Commercial hops are the female end of a slow-to-mature perennial rhizome that needs significant water to grow.
Natural HpSVd isolates were collected from commercial hops (Humulus lupulus) in Japan between 1992 and 2004, and from commercial hops in Xinjiang, China in 2007.
Seven major natural HpSVd-hop variants were previously reported in commercial hops in Northern Japan [44] [46].
Hop stunt was a mysterious disorder that first emerged in the 1940s in commercial hops in Japan.
In parallel, a major variant of HpSVd-grapevine was introduced into hops and was shown to be modified into natural HpSVd-hop variants currently endemic in commercial hops.
Four of the five mutation hotspots in HpSVd-grapevine matched those found in HpSVd-hop, as well as those in the natural HpSVd-hop population from commercial hops.
Some of them showed nucleotide sequences identical to those currently responsible for hop stunt epidemics in commercial hops in Japan, China, and the United States.
Furthermore, mutants (G54A), (U25del), (C26A+U281A), (U25A+C26A+G54A+U281A), and (U25A+C26A+G54A+U193C+U291A) are identical to the natural HpSVd variants endemic in commercial hops: hJType, hAIw36, hAIw5, hKF76, and hKFKi, respectively [45].
Consequently, we have identified a total of eight major natural HpSVd variants from commercial hops in Japan: hJType, hKY04-1, hKIw36, hAIw, hKF76 hKFKi, hKFKi, and hSIw.
Our studies demonstrate that 15 years of persistent infection in hops resulted in the evolution of natural HpSVd-grapevine variants into HpSVd-hop variants identical to those currently responsible for the epidemic in commercial hops in Japan.
