Macrocyclic trichothecenes are undetectable in kudzu (Pueraria montana) plants treated with a high-producing isolate of Myrothecium verrucaria

Myrothecium verrucaria was found to be an effective pathogen against kudzu grown in the greenhouse and the field. M. verrucaria produced large amounts of macrocyclic trichothecenes when cultured on solid rice medium, includin g epiroridin E (16.8 mg/g crude extract), epiisororidin E (1 mg/g), roridin E (8.7 mg/g), roridin H (31.3 mg/g), trichoverrin A (0.6 mg/g), trichoverr in B (0.1 mg/g), verrucarin A (37.4 mg/g), and verrucarin J (2.2 mg/g). Mos t of these toxins were also isolated from rif. verrucaria spores and myceli a grown on potato dextrose agar medium, including epiroridin E (32.3 mg/g), epiisororidin E (28.6 mg/g), roridin E (0 mg/g), roridin H (60 mg/g), tric hoverrin A (1.3 mg/g), trichoverrin B (1.8 mg/g), verrucarin A (13.8 mg/g), and verrucarin J (131 mg/g). When ill. verrucaria was cultured on liquid m edia, the numbers but not the amounts of toxins decreased. Only epiroridin E (28.3 mg/g), epiisororidin E (29.6 mg/g), verrucarin B (195 mg/g) and ver rucarin J (52.6 mg/g) were measured when the fungus was cultured on cornste ep medium. On soyflour-cornmeal broth M. verrucaria produced several toxins , including epiroridin E (58.1 mg/g), epiisororidin E (5.8 mg/g), verrucari n B (29.9 mg/g) and verrucarin J (32 mg/g). In contrast, no macrocyclic tri chothecenes were detected by HPLC analysis of plant tissues of kudzu, sickl epod, and soybean treated with aqueous suspensions of M. verrucaria spores formulated with a surfactant. Chloroform-methanol extracts of kudzu leaves and stems treated with M. verrucaria spores were less cytotoxic to four cul tured mammalian cell lines than the corresponding extracts from control pla nts. Purified macrocyclic trichothecenes (verrucarin A and T-2 toxin) were very cytotoxic to the same cell lines (less than or equal to2 ng/ml). These results show that neither intact macrocyclic trichothecenes nor toxic meta bolites could be detected in plant tissues after treatment with M. verrucar ia spores. These results argue for both safety and efficacy for the use of M. verrucaria in biological control of kudzu and other noxious weeds, and s upport proceeding to animal feeding trials for further evaluation of safety . (C) 2001 Elsevier Science Ltd. All rights reserved.