Geographic Distribution and Molecular Variation of Isolates of Three Whitefly-Borne Closteroviruses of Cucurbits: Lettuce Infectious Yellows Virus, Cucurbit Yellow Stunting Disorder Virus, and Beet Pseudo-Yellows Virus

Abstract

The geographic incidence and molecular variation of three whitefly-borne closteroviruses (lettuce infectious yellows virus [LIYV], cucurbit yellow stunting disorder virus [CYSDV], and beet pseudo-yellows virus [BPYV]) were studied in cucurbits collected from several distinct geographic locations. Of 498 samples analyzed, none were found to be infected by LIYV. Sixty-nine samples collected in the Middle East and Mediterranean Europe were found infected by CYSDV, and twelve samples from Crete and Italy were infected by BPYV. Reverse-transcription poly-merase chain reaction of a portion of the heat shock protein 70 homolog coding region, followed by single-strand conformation polymorphism and nucleotide sequence analysis, was used to estimate the intra- and inter-isolate molecular variability. These analyses showed that each BPYV and CYSDV isolate was composed of a population of sequence variants with a nucleotide identity greater than 98%. CYSDV isolates could be divided into two divergent groups. Group I was only composed of isolates from Spain, Jordan, and Turkey, and group II isolates were predominantly found in Saudi Arabia. Nucleotide identity between isolates of the same group was greater than 99%, whereas identity between both groups was less than 92%. All BPYV isolates showed a nucleotide identity greater than 98%.

Whitefly-transmitted criniviruses of cucurbits: current status and future prospects

“…Analysis of CYSDV CP showed that the studied isolates had low genetic diversity in the CP and complemented previous studies [72]. Thus, CYSDV could be divided into two divergent subpopulations: a 'western' (isolates from Jordan, Lebanon, North America, Spain, France, Tunisia, Greece and Turkey) and an 'eastern' subpopulation (isolates form Saudi Arabia and Iran) [12,72,73,80,95]. Five coding and one non-coding genomic regions of a CYSDV population were examined in different cucurbit hosts in Spain [51].…”

“…Early studies based on single-strand conformational polymorphism (SSCP) and sequencing of the Hsp70h and CP gene of CYSDV isolates from different geographical areas showed slightly distinct CP and Hsp70h patterns [51,72,73,80]. Hsp70h-based analysis showed that CYSDV population in the same plant was closely related but had one predominant variant independent of the host [73].…”

“…Two major differences are an insertion in ORF1a and an additional 3 0 -terminal ORF in RNA 1 [83]. The BPYV Hsp70h showed a homogenous population among a few number of isolates [73]. BPYV isolates recovered from cucurbits in Costa Rica showed high Hsp70h or CPm homology to the strawberry strain [71].…”

“…This was attributed to the introduction of an exotic B. tabaci MEAM-1 (B) species complex which completely displaced the indigenous LIYV vector, B. tabaci New World species complex (biotype A) [73,94]. CYSDV is the most widely spread followed by BPYV and CCYV (Table 1).…”

Genetic diversity and biological variation among California isolates of Cucumber mosaic virus

“…RT-PCR products, as used here, represent the mixture of virus sequence variants with the major sequence reflected as the prominent bands in the SSCP patterns (Rubio et al, 1999(Rubio et al, , 2001. To assess whether the major sequence variants of 33 CMV isolates from CMV-infected plants of Destiny III were different from those in the original inocula (CMVinfected plants of small sugar pumpkin), SSCP analysis of the XhoI-digested RT-PCR products of the CP+39NTR region (972 bp, see Fig.…”