Genetic mapping reveals a major QTL associated with tolerance to the aphid, Uroleucon compositae (Theobald) in safflower ( Carthamus tinctorius )

Host plant resistance is an effective means of managing aphid pests in safflower but its genetic basis is not known. In this study, F 1 and F 6 ‐recombinant inbred lines (RILs) produced from the CO‐1 × EC‐523368‐2 cross were phenotyped for tolerance to the aphid, Uroleucon compositae based on days‐to‐wilt (DW) after infestation. The F 1 plants showed the dominance effect and RILs exhibited quantitative variation. The RIL population was genotyped with 242 simple sequence repeat (SSR) markers, which included a set of 150 new SSRs designed through next‐generation sequencing and bioinformatics approaches. Two quantitative trait loci (QTLs), QUc‐Ct3 . 1 and QUc‐Ct5.1 , putatively associated with DW after aphid infestation were detected. QUc‐Ct3 . 1 was a major QTL located on linkage group (LG) 3 with the closest marker SafM‐290 (LOD = 18.3), which explained 31.5% of the phenotypic variation. QUc‐Ct5.1 was a minor QTL located on LG‐5 with the closest marker CtDES‐237 (LOD = 7.0), which explained 9.1% of the phenotypic variation. This is the first report and a significant lead towards discovering genes for tolerance to aphids in safflower.