Fungicides resistance: implications on biological process of pathogens populations

Abstract

Wheat blast, caused by Pyricularia oryzae pathotype Triticum (PoTl), is one of the most important and devastating fungal diseases affecting wheat crops in South America, Southeast Asia, Southern Africa and now in Germany and in central Europe. In Brazil, PoTl populations have been associated with resistance to three different chemical groups, including quinone outside inhibitor fungicides (QoIs), demethylation inhibitor fungicides (DMIs), and succinate dehydrogenase inhibitors fungicides (SDHIs). In the first chapter, we discuss a review of the mechanisms underlying fungicide resistance in crop pathogens, with a specific emphasis on point mutations and non-target site mechanisms associated with different fungicide classes. With the increasing use of fungicides in agriculture, the rapid emergence and evolution of fungicide resistance have become a critical issue, posing significant challenges to sustainable crop production. Our review sheds light on non-synonymous mutations in the target genes of fungicides, target gene overexpression, and efflux pump upregulation, and how these mechanisms affect the QoI fungicides, methyl-benzimidazole (MBCs), DMI and SDHI fungicides. In the second chapter, we present the result of that QoI-R PoTl isolate maintaining an adaptive advantage in disease severity on leaves and heads over time. For the QoI-R PoTl isolate, the nonlinear logistic model exhibits a better fit to the progress curves of wheat blast over the course of five successive infection cycles. In the third chapter, the results of this study demonstrate that the QoI-R PoTl isolate maintains higher fitness and competitive advantages over time. Based on molecular studies, the G143A mutation was found in 100% of the QoI-resistant isolates, indicating that the G143A mutation of the QoI-R PoTl isolates remains stable. These findings can have significant implications for the integrated management of the wheat blast pathosystem since fitness advantages stability can contribute to fixing and increasing the proportion of resistant isolates in field populations of the pathogen. Hence, resistant genotypes of the PoTl populations with fitness advantages may prevail on wheat fields, even after successive infection cycles in the absence of selection pressure, and QoIs may lose their efficacy permanently. We discuss the ecological importance of populations of pathogens that have evolutionary advantages, higher fitness, and resistance to QoIs stable. We hope our results can help insights into the integrated management of wheat blast in Brazilian wheat fields.