Tolerance to Oxidative Stress is Associated with Both Oxidative Stress Response and Inherent Growth in a Fungal Wheat Pathogen

Reactive oxygen species are toxic byproducts of aerobic respiration that are also important in mediating a diversity of cellular functions. Reactive oxygen species form an important component of plant defenses to inhibit microbial pathogens during pathogen-plant interactions. Tolerance to oxidative stress is likely to make a significant contribution to the viability and pathogenicity of plant pathogens, but the complex network of oxidative stress responses hinders identification of the genes contributing to this trait. Here, we employed a forward genetic approach to investigate the genetic architecture of oxidative stress tolerance in the fungal wheat pathogen Zymoseptoria tritici. We used quantitative trait locus (QTL) mapping of growth and melanization under axenic conditions in two cross-populations to identify genomic regions associated with tolerance to oxidative stress. We found that QTLs associated with growth under oxidative stress as well as inherent growth can affect oxidative stress tolerance, and we identified two uncharacterized genes in a major QTL associated with this trait. Our data suggest that melanization does not affect tolerance to oxidative stress, which differs from what was found for animal pathogens. This study provides a whole-genome perspective on the genetic basis of oxidative stress tolerance in a plant pathogen.