Advances on tetraploid Cannabis sativa L.: Morpho-anatomy, ionomics and chemical profile

Tetraploidy was induced using colchicine in the CBD-dominant Cannabis sativa cultivar ‘CBD Zero’ to assess the impact of ploidy change on plant desirable traits. Biometry, stem anatomy productivity, CBD and THC con centrations in the inflorescences, ionome composition of above-ground organs (i.e. stem, leaf and inflorescence) and VOC emission profile from the vegetative to the flowering phases were investigated. Tetraploids exhibited reduced stature and lower inflorescence biomass compared to diploids. These phenotypic shifts are likely a consequence of broad morphological and anatomical reorganization driven by increased genome size, as evi denced by comparative cross-sectional analyses. The tetraploid structural remodelling was characterized by a decreasing trend in stem fiber number and increased tissue thickness in both fan and sugar leaf. These obser vations were coupled to a distinct nutrient profile of polyploids, which showed higher concentrations of K, Fe and Ni, especially in leaves, and to their enhanced emissions of VOCs. The disparity was most pronounced towards the end of the flowering period, with the tetraploids showing a marked increase in monoterpene (e.g. p-cymene) and sesquiterpene production, compounds of considerable interest for their aromatic properties and potential health benefits. In contrast, the concentrations of the primary cannabinoids CBD and THC in dried buds showed no significant difference between ploidy levels. Some of the novel traits emerging in our induced polyploids, i.e., reduced height and increased emission of specific VOCs following leaf tissue-level changes, offer direct utility for new breeding strategies.