Exploring phenotypic and genetic variability in hemp (Cannabis sativa)

Hemp (Cannabis sativa L.) is a high-value multi-purpose crop with applications ranging from the medicinal use of its secondary metabolites to carbon-sequestering building materials. To fully capitalise on the potential of hemp as a crop for more sustainable agriculture, detailed phenotypic and genotypic characterisations are required to inform targeted breeding programmes. This study presents a detailed morphological and genomic analysis of 10 hemp cultivars. We find high variability in agronomically important traits such as flowering time, plant height, and fresh biomass in most of the hemp cultivars tested. Additionally, genotyping-by-sequencing demonstrates that the investigated hemp cultivars exhibit high levels of heterozygosity. Furthermore, while clustering analysis shows genetic similarity among individuals of the same cultivar, confirming known breeding histories, these individuals share only up to 43% of single nucleotide variant positions. The significant genetic and phenotypic variability we observe in hemp contrasts with other crops, where cultivars are often phenotypically and genetically relatively uniform. We argue that the variability of hemp is an asset for breeding and can be exploited through genomics-assisted selection in future.