Alternaric Acid, a Biologically Active Metabolic Product of the Fungus Alternaria solani

Abstract

SEVERAL strains of Alternaria solani (E. and M.) Jones and Grout and one of A. porri (Ell.) Saw. have been found to produce in liquid media a substance which causes a characteristic stunting effect on developing germ tubes of Botrytis allii, in our standard germination test¹, without reducing percentage germination. We have also found that germination of spores of other fungi, notably those of Myrothecium verrucaria, is inhibited, so that a more satisfactory assay can be developed. Greatest activity develops in cultures on Czapek–Dox medium containing 10–15 per cent sucrose ; sucrose is appreciably superior to glucose or other sugars. From such culture filtrates, using a strain of Alternaria solani (No. 408 in our collection), we have isolated a material, for which we propose the name alternaric acid, which appears to be responsible for both the antifungal effects mentioned above.