Micropropagation of Mapuche hop and evaluation of synthetic seed storage conditions

Abstract

Traditional asexual propagation of hop (Humulus lupulus L.) faces limitations deepened by the effects of global climate change and the inappropriate agronomic practices, potentially impacting its phytosanitary quality and future availability. This study aimed to evaluate the in vitro propagation of Humulus lupulus L. cv ‘Mapuche’, offering innovative solutions for hop producers and the brewing industry in the context of current challenges facing the sector. Two types of initial explants were used: shoot tips, from field material collected in Río Negro province (Argentina) to ensure quality, and nodal segments, derived from in vitro plants for mass multiplication. Murashige & Skoog medium at half strength, with or without different plant growth regulators (PGR), were used to induce desired morphogenic responses. The study also investigated the feasibility of producing synthetic seeds with storage at 4°C or 10°C, with or without photoperiod, to enhance storage and plant material transport, ensuring a constant supply of female plants. PGRs, such as 6-benzylaminopurine 0.88 µM or gibberellic acid 2.89 µM, were necessary for shoot differentiation and regeneration in shoot tip culture, whereas PGRs were not necessary for rooting of nodal segments. The methodology for the production of synthetic seeds was feasible; however, it was observed that prolonged cold storage compromised their conversion to complete plants. This approach addresses current demands of hop producers and emerging challenges. This study allowed the development of efficient micropropagation protocols for H. lupulus L. cv ‘Mapuche’, which could have significant implications for the brewing industry and related sectors.