QTL Mapping of Quality Traits for A Peanut Germplasm SW9721-3 with Ultra-High Oil Content

High quality is a critical objective in peanut breeding. However, the poor genetic base of cultivated peanuts has significantly limited the breeding efficiency for high-quality peanut. Therefore, unearthing valuable allelic gene resources associated with quality traits would provide basis for expanding genetic diversity of cultivated peanut germplasm resources.

A wild peanut (Arachis villosa), PI 210553, carried diploid A type genome, was used as a donor parent for crossing with cultivated peanuts. Ultra-high oil peanut germplasm with wild ancestry was selected from the progeny, and a recombinant inbred line (RIL) population, derived from this germplasm and the cultivated variety Jihua 5, was used for genetic dissection and QTL mapping of four quality traits across three environments.

Four ultra-high oil accessions of the SW9721 series were selected from the cross population between Yueyou 551 and PI 210553. Notably, SW9721-3 showcased an oil content of 62.50%, exceeding the national high-oil-content peanut standard by 7.5 percent points. Phenotypic analysis of the RIL population revealed that environmental influences caused variations in the mean values of quality traits from 11.02% to 40.80%. Correlation coefficients among these traits varied from 0.23 to 0.97 (P<0.001), with significant associations observed between oil and protein contents, and between oleic and linoleic acid contents. Furthermore, the phenotypic variation of quality traits was found to be between 3.78% and 10.61%, with heritability values above 0.6, absolute values of skewness and kurtosis were less than 1. These phenotypic values were approximately normally distributed, indicating that these traits are quantitatively inherited. In addition, a total of 12 QTLs were identified across the three environments, with LOD scores ranging from 3.26 to 17.82, accounting for 1.97% to 24.56% of the phenotypic variation. Particularly, The QTL locus qPOC_7 was consistently detected in all environments, with LOD scores between 6.01 and 17.82, explaining 4.59% to 24.56% of the phenotypic variation in both protein and oil content. The oil content increase was attributed to the allele from SW9721-3, highlighting the significant breeding value of this QTL. The physical position of flanking molecular markers for qPOC_7 suggested that the corresponding genes are located within a 180 kb interval from 426 363 to 606 659 bp at the end of chromosome 7. Within this candidate region, 22 annotated genes were identified, including two glucose metabolism-related genes, Ah.CKCA5J and Ah.805HV8, which are considered the high-potential candidate genes.

In summary, this study successfully developed an ultra-high oil peanut germplasm, SW9721-3, and identified a major QTL locus, qPOC_7, with significant implications for peanut breeding.