Genetic architecture of disease resistance and tolerance in Douglas-fir trees

<b>Abstract</b><br/><p class="MsoNormal"><span lang="EN-CA">Understanding the genetic architecture of tolerance and resistance to pathogens is important to monitor and maintain resilient tree populations. Here we investigate the genetic basis of tolerance and resistance to needle cast disease in Douglas-fir (<em>Pseudotsuga menziesii</em>) caused by two fungal pathogens: Swiss needle cast (SNC) caused by <em>Nothophaeocryptopus gaeumannii</em>, and Rhabdocline needle cast (RNC) caused by <em>Rhabdocline pseudotsugae</em>). We performed a case-control genome-wide association analysis (GWA) and found these traits to be polygenic and under selection.</span> <span lang="EN-CA">We showed that stomatal regulation as well as ethylene and jasmonic acid pathways are important for resisting SNC infection and secondary metabolite pathways play a role in tolerating SNC once the plant is infected. We identified a key upstream transcription factor of plant defence, ERF1, as the main candidate for RNC resistance. Our findings contribute to the understanding of the highly polygenic architectures underlying disease resistance and tolerance in Douglas-fir and have important implications for forestry and conservation as the climate changes.</span></p>