Agricultural herbicides and fungi in soil exposed to herbicides

Abstract

Agriculture is one of the bases of worldwide economy. In recent decades, the use of genetically modified crops caused a continuous increase in pesticide and fertilizer application. In productive countries, the adoption of these products together with other technologies allowed the maximization of world crop production with great economic benefits. Herbicides represent about 40–60% of the total pesticides used in the agricultural environment. Several herbicides are used for control of weeds worldwide, glyphosate being one of the most common. The excessive use of this product has resulted in the emergence of tolerant weeds, thus a wider variety of herbicides are being used, such has clodinafop propargyl, atrazine, and 2,4 dichlorophenoxyacetic acid among others. Because of the potential negative effects of these chemicals on the soil ecosystem and public health, the application of herbicides has become a matter of great concern by the regulatory organisation. The extensive incorporation of herbicides in this ecosystem involves an important impact on the natural microbiota. Herbicides interact with target and non‐target organisms, so they could damage the ecosystem and also they can enter the food chain. Microbial degradation is the most frequent mechanism implied in the destruction of these contaminants. In this process, fungal species have a great participation in xenobiotocs dissipation. They present propitiate metabolic characteristics in bioremediation due to their mycelia growth, rapid colonization of solid substrates and enzymatic capacity. In addition, these microorganisms have a great tolerance to pollutants and unfavorable environmental conditions. Fungal genera such as Cladosporium spp., Fusarium spp., Mucor spp., Penicillium spp., Aspergillus spp., Trichoderma spp., and Saccharomyces spp. have shown the ability to degrade herbicides. They are capable of producing several hydrolytic enzymes during their development, resulting in significant pesticides disipation rates. Recently, this aspect has focused on the development of harmless bioremediation strategies. The present chapter presents information about the toxicity of the main herbicides used in agriculture and also about the tolerance and degradation of them by fungal species.