Fine Mapping Of Major QTLs For Resistance To Head Smut In Maize Inbred Line T32

Maize head smut（HS）is a world-class fungal disease caused by the fungus smut,which seriously endangers the healthy development of the corn industry.In maize production,planting disease-resistant varieties can effectively prevent the widespread occurrence of this disease.In the early stage of this research group,we used the high-resistance maize head smut inbred line T32 and the maize head smut-susceptible inbred line Huang C with the F_2:3population to locate the head smut resistance QTL to the marker umc1006-nc013 on the 6th chromosome of maize,and can be stably expressed in 3 sites,so this QTL will be further studied by fine mapping.Based on the results of the previous study,the T32 selbred as the donor parent and the susceptible selfer Huang C as the recurrent parent,and the BC₄F₂backcrossing population was constructed by F₁backcrossing C 4 generation of T32Huang C and selfing,supplemented by molecular marker-assisted selection and genetic background screening.Fine mapping of QTL-q HS6 on chromosome 6 using populations of near-isogenic line NILs,the results are as follows:（1）Using 180 individual plants of the BC₄F₂-Hua Xi population,the QTL-q HS6locus of chromosome 6 resistance to maize head smut was mapped.QTL-q HS6 was further mapped between the markers umc1857-mmc0523 by combining the pre-positioned markers with the published SSR markers with polymorphisms,and the physical distance between the markers was 5236 kb.（2）By downloading the sequence of the target segment and designing SSR primers,a total of 5 pairs of primers with polymorphisms were obtained,and QTL-q HS6 was mapped using Join Map 4.0 and QTL-Icimapping software.Among180 individuals in the BC₄F₂-Hua Xi population,QTL-q HS6 was further mapped between markers umc1857-Zm31,with a physical distance of 343 kb between markers.Among 1543 individuals of the BC₄F₂population,QTL-q HS6 was fine-mapped between markers umc1857-Zm31.The results of localization analysis were further verified by the exchange of BC₄F₂-Hua Xi population and BC₄F₂population.Through the fine mapping of the major gene QTL-q HS6 for maize inbred line T32 resistance to maize head smut,8 candidate genes for controlling QTL-q HS6 were obtained,which will be verified in subsequent experiments.It is expected to provide a new theoretical reference for the breeding practice and molecular marker-assisted breeding of maize resistance to head smut,lay a foundation for subsequent gene cloning and functional verification and other related research,and accelerate the breeding process of maize resistance to head smut.