In vitro conservation of hops – Cascade and Nugget cultivar under slow-growing conditions

Abstract

Hops (Humulus lupulus L.) is economically relevant in the brewing industry. Although Brazil has a big beer market, the unfavorable climate makes the hop growing difficult. Micropropagation is an alternative way to clone plants, but in this process somaclonal subculture variations may occur. In order to reduce consecutive subcultures, the slow growth technique can be used. To develop a slow growth protocol for the conservation of hop plants and Cascade and Nugget cultivars in vitro, Murashige and Skoog (MS) medium was supplemented with doses of osmotic agents: sucrose and sorbitol. The plants were kept at 25°C or 4°C during 120 days. After 4 months, the plants were transferred to a new MS medium containing sucrose (30 g.L-1) and kept for 30 days under optimal growing conditions. After evaluation, the plants were transplanted and underwent a 30-day acclimatization period, and then the ex vitro survival was evaluated. For both cultivars, reduced growth was observed at 4°C, with a satisfactory survival rate. There was no significant interaction between the osmotic agent and temperature for Cascade cultivar Conversely, the Nugget cultivar did have interaction, and the treatment with sucrose (60 g.L-1) at 4 ºC reduced plant length, brought largest root length and fresh mass.