Mapping FAD2 Genes on Peanut (Arachis hypogaea L.) Genome and Contribution to Oil Quality

Improvement of oil quality traits in peanut is the second most important research goal other than yield because of high impact on market and consumers due to profitability and several health benefits. Although FAD genes are known to control some of these traits but their position on the peanut genome and their relative contribution towards total phenotypic variance for these quality traits (total oil content, oleic and linoleic fatty acids, and O/L ratio) is still unknown. Two recombinant inbred line (RIL) mapping populations were used in this study, which were derived from SunOleic 97R × NC94022 and Tifrunner × GT-C20. Total 249 marker loci were mapped and FAD2A (A-genome) and FAD2B (B-genome) were mapped on AhIX and AhV linkage groups, respectively. Further, QTL analysis detected a total of 49 main-effect QTLs (M-QTLs) explaining upto 74% phenotypic variance (PVE) and 115 epistatic QTLs (E-QTLs) upto 72.7% PVE for all the four quality traits. Two marker intervals representing mutant alleles FAD2A and FAD2B contributed up to 23.46% and 39.3% phenotypic variance (PVE), respectively for oleic acid; up to 26.1% and 41.2%, respectively for linoleic acid; and up to 10.8% and 30.5 – 74%, respectively for O/L ratio, respectively. All the interactions detected through QTLNetwork were two-locus while GMM 98 interactions were among three loci. The phenotypic effect of E-QTLs detected through QTLNetwork showed lower PVE (0.5 - 16.2%) as compared to E-QTLs from GMM (25.8 to 72.7% PVE). In summary, present study identified 49 M-QTLs and 115 E-QTLs with PVE up to 74% and 72.7%, respectively. More importantly this is the first report of estimating PVE of these two FAD2 genes for total oil content, oleic acid, linoleic acid and O/L ratio in addition to mapping these genes. It is clear that contribution of FAD2B is higher than the FAD2A gene. Thus, the information generated through present study is very useful for marker-assisted accelerated improvement of peanut oil quality.