Abstract
The presence of Citrus tristeza virus (CTV) in Turkey has been known since the 1960s and the virus was detected in all citrus growing regions of the country. Even though serological and biological characteristics of CTV have been studied since the 1980s, molecular characteristics of CTV isolates have not been studied to date in Turkey. In this study, molecular characteristics of 15 CTV isolates collected from different citrus growing regions of Turkey were determined by amplification, cloning, and sequencing of their major coat protein (CP) genes. The sequence analysis showed that the CP genes were highly conserved among Turkish isolates. However, isolates from different regions showed more genetic variation than isolates from the same region. Turkish isolates were clustered into three phylogenetic groups showing no association with geographical origins, host, or symptoms induced in indicator plants. Phylogenetic analysis of Turkish isolates with isolates from different citrus growing regions of the world including well-characterized type isolates of previously established strain specific groups revealed that some Turkish isolates were closely related to severe quick decline or stem pitting isolates. The results demonstrated that although CTV isolates from Turkey are considered biologically mild, majority of them contain severe components potentially causing quick decline or stem pitting.
Highlights
Tristeza disease caused by Citrus tristeza virus (CTV) has been the most commonly observed viral disease of citrus causing significant economical losses in different countries for more than a century [1, 2]
About a 700 bp band corresponding to the capsid protein (CP) gene of CTV (672 bp) was amplified from total RNA isolated from Iğdır isolate which was used as positive control and 15 isolates collected from different regions using two-step reverse transcription polymerase chain reaction (RT-PCR) method
These results indicated that the CP gene was amplified from 15 different
Summary
Tristeza disease caused by Citrus tristeza virus (CTV) has been the most commonly observed viral disease of citrus causing significant economical losses in different countries for more than a century [1, 2]. The complete genome sequences of CTV isolates from different geographical origins and various biological properties were determined. CTV has the largest plant virus genome ranging from 19226 to 19306 nt and organized into 12 open reading frames (ORF) potentially encoding 17 proteins. Comparison of these genomes revealed that biologically and geographically different isolates contained a certain degree of sequence variation in different parts of their genomes [3,4,5,6,7,8,9,10,11].
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