Stem pitting and seedling yellows symptoms of Citrus tristeza virus infection may be determined by minor sequence variants.
The isolates of Citrus tristeza virus (CTV), the most destructive viral pathogen of citrus, display a high level of variability. As a result of genetic bottleneck induced by the bud-inoculation of CTV-infected material, inoculated seedlings of Citrus wilsonii Tanaka displayed different symptoms. All successfully grafted plants showed severe symptoms of stem pitting and seedling yellows, while plants in which inoculated buds died displayed mild symptoms. Since complex CTV population structure was detected in the parental host, the aim of this work was to investigate how it changed after the virus transmission, and to correlate it with observed symptoms. The coat protein gene sequence of the predominant genotype was identical in parental and grafted plants and clustered to the phylogenetic group 5 encompassing severe reference isolates. In seedlings displaying severe symptoms, the low-frequency variants clustering to other phylogenetic groups were detected, as well. Indicator plants were inoculated with buds taken from unsuccessfully grafted C. wilsonii seedlings. Surprisingly, they displayed no severe symptoms despite the presence of phylogenetic group 5 genomic variants. The results suggest that the appearance of severe symptoms in this case is probably induced by a complex CTV population structure found in seedlings displaying severe symptoms, and not directly by the predominant genomic variant.
Cerni
Silvija
S
Department of Biology, Faculty of Science, University of Zagreb, Rooseveltov trg 6, 10000 Zagreb, Croatia. scerni@botanic.hr
Ruscić
Jelena
J
Nolasco
Gustavo
G
Gatin
Zivko
Z
Krajacić
Mladen
M
Skorić
Dijana
D
D001483:Base Sequence; D036022:Capsid Proteins / Q000235:genetics*; D002957:Citrus / Q000821:virology*; D017790:Closterovirus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D014644:Genetic Variation; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000821:virology*; D018807:Polymorphism, Single-Stranded Conformational; D014764:Viral Proteins / Q000235:genetics
D036022:Capsid Proteins; D014764:Viral Proteins