Egea. C, Alcazar, M, D. and Candela. M. E. 1996. Capsidioi; Its role in the resistance of Capsicum annuum to Phytophthora capsici. Plant. 98;[737][738][739][740][741][742] Inoculation ofthe stems of three Capsicum annuum h. cultivars showing different degrees of sensitivity to the fungal pathogen Phytophthora capsici, resulted in a hypersensitive reaction being expressed along the stems,. One of the peppers (cv. Smith-5) showed resistance by total inhibition of fungal growth. Capsidiol, a ph>1oalexin, which accumulates in tbe area of necrosis appears to be involved in this resistance. Capsidiol accumulation was analyzed by gas chromatograpby and was correlated with the restricted growth of P. capsici, in vivo and in vitro, confirming the former's fnngistatic and fungitoxic properties. The capacity to inhibit pathogenic growth was evident only wben capsidiol production exceeded i 204 ^g mT', a level reached in the resistant variety after 6 days of incubation. Experiments on induced resistance showed that a second inoculation of the stems of the three cultivars also resulted in necrosis and in an accumulation of capsidio), although to a lesser extent than in the first inoculation. The greater accumulation of capsidiol in the stems of cv. Smith-5 is in accordance with tbe resistance shown hy this cultivar to P. capsici, and confirms the implication of capsidioi in the disease resistance of this cultivar to fungal pathogens. Capsidiol has a fungistatic character at a mean concentration of 3.75 m.W, and is funsritoxic at levels above 5 mM. This level must be exceeded and all the growing h\pbae must be affected for capsidiol to qualify from being fungistatic to being fungitoxic.

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