A One-Step Grafting Methodology Can Adjust Stem Morphology and Increase THCA Yield in Medicinal Cannabis
Sarah Jane Purdy; Amitha K. Hewavitharana; Razlin Azman Halimi; Nelson Joel Magner; Tyson James Peterswald; Amy Trebilco; Tobias Kretzschmar; Deborah Hailstones
The standard two-step methods for grafting horticultural crops involve cultivating the rootstock for a period of time and then connecting the scion. Medicinal Cannabis differs from most annual horticultural crops because it is usually clonally propagated from cuttings. We developed a grafting methodology specifically for medicinal Cannabis, involving a single step, in which a freshly cut scion is grafted to a freshly cut donor stem that will become the rootstock. This study also aimed to uncover a potential role for roots in influencing cannabinoid content. Two varieties with desirable attributes but cultivation limitations were selected to act as scions. The first, &ldquo:CBD1&rdquo: was a high CBDA accumulating variety with low biomass yield, and the second, &ldquo:THC2&rdquo:, was a high yielding, high THCA accumulating line with inconsistent root development during cloning. Two candidate rootstocks, &ldquo:THC9r&rdquo: and &ldquo:THC8r&rdquo:, were identified: both were high THCA, low CBDA varieties. Biomass yields in the THC2 scions grafted to THC9 rootstocks (THC9r_2s) were 20% higher than in the non-grafted THC2 plants. In CBD1 grafted plants, the concentrations of CBDA and some minor cannabinoids were significantly different to non-grafted CBD1, but biomass yields were lower. There was a trend towards a higher concentration of THCA in THC9r_2s plants, and when combined with the increased biomass, yield of THCA was increased from 8 g Plant&minus:1 to 13 g Plant&minus:1. Our results present a new grafting method for medicinal Cannabis that improved yield in THC2 and required no additional cultivation time.
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