Genome size in Humulus lupulus L. and H. japonicus Siebold & Zucc. (Cannabaceae)

Abstract

We analysed chromosome lengths, karyotype structure, and nuclear DNA content (flow cytometry) in diploid (2n=20) and triploid (2n=30) European H. lupulus var. lupulus, American H. lupulus var. neomexicanus (2n=20) and Japanese ornamental hop, H. japonicus (F/2n=16; M/2n=17). Diploid female representatives of H. lupulus var. lupulus and H. l. var. neomexicanus differed in total length of the basal chromosome set (23.16 μm and 25.99 μm, respectively) and nuclear 2C DNA amount (5.598 pg and 6.064 pg) but showed similar karyotype structure. No deviation from the additivity, both in chromosome length and 2C DNA amount was evidenced in triploid monoecious H. lupulus (2n=30, XXY). H. japonicus showed different karyotype structure, smaller basal chromosome set (F/18.04 μm, M/20.66 μm) and lower nuclear DNA amount (F/3.208 pg and M/3.522 pg). There are first evaluations of nuclear genome size in diploid, not commercial representative of European H. lupulus var. lupulus and American H. lupulus var. neomexicanus and first attempt to determine the absolute male and female genome size in two Humulus species.