Beauveria caledonica as an Antagonist Controlling Fusarium oxysporum f. sp. cubense Tropical Race 4 in Bananas.

Beauveria caledonica offers great potential as a biocontrol agent for certain pests and diseases. However, its ability to colonize plants as an endophyte and its interactions with pathogenic microorganisms within the plant are still not fully understood. In this study, we investigated the potential of B. caledonica isolated from banana weevils to colonize banana cultivar "Baxijiao" (Musa spp. AAA) and control the Tropical Race 4 (TR4) strain of Fusarium Wilt of Banana (Fusarium oxysporum f. sp. cubense (Foc). A four-point dual-culture confrontation test revealed that B. caledonica effectively inhibited the in vitro growth of Foc TR4, with an inhibition rate of 70.14%. Colonization experiments showed that B. caledonica could colonize the roots, corms, and pseudostems of banana plantlets. Finally, greenhouse experiments, arranged in a randomized complete block design, confirmed that B. caledonica could act as an endophyte, surviving inside the banana plant, and demonstrated that it significantly reduced Foc TR4 in the host plant, with an efficacy of 34.73%, without adversely affecting plant growth. This groundbreaking study confirms that an insect-pathogenic fungus, B. caledonica, isolated from banana weevils, can colonize banana plants and establish itself as an endophyte within host plants. Its demonstrated potential to antagonize Foc TR4 highlights its effectiveness as a biocontrol agent in banana production, which opens a new possibility for B. caledonica's dual roles in disease and pest management to be validated in large-scale field trials.