Protocol of clonal micropropagation of Humulus lupulus (Cannabaceae)

Hops are a promising agricultural crop, in demand in the food, pharmaceutical and cosmetic industries. The problem of mass production of planting material for the establishment of industrial plantations and mother plantings can be solved using biotechnological methods. We have developed an effective protocol for clonal micropropagation of Humulus lupulus, including all stages from the preparation of mother plants and the introduction of explants into in vitro culture to the adaptation of regenerants to non-sterile conditions. The protocol was tested on 13 varietal and wild genotypes. For the first time, a well-growing aseptic culture of national cultivars was obtained. The dependence of the multiplication efficiency on the genotype and the number of passages was confirmed. Conditions were selected that ensure a high rate of reproduction of the in vitro hop culture, starting from passage IV. It was found that the maximum number of regenerated microcuttings can be obtained on the 24th–26th day of culturing the primary explants on the MS nutrient medium supplemented with 2 mg∙L-1 BAP and 1 mg∙L-1 GK3. For the first time, the possibility of combining the stages of micropropagation and rooting on the MS medium supplemented with 0.5 mg∙L-1 IBA was demonstrated. With the availability of in vitro hop collection, the cloning process is reduced by one passage. To proceed to the adaptation stage, it is enough to form two nodes and a well-developed root system on the shoot. Two-stage adaptation to non-sterile growing conditions using hydroponics ensures plant survival of up to 100 %. The proposed protocol for clonal micropropagation of hops can be used to replicate valuable genotypes for scientific, breeding and production purposes.