PRODUCTION OF THE PHYTOALEXIN RESVERATROL BY GRAPES AS A RESPONSE TO BOTRYTIS ATTACK UNDER NATURAL CONDITIONS

Resveratrol (3,5,4'-trihydroxystilbene) is one of the stress metabolit es produced by grapevines in response to fungal infection or injury. T he distribution of this compound in limited lesions caused by Botrytis cinerea on ripe grape clusters in the vineyard has been examined. Res veratrol was present predominantly in the non-infected fruits close to the necrotic area, This localized response can help to arrest the spr ead of established B. cinerea lesions as long as climatic conditions a re unfavourable to the pathogen. When conditions become favourable, i. e. after a mild and humid period, rapidly spreading lesions are observ ed on fruits despite the continued increasing production of resveratro l in the grapes which can reach three- to five-fold the value found be fore rot intensification. Significant amounts of resveratrol can be fo und prior to any detectable lesions in Fruits collected from apparentl y healthy clusters, thus suggesting that phytoalexin response is initi ated soon after the recognition of the pathogen by the plant. The invo lvement of one or more endogenous signals coming from either the fungu s or the plant in the induction of host defence responses has also bee n discussed.