QIAN Xin, CHEN Yali, LI Meixia, CAO Kaige, ZHOU Changyong, CHEN Xianghua, LUO Dexu, FU Yousheng, CHEN Chengyu, SUN Yudong
Pepper Phytophthora blight, caused by Phytophthora capsici, is a devastating soil-borne disease leading to reduced or even no harvest of pepper and causes huge economic losses. The bacterial strain 1LN2 showed good inhibitory effect against P. capsici in dual culture test, and it was identified as Bacillus amyloliquefaciens according to physiological and biochemical properities, 16S rRNA-based phylogenetic analysis, combined with nucleic acid sequence analysis result. 1LN2 exhibited a wide antimicrobial spectrum, including Fusarium graminearum, Rhizoctonia cerealis, Colletotrichum gloeosporioides, Alternaria solani, Bipolaris maydis, Verticillium dahliae, Corynespora cassiicola, Sclerotinia sclerotiorum, Phomopsis asparagi, and Mycosphaerella. The strain 1LN2 could strongly inhibit mycelial growth of P. capsici and cause hyphal deformities. In pot experiments, the control efficiencies of 1LN2 on pepper Phytophthora blight at 6-8 leaf stage, 9-11 leaf stage, and bud stage were 85.26%, 61.27%, and 49.73%, respectively. In field experiments, the control efficiency of 1LN2 on the disease was 62.35%. Further detection of antagonistic metabolites showed that strain 1LN2 could produce cell wall-degrading enzymes such as cellulase and protease. Whole genome sequencing and analysis results demonstrated that the genome of 1LN2 contains 8 secondary metabolite biosynthetic gene clusters, including bacillaene, fengycin, bacillibactin, bacilysin, butirosin, surfactin, macrolactin and subtilin, and there are unknown gene clusters for synthetic antimicrobial substances. Treatment of pepper plants with biocontrol strain 1LN2 could significantly promote the growth of pepper seedlings and increase the activity of several defense enzymes including PAL, POD, and SOD in peppers. Overall, this study provides a valuable resource for the biocontrol of pepper Phytophthora blight, and lays a basis for further revealing the underlying mechanism of the biocontrol strain against this disease.
