Plant-fungus interactions usually generate H(2)O(2) in the infected plant tissue. H(2)O(2) has a direct antimicrobial effect and is involved in the cross-linking of cell walls, signaling, induction of gene expression, hypersensitive cell death and induced systemic acquired resistance. This has raised the hypothesis that H(2)O(2) manipulation by pharmacological compounds could alter the lifestyle of Colletotrichum gloeosporioides during interaction with the BR-3-Tracuateua cowpea genotype. The primary leaves of cowpea were excised, infiltrated with salicylic acid (SA), glucose oxidase + glucose (GO/G), catalase (CAT) or diphenyliodonium chloride (DPI), followed by spore inoculation on the adaxial leaf surface. SA or GO/G-treated plantlets showed increased H(2)O(2) accumulation and lipid peroxidation. The fungus used a subcuticular, intramural necrotrophic strategy, and developed secondary hyphae associated with the quick spread and rapid killing of host cells. However, CAT or DPI-treated leaves exhibited decreased H(2)O(2) concentration and lipid peroxidation and the fungus developed intracellular hemibiotrophic infection with vesicles, in addition to primary and secondary hyphal formation. These results suggest that H(2)O(2) plays an important role in the cowpea (C. gloeosporioides) pathosystem given that it affected fungal lifestyle during interaction.
Keywords: Cowpea; Fungal life mode; Hydrogen peroxide.
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