A new begomovirus associated with yellow vein disease of Siegesbeckia glabrescens

In January 2005, three virus isolates (G110, G111 and G112) were obtained from Siegesbeckia glabrescens plants showing stunting and yellow vein symptoms (Fig. 1), collected in Guangxi, China.

To identify possible begomoviruses, total DNA was extracted from leaves with symptoms. The degenerate primer pair PA /PB was used to amplify part of the intergenic region and AV2 gene of DNA-A like molecule (Xie et al., 2002). A 500 bp DNA fragment was amplified from all the samples, and these were cloned and sequenced. Alignment of the sequences showed the cloned products shared 94.9 to 99.4% nucleotide sequence identities (Acc. No. AM238692-94), indicating these samples were infected by a single virus. Overlap primers Full/F (5’-CTGCAGATA TAGTCATTTCCAC-3’) and Full/R (5’-GTGGAAATGACTATAT CTGCAG-3’) were then designed to amplify the full length DNA-A of G111. The complete G111 DNA-A sequence is 2784 nucleotides (Acc. No. AM238692) and shares the highest nucleotide sequence identity (85.4%) with Siegesbeckia yellow vein virus-[GD13] (SgYVV-[GD13]; Acc. No. AM183224) (Fig. 2A. To test whether DNA-β was associated with the three viral isolates, a universal DNA-β primer pair (beta 01 and beta 02) was used (Zhou et al., 2003). An amplicon of about 1.3 kb was obtained from all the samples. Sequence analysis revealed that DNA-β of G111 was 1355 nucleotides (Acc. No. AM238695); sharing the highest nucleotide sequence identity (68.2%) with DNA β of SgYVV-[GD13] (Acc. No. AM230643) (Fig. 2B).

These results confirmed that the virus associated with yellow vein disease of S. glabrescens in Guangxi is a new begomovirus associating with a satellite DNA molecule, for which the name Siegesbeckia yellow vein Guangxi virus (SgYVGdV) is proposed. Plants infected with SgYVGdV had yellow vein symptoms but no enations on the leaves as associated with SgYVV.