Identification And Utilization Of QTL-qRgls1.06 For Resistance To Gray Leaf Spot In Maize

Maize gray leaf spot（GLS）is a global leaf fungal disease which seriously damages maize production.Utilization of GLS-resistant hybrids is the most cost-effective and environmentally friendly method for controlling GLS.Therefore,identifying the loci for GLS resistance is an important prerequisite for genetic improvement of GLS resistance by molecular breeding.In this study,the mapping population from resistant parent WGR and susceptible parent DZ01 were used to identify GLS resistance locus,and GLS resistance of elite lines was improved by marker-assisted selection（MAS）.The main results are shown as follows:1. Identification of a major resistance QTL-qRgls1.06 to GLS in maize.A BC₁F₁mapping population was developed by the crossing WGR（resistant line）to DZ01（susceptible line）with DZ01 as a recurrent parent.The Chi-square test showed that the resistance to GLS was controlled by one dominant locus（p=0.7117）.Moreover,a major resistance locus,named qRgls1.06 was mapped on the bin1.06 of the chromosome 1 in maize,which explained 55.77%of phenotypic variation,through bulked segregant analysis（BSA）and genetic linkage mapping.2. Fine mapping of qRgls1.06.A total of 61 recombinant individuals were detected from BC₁F₁individuals,and qRgls1.06 was then mapped within a 6.02 Mb interval flanked by M3 and M5 through the phenotype evaluation.In addition,95 recombinant individuals,which occurred crossover within the M3-M5 interval,were identified in a BC₂F₁population,and qRgls1.06 was then fine mapped into a 2.38 Mb region flanked by M13 and M4.Within the region of the B73 Ref Gen＿v4.0,five wall-associated kinase genes related to disease resistance were annotated in qRgls1.06.3. qRgls1.06 is an available locus for resistance improvement of gray leaf spot.Two genotypes qRgls1.06^WGR/WGRand qRgls1.06^DZ01/DZ01were identified from segregating population BC₃F₂.The results of phenotype evaluation showed that both qRgls1.06^WGR/WGRand qRgls1.06^DZ01/DZ01showed a significant difference in hundred-grain weight（HGW）(p=4.46×10^-5),but not in agriculturally important traits,such as flowering time and grain yield-related traits,suggesting that qRgls1.06^WGR/WGRreduced the yield loss by decreasing hundred-grain weight of plants exposed to Cercospora zeina.The resistant inbred line WGR was used as the donor of qRgls1.06 to introduce the qRgls1.06^WGRallele into 7 elite inbred lines through marker-assisted selection（MAS）,and showed the introduction of qRgls1.06^WGRcould significantly improve the resistance of the recipient lines to GLS.This result not only effectively proved the important application value of qRgls1.06,but also provided molecular makers and intermediate materials for the genetic improvement of resistance to GLS in maize.