infestans</i> that can affect all parts of the plant. This study mainly screened antagonistic strains for good control of potato late blight and identified strain SDTB038 as <i>Bacillus velezensis</i> according to its morphological and chemical properties and the 16S rRNA, <i>gyrA</i>, and <i>gyrB</i> gene sequences. This antagonistic strain achieved good control of potato late blight in greenhouses and fields and promoted potato plant growth. Two-year field trials (2018 and 2019) showed that <i>B. velezensis</i> SDTB038 can be used to reduce food losses caused by late blight, achieving late blight reductions of 40.79% (2018) and 37.67% (2019). In two-year field trials, the control effects of the highest concentrations of fluopimomide and <i>B. velezensis</i> SDTB038 were better than those of the other treatments. The control effect of 85 g ha^-1 fluopimomide and <i>B. velezensis</i> SDTB038 and that of 170 g ha^-1 fluopimomide alone showed no significant differences. These field results indicate that a low concentration of fungicide and a high concentration of SDTB038 can be effective in controlling potato late blight. Foliar detection showed that lipopeptides have an inhibitory effect on <i>P. infestans</i>. The amplification of lipopeptide genes revealed surfactin (<i>srfAB</i> and <i>srfAC</i>) and fengycin (<i>fenB</i>) genes in SDTB038, but only surfactin production by <i>B. velezensis</i> SDTB038 was observed by ultra-high-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry analysis. Therefore, the strain <i>B. velezensis</i> SDTB038 can produce secondary metabolites that help potato plants resist late blight development, can effectively inhibit the infection of potato leaves by <i>P. infestans</i>, and has potential value for development as a biological pesticide against potato late blight.