Two Naphthalenone Pentakides from Liquid Cultures of "Phaeoacremonium aleophilum", a Fungus Associated with Esca of Grapevine

Several phytotoxic metabolites were extracted from culture filtrates of Phaeoacremonium aleophilum, a fungus associated with the esca of grapevine and related diseases. Two of these metabolites were identified by chemical and spectroscopic methods as scytalone (23.9 mg l-1) and isosclerone (2.4 mg l-1), two naphthalenone pentaketides already known as fungal metabolites. Assayed on detached leaves of grapevine cv. Italia, scytalone at 0.05 mg ml-1 caused light green to chlorotic, rounded to irregular, interveinal or marginal spots, and isosclerone at 0.1 mg ml-1 caused large, coalescent chlorotic and necrotic spots followed by distortion of the lamina and withering. This is the first report on the production in vitro of scytalone and isosclerone by P. aleophilum, and on the phytotoxic activity of these compounds.