Identification of phytotoxins from Botryosphaeria obtusa, a pathogen of black dead arm disease of grapevine

Abstract

A bioassay-guided fractionation of a culture filtrate of Botryosphaeria obtusa led to the isolation of four dihydroisocoumarins, named mellein 1, 4-hydroxymellein 2, 7-hydroxymellein 3 and the new 4,7-dihydroxymellein 4. LC-UV-DAD-MS analysis of vine wood infected by B. obtusa revealed the presence of mellein (1). Botryosphaeria obtusa was also able to oxidise wood δ-resveratrol into the dimer delta-viniferin. The structures of isolated phytotoxins were established on the basis of IR, MS, 1D and 2D NMR.