Cultivated grapevines represent a symptomless reservoir for the transmission of hop stunt viroid to hop crops: 15 years of evolutionary analysis.
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.
Kawaguchi-Ito
Yoko
Y
United Graduate School of Agricultural Sciences, Iwate University, Morioka, Japan.
Li
Shi-Fang
SF
Tagawa
Masaya
M
Araki
Hiroyuki
H
Goshono
Masafumi
M
Yamamoto
Shingen
S
Tanaka
Mayumi
M
Narita
Masako
M
Tanaka
Kazuaki
K
Liu
Sheng-Xue
SX
Shikata
Eishiro
E
Sano
Teruo
T
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*
D018076:DNA, Complementary; D012333:RNA, Messenger