Mechanism of Brevibacillus brevis strain TR-4 against leaf disease of Photinia×fraseri Dress.

ABSTRACT

Background: Colletotrichum species are among the most common pathogens in agriculture and forestry, and their control is urgently needed. Methods: In this study, a total of 68 strains of biocontrol bacteria were isolated and identified from Photinia × fraseri rhizosphere soil. Results: The isolates were identified as Brevibacillus brevis by 16S rRNA. The inhibitory effect of TR-4 on Colletotrichum was confirmed by an in vitro antagonistic experiment. The inhibitory effect of TR-4 was 98% at a concentration of 10 µl/ml bacterial solution, protection of the plant and inhibition of C. siamense was evident. Moreover, the secretion of cellulase and chitosan enzymes in the TR-4 fermentation liquid cultured for three days was 9.07 mol/L and 2.15 µl/mol, respectively. Scanning electron microscopy and transmission electron microscopy confirmed that TR-4 destroyed the cell wall of C. siamense, resulting in leakage of the cell contents, thus weakening the pathogenicity of the bacteria.