Mapping genomic regions associated with temperature stress in the wheat pathogen Zymoseptoria tritici

Climate change can alter interactions between plants and their pathogens, which could adversely affect crop production. To better understand the molecular mechanisms underlying the responses of pathogenic fungal to temperature stress, we conducted a quantitative trait loci (QTL) mapping study in the wheat pathogen Zymoseptoria tritici to identify genomic regions associated with colony growth and melanisation at three temperatures (100C, 180C, 270C). We then identified likely candidate genes for thermal adaptation within these intervals by combining information regarding gene function, GO annotation enrichment, transcriptional profile, and results from previous genome wide association studies (GWAS) investigating responses to climate, temperature and thermal adaptation. The QTL mapping, conducted for two separate crosses involving four Swiss parents, found significant QTL uniquely associated with traits measured in high and low temperatures. These intervals contained many genes known to regulate responses to temperature stress, including heat shock proteins (HSPs) and proteins involved in the mitogen-activated protein kinase (MAPK) pathways, and were enriched for genes with a zinc ion binding GO annotation. We highlight the most promising candidate genes for thermal adaptation, including an ammonium transporter gene, a stress response factor (Whi1) and two MAPK pathway genes - SSk2 and Opy2. Future validation work on these candidate genes could provide novel insight into the molecular mechanisms underlying temperature adaptation in this important wheat pathogen.