Morphometric relationships and their contribution to biomass and cannabinoid yield in hybrids of hemp (Cannabis sativa)

Abstract

The breeding of hybrid cultivars of hemp (Cannabis sativa L.) is not well described, especially the segregation and inheritance of traits that are important for yield. A total of 23 families were produced from genetically diverse parents to investigate the inheritance of morphological traits and their association with biomass accumulation and cannabinoid yield. In addition, a novel classification method for canopy architecture was developed. The strong linear relationship between wet and dry biomass provided an accurate estimate of final dry stripped floral biomass. Of all field and aerial measurements, basal stem diameter was determined to be the single best selection criterion for final dry stripped floral biomass yield. Along with stem diameter, canopy architecture and stem growth predictors described the majority of the explainable variation of biomass yield. Within-family variance for morphological and cannabinoid measurements reflected the heterozygosity of the parents. While selfed populations suffered from inbreeding depression, hybrid development in hemp will require at least one inbred parent to achieve uniform growth and biomass yield. Nevertheless, floral phenology remains a confounding factor in selection because of its underlying influence on biomass production highlighting the need to understand the genetic basis for flowering time in the breeding of uniform cultivars.

Identification and mapping of major-effect flowering time loci Autoflower1 and Early1 in Cannabis sativa L.

“… 1 XY plants present in population; yes (+), no (–); Alleles; non-WT (+), WT (–); Flowers present on date, yes (+), no (–). 2 Taxonomical group data described in Carlson et al (2021) . …”

“…Further work to identify the taxonomic origin of Autoflower1 is pertinent. Autoflower1 is often ascribed in the gray literature as derived from C. ruderalis , but the most recent and in-depth genomic studies do not support the existence of this group ( Green, 2005 ; Carlson et al, 2021 ; Ren et al, 2021 ). Autoflower1 would be expected to have evolved either at very high or very low latitudes, where photoperiod insensitivity is evolutionarily advantageous because seasonal variation in daylength is minimal.…”

“…These parental cultivar populations were previously trialed in the 2019 Cornell high-cannabinoid hemp field trial ( Stack et al, 2021 ). One selected photoperiod-sensitive female F 1 plant (GVA-H-19-1148-002) was multiplied by rooting stem cuttings, then one ramet was treated with silver thiosulfate to induce male flowers that pollinated multiple genetically identical female plants to generate F 2 seed labeled GVA-H-20-1080 ( Carlson et al, 2021 ). This technique results in an entirely female, or feminized, population ( Lubell and Brand, 2018 ).…”

“…It is a well-established phenomenon that there is significant population structure in C. sativa , associated at least in part with recent breeding history and geography ( Carlson et al, 2021 ). While there is ongoing debate on the specifics of the nature of this population structure (hindered in part because of the ease of intercrossing between subgroups of C. sativa ), there is strong support for at least two subpopulations, which have been described as subspecies ( McPartland, 2018 ).…”

“…indica grown for cannabinoid production originally in Southeast Asia, including India. Various other subpopulations have been described, including a distinct clade of C. sativa with geographic origins in China ( Carlson et al, 2021 ; Ren et al, 2021 ). Different taxonomic classifications have also been proposed, including the putative species C. ruderalis , which has been considered the source of the “autoflower” trait in all C. sativa populations ( Green, 2005 ).…”