Molecular Plant Virology, National Botanical Research Institute, Lucknow, India Molecular Characterization of a Strain of Squash leaf curl China Virus from North India R. R. Singh ingh 1 , S. K. S. K. Raj aj 1 and and V. V. Prasad rasad 2 AuthorsÕ addresses: 1 Molecular Plant Virology, National Botanical Research Institute, Lucknow 226 001, India; 2 Molecular Plant Virology Lab, Department of Botany, Lucknow University, Lucknow 226 007, India (correspondence to S. K. Raj. E-mail: skraj2@rediffmail.com) Received June 21, 2007; accepted August 15, 2007 Keywords: Squash leaf curl China virus, yellow vein mosaic disease of pumpkin, DNA-A, sequence identities, phylogenetic analysis, India Abstract A Begomovirus causing yellow vein mosaic disease of pumpkin (Cucurbita maxima L.) was characterized at molecular level by cloning and sequence analysis of its complete DNA-A genome. The DNA-A of the isolate contains 2758 nucleotides which encode six open read- ing frames (ORFs): AV1 and AV2 in the virion-sense and AC1, AC2, AC3 and AC4 in the complementary- sense. Based on the highest (96%) sequence identities and close phylogenetic relationships with Squash leaf curl China virus species, the Begomovirus was identified as strain of Squash leaf curl China virus. The presence of DNA-B genome of the virus strain was also detected by dot blot hybridization test using DNA-B specific probe. Introduction Begomoviruses (Family Geminiviridae) cause serious diseases of crop plants including cassava, cotton, cucurbits, bean, pepper and tomato (Deng et al., 1997; Harrison and Robinson, 1999; Moffat, 1999; Yin et al., 2001; Zhou et al., 2003). Begomoviruses are transmitted by the whitefly Bemisia tabaci Gen. and have a bipartite genome, DNA-A and DNA-B, both of which are required for systemic infection. However, a few begomoviruses, such as Tomato leaf curl virus (ToLCV) and Tomato yellow leaf curl virus (TYLCV) have a single genomic component, which resembles DNA-A of the bipartite begomoviruses (Navot et al., 1991; Dry et al., 1993). The DNA-A of these begom- oviruses is known to be capable of infection and main- tenance of the disease (Xie et al., 2006). With several diseases caused by monopartite begomoviruses, the association of an extra single stranded circular satellite molecule known as b DNA has been found which is responsible for the symptom development and severity of the disease (Briddon et al., 2003; Jose and Usha, 2003; Mansoor et al., 2003; Saunders et al., 2003; Zhou et al., 2003). Pumpkin (Cucurbita maxima) is an important crop grown extensively in the Indian subcontinent. The crop was first reported to be affected by a yellow vein mosaic disease in northern India in the early 1940s (Vasudeva and Lal, 1943) and subsequently reported throughout India (Verma, 1955; Capoor and Ahmad, 1975; Laths and Gopalkrishnan, 1993) but the causal virus remained unidentified. Yellow vein mosaic and leaf distortion on Cucur. maxima was observed around Lucknow (northern India) during 1998–1999 and the association of a Begomovirus was reported (Singh et al., 2001). Pumpkin yellow vein mosaic virus (PYVMV) was found in pumpkin in southern India but was later identified as Squash leaf curl China virus-(Pumpkin: Coimbatore) on the basis of its com- plete nucleotide sequence (Acc. AY184487, Muniyap- pa et al., 2003). The strains of Squash leaf curl virus viz. Squash leaf curl virus (SLCV, Lazarowitz and Laz- dins, 1991), Squash mild leaf curl virus (SMLCV, Brown et al., 2002), Squash leaf curl China virus (SLCCNV: Acc. AB027465), Squash leaf curl China virus-Philippines (SLCCNV-Ph, Kon et al., 2003), Squash leaf curl Yunnan virus (SLCYV, Xie and Zhou, 2003) have been reported earlier from other parts of the world. We report here sequence identities, phylogenetic analysis of the DNA-A genome and the molecular characterization of a strain of SLCCNV causing yel- low vein mosaic disease on Cucur. maxima in north India. Materials and Methods Virus source and whitefly transmission Naturally infected pumpkin plants showing yellow vein mosaic symptoms were collected from the banks of Gomti river in Lucknow (northern India) during 1998– www.blackwell-synergy.com J. Phytopathology 156, 222–228 (2008) Ó 2008 The Authors Journal compilation Ó 2008 Blackwell Verlag, Berlin doi: 10.1111/j.1439-0434.2007.01347.x