Clyde D. Boyette

Phytotoxicity of fumonisin B1 on weed and crop species

Fumonisin B1 (FB1) sprayed on intact jimsonweed plants at 10 to 200 ,g mi-I caused chlorosis and necrosis on threeto four-leaf plants and reduced their height and biomass. Excised leaves of jimsonweed were necrotic on both surfaces after treatment with FB1 at 10 to 200 Fg ml-1. The degree of damage increased with the concentration of FB1. The minimum amount of FB1 that damaged excised leaves was 0.05 kg. The symptoms of toxicity on sensitive plants varied with concentration of FB1. Symptoms observed included: chlorosis (creeping cucumber), necrosis (jimsonweed and common sunflower), black leaf lesions (sicklepod), curl of tissues (soybean), stunting, defoliation (hemp sesbania and northern jointvetch), and death (prickly sida, spurred anoda, northern jointvetch, and jimsonweed). Monocots (barley, bermudagrass, corn, johnsongrass, rice, sorghum, and wheat) were not visibly affected by FB1. This is the first evidence of the phytotoxic properties of fumonisin B1 against a wide variety of weeds and crop cultivars. Nomenclature: Fumonisin, propane-1,2,3-tricarboxylic acid diesters of long chain aminopentals; Fusarium moniliforme Sheldon; barley, Hordeum vulgare L.; bermudagrass, Cynodon dactylon (L.) Pers. #3 CYNDA; common sunflower, Helianthus annus L. # HELAN; corn, Zea mays L.; creeping cucumber, Melothria pendula L. # MEEPE; hemp sesbania, Sesbania exaltata (Raf.) Rydb. ex A. W. Hill # SEBEX; jimsonweed, Datura stramonium L. # DATST; johnsongrass, Sorghum halepense (L.) Pers. # SORHA; northern jointvetch, Aeschynomene virginica (L.) B. S. P. # AESVI; prickly sida, Sida spinosa L. # SIDSP; rice, Oryza sativa L.; sicklepod, Cassia obtusifolia L. # CASOB; sorghum, Sorghum bicolor (L.) Moench # SORVU; soybean, Glycine max (L.) Merr.; spurred anoda, Anoda cristata (L.) Schlecht. # ANVCR; wheat, Triticum aestivum L. Additional index words: Biological activity, natural product, fungal product, bioherbicide, mycotoxin.

Macrocyclic trichothecene production and sporulation by a biological control strain of Myrothecium verrucaria is regulated by cultural conditions

Myrothecium verrucaria is a pathogen of several invasive weed species, including kudzu, and is currently being evaluated for use as a bioherbicide. However, the fungus also produces macrocyclic trichothecene mycotoxins. The safety of this biological control agent during production and handling would be improved if an inoculum could be produced without concomitant accumulation of macrocyclic trichothecenes. Sporulation and trichothecene production by M. verrucaria was evaluated on standard potato dextrose agar (PDA) and a series of complex and defined media. Sporulation on PDA and on agar media with nitrogen as ammonium nitrate or potassium nitrate was more than ten-fold greater then sporulation on the medium with ammonium sulphate as the nitrogen source. Accumulation of macrocyclic trichothecenes was strongly affected by the media composition, with higher levels often associated with higher carbon content in the media. Overall, incubation in continuous darkness resulted in higher macrocyclic trichothecene...