## 1 Introduction  
Hop (_Humulus lupulus_ L.) is a dioecious, perennial, wind-pollinated climbing plant species which belongs to the family Cannabinaceae. Generally, wild hop populations inhabit marshy or wet depressions in fans and moist alder-oak woodlands [1]. It is native to North America, Southeast Asia, and Europe [2]. In wild hop, five taxonomic varieties are distinguished on the basis of leaf morphology and geographical distribution: var. _lupulus_ for European hop, var. _coridilius_ for Japanese hop, and var. _neonexicanus_, _pubescens_, and _lupuloides_ for North American hop [3]. Wild hop populations have been collected from their natural habitat since ancient times. Higher demands on the plant and consequently its introduction into cultivation began in the 12 th century when it became widely used as a preservative and clarifier in the brewing process of beer [4, 5]. It was domesticated mainly in Central Europe [6] and the first plantations were established with several wild and adapted genotypes with desirable traits, propagated with cuttings [7]. The noble cultivars Saaz, Spalt, Tettnanger, and Hallertauer Mittelfrueh are descended from these genotypes [8]. They represent typical European aroma hop, with a relatively low yield and resin content [9]. In hop, female and male plants are distinguished on the basis of flower morphology. Female plants are pollinated by wind [7]. Exclusively female flowers are of economic value as they develop umbels with numerous lupulin glands on their bracts [10], which produce secondary metabolites used as flavoring agents in beer brewing to add bitterness and aroma [11; 12]. Secondary metabolites include resins, essential oils, and tannins [7]. Resins include hard resins (xanthohumol and iso-xanthohumol), flavones, and soft resins (hop acids) dominated by humulones (\(\alpha\)-acids) and lupulones (\(\beta\)-acids) [13]. Both \(\alpha\)- and \(\beta\)-acids provide the bitter taste of beer, while \(\beta\)-acids also provide the preservative effect [7]. Essential oils of hop are responsible for the taste and aroma of beer and their main components are mircenes and humulene [6; 14]. Secondary hop metabolites also show potent antibacterial, antifungal, antifungal, antiviral, antiparasitic [15; 16], osteogenic [6], and anticancer activity [17], thus could be used for nonbrewing purposes. A number of studies have focused on identifying chemical profiles of hop [18; 19] and hop aroma in beer [20; 21; 22; 23; 24]. Hop genotypes differ in the presence, amount and relative proportion of secondary metabolites and consequently in aroma, bitterness and flavor [25], which offers great potential for the development of new varieties. Apart from different chemical profiles and higher content and quality of metabolites accumulated in lupulin glands [26] and desirable brewing property, modern breeding programs are constantly searching for new plant varieties with higher yield per hectare and resistance to diseases [27; 28]. They involve hybridization and the basic source of plant material (wild hop, cultivars, breeding lines) is maintained in established large hop breeding centers. Due to their dioiceous nature, hop plants are unable to self-fertilize and plants grown from seed are naturally very heterozygous and rarely resemble either parent. Therefore, hop is commercially clonally propagated, which maintains clonal fidelity and specific brewing characteristics [29; 30]. Genetic variation in wild hops and hop cultivars has been studied using a variety of molecular tools, allowing their molecular characterization and identification of their genetic relationship. The studies that aimed to unravel the extent of genetic diversity and differentiation among hop cultivars mostly reported a clear separation into clusters based on their geographical origin.