Capsidiol accumulation in Capsicum annuum stems during the hypersensitive reaction to Phytophthora capsici

Abstract

Summary Inoculation of the stems of the three varieties of C. annuum (L.), with different sensitivities to the pepper pathogen, P. capsici, resulted in a hypersensitive reaction of different length along the stems and the accumulation of capsidiol. This suggests that all the pepper cultivars analyzed contain a mechanism for recognizing this pathogen and the genetic information for initiating the defense response. The differences lie in the inhibitory capacity towards the fungal hyphae, which is only really effective in Smith-5, the sole variety in which pathogenic attack is stopped totally. Capsidiol accumulates in the stems of all the pepper cultivars when inoculated with P. capsici, although there are significant differences depending on the cultivar and on the histological zone of the stem studied. The greatest accumulation of capsidiol corresponds to the 6th day of infection in the necrotic zone of the resistant variety (Smith-5), suggesting that this variety alone has the ability to accumulate sufficiently high phytoalexin levels to inhibit fungal development.