Seed the Difference: QTL Mapping Reveals Several Major Loci for Seed Size in Cannabis sativa L

Cannabis sativa L. has been cultivated for millennia as a source of food and fibre. Increasing demand for functional foods has renewed interest in C. sativa seeds (hempseeds), which are rich in essential fatty acids and amino acids. However, a near-global moratorium on C. sativa cultivation and research throughout most of the 20th century has delayed crop improvement using modern breeding approaches. As a result, genetic loci contributing to key agronomic traits, including with respect to maximizing yield as a seed crop, remain largely unknown. In this study, a feminized segregating F₂ mapping population, derived from a tall parent with spacious inflorescences and large seeds and a short-stature parent with compact inflorescences and small seeds, was phenotyped for key seed and agronomic traits related to yield. A mid-density Single Nucleotide Polymorphism (SNP) genotyping panel was used to generate a genetic linkage map of 291.5 cM with 455 SNPs. Quantitative Trait Locus (QTL) mapping identified major loci for hundred-seed weight-qHSW3, 26.59 percent variance explained (PVE), seed volume-qSV1, 33.24 PVE, and plant height-qPH9, 46.99 PVE. Our results provide novel target regions, associated molecular markers, and candidate genes for future breeding efforts to improve C. sativa.