Are Humulus lupulus L. ecotypes and cultivars suitable for the cultivation of aromatic hop in Italy? A phytochemical approach

Breeding programs are increasingly interested in the introduction of traits from wild hops and in the detection of the cultivars most suitable under different climatic conditions. Eleven Humulus lupulus ecotypes were selected from distinct populations in Northern Italy, grown in a collection field and evaluated for their yield and cone aromatic profiles after a three-year acclimatization. At the same time, the performance of 10 H. lupulus cultivars (Bramling Cross, Cascade, Challenger, Fuggle, Magnum, Marynka, Nugget, Target, Tettnanger, Willamette) grown under the same conditions was investigated by comparing them to commercially available material. Estimated gross yield for ecotypes ranged between 636 and 2491 kg/ha, largely exceeding hop production for commercial cultivars (277-1442 kg/ha), while essential oil accumulation was inverted. Essential oils obtained from mature cones were characterized by GC-MS. In the volatile fraction of most ecotypes, selinene isomers were extremely abundant and myrcene was low, while α-humulene/β-caryophyllene ratio was comprised between 0.15 (Pasqui 1) and 1.68 (Tavernelle and Roggino 2). The phytochemical variability among the genetic pool screened suggests its potential use for breeding and improvement of cultivated varieties, in particular for plant material aimed to be used in the dry hopping stage of brewing. Northern Italy seem to be particularly suitable for the cultivation of finishing, aromatic hops like Bramling Cross, Magnum, Marynka and Tettnanger.