Genetic Diversity among World Hop Accessions Grown in the USA

Abstract

Hop ( Humulus lupulus L.) is an important cash crop in the U.S. Pacific Northwest. Classifying groups of hop accessions presently held in the USDA‐ARS world collection is vital toward categorizing newly imported accessions and identifying closely related (if not identical) cultivars. The objective of this study was to identify hop germplasm diversity pools on the basis on morphological and chemical data by cluster analysis. Eight hop quality characteristics including yield (YLD), α acids, β acids, hop‐storage index (HSI), cohumulone (CoH), myrcene (M), caryophyllene (C), and humulene (H) were obtained from historical databases for 129 accessions from the USDA‐ARS hop germplasm field collection located near Corvallis, OR. Three distinct genetic diversity pools were identified and named: (i) European, (ii) Wild North American, and (iii) Hybrids. The European pool was divided into English and Continental European subgroups distinguished by their α‐acids and CoH contents. The Hybrid pool was divided into five subgroups distinguished by their geographic origins. The variables YLD and CoH content differentiated these five subgroups ( r = 0.92; P ≤ 0.05). The information presented in our study will help categorize newly imported accessions into the current U.S. hop germplasm collection and will help in identifying closely related or similar accessions.