AFLP discrimination of native north American and cultivated hop
Hop (Humulus lupulus L.) is cultivated for the female flowers, or 'cones,' which traditionally have been used as a bittering and flavoring agent in beer. Hop breeding historically relied on relatively simple selection techniques within established breeding lines. Supplementing current breeding material with new genetic sources would enhance a hop breeder's ability to select for new traits. The objective of this research was to assess the genetic relationship of H. lupulus var. lupuloides and H. lupulus var. pubescens accessions with hop germplasm currently utilized by hop breeding programs. A total of 60 hop accessions representing both cultivated (n = 21) and native (n = 39) Humulus were evaluated using amplified fragment length polymorphism (AFLP) molecular markers. The four primer combinations used generated 296 scorable fragments of which 176 (59.5%) were polymorphic. Principal components analysis and hierarchal cluster analysis showed the native American accessions clustering separately from the cultivated germplasm. Within each of the two main groups, two smaller subgroups were evident with H. lupulus var. lupuloides and H. lupulus var. pubescens segregated into unique clusters. This research provides the first molecular genetic evidence of H. lupulus var. pubescens and H. lupulus var. lupuloides being two separate botanical varieties. Results from this research suggest incorporating the native American hop accessions studied in this experiment would enhance the genetic diversity within hop breeding programs.