Submitted to: American Phytopathological Society
Publication Type: Abstract Only
Publication Acceptance Date: 7/27/1996
Publication Date: N/A
Technical Abstract: Equisetin, isolated from F. equiseti, has been shown to be an antibiotic against certain Gram-positive bacteria. We now report that it is also a phytotoxin. In the present study, F. equiseti and F. semitectum were isolated from embryos of weathered cottonseed. Several isolates of the two fungi produced equisetin when grown on moist rice, surface-sterilized cottonseed, and autoclaved cottonseed. Equisetin was extracted from these substrates using a two-step procedure with acetone and dichloromethane, then purified by TLC. The compound exists as two stable tautomers, one of which (B-1) was isolated in pure form by HPLC. Equisetin (B-1) at 10 ug/ml strongly inhibited germination of various monocotyledonous and dicotyledonous seed, including cotton, when the seed were germinated at 30 C under aqueous, shake conditions. It also caused necrotic lesions on the cotyledons and radicles of young seedlings. Our results show that under certain conditions equisetin is highly toxic to rapidly growing plant tissues; therefore, it may affect seed and seedlings infected by F. equiseti or F. semitectum.