First report of Papaya leaf curl China virus infecting Corchoropsis timentosa in China

Papaya leaf curl China virus (PaLCuCNV) is a distinct begomovirus found in Guangxi province of China (Wang et al., 2004). In recent years the virus has caused a severe leaf curl disease on papaya in southern China. To identify alternative hosts of this virus, a survey of weed samples with typical leaf curling, vein thickening and yellow vein symptoms were collected in papaya-growing areas. Virus isolates G43 and G45 were obtained from Corchoropsis timentosa plants showing yellow vein symptoms in Nanning, Guangxi Province in October, 2003. Using degenerate primer pair PA and PB, designed to amplify part of the intergenic region and AV2 gene of DNA-A (Deng et al., 1994), a 500 bp DNA fragment was produced using total plant DNA extracted from both G43 and G45. The PCR products were cloned and sequenced. Alignment of the sequences showed that products from the two isolates were identical (AJ876548 and AJ876549), and most closely related to PaLCuCNV- [G10] (AJ558125) (98.8% identity). Overlap primers G43F (5'-ATGGGTGAATCGGC CCATGTA-3') and G43R (5'-CGCTTCGACATAATCTCTAGCAC-3') were then designed and used to amplify full length DNA-A of G43. The complete DNA-A sequence of G43 was determined to be 2735 nucleotides (AJ876548). A comparison with other begomoviruses shows that DNA-A of G43 is closely related to PaLCuCNV- [G10] (98.9% identity). PCR was used to try to detect a putative DNA-B component using DNA-B specific degenerate primer pairs PCRc1/PBL1v2040 and CR01/CR02 (Li et al., 2004); no amplification product was detected with either of these primer pairs. To test whether a satellite molecule is associated with the two isolates, a universal abutting primer pair specific for DNA-β (beta01/beta02,) was used (Zhou et al., 2003). No product was detected. These results are consistent with Wang et al. (2004), who could not detect either DNA-B or DNA-β components in PaLCuCNV-infected papaya samples. The above results confirm that samples G43 and G45 were infected by PaLCuCNV. This is the first report of PaLCuCNV infecting C. timentosa; a common and widespread weed species which thrives in roadsides and fields, and which may play an important role in papaya leaf curl disease epidemiology.