Speaker: Shunyuan Xiao, Professor, University of Maryland

Plants have evolved effective immune mechanisms to fight off various (potential) pathogens. The complete resistance of all genotypes of a plant species against any non-adapted pathogens is defined as non-host resistance (NHR). A prime example of NHR is rice's immunity against all rust and powdery mildew fungi. Because NHR is robust and durable, its potential application in improving resistance against adapted pathogens in crops has long been envisioned. However, this potential has not been explored because the molecular basis of NHR remains poorly characterized due to its high genetic complexity and lack of intraspecific genetic variation. To genetically dissect NHR, a combinatory approach that includes stepwise forward and reverse genetic screens has been taken to break down NHR of Arabidopsis against non-adapted and evolutionarily distant powdery mildew species. Our recent efforts have led to the identification of several novel immunity genes that contribute to NHR at both penetration and post-penetration stages. A higher-order Arabidopsis mutant fully susceptible to barley and powdery mildew has been obtained and used for screening mutants susceptible to rust pathogens. Similar research is being conducted in rice and wheat through collaborations. A complete dissection of NHR may improve our understanding of the multi-layered plant immune system and inspire novel strategies to boost crop resistance against adapted pathogens.