Identification of novel QTLs for resistance to late leaf spot in peanut by SNP array and QTL-seq

Abstract

Late leaf spot (LLS) is one of important diseases that causes severe yield losses in peanut. Peanut has various sources of resistance to LLS, and the identification of resistant QTLs and the development of related molecular markers are of great importance for breeding of LLS-resistant peanut. In this study, 173 individual lines of a recombinant inbred line (RIL) population and 48K SNP array for genotyping were used to construct a high-density genetic map with 1475 SNP marker and 20 linkage groups. A total of 11 QTLs were obtained through QTL analysis using the constructed genetic map. Among them, a stable major QTL qLLS.LG02 was identified on linkage group 2 in all six environments, with a phenotypic variation explained (PVE) ranging from 15.57 to 31.09%. Additionally, QTL-seq technology was also employed for QTL analysis of LLS resistance. As a result, 14 QTL loci related to LLS resistance were identified using the G prime algorithm. Notably, physical position of qLLS02 and qLLS03 are coincided with that of qLLS.LG02 and qLLS.LG03 respectively. Gene annotation analysis within the 14 QTL intervals by QTL-seq revealed that there were a total of 163 NBS-LRR disease resistance genes, accounting for 22.86% of all R genes in peanut genome and showing a 4.26-fold enrichment with a p-value of 5.19e-57. Within the QTL region qLLS02 of the resistant parent Mi-2, there was a 5 Mb structural variation interval (SV) containing 81 NBS-LRR genes. A PCR diagnostic marker was developed, and validation data suggest that this SV might lead to gene deletion or replacement with other genes. This SV has the potential to enhance peanut resistance to late leaf spot disease. This study holds significant implications for improving peanut breeding for LLS resistance through development of associated molecular markers.