Genetic Analysis And Fine Mapping Of A Major QTL For Resistance To Gray Leaf Spot In Maize

Gray leaf spot?GLS?,caused by the Cercospora,is a relatively serious maize leaf disease in production,and the degree of threat has even exceeded that of maize leaf spot,which occurs in corn planting areas around the world.To explore resistance to gray leaf spot for resistance materials and disease resistance genes,and applied to the breeding of resistant varieties would provide a cost-effective mean of controlling GLS.In this study,Qi319 and the level of resistance to the GLS of 10 maize inbred lines were used to produce F₁,and a highly resistance inbred lines Qi319 and susceptible inbred lines Dan340,Longkang11 were used to produce segregating population for inheritance of resistance to gray leaf spot by using artificial inoculation identification method.QTL verification through segment substitutions constructed by the research group,and a large-scale F₂ population constructed with 1218 and 81162 were used for gene mapping to discover major QTL loci.Then,a major QTL were finely mapped by screening for recombinants.The following results for this study:The results showed that the incidence of gray leaf spot of the hybrid would be significant reduced when the Qi319 as a resistant parent in addition to cross with high susceptible inbred lines,the level of resistance to the GLS was increased to the middle level.The segregation analysis of single separate generation was adopted to study the genetic laws of GLS,the result showed that parents Qi319 and Longkang11 were in accordance with the B-2 model,namely two pairs of major genes with additive-dominant effects.The parents Qi319 and Longkang11 were in accordance with the B-1 model,namely two pairs of major genes with additive-dominant-epistatic effects.Qi319 was used to produce population,it could show two pairs of major resistance genes in different genetic background,but Qi319could show a higher genetic rate of the main gene in the background of the parent LongKang11.Based on the background test results,selected family 1218 with higher background recovery and disease resistance,and obtained the segregation group are crossed with 81162,used for QTL positioning.Using QTL IciMapping V4.1 software and the complete interval mapping method,the primary QTL for chromosome 1 was located between umc1243 and SYLY₂9,the physical distance was 4.47 Mb,and the interpretable phenotypic variation rate was 25.69%.According to the physical map of B73 RefGen-v2,76 pairs of SSR primers were designed and developed in the initial positioning interval,and 8 pairs of primers with polymorphism were screened in the segregation group.A total of 938 high-resistance and124 high-inducted single plants were screened for recombinants and a total of 26recombinants were found.The main effect QTL range for anti-foliar disease was fine-mapped between the markers snym147-SYLY₂9.The physical positions of the two markers were 86945778bp-87994753bp,and the physical distance was 1.04Mb.By identifying the main QTL in the chromosome 1 of the disease-resistant material1218,it was explored to provide a theoretical reference for the breeding and functional analysis of the resistance to the grey leaf spot disease gene.Combining maize molecular marker-assisted selection breeding,accelerated the breeding of maize gray leaf spot resistance.