Biocontrol activities of Bacillus amyloliquefaciens DGA14 isolated from banana fruit surface against banana crown rot-causing pathogens

Two bacteria, isolated from the surface of banana fruits, one forming a creamy white colony and the other, dry yeast like colony were screened for in vitro antagonism toward Lasiodiplodia theobromae. Both isolates, identified as Bacillus amyloliquefaciens, were further tested for antibiosis against other crown rot-causing pathogens (Thielaviopsis paradoxa, Colletotrichum musae, and Fusarium verticillioides). The creamy white colony strain, coded as B. amyloliquefaciens DGA14, was subjected to laboratory and field studies. B. amyloliquefaciens DGA14 produced a diffusible metabolite that inhibited all test pathogens in culture. In addition, bacteria moved and attached to pathogens significantly affecting mycelial growth and conidial germination in liquid medium. Following inoculation, B. amyloliquefaciens DGA14 survived and colonized banana fruits after 2 d. Interparasitic relationships were observed between the antagonist and pathogens on artificial media and the natural substrate. Postharvest application of B. amyloliquefaciens DGA14 in the packing house reduced the incidence of crown rot to a level significantly lower than in fungicide treated or control fruits.