Resisting the Resistance-Mechanism, Evolution, and Management Strategies for Resistance Development in Phytopathogenic Fungi to Azole Fungicides

Climate change presents considerable challenges to international food reassurance and protection, not only by affecting productivity of crops but also by promoting situations that support the appearance and development of devastating fungal phytopathogens. Plant diseases incited by these pathogens have factually led to disastrous food shortages such as the Potato Famine (1845) in Ireland and the infamous Bengal Famine (1943), accentuating their overwhelming impact. Today, fungal phytopathogens remain the reason for extensive pre- and post-harvest losses in agricultural produce and contamination of food and feed through production of mycotoxins. To combat such menaces, a number of chemical fungicidal molecules have been developed, extending from primary use of sulfur, lime and copper (as Bordeaux mixture) to contemporary systemic agents like azoles. However, the extensive and recurrent use of antimycotics, particularly those with single-site approaches of action, has headed to the quick advent of fungal strains that were fungicide-resistant. Azoles, the most generally used systemic antifungals, impede sterol 14α-demethylase (CYP51), a vital enzyme in biosynthesis of ergosterol. Resistance to these compounds arises through heritable mutations that moderate binding efficacy of fungicide, posing a greater threat to the effectivity of chemical means of plant disease management. The development of resistance is affected by mode of action of fungicide, frequency of its use, factors related to environment, and the inherent flexibility of fungal populaces. Resistance among fungal plant pathogens to prevailing azole fungicides may lead to augmented severity of disease, reduction in yield and quality of the produce, resulting in monetary losses to the farmers. The present review highlights the mechanism of resistance to fungicides, monitoring of resistance, risk assessment, and resistance management strategies for azole fungicides.