A Comparison of Two Media Formulations and Two Vented Culture Vessels for Shoot Multiplication and Rooting of Hemp Shoot Tip Cultures

Micropropagation of hemp (Cannabis sativa) is constrained by problems with hyperhydricity and culture decline of microshoots. These problems can be reduced by increasing agar and nutrients in the media during micropropagation stages 1 and 2, respectfully. Performance of microshoots of ‘Abacus’ and ‘Wife’ hemp cultured in Driver and Kuniyuki Walnut medium (DKW) for 15 weeks (6 weeks of stage 1 + 9 weeks of stage 2), with subculturing every 3 weeks during both stages 1 and 2, or in Murashige and Skoog with vitamins medium (MS) for 6 weeks (stage 1) followed by Lubell-Brand Cannabis medium (LBC) for 9 weeks (stage 2), with subculturing every 3 weeks during both stages 1 and 2, was evaluated. In a separate study, microshoot performance of ‘Abacus’ and ‘Wife’ in MS for 3 weeks (stage 1) followed by LBC for 6 weeks (stage 2), with subculturing every 3 weeks, using boxes (Magenta GA-7) with lids featuring a vent with a diameter of 10 mm and a pore size of 0.2 µM or using microboxes (Sac O2 O95/114 + OD95) with lids featuring a filter (Sac O2 #10) were evaluated. Shoot multiplication rate (SMR) and explant height were greater for ‘Abacus’ in LBC than DKW. For ‘Wife’, SMR at 9 weeks was greater in LBC, as LBC provided more nutrients and water than cultures had received in MS initially during stage 1. Culture medium did not influence ex vitro rooting success, which was 75% for ‘Abacus’ and ≥ 90% for ‘Wife’. Microboxes resulted in greater hyperhydricity of shoots and a lower ex vitro rooting percentage than boxes. For cultivars that are highly prone to developing hyperhydricity, like ‘Abacus’, the microboxes were not adequate to control this condition.