Genetic Dissection of Resistance to Northern Corn Leaf Blight in a Large Commercial Maize Hybrid Population

Northern corn leaf blight (NCLB), caused by Setosphaeria turcica, is a major foliar disease of maize. To dissect the genetic basis of NCLB resistance in breeding-relevant germplasm, we evaluated NCLB severity in a panel of 500 commercial maize hybrids under natural disease pressure over a single growing season. High-throughput genotyping generated densely distributed SNP markers. The stratification of the panel into four major genetic subgroups, together with the relatively rapid LD decay (approximately 84.9 kb), indicated abundant genetic variation and favorable mapping resolution in the hybrid population. Phenotypic analysis revealed that most hybrids showed resistance or moderate resistance to NCLB. The broad-sense heritability of NCLB severity was estimated at 0.6588. Genome-wide association studies using the FarmCPU, BLINK, and MLMM models identified 17 consensus association signals, and four candidate genes were prioritized, including ZmCW1, CALS2, ZmCW2, and NCED8. A candidate gene-centered network identified 27 direct connections related to ZmCW1, CALS2, and ZmCW2. GO enrichment analysis showed that genes in these networks may regulate NCLB resistance through oxidative stress and redox-related processes. These results unravel the genetic architecture underlying NCLB resistance in commercial maize hybrids and nominate target loci for maize resistance breeding.