Phytotoxic fungal secondary metabolites as herbicides

Abstract

Among the alternatives to synthetic plant protection products, biocontrol appears as a promising method. This review reports on the diversity of fungal secondary metabolites phytotoxic to weeds and on the approach generally used to extract, characterize, identify and exploit them for weed management. The 183 phytotoxic fungal secondary metabolites discussed in this review fall into five main classes of molecules: 61 polyketides, 53 terpenoids, 36 nitrogenous metabolites, 18 phenols and phenolic acids, and 15 miscellaneous. They are mainly produced by the genera Drechslera, Fusarium and Alternaria. The phytotoxic effects, more often described by the symptoms they produce on plants than by their mode of action, range from inhibition of germination to inhibition of root and vegetative growth, including tissue and organ alterations. The biochemical characterization of fungal secondary metabolites requires expertise and tools to carry out fungal cultivation and metabolite extraction, phytotoxicity tests, purification and fractionation of the extracts, and chemical identification procedures. Phytotoxicity tests are mainly carried out under controlled laboratory conditions (not always on whole plants), while effectiveness against targeted weeds and environmental impacts must be assessed in greenhouses and open fields. These steps are necessary for the formulation of effective, environment‐friendly fungal secondary metabolites‐derived bioherbicides using new technologies such as nanomaterials.This article is protected by copyright. All rights reserved.

Scope and potential of herbicidal values of the fungal pathogens and its secondary metabolites for sustainable weed management

“…Most of the phytotoxic fungal toxins belong to the classes of terpenoids (Bipolaroxin, Chenopodolin, Ophiobolins, Prehelminthosporol), polyketides (Ascochytine, De-O-methyldiaporthin, Monocerin, Putaminoxin), nitrogenous metabolites (Ascosonchine, Cytochalasins, Fumonisin B 1 , Fusaric acid, β-nitropropionic acid, Tryptophol) and phenols and phenolic acids (Curvulin) (Xu et al 2021;Bendejacq-Seychelles et al 2024). The exploration for alternate ways of weed control resulted in the utilization of phytotoxic fungal toxins or sec-ondary metabolites, and they were regarded as one of the most efficacious and eco-friendly approaches to weed management (Evidente 2023;Bendejacq-Seychelles et al 2024). These phytotoxic fungal metabolites play a vital role in the biological control of weeds by causing chlorosis, necrosis, wilting, halting the germination of seeds and growth inhibition (Liu & Li 2004).…”

The future of microbial bioherbicides

“…The meeting was organized into twenty‐two 50‐min presentations with ample time for discussion. Sixteen of the articles in this issue are from conference participants 2–17 . Four related articles from non‐participants are also included 18–21 .…”

“…Bendejacq‐Seychelles et al 17 . review the many phytotoxins produced by plant pathogens and other microbes as potential natural herbicides or as leads for semi‐synthetic or synthetic herbicides.…”