QTL mapping for late leaf spot and rust resistance using an improved genetic map and extensive phenotypic data on a recombinant inbred line population in peanut (Arachis hypogaea L.)

The linkage map for the recombinant inbred line (RIL) mapping population derived from late leaf spot (LLS) and rust disease susceptible (TAG 24) and resistant (GPBD 4) varieties of peanut was improved by adding 139 new SSR and transposable element (TE) markers. The improved map now has 289 mapped loci with a total map distance of 1730.8 cM and average inter-marker distance of 6.0 cM across 20 linkage groups. Quantitative trait loci (QTL) analysis using improved genetic map with 289 markers and comprehensive phenotypic data for LLS and rust from 11 seasons could identify a region on linkage group AhXV (B03 linkage group of B genome) which contributed significantly towards LLS and rust resistance. Of the five QTL mapped in this region, three showed high phenotypic variance explained (PVE) for both LLS and rust, and two QTL showed high PVE for only rust. The QTL flanked by GM2009-IPAHM103 had very high PVE of 44.5 % and 53.7 %, respectively for LLS and rust response. Another genomic region on AhXII (B10 linkage group of B genome) contained a QTL flanked by GM1839-GM1009 which had a PVE of 14.1–35.2 % for LLS resistance. A new QTL with marker interval GM1989-AhTE0839 on AhV (A05 linkage group of A genome) showed a PVE of 10.2 % for rust resistance. The new markers, AhTE0498 and AhTE0928 linked to rust resistance were validated using another RIL population of TG 26 × GPBD 4. The marker AhTE0498 showed 49.3–52.3 % PVE, indicating a strong marker validation in the new population. The improved map, QTL and markers for LLS and rust resistance reported in this study will be of immense utility in peanut molecular breeding.