Bioactive extract of Pseudomonas sp. BC42 suppresses the infection stages of Colletotrichum orbiculare

Colletotrichum orbiculare is a pathogenic fungus that causes anthracnose in several cucurbit crops. The antifungal bacterial strain Pseudomonas sp. BC42 was tested against C. orbiculare, and the ethyl acetate extract of BC42 suppressed mycelial growth, sporulation, and appressorium formation. The conidial RNA expression of C. orbiculare grown on culture media amended with BC42-extract was investigated, and adenylate cyclase, cyaA, mitogen activated protein kinase, hog1, and threonine synthase thr4 were downregulated. In a cucumber seedling assay, spraying the extract onto the seedlings after pathogen inoculation decreased the number of lesions compared to the control. These results suggest that the bioactive metabolite of the BC42-extract could affect pathogen development related to infection of host plants by C. orbiculare and that the extract could be used as a potential biological control agent against anthracnose in cucumber plants.