“Cannabis propagators should consider retipping to expand their liner production”

“There are limitations when relying on mother stock plants and stem cuttings for propagation, as they can accumulate pathogens and lose vigor over time. Therefore, there is interest in the micropropagation of cannabis for the production of uniform, vigorous and pathogen-free clones. However, hyperhydricity, culture decline, and poor ex vitro rooting have limited the availability of micropropagated liner plants.” A recent study done by the University of Connecticut explored the process of retipping, which is the repeated harvesting of new shoots from recently micropropagated plants that are then stuck as cuttings called retips. “Retipping can enhance output from the micropropagation process while still producing clonal, uniform liner plants.”

“Same desirable attributes”
For the study regarding rooting timing, two cannabis strains, ‘Wife’ and ‘Abacus’, were initiated in tissue culture from stock plants maintained in a greenhouse. Ex vitro rooting success of microcuttings was evaluated when cultures were 6, 9, 12, 15, and 18 weeks old from initiation. Microcuttings of ‘Wife’ harvested from 6, 9, and 12-week-old cultures rooted at or above 80%, but rooting declined to 50% and 30% for 15- and 18-week-old cultures, respectively. Rooting for ‘Abacus’ remained relatively constant between 47% and 70% for microcuttings harvested from 6- to 18-week-old cuttings.

‘Wife’ plants grown from microcuttings, stem cuttings, and retip cuttings had equivalent total shoot length, number of shoots, and flower dry weight. Micropropagated ‘Abacus’ plants, on the other hand, had less shoot length and flower dry weight than plants from stem cuttings. However, when micropropagated ‘Abacus’ plants were provided an extra week of vegetative growth, all plants performed the same. The propagation method did not change the cannabinoid content for both strains. Retip cuttings of ‘Abacus’ and ‘Wife’ are rooted at 76% to 81% without rooting hormone, which is comparable to rates reported for stem cuttings of cannabis treated with rooting hormone.

“Our results demonstrate that retip cuttings can be as successful as stem cuttings for producing liner plants of cannabis. Therefore, propagators should consider retipping to expand their liner production because retips root well and possess the same desirable attributes as micropropagated plants,” the researchers conclude.

To read the complete study, go to www.researchgate.net


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