Phytotoxicity of Fusarium, other fungal isolates, and of the phytotoxins fumonisin, fusaric acid, and moniliformin to jimsonweed

Abstract

Ten fungal isolates from jimsonweed ( Datura stramonium L. ) and 7 from crop species were examined for phytotoxin production and pathogenicity on jimsonweed seedlings in the greenhouse. Four isolates of Fusarium moniliforme , three F. semitectum isolates, a F. oxysporum isolate, a Cephalosporium spp . isolate, and an Alternaria crassa isolate from diseased jimsonweed seedlings, plus seven additional F. moniliforme isolates from seeds and seedlings of crop species were grown on autoclaved rice ( Oryza sativa ). The fungus-rice mixtures were ground and tested for phytotoxicity on 1- and 2-wk-old jimsonweed seedlings via foliar application. All fungus-infested rice extracts (5 g fungus-rice mixture 50 mL -1 water) caused injury or mortality to the seedlings except the extracts from isolates of F. semitectum , Cephalosporium spp ., and A. crassa . Fungus-rice mixtures were quantitatively analyzed for the presence of Fusarium phytotoxins [fumonisin B 1 (FB 1 fusaric acid, and moniliformin]. No isolate produced more thanoneof these phytotoxins in the fungus-rice extract. FB 1 was produced by ail F. moniliforme isoletes in a concentration range of ≤ 5 to 850 μg mL -1 of fungus-rice extract. The F. oxysporum isolate produced moniliformin at 3.5 g mL -1 , and no phytotoxins were detected in extracts of F. semitectum , Cephalosporium spp ., or A. crassa . Pure fumonisin, fusaric acid, and moniliformin applied to jimsonweed foliage at 6-50, 25-800, and 50-800 (μg mL -1 , respectively, caused symptoms similar to that of the fungal isolates that produced these compounds. Pathogenicity tests of spores of all isolates on jimsonweed indicated that the isolates were avirulent, except for A crassa which infected only after a dew period ≥ 12 h.