Weeding out variability: A proof-of-concept for producing uniform F1 hybrid <i>Cannabis sativa</i> L. using single seed descent

Abstract Cannabis sativa is a wind-pollinated, predominantly dioecious and outcrossing crop associated with high levels of genetic variability even within a single cultivar. As such, seed-grown crops are often constrained by variability issues, decreasing production efficiency and product consistency. F1 hybrid seed technology offers great potential to address these limitations by generating genetically uniform populations from a cross of two inbred parental lines. In C. sativa, single seed descent is currently the most viable method to produce these homozygous parental lines necessary for F1 hybrid seed production. This study exemplifies the potential of single-seed descent coupled with chemically induced sex reversion to produce fully homozygous lines and its subsequent application in creating five F1 hybrid accessions. Up to six rounds of single seed descent were performed in an 18-month period on 16 different lines, highlighting the speed of methodology. Inbreeding through XY males was most successful and offered the greatest advantages of the lines assessed. The F1 hybrid lines were statistically more uniform than the inbred or original lines, and more vigorous than the inbred lines, with F1 lines increasing seed yield between 3.9-155% when compared to their mid-parents indicating the potential to exploit heterosis. Chemotype stability was achieved in some F1 hybrid lines, showing that seed-grown cannabinoid crops would be possible in some contexts using F1 hybrid methodology, paving the way for the validation of this breeding technique in field settings and highlighting a path toward commercial hybrid seed systems in C. sativa.