Fine mapping of a major QTL qHYF_B06 for peanut yield

Abstract

High yield is a major objective for peanut (Arachis hypogaea L.) breeding worldwide. However, fewer yield-related quantitative trait loci (QTL) have been reported in peanut than in other staple food crops such as rice (Oryza sativa), wheat (Triticum aestivum), and maize (Zea mays). This study aimed to identify stable major-effect QTL associated with pod yield per plant, hundred-pod weight for double-seeded pods, hundred-seed weight, shelling percentage, and pod number per plant, allowing us to predict candidate genes by means of transcriptome and genome sequencing. To this end, we used a population of recombinant inbred lines comprising 192 F9:11 families derived from a JH6 × KX01-6 cross to construct a high-resolution genetic map (1705.7 cM) consisting of 2273 polymorphic SNPs, with 0.75 cM (on average) between adjacent SNPs. We identified two high-confidence, yield-related QTL, qHYF_A08 and qHYF_B06, explaining 5.78%–31.40% of phenotypic variation and with LOD values of 5.10–24.48, in six environments. qHYF_A08 mainly explained the variation in shelling percentage, whereas qHYF_B06 explained variation in hundred-pod weight and hundred-seed weight and accounted for 8.77%–31.40% of the variation in effective pod number per plant, pod number per plant, and shelling percentage. We narrowed down qHYF_B06 to an 890-kb interval using an advanced mapping population. Transcriptome and genome analyses revealed that only Arahy.129FS0 and Arahy.3R9A5K in the candidate mapping interval were differentially expressed between JH6 and KX01-6, with substantial structural variations in their promoter and coding regions. Genotypes of 208 peanut accessions determined using a diagnostic CAPS marker suggested that the two haplotypes of Arahy.3R9A5K were highly associated with hundred-seed weight and hundred-pod weight; this diagnostic CAPs marker could therefore be useful for selecting high-yielding lines during peanut breeding. Overall, our results provide valuable information for cloning alleles with favorable effects on peanut yield.