title: Cultivated grapevines represent a symptomless reservoir for the transmission of hop stunt viroid to hop crops: 15 years of evolutionary analysis.
abstract: Hop stunt was a mysterious disorder that first emerged in the 1940s in commercial hops in Japan. To investigate the origin of this disorder, we infected hops with natural Hop stunt viroid (HpSVd) isolates derived from four host species (hop, grapevine, plum and citrus), which except for hop represent possible sources of the ancestral viroid. These plants were maintained for 15 years, then analyzed the HpSVd variants present. Here we show that the variant originally found in cultivated grapevines gave rise to various combinations of mutations at positions 25, 26, 54, 193, and 281. However, upon prolonged infection, these variants underwent convergent evolution resulting in a limited number of adapted mutants. 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. Therefore, these results indicate that we have successfully reproduced the original process by which a natural HpSVd variant naturally introduced into cultivated hops was able to mutate into the HpSVd variants that are currently present in commercial hops. Furthermore, and importantly, we have identified cultivated grapevines as a symptomless reservoir in which HSVd can evolve and be transmitted to hop crops to cause epidemics.
authors.affiliation: United Graduate School of Agricultural Sciences, Iwate University, Morioka, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Kawaguchi-Ito
authors.forename: Shi-Fang
authors.initials: SF
authors.lastname: Li
authors.forename: Masaya
authors.initials: M
authors.lastname: Tagawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Araki
authors.forename: Masafumi
authors.initials: M
authors.lastname: Goshono
authors.forename: Shingen
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Mayumi
authors.initials: M
authors.lastname: Tanaka
authors.forename: Masako
authors.initials: M
authors.lastname: Narita
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Tanaka
authors.forename: Sheng-Xue
authors.initials: SX
authors.lastname: Liu
authors.forename: Eishiro
authors.initials: E
authors.lastname: Shikata
authors.forename: Teruo
authors.initials: T
authors.lastname: Sano
mesh_terms: D000383:Agriculture; D001483:Base Sequence; D002681:China; D002957:Citrus / Q000821:virology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004197:Disease Reservoirs / Q000821:virology*; D019143:Evolution, Molecular; D014644:Genetic Variation; D027582:Humulus / Q000254:growth & development / Q000821:virology*; D007564:Japan; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010802:Phylogeny; D010935:Plant Diseases / Q000821:virology*; D027861:Prunus / Q000821:virology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014772:Viroids / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D027843:Vitis / Q000821:virology*
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger