RESEARCH-PGR: Exploring the genetic and mechanistic bases of quantitative disease resistance in maize

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Plant diseases cause an estimated 13% loss of global crop yields annually, reducing incomes and food quality/safety. Host resistance is the most effective method of managing plant diseases. Quantitative disease resistance is generally durable and usually works against all variants of pathogens, and thus is an effective disease management tool. This proposal aims to improve the understanding of quantitative disease resistance at multiple levels, from genes to tradeoffs at the whole plant level. The research will focus on some of the most important diseases of corn. The broader impacts of this proposal are twofold. First, the proposed research will identify disease resistance mechanisms in corn, which is both a model species for plant quantitative genetics and the most valuable crop in the US. These results directly relate to ongoing genetic improvement of corn and other important crop species. The second impact is through training of students and postdoctoral scholars during research activities and the education of high school students and teachers during outreach activities. This includes working with a specialist educational organization, The Science House at North Carolina State University. North Carolina State University will participate in and provide funds to continue and update a successful plant breeding and genetics workshop for science teachers that has run annually from 2013 to 2019, as well as participate in a residential Ag-Discovery camp for high school students. In addition, the researchers will engage high school students through the 4-H Illini Summer Academy and Discovering STEM in ACES at the University of Illinois. Quantitative disease resistance (QDR) is the most important form of resistance for maize and crops more broadly. Prior work by this research team and others has shown that QDR is based on diverse genes and mechanisms, most of which are not yet understood. Several quantitative trait loci and genes associated with resistance to multiple maize diseases have been previously identified and characterized. To further dissect disease resistance, as well as other traits, a large population of near-isogenic lines (NILs) has been developed and evaluated for resistance to several diseases. This proposal aims to exploit and develop these data and resources to expand the understanding of QDR and focuses on the following four objectives: 1) develop the NIL population as a resource for the maize genetics community; 2) study QDR, its mechanistic bases, and associated pleiotropies; 3) study the mechanistic bases of vascular disease resistance in maize using microscopy; and 4) identify QDR causal genes using fine mapping and gene editing. This effort will use an integrative approach incorporating genetics, genomics, transcriptomics, histology, pathology/microbiology, quantitative genetics, field research, and CRISPR- mediated gene-editing. Successful completion of this project is expected to result in the identification of key genes, mechanisms and tradeoffs that can inform the deployment of quantitative disease resistance in crops. Since many of the mechanisms under investigation in maize are likely to be broadly applicable, the proposed work will ultimately contribute to a holistic understanding of QDR with a focus on its application to improved crop production and resilience.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.