Optimization of Myrothecium roridum tode: fries phytotoxin production and bioactivity on water hyacinth (Eichhornia crassipes)

Phytotoxin production by Myrothecium roridum Tode: Fries (IMI 394934) and in vitro bioactivity on water hyacinth leaves (WHL) were evaluated. Phytotoxin produced caused necrosis of WHL three days postapplication. Potato carrot broth and WHL broth formulations gave the highest phytotoxin production in culture. Phytotoxin production was light-dependent and peaked at pH 4.5. Xylose and glutamine were the best carbon and nitrogen sources, respectively. The phytotoxin was thermostable, and phytotoxicity was pH-dependent, but photoperiod-independent. Bioassay-guided fractionation indicated the active phytotoxin was roridin A. Phytotoxicity of roridin A and roridin E was similar (p > 0.05) to paraquat used for water hyacinth control.