The biological control effect of Bacillus cereus on strawberry leaf spot disease caused by Neopestalotiopsis clavispora

Abstract

With their distinctive flavor, fragrance, and nutritional value, strawberry (Fragaria × ananassa Duch.) fruits are popular worldwide. However, strawberry is susceptible to pathogenic fungi in production, which can severely affect yields. In this study, we found a fungal disease in strawberries in Shenyang. The pathogen was identified from morphological characteristics and molecular data as Neopestalotiopsis clavispora. This fungus causes enormous economic losses in strawberry cultivation and production. It is essential to explore effective methods of controlling this disease, including chemical fungicides and biocontrol agents. This study evaluated the antifungal activity of 17 Bacillus strains isolated from soil against N. clavispora. These Bacillus strains showed significant antagonistic effects, with inhibition rates in the dual culture test of 50.22 %–79.48 %. Among these, Bacillus cereus (Bce-2) had the highest inhibition rate of 79.48 %. The ability of different working concentrations of Bacillus cereus culture solution to inhibit mycelium growth was variable, when the working concentration of Bacillus cereus culture solution was 0 %, 2 %, 4 %, 6 % and 8 %, the mycelium dry weight was 0.05–0.52 g. Furthermore, we optimized the fermentation method and evaluated the ability of the Bacillus cereus fermentation solution (BCFS) to control this disease in the field, the disease index of strawberry plants pre-treated with BCFS was reduced by 57.85 %. BCFS treatment improved the activities of peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) and phenylalanine lyase (PAL). BCFS also prevents strawberry leaf spot disease caused by N. clavispora by increasing the expression of the following genes (WRKY22, WRKY29, ChiB, RbohD, HSP90, Rd19, PR1 and PP2C) in strawberry leaves. This study suggests that Bacillus cereus (Bce-2) may be effective in controlling N. clavispora.