Bioherbicidal effect of secondary metabolites from Lasiodiplodia theobromae for management of narrow-leaf and broad-leaf weeds

Herbicides are the most used form of weed management worldwide but their excessive use could lead to negative impacts on human health and the environment. Biological weed management utilizing microorganisms and their metabolites presents a promising alternative. The weed-associated fungus Lasiodiplodia theobromae TBRC 15112 produces a broad spectrum of biological molecules, and shows potential as a bioherbicide. In this study, L. theobromae crude extracts from cultures caused leaf lesions in crowfoot grass (Dactyloctenium aegyptium L.) and tridax daisy (Tridax procumbens L.). The treated tridax daisy plants wilted and collapsed in three days. Using HP-20SS column chromatography, the 20, 30 and 40% acetone fractions caused leaf lesions covering 54, 30 and 34% of whole leaf areas of D. aegyptium, respectively, whereas relatively lower severities were observed for the 50–70% fractions. Eight compounds, including one new metabolite, were isolated and characterized for their structures using NMR spectroscopic data. Of these, five exhibited bioherbicidal activity, namely uracil, tyrosol, N-(4-hydroxyphenyl) acetic acid, N-(4-hydroxyphenyl) acetamide (4HPA), and the new metabolite. This metabolite, which we named lasiodiplin, is similar to alboatrin but distinct at two positions. Intriguingly, the mixture of tyrosol and 4HPA had a greater effect on weed leaves than pure compounds alone, suggesting a synergistic effect. The crude extracts also caused leaf lesions on five of six tested crops. Our study revealed that L. theobromae crude extracts have bioherbicidal activity on the narrow-leaf and broad-leaf weeds. The data could pave a way for further development of bioherbicides based on microorganisms and microbial products.