Fungicide Resistance in Powdery Mildew Fungi

Abstract

Powdery mildew fungi (Erysiphales) are among the most common and important plant fungal pathogens. These fungi are obligate biotrophic parasites that attack nearly 10,000 species of angiosperms, including major crops, such as cereals and grapes. Although cultural and biological practices may reduce the risk of infection by powdery mildew, they do not provide sufficient protection. Therefore, in practice, chemical control, including the use of fungicides from multiple chemical groups, is the most effective tool for managing powdery mildew. Unfortunately, the risk of resistance development is high because typical spray programs include multiple applications per season. In addition, some of the most economically destructive species of powdery mildew fungi are considered to be high-risk pathogens and are able to develop resistance to several chemical classes within a few years. This situation has decreased the efficacy of the major fungicide classes, such as sterol demethylation inhibitors, quinone outside inhibitors and succinate dehydrogenase inhibitors, that are employed against powdery mildews. In this review, we present cases of reduction in sensitivity, development of resistance and failure of control by fungicides that have been or are being used to manage powdery mildew. In addition, the molecular mechanisms underlying resistance to fungicides are also outlined. Finally, a number of recommendations are provided to decrease the probability of resistance development when fungicides are employed.

Examination of gene loss in the DNA mismatch repair pathway and its mutational consequences in a fungal phylum

“…Previous studies of genome structure in E. necator have found genome expansion largely driven by transposable elements and suggest that genome instability, particularly in copy number variants, can mediate rapid evolution of fungicidal resistance (Jones et al 2014). The evolution of fungicide resistance in powdery mildews has massive implications for agriculture; major crops are impacted by these pathogens and some are able to quickly evolve resistance to antifungal chemicals, with resistance evolution accelerated by increased use (Jones et al 2014;Vielba-Fernández et al 2020). More broadly, genome instability among HLT taxa reflects their parasitic lifestyle, which is associated with gene loss and plastic genomic architecture (Schmidt & Panstruga 2011).…”

Grapevine Powdery Mildew: Fungicides for Its Management and Advances in Molecular Detection of Markers Associated with Resistance

“…A detailed overview of fungicides used against powdery mildews in different crop systems has been published recently [ 23 ]; here we will shortly describe those applied specifically for E. necator management. Currently, more than 20 fungicides belonging to different chemical classes are registered in the EU for powdery mildew management in vineyards ( Table 1 ).…”

“…Only two years after their introduction in practice, field resistance was detected in multiple pathogens [ 38 ]. Currently, resistance to MBC was described in more than 100 fungal species, including different powdery mildew species [ 23 , 39 ]. A variety of single point mutations in the β-tubulin gene were described in laboratory-induced and field mutants, but the most important are E198A/G/K/Q and F200Y [ 39 ].…”

“…Moreover, proquinazid induced the expression of Arabidopsis thaliana genes associated with resistance responses such as ethylene-mediated response pathway, phytoalexin biosynthesis, ROS generation, and induction of pathogenesis-related genes [ 49 ]. Gene-expression analysis of several genes involved in signal transduction evidenced differences in the mode of action between quinoxyfen and proquinazid, which indicates that, even though both interfere with signal transduction, their molecular targets might be different [ 23 , 74 ]. Erysiphe necator isolates collected in Europe, South Africa [ 75 ], and the US [ 76 , 77 ], with lower sensitivity to quinoxyfen were described, and a strong correlation ( r = 0.874) between the sensitivity to proquinazid and quinoxyfen was observed [ 49 ].…”

Genome-wide characterization of the MLO gene family in Cannabis sativa reveals two genes as strong candidates for powdery mildew susceptibility

“…However, a scarce amount of such products are currently approved by Health Canada as the presence of fungicide residues in the inflorescences raises concerns (Punja, 2021). Besides, they are costly, and fungicide resistance in PM has been observed and documented in other plant species in recent years (Vielba-Fernández et al, 2020). Alternative approaches to managing this disease have been described, such as the use of biological control (e.g., Bacillus subtilis strain QST 713), reduced risk products (e.g., potassium bicarbonate, knotweed extract), and physical methods (e.g., deleafing, irradiation) (Punja, 2021).…”