Antagonistic effects of Beauveria bassiana on seed-borne fungi of cowpea (Vigna unguiculata)

Cowpea is cultivated worldwide as a protein source. However, various factors, such as climate change, pest attacks, and pathogens limit the yield of cowpea production. Fungi are primary cowpea pathogens, which are often transmitted by seeds and spread over long distances through the infected seeds. Here, we assessed the diversity of seed-borne fungi associated with cowpeas, and evaluated the antagonistic effect of B. bassiana on phytopathogenic fungi in vivo and in vitro. Seed health tests were performed using the blotter test method. The isolated phytopathogens were molecularly identified and subjected to Koch's postulates. The antagonistic effects of B. bassiana against pathogens were tested in vitro using a paired culture method, and in vivo by inoculating plants under greenhouse conditions. Seed health test results revealed three fungal pathogens (Fusarium sp., Alternaria aff. burnsii, Epicoccum sp.) in addition to the saprophytes (Aspergillus, Penicillium, Rhizopus, Mucor). B. bassiana showed greater inhibition of Fusarium sp. isolate JP1 growth. Growth of Alternaria burnsii isolate JP2 was inhibited by 18.54 to 35.67% and that of Epicoccum sp by 22.73 to 25.23%. The inoculation of plants with B. bassiana also reduced Fusarium symptoms by 58.33%. Alternaria aff. burnsii by 40.08%, Epicoccum sp. by 22.22%. This is the first study reporting isolation of Epicoccum sp. from cowpea seeds in Brazil, and its inhibition by B. bassiana.