Phytotoxins produced by germinating spores of Bipolaris oryzae

Bipolaris oryzae produces ophiobolin A and ophiobolin B during spore germination. Ophiobolin A, 6-epiophiobolin A, anhydroophiobolin A, 6-epianhydroophiobolin A, and ophiobolin I are produced during culture in a nutrient medium. Each compound showed nonselective phytotoxicity to host and nonhost plants in assays for root elongation and induction of leaf chlorosis. Ophiobolin A was most toxic, with an ID 50 value of 5 μg/ml, followed by 6-epiophiobolin A, with an ID 50 value of 10 μg/ml for inhibition of root elongation. Others were toxic only at levels of more than 100 μg/ml (...)