Pepper (Capsicum spp.) Wound Volatiles Suppress the Growth of Alternaria alternata, the Causal Agent of Internal Mold of Pepper

in HortScience
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  • 1 USDA–Agricultural Research Service, National Center for Agricultural Utilization Research, Peoria, IL 61604

Internal mold of sweet and hot peppers (Capsicum spp.) is caused by the pathogen Alternaria alternata. The pepper weevil, Anthomonus eugenii Cano (Coleoptera: Curculionidae), is an important pest of peppers in the southern U.S., Mexico, and Central America, and has been implicated in the transmission of the disease. We identified several volatiles released by pepper fruit during wounding by pepper weevils, including (E)-3-hexenyl acetate, linalool, beta-ocimene, and 3,7-dimethyl-1,3,6 octatriene (homoterpene). To study the roles of these volatiles in the interaction of the plant and fungus, we determined their effect on the growth of isolated cultures of A. alternata. Fungi were unaffected by any of the compounds when exposed to individual volatiles at 1 ppm; however, a 1 ppm mixture of the four compounds significantly reduced growth. All four compounds were inhibitory individually at 10 ppm, with linalool completely inhibiting fungal growth. These results indicate a role for these volatiles in the plant's response to infection by A. alternata.

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