Phytotoxic metabolite from QTYC01, a fungus residing in the gut of Pantala flavescens larvae

Abstract:

[Objective] To isolate the fungus with phytotoxic activity from the gut of Pantala flavescens larvae and find the phytotoxic lead compound from the fungal metabolites.[Methods] QTYC01 was isolated from the gut of P. flavescens larvae by means of spread plate and identified by 5.8S rRNA sequence analysis and morphologic observation. Phytotoxic activities of the fermentation broth and ethyl acetate extracts against the radical growth of weeds as well as the safety of crude extract to the selected crops were tested by Petri dish bioassay. The herbicidal activity of QTYC01 against Echinochloa crusgalli seedlings was carried out by potted bioassay. Fermentation product was purified by recrystallization and identified by extensive spectroscopic analysis.[Results] QTYC01 was identified as Curvularia crepinii. The fermentation broth of QTYC01 significantly inhibited the radical growth of E. crusgalli and Amaranthus retroflexus with the inhibition rate of 95.0% and 90.1%, respectively. The fermented liquid showed significant inhibitory activity to the seedling of E. crusgalli with the victimization rate of 71.1%. Under the concentration of 100 μg/mL, ethyl acetate extracts exhibited significant phytotoxic activities against the radical growth of E. crusgalli and A. retroflexus with inhibitory rates of 56.8% and 71.2%, respectively, and showed good security to the selected common crops with the inhibition rate of lower than 33%. Therewith, a bioactive compound was isolated from the ethyl acetate extract and determined as (5Z)-7-oxozeaenol. The compound showed good phytotoxic activity against A. retroflexus with the IC₅₀ value of 4.8 μg/mL.[Conclusion] Strain QTYC01 could be potentially developed as a new microbial herbicide.