Characterizing antagonistic activities and host compatibility (via simple endophyte-calli test) of endophytes as biocontrol agents of Ganoderma boninense

Abstract

This study characterized the antagonistic activities of five fungal endophytes (Aspergillus calidoustous BTF07, Penicillium citrinum BTF08, Trichoderma asperellum T2, Diaporthe phaseolorum WAA02, Diaporthe phaseolorum MIF01) and evaluated their endophyte-host compatibility with the host plant (oil palm). The antifungal activities of the endophytes towards Ganoderma boninense (GB) were first established using the dual culture test, revealing antagonistic nature of endophytes via production of non-volatiles, volatiles and competitive exclusion. Endophyte-host compatibility was then assessed using a simple but rapid endophyte-calli dual-culture assay, and results validated using endophyte-ramet test. Results revealed that endophytes elicited different responses in oil palm calli. BTF08 had growth promoting effects towards the host tissues with the highest calli weight (1013mg) obtained, while BTF07 appeared to inhibit calli (1006mg) leading to browning and necrosis. This endophyte-calli test also revealed the influence of calli on endophyte growth. Isolates BTF08 and GB benefited from host association, with increased radial growth (2.36cm and 2.31cm, respectively) compared to growth in the absence of calli (2.10cm and 2.15cm, respectively). Endophytes and GB were also isolated from host tissues, suggesting compatibility and ability to colonize host tissues (root, stem, leaf). This suggested the reliability of the endophyte-calli test as a rapid assay to provide an insight on the endophyte-host compatibility.