Production of phytotoxic metabolites by species of Botryosphaeriaceae causing decline on grapevines, with interest in the species Neofusicoccum luteum and N. parvum

In recent years an increasing no. of species of Botryosphaeriaceae have been assocd. with grapevine decline worldwide. Five species isolated from declining grapevines in Spain (Botryosphaeria dothidea, Diplodia seriata, Dothiorella viticola, Neofusicoccum luteum and N. parvum) were checked for toxin prodn. in liq. cultures. Cultural conditions for all fungi were adjusted to obtain optimal prodn. of phytotoxic culture filtrates, by growing the fungi in steady liq. cultures of Czapek-Dox broth for different time intervals. Phytotoxicity of D. seriata and N. parvum reached a max. after 14 days while the remaining species showed the highest phytotoxicity levels after 21 days in culture. All fungi produced hydrophilic high-mol. wt. compds. with phytotoxic properties. In addn., N. luteum and N. parvum produced lipophilic low-mol. wt. phytotoxins, not detected consistently among the remaining species. This led to a more exhaustive study on the phytotoxicity of N. luteum and N. parvum. Culture filtrates and corresponding exts. of both species were consistently highly phytotoxic in different assays. The gas-chromatog. anal. of the acetylated O-Me glycosides of the phytotoxic exopolysaccharides produced by N. parvum showed these substances to be composed mainly of glucose, mannose and galactose. Results suggest that phytotoxic metabolites could be involved in the virulence of both species in planta.