Diversity of Tomato Yellow Leaf Curl Virus Causing Leaf Curl and Yellowing Symptoms in Solanaceous and Cucurbit Crops in Asia

              Tomato yellow leaf curl virus (TYLCV) is a whitefly (Bemisia tabaci) transmitted geminivirus (Family Geminiviridae, Genus Begomovirus) causing the tomato yellow leaf curl disease (TYLCD) in tomato worldwide. While TYLCV isolates have a single genomic component (designated DNA-A), Tomato yellow leaf curl Thailand virus (TYLCTHV) have two components (DNA-A and DNA-B) which are responsible for epidemics in Thailand. The begomovirus DNA-A-specific PCR primers amplified the predicted 1.2-kb DNA fragment from five symptomatic tomato samples collected from Thailand and India, and one symptomatic eggplant sample from Thailand. The amplicons were cloned, sequenced and DNA sequence analyses of these isolates revealed high nucleotide sequence identities with the partially sequenced Tomato yellow leaf curl Thailand virus available in the GenBank database. Based on the high sequence identities and phylogenetic analysis of the tomato isolates from Thailand and India, these two isolates are considered to be highly similar. In this study, the DNA-A specific primer pair was also used to clone the 1.2-kb DNA fragment from two symptomatic pumpkin and two symptomatic cucumber with unknown begomoviruses. Sequence comparisons with full-length DNA-A sequences of begomoviruses indicated high sequence identities with Tomato yellow leaf curl Thailand virus and a tomato isolate of Tomato yellow leaf curl Kanchanaburi virus from Thailand for the pumpkin and cucumber isolates, respectively. Results indicate that TYLCV is able to infect not only Solanaceous crops but also Cucurbits which may serve as reservoirs for viruses that cause TYLCD in Asia.