Begomoviruses are a large group of whitefly-transmitted plant viruses containing single-stranded circular DNA encapsidated in geminate particles. They are responsible for significant yield losses in a wide variety of crops in India. Research on begomoviruses has focussed on the molecular characterization of the viruses, their phylogenetic analyses, infectivities on host plants, DNA replication, transgenic resistance, promoter analysis and development of virus-based gene silencing vectors. There have been a number of reports of satellite molecules associated with begomoviruses. This article aims to summarize the major developments in begomoviral research in India in the last approximately 15 years and identifies future areas that need more attention.

Begomovirus research in India: a critical appraisal and the way ahead.

Diseased cotton plants showing typical leaf curl symptoms were collected from experimental plot of Agriculture Research Station—Sriganganagar, Rajasthan. Complete DNA-A component from samples taken from two areas were amplified through rolling circle amplification (RCA) using templiphi kit (GE Healthcare) and characterized. DNA-A of one isolate consists of 2751 nucleotides and second isolate of 2759 nucleotide. Both sequences comprised six ORF’s. Genome organization of DNA-A of one isolate shows high sequence similarity with other characterized local begomovirus isolates of Rajasthan, while other isolate shows high sequence similarity with CLCuV reported from Pakistan. The maximum similarity of first isolate, CLCuV-SG01, shows highest sequence identity with Cotton leaf curl Abohar (Rajasthan) virus, and second isolate, CLCuV-SG02, shows highest sequence identity with cotton leaf curl virus from Pakistan. Both isolates showed 85% similarities with each other. The sequence data revealed probable infiltration of some strains of Cotton leaf curl virus from Pakistan to India, or co-existence of different isolates under similar geographical conditions. While CLCuV-SG01 shows highest nt sequence similarity with CLCuV Rajasthan (Abohar), nt identity of V1 ORF (encoding coat protein) of SG01 shows the highest nt identity (100%) with CLCuV Multan (Bhatinda) and Abohar virus while AC1 region also showed difference. Complete nucleotide sequence of SG01 shows only 86% similarity with CLCuV Multan virus. Similarity search revealed significant difference in AV1 and AC1 regions with respect to DNA-A suggesting an evolutionary history of recombination. Computer based analysis, recombination detection Program (RDP) supports the recombination hypothesis, indicated that recombination with other begomoviruses had taken place within V1 ORF and AC1 ORF of CLCuV-SG01 and AC1 ORF of CLCuV-SG02 and also in noncoding intergenic region (IR).

Sequence characterization of cotton leaf curl virus from Rajasthan: phylogenetic relationship with other members of geminiviruses and detection of recombination

A Sweet potato-infecting sweet potato leaf curl virus (SPLCV) isolated in China was detected by Polymerase Chain Reaction (PCR). PCR products amplified from DNA-A were cloned and sequenced. The isolates of SPLCV from China(SPLCV-CN)has a genome organization similar to that of monopartite begomoviruses. The DNA-A had two ORFs (AV1 and AV2) in the virion sense and four ORFs (AC1, AC2, AC3, and AC4) in the complementary sense, separated by an intergenic region (IR) containing a conserved stem-loop motif. Three incomplete direct repeat iterons were also found within the IR. The presence of AV2 ORF supports the relationship of SPLCV-CN to the Old World gemimiviruses. Sequence comparisons showed that the DNA-A sequence of SPLCV-CN were closely related to those of sweet potato leaf curl Georgia virus-[16] (SPLCGV-[16]), Ipomoea yellow vein virus (IYVV-SI), and sweet potato leaf curl virus (SPLCV) with nucleotide sequence identity ranging from 88% to 91%. Comparison of individual encoded proteins between SPLCV-CN and that of three other SPLCV isolates showed the coat protein (AV1) shared the highest amino acid sequence identity (93%–96%), suggesting the coat protein of these viruses may have identical ancestor. The relationships between SPLCV-CN and other whitefly-transmitted geminiviruses were investigated by using phylogeny of derived AV1, AC1, and AV2 amino acid sequences. In all phylogenetic trees, SPLCV-CN clustered with three other isolates of SPLCV. The analyses revealed that the four isolates of SPLCV have coat proteins which are unique from its counterparts from both the Old World and New World. The present of AV2 and phylogenic analysis of AC1 suggest that SPLCV is more close to begomoviruses from the Old World but isolates of this virus seems to form a separate subset.

/pdf/molecular-characterization-of-sweet-potato-leaf-curl-virus-2somj9cfqz.pdf

Molecular characterization of sweet potato leaf curl virus isolate from China (SPLCV-CN) and its phylogenetic relationship with other members of the Geminiviridae

. Subiastuti AS, Hartono S, Daryono BS. 2019. Detection and Identification of Begomovirus infecting Cucurbitaceae and Solanaceae in Yogyakarta, Indonesia. Biodiversitas 20: 738-744. Begomovirus genome has high plasticity that led to evolve rapidly. Begomovirus is one of a remarkably successful group of emerging viruses as the results from combination of many factors. Planting systems in Indonesia which often overlapping two or more plant species in one land has high possibility for occurring mixed infection. It is also suggested has high contribution to increase Begomovirus diversity. The aim of this research is to do preliminary identification of Begomovirus infected-Solanaceae and Cucurbitaceae in Yogyakarta based core coat protein (CP) gene sequence. A total of 50 melon, 50 chili, 30 eggplants, and 30 watermelon samples which showed Begomovirus symptoms were observed from several fields in Yogyakarta and Purworejo, Indonesia during 2016. Almost 90% of infected samples for each plant were tested by PCR and showed positive for Begomovirus. Based on coat protein (CP) gene nucleotide sequence identity, Begomovirus infected Solanaceae in Indonesia has close relationship with Pepper yellow leaf curl Indonesia virus (PepYLCIV) and Tomato yellow leaf curl Kanchanaburi virus (TYLCVKaV), while in Cucurbitaceae has close relationship with Squash leaf curl China virus (SLCCV) Tomato leaf curl New Delhi virus (ToLCNDV). All collected isolates showed highest sequence identity with isolates from South-East Asia and China. However, further analysis that including full genome characterization is still needed to explain Begomovirus evolution in Indonesia.

/pdf/detection-and-identification-of-begomovirus-infecting-2200xeaiww.pdf

Detection and identification of Begomovirus infecting Cucurbitaceae and Solanaceae in Yogyakarta, Indonesia

Betasatellites are symptom-modulating DNA satellites that are associated with the majority of mono- partite begomoviruses in the Old World. Betasatellites show both geographical and host-specific relatedness; those isolated from malvaceous hosts form one group and those isolated from non-malvaceous hosts form the second group. Real-time PCR based estimation of begomovirus DNA in cotton species grown in a living herbarium under field conditions at the Central Cotton Research Institute (CCRI), Multan was carried out to understand their role in the ongoing cotton leaf curl disease (CLCuD) epidemic in Pakistan. The levels of begomovirus DNA in cotton species from the herbarium was found to be several folds lower than symptomatic plants of commercially grown cotton. Among herbarium species Gossypium anomalum, G. rob- insoni and G. somalense contained higher levels of begomovirus DNA in comparison to other wild species. Characterization of betasatellites from two cotton species (G. anomalum and G. somalense) was carried out to understand their role in accumulation of begomo- virus DNA. Here, we show that the two wild species of cotton are associated with Cotton leaf Multan betasatel- lite (CLCuMB), a malvaceous betasatellite associated with CLCuD, as well as Chili leaf curl betasatellite, a non-malvaceous betasatellite not previously identified in a malvaceous host. This is the first evidence of the presence of a non-malvaceous betasatellite in malvaceous hosts.

Both malvaceous and non-malvaceous betasatellites are associated with two wild cotton species grown under field conditions in Pakistan

Cotton leaf curl geminivirus is a whitefly (Bemisia tabaci Genn.) transmitted Begomovirus (Family Geminiviridae) causing a serious disease of cotton in northern India. The very typical symptoms of present isolate (CLCuV-HS2) showed thickened veins, dark green discoloration of the leaves with upward curling and leaf like structure known as enation (one in number), which develops into cup-shaped on the reverse side of leaves. The polymerase chain reaction (PCR) based technique can detect the viral DNA in samples stored upto 3 days after the collection and have wide application for the field diagnosis. The complete nucleotide sequence of the Indian isolate of cotton leaf curl geminivirus (CLCuV-HS2) coat protein (CP) gene component was determined using CP specific primers through PCR amplification from field infected cotton plants growing in Haryana, India. Comparison of the amino acid sequence of the putative CP with some other mono and bipartite geminiviruses revealed a maximum of 97.3% identity with Pakistan cotton leaf curl virus (CLCuV-62). A nuclear localization signal located close to the N-terminal of CP gene was determined.

Molecular cloning of coat protein gene of an Indian cotton leaf curl virus (CLCuV-HS2) isolate and its phylogenetic relationship with others members of Geminiviridae.

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Molecular cloning of coat protein gene of an Indian cotton leaf curl virus (CLCuV-HS2) isolate and its phylogenetic relationship with others members of Geminiviridae.