Genetic relationships in cultivars of hop, Humulus lupulus L., determined by RAPD analysis

Random amplified polymorphic DNA (RAPD) was used to evaluate the genetic va riability and relationship of 65 hop cultivars from all the major hoy-growi ng regions in the world. Twenty-eight selected random primers used in the R APD reaction generated an average of 38.6% polymorphic fragments, which was sufficient to produce 47 different RAPD profiles among the cultivars exami ned. The level of genetic variability was much higher than previously repor ted. Genetic similarity was estimated and UPGMA cluster analysis was perfor med using the RAPD data. Cluster analysis separated the cultivars into gene tically related RAPD groups which were compared with pedigree data and grou ping of the hop cultivars by essential oil type. The RAPD groups, strongly supported by pedigree data, gave more precise information on the level and distribution of generic variability within hop cultivars than characterizat ion by essential oils. Cultivars were divided into American and European gr oups, supporting the distinction between two geographically distinct hop ge rmplasms. Five genetically distinct groups revealed differences within the European germplasm, reflecting past hop breeding practices which have been adopted in different regions. The use of RAPD markers for hop germplasm cha racterization and genetic diversity study is discussed.