First report of Squash leaf curl China virus in Pakistan M. Tahir A,D , M. S. Haider B and R. W. Briddon C A NUST Centre of Virology and Immunology, National University of Science and Technology, Tamiz ud Din Road, Lalkurti, Rawalpindi, Pakistan. B School of Biological Sciences, University of the Punjab, Lahore, Pakistan. C National Institute for Biotechnology and Genetic Engineering, Jhang Road, Faisalabad, Pakistan. D Corresponding author. Email: gullsbs@yahoo.com Abstract. Leaf samples of Cucurbita pepo plants showing yellow mosaic symptoms were collected from Lahore, Pakistan. Full-length clones of a bipartite begomovirus were isolated and sequenced in their entirety. The sequences showed the highest levels of nucleotide sequence identity (98.4% for the DNA-A and 89.6% for the DNA-B) to the ‘Indian’ strain of Squash leaf curl China virus (SLCCNV). The Geminiviridae is a family of circular, single-stranded DNA viruses with characteristic quasi-icosahedral particles (Zhang et al. 2001; Böttcher et al. 2004). The viruses in this family are divided across four genera that are distinguished on the basis of host range, insect vector and genome arrangement (Fauquet et al. 2008). Economically the most important geminiviruses are in the genus Begomovirus. Begomoviruses are transmitted exclusively by the whitefly Bemisia tabaci (Jones 2003). In the Old World the majority of begomoviruses have monopartite genomes, although a small number have genomes consisting of two components, of approximately equal size, which are known as DNA-A and DNA-B. The DNA-A encodes all factors required for virus replication, overcoming host defences, insect transmission and control of gene expression, while DNA-B encodes factors required for inter- and intra- cellular movement in host plants (Hanley-Bowdoin et al. 1999). The majority of the monopartite begomoviruses instead associate with a newly identified class of single-stranded DNA satellites termed betasatellites (Briddon and Stanley 2006). Several cucurbits are important vegetable crops grown across the Indian subcontinent. Cucurbits throughout Pakistan are affected by several phytopathogenic RNA-containing viruses Table 1. Characteristic features of the genomic components of the begomovirus isolated from Cucurbita pepo Component ORF Start codon coordinates Stop codon coordinates Predicted size (no. of amino acids) Predicted molecular weight (kDa) DNA-A AV2 121 459 112 13.0 CP 281 1051 256 29.4 Rep 2603 1500 367 41.7 TrAP 1597 1193 134 15.2 REn 1458 1048 136 15.9 AC4 2446 2270 58 6.5 DNA-B NSP 582 (468) A 1274 230 (268) A 26.4 (30.8) A MP 2173 1328 281 31.3 A A stop codon at the N-terminus of the product (position 525) truncates the gene with respect to other isolates of SLCCNV. The figures in brackets are for the features ignoring the premature stop codon. Fig. 1. Foliar symptoms of the Cucurbita pepo plant from which Squash leaf curl China virus (SLCCNV) was isolated. CSIRO PUBLISHING www.publish.csiro.au/journals/apdn Australasian Plant Disease Notes, 2010, 5, 21–24 Ó Australasian Plant Pathology Society 2010 10.1071/DN10009 1833-928X/10/010021