The effects of Beauveria bassiana dose and exposure duration on colonization and growth of tissue cultured banana (Musa sp.) plants

Beauveria bassiana (Balsamo) Vuillemin, an entomopathogenic fungus, can exist asymptomatically as an endophyte in banana (Musa spp.) and potentially provide management against the banana weevil Cosmopolites sordidus (Germar). However, in order to optimize its biological control potential when deployed as an endophyte, it is essential to establish the inoculum dose and exposure duration that provides suitable levels and distribution of the pathogen within the plant. It is equally important to determine any negative fitness costs that might be associated with increased population of the fungus in the host plant. In an attempt to optimize plant colonization by this fungus, the effects of B. bassiana doses and exposure durations on colonization and growth of tissue cultured banana (AAA-EA, cv. Kibuzi) plants were investigated. The plants were inoculated by dipping in B. bassiana suspension and then grown in the screenhouse for a month. B. bassiana successfully colonized banana plants with 96.7% of B. bassiana-treated plants colonized, 1 month after inoculation. The optimal dose and exposure duration for effective colonization of tissue cultured banana plants varied, but dipping plants in a dose of 1.5 × 107 conidia/ml for 2 h produced the best percentage colonization. Endophytic colonization of tissue cultured banana plants by B. bassiana had no negative impact on plant growth, even when plants were inoculated at the highest dose.