Genome-Wide Association Mapping of Oil Content and Seed-Related Traits in Shea Tree (Vitellaria paradoxa subsp. nilotica) Populations

Shea tree (Vitellaria paradoxa) is an important fruit tree crop because of its oil used for cooking and the industrial manufacture of cosmetics. Despite its essential benefits, quantitative trait loci linked to the economic traits have not yet been studied. In this study, we performed association mapping on a panel of 374 shea tree accessions using 7530 Single-Nucleotide Polymorphisms (SNPs) markers for oil yield and seed-related traits. Twenty-three SNP markers significantly (-log10 (p) = 4.87) associated with kernel oil content, kernel length, width, and weight were identified. The kernel oil content and kernel width had the most significant marker-trait associations (MTAs) on chromosomes 1 and 8, respectively. Sixteen candidate genes identified were linked to early induction of flower buds and somatic embryos, seed growth and development, substrate binding, transport, lipid biosynthesis, metabolic processes during seed germination, and disease resistance and abiotic stress adaptation. The presence of these genes suggests their role in promoting bioactive functions that condition high oil synthesis in shea seeds. This study provides insights into the important marker-linked seed traits and the genes controlling them, useful for molecular breeding for improving oil yield in the species.

Automated summary

Shea tree is a significant fruit tree crop known for its oil used in cooking and cosmetic production. This study used association mapping to identify SNP markers associated with oil yield and seed-related traits in a panel of 374 shea tree accessions. The results identified 23 significant SNP markers associated with kernel oil content, kernel length, width, and weight. Sixteen candidate genes were also identified, which are involved in various processes related to seed growth, lipid biosynthesis, and stress adaptation.