Quantitative trait locus mapping of osmotic stress response in the wheat pathogen Zymoseptoria tritici

Osmotic stress is a ubiquitous and potent stress for all living organisms, but few studies have investigated the genetic basis of salt tolerance in filamentous fungi. The main aim of this study was to identify regions of the genome associated with tolerance to potassium chloride in the wheat pathogen Zymoseptoria tritici. A secondary aim was to identify candidate genes affecting salt tolerance within the most promising chromosomal regions. We achieved these aims with a quantitative trait locus (QTL) mapping study using offspring from two crosses grown in vitro in the presence or absence of osmotic stress imposed by 0.75M KCl. We identified significant QTL for most of the traits in both crosses. Several QTL overlapped with QTL identified in earlier studies for other traits and some QTL explained trait variation in both the control and salt stress environments. A significant QTL on chromosome 3 explained variation in colony radius at 8 days post inoculation (dpi) in the KCl environment as well as colony radius KCl tolerance at 8 dpi. The QTL peak had a high LOD and encompassed an interval containing only 36 genes. Six of these genes present promising candidates for functional analyses. A GO enrichment analysis of QTL unique to the KCl environment found evidence for enrichment of functions involved in osmotic stress responses.