QTL Mapping of Fusarium Ear Rot Resistance in Maize

Ear rot is a globally prevalent class of disease in maize, of which Fusarium ear rot (FER), caused by the fungal pathogen Fusarium verticillioides, is the most commonly reported. In this study, three F₂ populations, namely F₂-C, F₂-D, and F₂-J, and their corresponding F_2:3 families were produced by crossing three highly FER-resistant inbred lines, Cheng351, Dan598, and JiV203, with the same susceptible line, ZW18, for quantitative trait locus (QTL) mapping of FER resistance. The individual crop plants were inoculated with a spore suspension of the pathogen injected into the kernels of the maize ears. The broad-sense heritability (H) for FER resistance was estimated to be as high as 0.76, 0.81, and 0.78 in F₂-C, F₂-D, and F₂-J, respectively, indicating that genetic factors played a key role in the phenotypic variation. We detected a total of 20 FER-resistant QTLs in the three F₂ populations, among which QTLs derived from the resistant parent Cheng351, Dan598, and JiV203 explained 62.89 to 82.25%, 43.19 to 61.51%, and 54.70 to 75.77% of the phenotypic variation, respectively. Among all FER-resistant QTLs detected, qRfer1, qRfer10, and qRfer17 accounted for the phenotypic variation as high as 26.58 to 43.36%, 11.76 to 18.02%, and 12.02 to 21.81%, respectively. Furthermore, QTLs mapped in different F₂ populations showed some extent of overlaps indicating potential resistance hotspots. The FER-resistant QTLs detected in this study can be explored as useful candidates to improve FER resistance in maize by introducing these QTLs into susceptible maize inbred lines via molecular marker-assisted selection.