Virus Research 142 (2009) 208–212 Contents lists available at ScienceDirect Virus Research journal homepage: www.elsevier.com/locate/virusres Short communication Diverse and recombinant DNA betasatellites are associated with a begomovirus disease complex of Digera arvensis, a weed host M. Mubin, R.W. Briddon, S. Mansoor * Plant Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), P O Box 577, Jhang Road, Faisalabad, Punjab 38000, Pakistan article info Article history: Received 21 July 2008 Received in revised form 22 December 2008 Accepted 31 January 2009 Available online 12 February 2009 Keywords: Digera arvensis Geminiviruses Begomoviruses Alphasatellites Betasatellites Recombination abstract Weeds are considered as a source of new viruses and reservoirs of economically important viruses but are often neglected during diversity studies. Here, we report the complete nucleotide sequences and phylogenetic analyses of the components of a begomovirus disease complex associated with yellow vein disease of Digera arvensis, a common weed. The begomovirus associated with the disease showed 98% nucleotide sequence identity with Cotton leaf curl Rajasthan virus. Two species of betasatellite were iden- tified. The first betasatellite species was an isolate of Ageratum yellow leaf curl betasatellite. The second was a recombinant consisting for the most part of sequence derived from a Tobacco leaf curl betasatel- lite but with the satellite conserved region (SCR) and some sequence between the SCR and adenine-rich (A-rich) region derived from a Cotton leaf curl Multan betasatellite. The alphasatellite isolated from this weed was near identical to an isolate recently characterized from potato. The presence of multiple and recombinant betasatellites in D. arvensis indicates that weeds can be important sources of multiple bego- movirus components that affect crop plants. Furthermore, the presence of a recombinant betasatellite suggested that weeds are likely vessels for recombination and evolution of components of begomovirus complexes. © 2009 Elsevier B.V. All rights reserved. Geminiviruses are small single-stranded DNA viruses with cir- cular genomes and are transmitted by insect vectors. They have been classified into four genera based on insect vector and genome organization. Whitefly-transmitted geminiviruses are classified in the genus Begomovirus (Stanley et al., 2005). Begomoviruses have genomes consisting of either two genomic components (known as DNA A and DNA B) of about equal size (∼2800 nt), or a sin- gle component homologous to the DNA A component of bipartite viruses (Stanley et al., 2005). Recently numerous begomoviruses in the Old World have been identified that require satellites (col- lectively known as betasatellites) of about half the size of a begomovirus component to induce symptoms in the hosts from which they were isolated (Briddon and Stanley, 2006). In addi- tion to the begomovirus and betasatellite, begomovirus disease complexes are also associated with a third single-stranded DNA component termed an alphasatellite (previously known as DNA 1; Mansoor et al., 1999; Briddon et al., 2004). The alphasatel- lites encode a single product with similarity to the replication associated protein (Rep; a rolling-circle replication initiator pro- tein) of nanoviruses; another family of plant-infecting viruses with single-stranded DNA genomes (Gronenborn, 2004). Consequently, * Corresponding author. E-mail address: shahidmansoor7@gmail.com (S. Mansoor). alphasatellites are capable of autonomous replication but require the helper begomovirus for spread in plants and insect transmis- sion. Alphasatellites appear to have no role in the disease process, being dispensable both for infectivity and symptom induction in host plants. The propensity of betasatellites to be trans-replicated by more than one begomovirus possibly is a contributing factor to their success (Mansoor et al., 2003a; Saunders et al., 2008). Betasatellite requiring begomoviruses are now known to outnum- ber the bipartite and truly monopartite begomoviruses in the Old World. Begomoviruses are increasingly being reported on new hosts as well as spreading to more geographical locations and are responsi- ble for significant yield losses in many crops (Varma and Malathi, 2003; Mansoor et al., 2003a). The attributes responsible for the establishment and emergence of these viral diseases are difficult to pinpoint but multiple infections, recombination and mutations result in emergence of new strains/species which may overcome resistance barriers and adapt to changing environmental condi- tions (Mansoor et al., 2006). Recently there has been an epidemic of a resistance breaking strain of cotton leaf curl disease in Pakistan for which recombination, mutation and natural selection appear to have been major factors in its emergence (Amin et al., 2006). Geminiviruses replicate in nucleus and mixed virus infections are important for virus evolution because they provide the precondi- tion for recombination (Padidam et al., 1999), which may contribute to the appearance of more severe virus strains or new virus species. 0168-1702/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.virusres.2009.01.020