Endophytic fungi and their potential in controlling white root disease of cashew

Abstract

White root disease is a significant disease of cashew caused by Rigidoporus sp. Five endophytic fungal isolates, namely AR31D (Fusarium proliferatum), AR42D (Penicillium citrinum), BR32C (Trichoderma asperellum), VNTB1 (Chaetomium sp.), and EAGS14 (Curvularia lunata), were assessed as the biocontrol agents against Rigidoporus sp. in vitro and in planta. The research objective was to obtain endophytic fungi that effectively control Rigidoporus sp. and their mechanisms. The in vitro test results showed that all isolates could inhibit Rigidoporus sp. and promote plant growth by producing volatile organic compounds, chitinase enzymes, and indole acetic acid. Meanwhile, only four isolates could solubilize phosphate with low-medium solubilization efficiency. The isolates successfully colonized the root of cashew saplings in 10–65%. The effectiveness of endophytic fungal isolates in controlling white root disease was determined by the mechanisms involved, such as resistance induction (increased activity of defense enzymes like polyphenol oxidase), chitinase enzyme production, indole acetic acid production, phosphate solubilization, and suppression of plant stress which observed from decreased malondialdehyde concentrations in saplings’ roots. Trichoderma asperellum and Chaetomium sp. were the best isolates with the highest control effectiveness and stimulating plant growth.