Introgression of ZmCPK39 in maize hybrids enhances resistance to gray leaf spot disease without compromising yield

Gray leaf spot (GLS) is one of the most damaging foliar diseases in maize. In previous research, we identified the ZmCPK39 gene, which confers resistance to GLS. This study demonstrates the utility of ZmCPK39 in breeding resistant maize varieties. Two parental lines of Zhengdan958 (the most widely cultivated hybrid in China), Chang7-2 and Zheng58, were selected for resistance improvement. These lines were crossed with Y32, a donor line high resistance to GLS, followed by six rounds of backcrossing to their respective recurrent parents. Foreground selection was performed in each generation to detect ZmCPK39, while background selection was conducted in the BC6F1 generations using a Maize 6 K DNA chip. The converted lines, Chang7-2ZmCPK39 and Zheng58ZmCPK39, with a recovery rate of 94.67-96.48%, were crossed to produce the improved hybrid Zhengdan958ZmCPK39. This hybrid exhibited enhanced GLS resistance and an 11.95% higher yield under severe disease stress, while maintaining comparable yield performance under normal growth conditions relative to the original Zhengdan958. This study highlights the breeding potential of ZmCPK39 for improving GLS resistance in maize.