The Foliar Fungal Pathogenic Metabolites as Promising Alternatives to Chemical Herbicides: Recent Developments, Future Perspective and Commercialization

Weeds harbour wide variety of microorganisms having beneficial, neutral and phytopathogenic effects. Weed microbiome discoveries could fuel progress in sustainable agriculture, such as the development of microbial herbicide products. Weed infecting phytopathogenic living fungal cells (mycelia or spores) and their natural products have been studied as producers of mycoherbicides. The application of biological and biochemical (natural or biorational) herbicides based on specific weed pathogens and natural products, respectively, is believed to assist the decreasing harmful impact of the chemicals. Cell free broth of several plant pathogenic fungi have been enthusiastically investigated for substitutes of synthetic agrochemicals against weeds. However, all such studies conducted on pure compound with high purity which have limitations due to high costs. It was found that herbicide in cell-free culture broth of fungi were largely composed of various nature of different metabolites with the ratio varying with culture time. Crude broth in a form of cell-free culture broth showed high herbicidal activity against weeds. So, cell-free culture broth as a crude product could be serve as a potential cost-effective and environmental-friendly herbicide in agriculture. The application of mycometabolites in agricultural weed management are safer to the user and the environment. They were formulated and applied in the same manner as chemical herbicides. This review aims at summarizing the studies on the application of mycometabolites as a lucrative, novel source of secondary herbicidal compounds for management of weeds. More effort should be expended in this area of research in the future, despite the obstacles that exist.