Genetic mapping of trait plasticity in a plant pathogenic fungus reveals genetic architecture and candidate genes for plasticity

Understanding how plant pathogens respond to environmental change is needed to better manage plant diseases. Phenotypic plasticity, the ability of a single genotype to produce different phenotypes across different environments, can influence pathogen adaptation and host-pathogen dynamics. Few studies have investigated the mechanisms underlying phenotypic plasticity in plant pathogens. Here we used phenotypic and genotypic data collected over >15 years and across multiple environments to perform genetic mapping of plasticity traits in the wheat pathogen Zymoseptoria tritici . Most (75%) of the QTL for plasticity (plQTL) overlapped with their corresponding mean QTL (mnQTL), suggesting that plasticity is controlled mainly by pleiotropic genes or tightly linked genes. 25% of the plQTL mapped to genomic locations separate from the mnQTL, suggesting that plasticity in these cases results from epistasis between unlinked loci. In several cases plasticity measured across different environmental gradients mapped to the same genomic positions, suggesting a shared control of plasticity for unrelated factors. These cases of shared control could be due to master regulators of plasticity or gene clusters. This mapping study provides unprecedented insights into the genetic architecture of plasticity in fungal plant pathogens.