Molecular characterization of two distinct monopartite begomoviruses infecting tomato in india

Abstract

BackgroundTomato leaf curl viruses, which are the members of the genus Begomovirus, have emerged as devastating pathogens worldwide causing huge economic losses and threatening production of crops like cassava, cotton, grain legumes and vegetables. Even though the ToLCV isolates from Northern India have been shown to possess bipartite genome (designated as DNA A and DNA B), those from Australia, Taiwan and Southern India have a single genomic component (DNA A). We describe here the genetic diversity of two isolates of monopartite Tomato leaf curl virus infecting tomato in two extreme regions (North and South) of Indian subcontinent.ResultsThe rolling circle amplification (RCA) products obtained from symptomatic samples were digested, cloned and sequenced. The complete DNA sequence of two Tomato leaf curl virus isolates identified as ToLCV-CTM (India, New Delhi, 2005) and ToLCVK3/K5 (India, Kerala, 2008) are reported here. These isolates had the characteristic features of Begomovirus genome organization with six conserved open reading frames (ORFs). The ToLCV-K3 and ToLCV-K5 isolates may be the strains of the same virus since they show sequence homology of 97% over their entire genome. This, according to the guidelines established by the ICTV Geminiviridae Study-Group is higher than threshold (92%) for delineation of different viral variants and hence single, average value has been assigned for all their analyses presented here. The ToLCV-CTM and ToLCV-K3/K5 viruses were found to be monopartite, as neither DNA-B component nor betasatellite associated with begomovirus species, were detected. The complete nucleotide sequence of DNA-A genome of CTM exhibited highest sequence homology (88%) to Croton yellow vein mosaic virus (AJ507777), and of isolates K3/K5 (88.5%) to Tomato leaf curl Pakistan virus (DQ116884). This is less than the threshold value for demarcation of species in the genus Begomovirus.ConclusionK3/K5 and CTM are considered to be novel isolates of Tomato leaf curl virus. Sequence analyses and phylogenetic study indicate that these two ToLCV isolates might have evolved by recombination between viruses related to two or more viral ancestors. The existence of different ToLCV isolates having high genome diversity in India poses a threat to the tomato production in the Asian continent.

Molecular Characterization of Mungbean Yellow Mosaic Disease and Coat Protein Gene in Mungbean Varieties of Bangladesh

“…4). Pandey et al (2010) has reported similar findings in case of identification of ToLCV, a member of the genus begomovirus causing tomato leaf curl disease.…”

“…1c). Similarly, tomato leaf curl virus (ToLCV) infection was detected in tomato plants at molecular level using ToLCV specific primers (Pandey et al 2010). One PCR amplified sample from each location was gel purified and used for automated sequencing.…”

Biological Characterization and Complete Genome Sequence of a Possible Strain of Indian cassava mosaic virus from Jatropha curcas in India

“…However, several attempts of PCR using DNA-B-and DNA-b-specific primers failed indicating the absence of DNA-B and DNA-b molecules in infected samples; therefore, the Begomovirus was considered to be monopartite. Recently, some new monopartite Begomoviruses (Tomato leaf curl virus, Tomato yellow leaf curl virus and Papaya leaf curl China virus) have been reported from India (Pandey et al 2010), Australia (Van Brunschot et al 2010) and China (Zhang et al 2010) respectively, for which neither DNA-B nor DNA-b could be detected.…”

Evolutionary and Molecular Aspects of Indian Tomato Leaf Curl Virus Coat Protein

“…An increased symptom severity and shortened incubation period required for symptom expression was noticed when ToLCGV was coinoculated with betasatellite of tomato yellow leaf curl virus Thailand (TYLCTHB) resulted in yellow mottling [9]. The molecular relationship of ToLCGV-[Vad], an isolate from Vadodara district of Gujarat, with other strains revealed that it belongs to Old World Begomoviruses and established a closely related cluster with other North Indian strains including ToLCGV-(Varanasi)-[Var] and ToLCGV-(Mirzapur)-[Mir] based on the DNA-A sequence alignment [10]. …”