Characterization of agronomic performance and sterility in triploid and diploid cannabinoid hemp

Cannabinoid hemp is a dioecious crop where pistillate plants are selectively grown to maximize cannabinoid yields. Errant pollination can reduce pistillate flower yields, cannabinoid concentrations, and lead to unmarketable flowers due to the presence of undesirable seeds. We compared pollen sensitivity and agronomic performance of diploid (2n = 2x = 20 chromosomes) and triploid (2n = 3x = 30 chromosomes) cannabinoid hemp in open-field conditions. The high-CBD variety Lifter and high-CBG variety White CBG were evaluated in both their diploid and triploid counterparts in fields with and without pollen. Trials were conducted during the 2021 and 2022 field seasons in Kentucky, New York, and North Carolina (n = 6 site years). Triploids produced taller and wider plants than diploids; however, this did not result in yield differences in the pollen-free environment. In the presence of pollen, triploid Lifter and White CBG produced 87% and 77% fewer seeds than their diploid counterparts, respectively. Increased seed production in diploids also resulted in a significant reduction of seed-free biomass and cannabinoid concentrations compared to triploids. In the absence of pollen, we did not find any appreciable differences in seed-free biomass or cannabinoid concentrations between triploids and diploids. Though not completely pollen-insensitive, triploidy is an effective means to reduce seed production and improve yields and quality in cannabinoid hemp in the presence of pollen.