Title : Exploitation of fungal biodiversity to control weeds with mycoherbicides: An alternative to chemical herbicides
Abstract:
In the past few decades, the control of pests, weeds and diseases of cultivated plants using biocontrol agents has drawn increasing attention in the quest to reduce the level of dependence on chemical products for agriculture production.Weeds are the most severe and wide spread biological constraints to crop production and cause visible and invisible damage till the crop is harvested. Weeds are a problem in crop production associated with declines in crop yields and quality, as a source of allergenic pollen and as an aesthetic nuisance. Biological control agents, especially phytopathogenic fungi (i.e., fungi causing disease in plants), offer a tremendous opportunity to provide agriculture with effective tools for abandoned crop production while minimizing impacts on human health, plant health and the environment. The number and different kinds of life i.e., animals, plants, fungi, bacteria and other microorganisms, that make up our natural world is called biological diversity or biodiversity (bio = life +diversity = variety). Fungal biodiversity refers to variety and of fungi on earth. Fungi are among the most widely distributed organisms on earth and grow in a wide variety of aerobic habitats, including extreme such as deserts or areas with high salt concentrations, acidic, low- moisture, or ionizing radiation and in deep sea sediments. They show an enormous diversity of taxa with varied ecologies, life cycle strategies, producing a variety of asexual spores, sexual spores, and morphologies. The global diversity of fungi is not fully known. As per the current estimates, the kingdom Fungi contains between 2 and 12 million fungal species, but the number of described species globally is 1,50,000, a tiny fraction of the total. Over 19,000 fungi are known to be phytopathogenic, i.e., cause diseases in crop plants, worldwide. Biological weed control strategies with live plant pathogens are classified as: classical (or inoculative) and inundative (or bioherbicidal or mass exposer). The inoculative biocontrol strategy involves the import and release of one or more natural enemies which attack the target weed in its native ranges, into areas where the weed is introduced and is troublesome; and where natural enemies are absent. The bioherbicidal strategy involves the deliberate use of mass-produced selected microorganisms to suppress the growth/reduce the population of a weed species. The formulations of host-specific plant pathogenic microorganisms, such as fungi, bacteria and viruses, that are applied at high inoculum rates in a similar way as chemical herbicides used to control/manage weeds are called bioherbicides. In the majority of the bioherbicides, the fungal organisms are the active ingredients, therefore the term mycoherbicide has often been used interchangeably with bioherbicides. Widely, mycoherbicides are most effective for weed management in annual cropping systems. The development of a phytopathogenic fungus into a mycoherbicide involves three basic phases: discovery, development and deployment. Fungi have been preferred as mycoherbicides because they have all the desirable features for their development as bioherbicides, such as host-specificity; easy identification and easy mass culturing on artificial media; possess high levels of virulence and natural distribution mechanisms; efficacious under different environmental conditions; long shelf-life; genetically stable; and pose no risk to human health and environment. The number and different kinds of life i.e., animals, plants, fungi, bacteria and other microorganisms, that make up our natural world is called biological diversity or biodiversity (bio-means life and diversity means variety). Fungal biodiversity means variety and variability of fungi on earth. Fungi are among the most widely distributed organisms on earth and grow in a wide variety of aerobic habitats, including extreme environments such as deserts or areas with high salt concentrations, acidic, low- moisture, or ionizing radiation and in deep sea sediments. They show an enormous diversity of taxa with varied ecologies, life cycle strategies, producing a variety of asexual spores and sexual spores, and morphologies. However, the global biodiversity of the fungal kingdom is not fully known. It has been estimated that the kingdom Fungi contains 12 million fungal species. As of 2023, around 1,50,000 species have been described by the taxonomists globally. Over 19,000 fungi are known to cause diseases in crop plants worldwide. Several selected fungal pathogens have been extensively evaluated since 1970s and developed or are under development for commercial application. The number of reports on bioherbicide research has increased tremendously since the early discovery of two commercial mycoherbicides, such as DeVine(R), a liquid formulation of Phytophthora palmivora in the year 1981 to control Milkweed vine (Morrenia odorata); and CollegoTM a wettable powder formulation of Colletotrichum gloeosporioides f. sp. aeschynomene in the year 1982 for controlling Northern joint vetch (Aeschynomene virginica) Both the number of weeds targeted for control and the number of candidate pathogens studied have increased. Practical registered or unregistered uses of bioherbicides have also increased worldwide. Likewise, the number of US patents issued for the bioherbicidal use of fungi and the technologies have increased, perhaps foretelling an increased reliance on bioherbicides in the future. Globally, over 24 bioherbicides have been registered, most of these are based on hemi-biotrophic fungi, in which the biotrophic phase provides high-host-specific city and the necrotrophic phase causing extensive tissue death. Currently, DeVine, Collego, BioMal, Woad Warrior, Chontrol, Smolder and Sarritor are available in the market. The market share of bioherbicides is merely 10 percent of all biopesticides. Considering the rich fungal biodiversity there are good prospects for discovering and developing fungi as mycoherbicides for many types of weeds. For successful deployment of mycoherbicides into agriculture production system, the need of the hour is: to search for native highly virulent pathogenic stains, especially hemi-biotrophic in nature, in the unexplored areas; Better understanding of mode of action of mycoherbicides involved in the host-pathogen interactions; Improvement of fermentation, formulation and application technology, the three major constrains in the success of a mycoherbicide; Strong cooperation among the researchers, manufactures, growers (farmers) and the funding agencies: Use of dual and multiple pathogens in consortia to optimize weed control effectiveness; The integration of mycoherbicides with other weed management tools (e.g. chemical herbicides, cultural practices).
What will audience learn from your presentation?
- Help the audience to know how to develop a phytopathogens fungus into a commercial mycoherbicides
- Strengthen the knowledge of researchers regarding the strategies being used
to control weeds by biocontrol agents - Would help the audience to know why fungi are being preferred as
bioherbicides - Boost interest in this area of research for getting organic foods
