Vegetative propagation of hops (Humulus lupulus L.): Historical approach and perspectives

Hop (Humulus lupulus L.) female inflorescences are important raw materials used to produce beers, cosmetics, and medicines. Vegetative propagation is the preferred way of obtaining seedlings for commercial cultivations as female plants produce more lupulin than male plants, a component of commercial interest. It can be carried out by macropropagation (stem cuttings or rhizomes) or micropropagation. This review aimed to systematize different techniques of hop vegetative propagation, with no time frame, from searches in the main academic research bases: Capes Journal Portal, Scielo, Scopus, Web of Science, Science Direct, Google Scholar, and ResearchGate. Most studies are related to micropropagation, mainly addressing different plant regulators and concentrations, as well as types of explants and culture media, strategies to produce virus-free plants, artificial lighting, and cryopreservation. Experiments with stem cuttings are more common regarding macropropagation, but factors such as size and origin of cuttings, rooting period, and the response of different cultivars need to be better evaluated. Cultivation by cuttings allows the production of clones of female plants and micropropagation the production of virus-free clones in a short time and less physical space. Currently, micropropagation has been widely applied to cryopreservation.