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

Abstract

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.

Keywords:

• Herbicide
• Myrothecium roridum
• phytotoxin
• paraquat
• roridin
• water hyacinth

Acknowledgement

We are grateful to Bruce B. Jarvis, Emeritus Professor, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA for providing the roridin E, epi-isororidin E and roridin H used in this study. We also thank Ms. Bobbie J. Johnson for technical assistance and the reviewers (Drs. J. F. Shearer, C. D. Boyette, and R. E. Hoagland) for valuable suggestions. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.

Disclosure statement

The authors declare that they have no conflict of interest.