Genetic diversity and phylogenetic relationships among accessions of hop, Humulus lupulus, as determined by amplified fragment length polymorphism fingerprinting compared with pedigree data

DNA fingerprinting using amplified fragment length polymorphisms (AFLPs) was successfully employed to detect genetic relationships and variability among 90 hop cultivars and breeding lines comprising a collection of the world's hop germplasm. Seven AFLP primer combinations produced a total of 347 fragments of which 151 (43.5%) were polymorphic. One-hundred and thirty informative, highly reproducible DNA polymorphisms were used to estimate the genetic similarity (GS) which varied between 1.0 (e.g. 'Saazer' vs. 'Tettnanger') and 0.17 ('Columbus' vs. 'Tettnanger', 'Spalter' and 'Saazer'). UPGMA (unweighted pair-group method with arithmetic averages) clustering revealed two main clusters, reflecting the two main sources of origin and the two main breeding objectives: one cluster of mainly European origin representing the aroma pool and a second cluster associating accessions with European germplasm infiltrated by wild American genes with less aroma quality, but a higher bittering potential. Each main branch was composed of four or three subclusters with subgroups, respectively. Assignment of almost all genotypes in the dendrogram was consistent with the pedigree data as far as they are known. Consequently, AFLPs are shown to be suitable for assessing the genetic variability in hop germplasm and are useful for describing the genetic relationships among cultivars and accessions, which allows phylogenetic questions to be addressed.