Phytotoxicity of equisetin and epi-equisetin isolated from Fusarium equiseti and F-pallidoroseum

Fusarium equiseti and F. pallidoroseum are frequently reported as secondary colonizers of plant tissues. In this study they were isolated from the emb ryos of weathered cottonseed. Most isolates tested produced equisetin, an a ntibiotic, when grown on pot-ate dextrose agar, rice, surface-sterilized co ttonseed, or autoclaved cottonseed. This is the first report of equisetin f rom F, pallidoroseum. Equisetin was extracted from cultures of F. equiseti and F. pallidoroseum with acetone and dichloromethane, and partially purifi ed by TLC. Two epimers of equisetin, designated as EQ and epi-EQ, were sepa rated by HPLC. EQ or epi-EQ at 25-10 mu g ml(-1) suppressed germination or inhibited growth of various monocotyledonous and dicotyledonous seed, when the seed were incubated at 30 degrees C under aqueous shake conditions. The two epimers also inhibited the growth of young seedlings and caused necrot ic lesions on the roots, cotyledons, and coleoptiles of tested plant seedli ngs. The results suggest that equisetin may be a pathogenic factor of F. eq uiseti and F. pallidoroseum on seed and seedling health of cotton and other plants.