Influence of genotype and methyl jasmonate concentration on trichome development and yield traits in Cannabis sativa L.

Abstract Background Cannabinoids, such as cannabidiol and tetrahydrocannabinol, determine much of the economic and therapeutic value of Cannabis sativa L. Since these metabolites are synthesized and stored in glandular trichomes, production outcomes depend on both trichome abundance and their biochemical capacity to accumulate cannabinoids. Methyl jasmonate is a plant signaling compound that may stimulate defense-related metabolism and consequently trichome development. We tested whether foliar methyl jasmonate could (i) increase trichome density and (ii) alter cannabinoid content in field-grown high-CBD cannabis, and if responses were genotype-dependent. Methods Two field experiments were conducted at Southern Illinois University in Carbondale, Illinois, in the summer of 2021 and 2022. Three cultivars were grown each year (2021: Cherry Citrus, Baox, Super CBD; 2022: Cherry Citrus, Stout, Super CBD). Methyl jasmonate solutions (0, 0.125, 0.25, 0.5, 1.0, 2.0 mM in 0.1% surfactant Tween-20) were applied as foliar sprays at the flowering stage and twice more at two-week intervals. We measured plant height, width, biomass, and yield components at harvest; quantified trichome density on bract-subtending leaves using calibrated image analysis; and profiled cannabinoids using high-performance liquid chromatography. Effects of cultivar and treatment (and their interactions) were evaluated with mixed-effects models and Tukey post-hoc contrasts; blocks were treated as random effects. Results Methyl jasmonate did not significantly ( P > 0.05) change plant height, width, or biomass in either year; these traits were strongly shaped by cultivar. Yield components showed the same pattern. Trichome responses were context-dependent. In 2021, the main effect of methyl jasmonate was not significant ( P > 0.05), but there was a cultivar interaction: responses were positive in Baox, neutral in Cherry Citrus, and negative in Super CBD. In 2022, methyl jasmonate produced a significant ( P ≤ 0.05) concentration-dependent increase in trichome density across cultivars. Cannabinoid composition, including total cannabidiol, varied by cultivar and year; methyl jasmonate did not alter cannabinoid percentages in either year. Conclusions Foliar methyl jasmonate can increase trichome density in field-grown Cannabis sativa L. without detectable penalties to plant size or biomass, but efficacy depends on genotype and growing season. These results demonstrate that methyl jasmonate can influence trichome density, although further research is needed to determine how these effects are modulated by growing conditions, cultivar, and how it can interfere with cannabinoid levels.