Genetic basis of resistance to southern corn leaf blight in the maize multi-parent population and diversity panel.

Southern corn leaf blight (SLB), caused by the necrotrophic pathogen Cochliobolus heterostrophus, is one of maize foliar diseases and poses a great threat to corn production around the world. Identification of genetic variations underlying resistance to SLB is of paramount importance to maize yield and quality. Here, we used a Random-Open-parent Association Mapping (ROAM) population containing eight recombinant inbred line populations and one Association Mapping Panel (AMP) consisting of 513 diversity maize inbred lines with high-density genetic markers to dissect the genetic basis of SLB resistance. Overall, 109 quantitative trait loci (QTLs) with predominantly small or moderate additive effects, and little epistatic effects were identified. We found 35 (32.1%) novel loci in comparison with the reported QTLs. We revealed that resistant alleles were significantly enriched in tropical accessions and the frequency of about half of resistant alleles decreased during the adaptation process owing to the selection of agronomic traits. A large number of annotated genes located in the SLB resistant QTLs were shown to be involved in plant defense pathways. Integrating genome-wide association study (GWAS), transcriptomic profiling, resequencing and gene editing, we identified ZmFUT1 and MYBR92 as the putative genes responsible for the major QTLs for resistance to C. heterostrophus. Our results present a comprehensive insight on the genetic basis of SLB resistance and provide resistant loci or genes as direct targets for crop genetic improvement.