Evolutionary History and Rhizosphere Microbial Community Composition in Domesticated Hops ( <scp> <i>Humulus lupulus L</i> . </scp> )

Humulus lupulus L., commonly known as hop, is a perennial crop grown worldwide and is well known for its pharmacological, commercial, and most importantly brewing applications. For hundreds of years, hop has undergone intense artificial selection, with over 250 cultivated varieties being developed worldwide, all displaying differences in key characteristics such as bitter acid concentrations, flavour and aroma profiles, changes in photoperiod, growth, and pathogen/pest resistances. Previous studies have individually explored differences between cultivars, aiming to identify markers that can quickly and cost-effectively differentiate between cultivars. However, little is known about their evolutionary history and the variability in their associated rhizospheric microbial communities. Coupling phenotypic, genomic, and soil metagenomic data, our study explores the global population structure and domestication history of 98 hop cultivars. We assessed differences in growth rates, rates of viral infection, usage of dissolvable nitrogen, and soil microbial community compositions between US and non-US based cultivars. Our study revealed that worldwide hop cultivars cluster into four subpopulations: Central European, English, and American ancestry as previously reported, and one new group, the Nobles, revealing further substructure amongst Central European cultivars. Modelling the evolutionary history of domesticated hop reveals divergence of the common ancestors of modern US cultivars around 2800 years before present (ybp), and more recent divergences with gene flow across English, Central European, and Noble cultivars, reconciled with key events in human history and migrations. Furthermore, cultivars of US origin were shown to overall outperform non-US cultivars in both growth rates and usage of dissolvable nitrogen and display novel microbial composition under common-garden settings in the United States.