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The EFSA Panel on Plant Health conducted a pest categorisation of chickpea chlorotic dwarf virus (CpCDV) for the EU territory. The identity of CpCDV, a member of the genus

Nine complete nucleotide sequences of geminialphasatellites (subfamily Geminialphasatellitinae, family Alphasatellitidae) recovered from the wild Poaceae Sorghum arundinaceum collected in Reunion are described and analyzed. While the helper geminivirus was identified as an isolate of maize streak virus (genus Mastrevirus, family Geminiviridae), the geminialphasatellite genomes were most closely related to, and shared ~63% identity with, clecrusatellites. Even though the geminialphasatellite molecules lack an adenine rich-region, they have the typical size of geminialphasatellites, encode a replication-associated protein in the virion sense, and have probable stem-loop structures at their virion-strand origins of replication. According to the proposed geminialphasatellite species and genus demarcation thresholds (88% and 70% nucleotide identity, respectively), the genomes identified here represent a new species (within a new genus) for which we propose the name "Sorghum mastrevirus-associated alphasatellite" (genus "Sorgasalphasatellite").

Background: Geminiviridae is one of the best-characterized and hence, one of the largest plant-virus families with the highest economic importance. Its members characteristically have a circular ssDNA genome within the encapsidation of twinned quasi-icosaheadral virions (18-38 nm size-range). Objective: Construction of a narrative review on geminiviruses, to have a clearer picture of their genomic structure and taxonomic status. Methods: A thorough search was conducted for papers and patents regarding geminiviruses, where relevant information was used to study their genomic organization, diversity and taxonomic structure. Results: Geminiviruses have been classified into nine genera (viz., genus Begomovirus, Mastrevirus, Curtovirus, Topocuvirus, Becurtovirus, Turncurtovirus, Capulavirus, Eragrovirus and Grablovirus) having distinct genomic organizations, host ranges and insect vectors. Genomic organization of all genera generally shows the presence of 4-6 ORFs encoding for various proteins. For now, Citrus chlorotic dwarf-associated virus (CCDaV), Camellia chlorotic dwarf-associated virus (CaCDaV) and few other geminiviruses are still unassigned to any genera. The monopartite begomoviruses (and few mastreviruses) have been found associated with aplhasatellites and betasatellites (viz., ~1.3 kb circular ssDNA satellites). Recent reports suggest that deltasatellites potentially reduce the accumulation of helper-Begomovirus species in host plants. Some patents have revealed the methods to generate transgenic plants resistant to geminiviruses. Conclusion: Geminiviruses rapidly evolve and are a highly diverse group of plant-viruses. However, research has shown new horizons in tackling the acute begomoviral diseases in plants by generating a novel bio-control methodology in which deltasatellites can be used as bio-control agents and generate transgenic plants resistant to geminiviruses.

Maize striate mosaic virus (MSMV; genus Mastrevirus) was recently reported in maize plants in Brazil and also detected by metagenomic analyses in the corn leafhopper, Dalbulus maidis (DeLong & Wolcott). Although these findings suggested that D. maidis is a potential vector, no transmission studies have been performed. Here, we tested the transmission of MSMV by D. maidis from field-collected infected plants and plants infected with MSMV via leafhopper-mediated transmission in the laboratory; all plants were confirmed positive for MSMV by PCR. In each one of three transmission replicates, aviruliferous D. maidis nymphs and adults were confined together on a source plant during a 4-day acquisition access period (AAP) and subsequently transferred to healthy maize seedlings (10 individuals per test plant) in a series of 4-day inoculation access periods (IAPs). We also tested transmission by the corn aphid, Rhopalosiphum maidis (Fitch) and by mechanical inoculation of healthy maize seedlings. Only D. maidis transmitted MSMV, with overall transmission rates of 29.4 and 39.5% on field-collected infected plants and 18.5% on infected plants in laboratory. D. maidis transmitted MSMV until the third (8 to 12 days after the AAP) or fourth successive IAP (12 to 16 days), with gradual loss in transmission efficiency and rate of viruliferous insects over time, suggesting a persistent but nonpropagative mode of transmission. Infected test plants showed mottling symptoms with mild chlorotic streaks and height reduction. This is the first report of transmission of a mastrevirus by D. maidis, facilitating the completion of Koch’s postulate for MSMV.

Sweet potato symptomless virus 1 (SPSMV-1) is a member of genus Mastrevirus, in the family Geminiviridae. SPSMV-1 was detected from sweet potato (Ipomoea batatas) seedlings by small-RNA deep-sequencing. PCR analysis indicated that SPSMV-1 was detected in 12 out of 114 individual sweet potato seedlings from seeds collected from a SPSMV-1-infected sweet potato plant, and additionally, detected in whole seeds, seed coats attached with endosperm, and in embryos. The complete genome of the virus was subsequently cloned by using a polymerase chain reaction (PCR) method with back-to-back (full) primer pairs from sweet potato seedlings and seeds. In summary, the results suggest that SPSMV-1 may be a seed-borne virus and a seed transmissible virus in sweet potato. To our knowledge, this is the first evidence for seed transmission of SPSMV-1, and seed transmission under natural conditions for any mastrevirus as well.

In West and Central Africa, as in many regions of the world, vegetables are severely affected by geminivirus diseases. In Burkina Faso, observation of various virus-like symptoms, especially on tomato, suggests the involvement of several geminiviruses and underlines the pressing need for additional information on their diversity, distribution, prevalence and host plant reservoirs. Large-scale surveys conducted in Burkina Faso confirmed the presence of tomato (yellow) leaf curl diseases (ToLCD-TYLCD) and geminiviruses in all localities with mean prevalences of 25% and 45%, respectively. Five geminiviruses including four begomoviruses (pepper yellow vein Mali virus (PepYVMLV), tomato leaf curl Burkina Faso virus, tomato leaf curl Mali virus and tomato leaf curl Ghana virus) and a dicot-infecting mastrevirus (chickpea chlorotic dwarf virus) were characterized on tomato. In addition, PepYVMLV and cotton leaf curl Gezira virus (CLCuGeV) were characterized on pepper and okra, respectively, in combination or not with alphasatellites and betasatellites for CLCuGeV. The most severe, prevalent and widely distributed virus on vegetables was PepYVMLV, which was characterized for the first time in combination with a genetically divergent DNA-B component that may constitute a key factor of PepYVMLV pathogenicity. Of the eight weeds identified as potential reservoir hosts of begomoviruses, four host PepYVMLV. The results confirm the importance of geminivirus diseases on vegetable crops in Burkina Faso and highlight the complex association of geminiviruses and satellites. The detection of begomoviruses in weeds growing close to crops points to the increasing necessity to consider reservoir plants and virus communities in the control of virus diseases.

Sweet potato (Ipomoea batatas), a staple food for people in many of the least developed countries, is affected by many viral diseases. In 2017, complete genome sequences of sweet potato symptomless virus 1 (SPSMV-1, genus Mastrevirus, family Geminiviridae) isolates were reported, although a partial SPSMV-1 genome sequence had previously been identified by deep sequencing. To assess the presence of this virus in Spain, sweet potato leaf samples collected in Málaga (southern continental Spain) and the Spanish Canary Islands of Tenerife and Gran Canaria were analyzed. SPSMV-1 was detected in samples from all the geographical areas studied, as well as in plants of several entries obtained from a germplasm collection supposed to be virus-free. Sequence analysis of full-length genomes of isolates from Spain showed novel molecular features, i.e., a novel nonanucleotide in the intergenic region, TCTTATTAC, and a 24-nucleotide deletion in the V2 open reading frame. Additionally, an agroinfectious clone was developed and infectivity assays showed that the virus was able to asymptomatically infect Nicotiana benthamiana, Ipomoea nil, I. setosa, and sweet potato, thus confirming previous suggestions derived from observational studies. To our knowledge, this is the first report of the presence of SPSMV-1 in Spain and Europe and the first agroinfectious clone developed for this virus.

Background: Wheat dwarf virus (WDV) is a leafhopper-transmitted DNA virus which causes yellowing and stunting in wheat and barley fields leading to considerable crop loss around the world. Mainly, two host-specific forms of WDV have been characterized in wheat and barley (WDV-Wheat and WDV-Barley, respectively). Objectives: This study was aimed to amplify, sequence and describe subgenomic DNAs (sgDNAs) associated with WDV infection among wheat and barley plants. The nucleotide sequence of sgDNAs were then compared to that of parental genomic DNAs (gDNAs) and the differences were shown. Materials and Methods: A total of 65 symptomatic plants were surveyed for WDV infection using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and polymerase chain reaction (PCR). Rolling circle amplification followed by restriction analysis (RCA-RA) was applied to identify both gDNAs and sgDNAs in the infected wheat and barley plants. Nucleotide sequence of eight full-length WDV genomes and five sgDNAs were determined. Results: Genomic sequences of WDV-Wheat and WDV-Barley isolates obtained in this study were identified as WDV-F and WDV-B, respectively, forming a separate cluster in the phylogenetic tree with the highest bootstrap support (100%). Sequence analysis of sgDNA molecules revealed that they have undergone different mutation events including deletions in viral genes, duplication of coding regions, and insertion of host-derived sequences Conclusions: The association of different types of sgDNAs were found in WDV-infected wheat and barley plants. The sgDNAs exhibited remarkable changes compared to their parental molecules and they might play a role in symptom severity, host genome evolution and emergence of new virus variants/species.

Chickpea chlorotic dwarf virus (CpCDV), a member of genus Mastrevirus (family Geminiviridae) is an important viral pathogen of chickpea and other legume crops in Middle East, North Africa, India and Pakistan. Among sixteen known strains of CpCDV three are known to infect legume crops in Punjab province of Pakistan. In this study diversity of CpCDV was explored in Khyber Pakhtunkhwa (KP) province of Pakistan. In year 2016, during a survey in the chickpea growing areas of district Dera Ismail Khan, CpCDV infected plants were identified. Leaf samples were collected, and a diagnostic PCR confirmed mastreivrus infection in 4 out of 100 samples. From these samples full-length genome of CpCDV was amplified using specific back-to-back primers. Virus molecules were sequenced to their entirety and sequence analysis of a molecule KRF4 (GenBank accession # KY952837) showed the highest pair wise sequence identity of 97% with a CpCDV molecule (KM229787) isolated from chickpea plant. An SDT analysis revealed it to be the D strain of CpCDV and a recombination detection program (RDP) showed it to be a recombinant between C (KM229780) and L (KT634301) strains of CpCDV. Thus, further supporting the intra-species recombination for CpCDV and presence of the same strain in chickpea growing areas of Pakistan other than Punjab province. This is the first identification of CpCDV (genus Mastrevirus family Geminiviridae) from chickpea (Cicer arietinum) plants in District Dera Ismail Khan, KP province, Pakistan.

Viruses constitute the largest group of emerging pathogens, and geminiviruses (plant viruses with circular, single-stranded DNA genomes) are the major group of emerging plant viruses. With their high potential for genetic variation due to mutation and recombination, their efficient spread by vectors, and their wide host range as a group, including both wild and cultivated hosts, geminiviruses are attractive models for the study of the evolutionary and ecological factors driving virus emergence. Studies on the epidemiological features of geminivirus diseases have traditionally focused primarily on crop plants. Nevertheless, knowledge of geminivirus infection in wild plants, and especially at the interface between wild and cultivated plants, is necessary to provide a complete view of their ecology, evolution, and emergence. In this review, we address the most relevant aspects of geminivirus variability and evolution in wild and crop plants and geminiviruses’ potential to emerge in crops.

Chickpea chlorotic dwarf virus (CpCDV) a polyphagous mastrevirus, family Geminiviridae, is reported to infect several economically important hosts, among which tomato, in numerous world areas. NGS studies have recently linked the "hard fruit syndrome" of watermelon to CpCDV infection. In this study, we surveyed for CpCDV infection tomato fields in several Tunisian areas and we report this virus for the first time in tomato in this Mediterranean country. We detected CpCDV by PCR with specific primers and obtained a full-length sequence of a tomato-derived isolate, resulting identical to the Tunisian watermelon-derived isolate, and classifiable as CpCDV strain A. Following tomato agro-inoculation of the CpCDV infectious clone under controlled conditions, we checked infection by stem squash, dot blotting and PCR, and demonstrated the ability of CpCDV to replicate in tomato tissues. The alterations observed in fruits of CpCDV-infected tomatoes were similar to those previously described for watermelon, providing hints about the perturbation of fruit development mediated by this virus.

Soybean is one of the most important crops in Korea. To identify the viruses infecting soybean, we conducted RNA sequencing with samples displaying symptoms of viral disease. A contig displaying sequence similarity to the known Geminivirus was identified. A polymerase chain reaction (PCR) using two different pairs of back-to-back primers and rolling circle amplification (RCA) confirmed the complete genome of a novel virus named soybean geminivirus B (SGVB), consisting of a circular monopartite DNA genome measuring 2616 nucleotides (nt) in length. SGVB contains four open reading frames (ORFs) and three intergenic regions (IRs). IR1 includes a nonanucleotide origin of replication in the stem-loop structure. Phylogenetic and BLAST analyses demonstrated that SGVB could be a novel virus belonging to the genus Mastrevirus in the family Geminiviridae. We generated infectious clones for SGVB by adding a copy of the IR1 region of SGVB, comparing the V-ori in addition to the full-length genome of SGVB. Using the infectious clones, we observed chlorosis and leaf curling with a latent infection in the inoculated Nicotiana benthamiana plants, while none of the inoculated soybean plants showed any visible symptoms of disease. This study provides the complete genome sequence and infectious clones of a novel Mastrevirus referred to as SGVB from soybean in Korea.

Geminiviridae is one of the most important families in plant viruses with a single-stranded DNA genome comprises one or two genomes (DNA-A and DNA-B) of 2.5–5.2Kb. These viruses infect economically important food and fiber crops worldwide. Till to date nine genera (Mastrevirus, Curtovirus, Becurtovirus, Turncurtovirus, Begomovirus, Capulavirus, Topocuvirus, Eragrovirus, and Grablovirus) have been reported which are transmitted by four insect vectors (whiteflies, leafhoppers, aphids, and treehoppers). DNA-A encodes replication-associated protein, coat protein, replication enhancer protein, transcriptional activator protein, AV2, AC4, and AC5 while DNA-B encodes nuclear shuttle protein and movement protein. Satellite molecules have also been reported to be associated with the family Geminiviridae that includes alphasatellite, betasatellite which encode alpha rep and βC1 gene respectively. A non-coding deltasatellite has also been reported to be associated with geminivirus infections. Geminivirus encoded proteins interact with host proteins to perform a variety of functions which include reprogramming of cell cycle, inhibition of cell death pathways, transcriptional control of multiple genes, interference with cell signaling pathways and overcoming host defense response. Our current knowledge regarding interactions of geminivirus encoded proteins with the host has been described in the following chapter.

International audience; Maize streak disease (MSD) is one of the most significant biotic constraints on the production of Africa's most important cereal crop. Until recently, the only virus known to cause severe MSD was the A-strain of maize streak virus (MSV/A), a member of the genus Mastrevirus, family Geminiviridae. However, over the past decade, two other mastreviruses, MSV/C and maize streak Reunion virus (MSRV), have been repeatedly found in the absence of MSV/A in maize plants displaying severe MSD symptoms. Here, we report on infectious clones of MSV/C and MSRV and test their ability to cause severe MSD symptoms. Although cloned MSV/C and MSRV genomes could cause systemic symptomatic infections in MSD-sensitive maize genotypes, these infections yielded substantially milder symptoms than those observed in the field. The MSV/C and MSRV isolates that we have examined are therefore unlikely to cause severe MSD on their own. Furthermore, mixed infections of MSRV and MSV/C with other mild MSV strains also consistently yielded mild MSD symptoms. It is noteworthy that MSRV produces distinctive striate symptoms in maize that are similar in pattern, albeit not in severity, to those seen in the field, showing that this virus may contribute to the severe MSD symptoms seen in the field. Therefore, despite not fulfilling Koch's postulates for MSV/C and MSRV as causal agents of severe MSD, we cannot exclude the possibility that these viruses could be contributing to currently emerging maize diseases.

Presence of Wheat dwarf India virus (WDIV) and Ageratum yellow leaf curl betasatellite (AYLCB) was confirmed using polymerase chain reaction and sequencing in wheat samples originating from Pakistan for the first time. However, no alphasatellites were detected from the analyzed samples. Both, WDIV and AYLCB were highly similar to their counterparts reported from wheat in India. The findings of this study suggest a strong association between WDIV and AYLCB. This is also the first report of a monocot infecting mastrevirus and the presence of a satellite in a monocot plant in Pakistan.

Spinach is a common vegetable crop and very little data is available about its virus infection. Symptomatic leaves of spinach were collected during field survey. Circular DNA molecules were amplified from symptomatic samples using rolling circle amplification (RCA). After restriction analysis, presumed bands of virus and satellites were cloned, sequenced and analyzed. Analysis of sequenced RCA product revealed the presence of chickpea chlorotic dwarf virus (CpCDV; Mastrevirus). Further analyses of the cloned virus showed that strain "C" of CpCDV was present in symptomatic samples of spinach collected from field associated with vein darkening, curling and enations on leaves. Amplification of alpha- and betasatellites with universal primers was performed. CpCDV showed association with cotton leaf curl Multan betasatellite (CLCuMB) and cotton leaf curl Multan alphasatellites (CLCuMA). Infectivity analysis of CpCDV and CpCDV/CLCuMB were done in N. benthamiana using particle bombardment method and the results showed that CpCDV was able to transreplicates CLCuMB in this host. To our knowledge, this is the first report of a dicot infecting mastrevirus (CpCDV) along with CLCuMB and CLCuMA associated with leaf curl disease of spinach in Pakistan. The significance of the results is discussed.

Symptomless grape plants (Vitis vinifera) cultivated in Jind, Punjab, have been found to carry a Grapevine red blotch virus (GRBV). Evaluation of full length DNA sequence (3204 bp) of the virus (KU522121) has revealed similarity with mastrevirus, begomovirus, and other Grapevine red blotch viruses reported in the US and Canada. Similar to naturally growing plants, agroinfiltrated model plants with infectious clone of GRBV do not show any visible disease warning sign. To the best of our knowledge, this is the first report of a symptomless host Vitis vinifera from Indian vineyards harbouring a Grapevine geminivirus. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13337-018-0477-x) contains supplementary material, which is available to authorized users.

Colorimetric and real-time loop-mediated isothermal amplification (cr-LAMP) assays were developed targeting the coat protein region of genomic DNA of Wheat dwarf virus (WDV). The method was optimized relating to primer selection, determination of isothermal temperature, and determination of incubation duration. The specificity of the assay was tested using potential hosts of WDV and Maize streak virus (MSV) from Mastrevirus genus. No cross-reaction took place with MSV or with the potential hosts tested. For the naked eye observation of positive LAMP reaction, WarmStart 2X Master Mix from NEB (New England Biolabs) was used, where the change in colour from pink to yellowish points out a positive result. The amplification was monitored in real-time by smart-DART platform (Diagenetix Inc, USA) that allows connecting to a tablet or smartphone via bluetooth. The detection sensitivity of the LAMP assay was 100-fold more sensitive than conventional PCR after optimization of the cr-LAMP reaction conditions. The novel LAMP assay showed a high specificity in distinction of WDV detection from potential hosts and MSV. The cr-LAMP is considered to be fast and effective assay since it only requires very basic equipment and the results can be evaluated easily by using colorimetric and real time approaches. The simple, low-power, handheld smart-DART platform and colorimetric detection both have a major powerful advantage of the LAMP reaction in that it can be enabled in agricultural industries, where laboratory capacity is often rudimentary.

Maize streak virus (MSV), the causal agent of maize streak disease (MSD), is the most important viral pathogen of Africa’s staple food crop, maize. Previous phylogeographic analyses have revealed that the most widely-distributed and common MSV variant, MSV-A1, has been repeatedly traversing Africa over the past fifty years with long-range movements departing from either the Lake Victoria region of East Africa, or the region around the convergence of Zimbabwe, South Africa and Mozambique in southern Africa. Despite Kenya being the second most important maize producing country in East Africa, little is known about the Kenyan MSV population and its contribution to the ongoing diversification and trans-continental dissemination of MSV-A1. We therefore undertook a sampling survey in this country between 2008 and 2011, collecting MSD prevalence data in 119 farmers’ fields, symptom severity data for 170 maize plants and complete MSV genome sequence data for 159 MSV isolates. We then used phylogenetic and phylogeographic analyses to show that whereas the Kenyan MSV population is likely primarily derived from the MSV population in neighbouring Uganda, it displays considerably more geographical structure than the Ugandan population. Further, this geographical structure likely confounds apparent associations between virus genotypes and both symptom severity and MSD prevalence in Kenya. Finally, we find that Kenya is probably a sink rather than a source of MSV diversification and movement, and therefore, unlike Uganda, Kenya probably does not play a major role in the trans-continental dissemination of MSV-A1.

Sugarcane and maize plants showing symptoms typical of those described for the so-called "African streak viruses" (AfSVs) were encountered during field surveys conducted from February to July 2015 to document viruses infecting both crops across the northern Guinea savannah region of Nigeria. As part of this study, two categories of complete mastrevirus-like genome sequences were obtained from nine samples (maize = 2; sugarcane = 7). In pairwise comparisons, the full-length genomes of the first sequence category (2,687 nt each; maize = 2; sugarcane = 2) shared 96 to 99% identity with global isolates of the A-strain of maize streak virus (MSV-A), indicating that sugarcane may also serve as a reservoir host to MSV-A. Analysis of the complete genomes belonging to the second sequence category (2,757 nt each; sugarcane = 5) showed that they shared 42 to 67% identity with their closest AfSV relatives, thus indicating that they represent sequences of a novel mastrevirus. Both sequence categories shared 61-62% sequence identity with each other. Further analysis revealed that the novel sugarcane-infecting virus, tentatively named as sugarcane chlorotic streak virus (SCSV), arose from a putative interspecific recombination event involving two grass-infecting mastreviruses, eragrostis streak virus and urochloa streak virus, as putative parental sequences. The results of this study add to the repertoire of diverse AfSVs present in cereal and sugarcane mixed cropping landscapes in the northern Guinea savannah region of Nigeria, with implications for disease epidemiology.

In the last decade two mastreviruses, Wheat dwarf virus (WDV) and Oat dwarf virus (ODV) have been reported from cereal farms in Iran. In a survey, wild and cultivated hosts of these mastreviruses were studied during 2015 to 2017. Symptomatic small grain cereal samples and weed species were collected and assayed for WDV and/or ODV infection by PCR. While WDV which was detected in 139/284 (49%) of total symptomatic samples, low incidence (2%) was recorded for ODV which was detected only in slender wild oat (Avena barbata Pott ex Link) and red brome (Bromus rubens L.). In agroinfection studies, the clone of ODV infected common oat (A. sativa) and slender wild oat (A. barbata) with the low efficiency and did not infect wheat or barley. ODV was transmitted by the leafhopper Psammotettix alienus, from agroinfected common oat to healthy seedlings. The results show that, in contrast to WDV, ODV has a low incidence and a narrow host range in gramineous plants.

Despite the development and deployment of maize streak-resistant (SR) germ plasm, virus-induced symptoms are still commonly observed on maize in Lagos, Nigeria. Therefore, surveys were conducted between April 2001 and February 2002 to determine the identity, prevalence, and incidence of maize viruses in 18 local government areas (LGAs) in and around Lagos by visual examination and serodiagnostic screening of symptomatic plants. All 112 fields surveyed during the dry season (September to December) and 18 fields surveyed during the late dry season (December to February) had plants infected by Maize streak virus (MSV), whereas 97.1% of the 170 fields surveyed during the wet season (April to August) had plants infected by MSV. Maize mottle/chlorotic stunt virus (MMCSV) was prevalent in 99.1, 88.9, and 67.4% of the fields surveyed during the dry, late dry, and wet seasons, respectively. The incidence of MSV was higher in 16 of the LGAs. The highest incidence of MSV was 18.9%, whereas that of MMCSV was 7.4%. Serodiagnostic screening of leaf samples showing virus-induced symptoms, using antigen-coated plate enzyme-linked immunosorbent assay, indicated that 1,192/1,475 (80.8%) and 949/1,210 (78.4%) of the samples were positive for MSV and MMCSV, respectively. Vector transmission and host range studies confirmed the identity of the viruses. The results confirm the presence of MSV and MMCSV in Lagos and suggest that the use of MSV-susceptible cultivars is still widespread. Methods of ensuring effective utilization of existing SR germ plasm and controlling maize viruses in general are discussed.

Maize streak is the most widespread and important disease of maize in sub-Saharan Africa. Maize streak virus (MSV)-resistant maize germ plasm is available in several countries, but little is known about the stability of its resistance to MSV strains that may differ from one region to another. We used four maize inbred lines (CML312, CML206, CML216, and MSR) known to differ widely for their resistance to MSV in Harare, and evaluated their resistance to 20 MSV isolates collected from the wild during 2 years at locations across Zimbabwe. Maize streak development and symptom severity were evaluated in replicated greenhouse experiments using artificial inoculation via viruliferous leafhoppers. All 20 MSV isolates induced maize streak symptoms on moderately and highly susceptible genotypes by about 1 week after inoculation (WAI). Differences among isolates for severity of early maize streak symptoms were ephemeral, and resistance was accurately differentiated by all isolates by 3 to 4 WAI. Differences in final maize streak symptom scores induced by the isolates were statistically significant, but differed only by a maximum of 7% in 1999 and 19% in 2000. Although genotype, isolate, and genotype by isolate effects for maize streak symptom scores were significant (P < 0.01), relative MSV resistance of the genotypes was consistently ranked by all 20 MSV isolates.

Sweetpotato (Ipomea batatas L.) is grown widely from tropical to temperate regions and is an important food security crop in tropical countries. In Africa, sweetpotato is infected by RNA viruses of many taxa (4), but DNA viruses, such as the genus Begomovirus (family Geminiviridae), infecting sweetpotatoes in the Americas have been reported only in Kenya (3). A caulimo-like DNA virus (family Caulimoviridae) has been detected in sweetpotatoes in Uganda (1). Recently, two novel badnaviruses (genus Badnavirus, family Caulimoviridae) and a new mastrevirus (genus Mastrevirus, family Geminiviridae) were discovered in a local sweetpotato cultivar maintained in a germplasm collection in Peru (2) but were not reported elsewhere. This study examined the possible existence of these novel viruses in landrace sweetpotato varieties grown in Tanzania. Nine landrace sweetpotato varieties and one introduced cultivar (NIS 91 from the International Potato Centre, Peru) were sampled from six regions of Tanzania. DNA was extracted (2) and amplified by PCR using primers (MastvKF: 5′-GACAGACCCCTAGGGTGA-3′; MastvsR 5′-ACTGCATATAGTACATGCCACA-3′) designed in this study to amplify partial, putative movement and coat protein gene sequences of Sweetpotato symptomless virus 1 (SPSMV-1) (GenBank Accession No. FJ560945) (2). Products of the expected size were detected in seven samples (varieties Ex-London, Ex-Lyawaya, Gairo, Hombolo, Kagole white, Mbeya, and Shangazi) representing four regions surveyed (Dodoma, Mbeya, Morogoro, and Kagera). PCR products from five samples were sequenced (396 nt; GenBank Accession Nos. HQ316938 to HQ316942) and found to be identical to each other and the isolate described originally in Peru (2). Amplification with primers (BadnaBKF: 5′-CAAATTAGGAGGCAGATAAATG-3′; BadnaBsR: 5′-GGTCTTCTTATGTTCCACCTT-3′) designed in this study according to the sequence of Sweetpotato virus B (SPBV-B) (GenBank Accession No.FJ560944) resulted in products of the expected size in three samples (varieties Ex-Lyawaya, Gairo, and Hombolo collected in Mbeya, Morogoro, and Dodoma, respectively) that were positive also for SPSMV-1. Sequences of the products (787 nt; HQ316935 to HQ316937) were nearly identical (99.4%). They were 96.8 to 96.9% similar to a region (nts 830-1616) of Sweetpotato virus A (SPBV-A; FJ560943) (2), whereas they were only 83.2 to 83.6 % similar to the corresponding region (1,486 to 2,272 nt) of SPBV-B (FJ560944) (2). No virus was detected in cv. NIS 91. All plants sampled exhibited mild mottling or mosaic symptoms, but a contribution to the symptoms by other untested viruses cannot be excluded because few of the large number of sweetpotato viruses have been studied in Africa (4). To our knowledge, this is the first report of SPSMV-1 and SPBV-A outside South America and in sweetpotatoes grown in the field. The results show that the two viruses are distributed widely in local sweetpotato varieties in Tanzania, which suggests that they may be found in other sweetpotato-growing areas where they have not been studied. While the yield losses caused by SPSMV-1 and SPBV-A remains to be studied, the data from this study are of practical importance in terms of regional and international exchange of sweetpotato germplasm. References: (1) V. Aritua et al. Plant Pathol. 56:324, 2007. (2) J. F. Kreuze et al. Virology 388:1, 2009. (3) T. Paprotka et al. Virus Res. 149:224, 2010. (4) F. Tairo et al. Mol. Plant Pathol. 6:199, 2005.

Geminiviruses (family: Geminiviridae) are plant pathogenic viruses with single-stranded DNA (ssDNA) genome. Geminiviruses are classified into nine genera: Begomovirus, Mastrevirus, Curtovirus, Becurtovirus, Topocuvirus, Turncurtovirus, Capulavirus, Grablovirus, and Eragrovirus. Begomoviruses constitute the largest number of viruses in Geminiviridae family infecting most economically important crops in Australia, China, Europe, and the Middle East countries. Crops that have been infected with begomoviruses belong to the families, Malvaceae (cotton and okra), Cucurbitaceae (melon, watermelon, squash, and gourds), Euphorbiaceae (cassava), Solanaceae (tobacco, potato, tomato, and pepper), and Fabaceae (soybean, cowpea, common bean, and mungbean). Mastreviruses infect chickpea and pepper crops in Australia, Oman, Yemen, Jordan, Syria, and Iraq. Becurtoviruses infect some crops like sugar beet and tomato in Iran. Capulaviruses have been recorded in France and Finland infecting Alfalfa and Plantago plants, respectively. The geminiviruses pose a great challenge to the countries by their fast spread and infecting economic crops. Cooperation among these countries in exchanging information and adopting the most up-to-date system in quarantine can prevent further introduction of new viruses into new geographic regions.

Mastreviruses are the main causal viral agent of a variety of plant diseases in African continent posing a serious threat to economically important plant species, residing/harbouring chiefly in the uncultivated ones. Mastreviruses are known to have numerous diverse carrier vectors infecting either monocotyledons or dicotyledons plants. More than 1950 Mastreviruses sequences are publically available in nucleotide database of NCBI, majority (~850) of them are reported from Africa alone. All the known Mastreviruses encompass a monopartite genomic nature (ranges from 2.5 to 2.7 kb) encoding four genes. Reports and evidences suggest a strong intra- or inter-specific recombination among the identified Mastreviruses, but the extent to which it creates diversity is still a challenging task to understand and get a clear insight. Such diversity is also supported by gene acquisition and mutations (especially point mutations and small insertions or deletions). Current study focuses on the molecular diversity analysis and genomic characterization of the reported Mastreviruses from the African continent.

Geminiviruses and their diseases are a considerable economic threat to a vast number of crops worldwide. Investigating how and where these viruses replicate and accumulate in their hosts may lead to novel molecular resistance strategies. In this study, we used the Rep-inducible In Plant Activation (INPACT) expression platform, based on the genome of tobacco yellow dwarf virus (TYDV), to determine where this model mastrevirus replicates in its host tobacco. By developing an infectious clone of TYDV and optimizing its delivery by agroinfiltration, we first established an efficient artificial infection process. When delivered into transgenic tobacco plants containing a TYDV-based INPACT cassette encoding the β-glucuronidase (GUS) reporter, we showed the virus activates GUS expression. Histology revealed that reporter gene expression was limited to phloem-associated cell types suggesting TYDV replication has a restricted tissue tropism.

Wheat dwarf virus, transmitted by the leafhopper Psammotettix alienus in a persistent, non-propagative manner, infects numerous species from the Poaceae family. Data associated with wheat dwarf virus (WDV) suggest that some isolates preferentially infect wheat while other preferentially infect barley. This allowed to define the wheat strain and the barley strain. There are contradictory results in the literature regarding the ability of each of these two strains to infect its non-preferred host. To improve knowledge on the interactions between WDV strains and barley and wheat, transmission experiments were carried out using barcoded P. alienus and an experimental design based on single/sequential acquisitions of WDV strains and on transmissions to wheat and barley. Results showed that (I) WDV strains are transmitted with similar efficiencies by P. alienus males, females and larvae, (II) WDV wheat and barley strains do not infect barley and wheat plants, respectively, and (III) a functional transcomplementation between the wheat and barley strains allows a mixed infection of barley and wheat. The described ability of each WDV strain to infect a non-host plant in the presence of the other viral strain must be considered to analyze data available on WDV host range.

Over the past few decades, there has been more interest in Geminiviruses, especially Mastrevirus and Begomovirus, as many of the diseases they cause have now reached epidemic magnitude. Ornamental plants are widely distributed in India and across the globe having high environmental adaptability. Their farming forms a major branch of horticulture. At most of the places, crops stay in the field for a particular season, while different ornamental plants grow in or nearby these agricultural fields throughout the year. Ornamental plants serve as an alternative host for Geminiviruses in the absence of the main crops and considered as a source of new viruses or reservoirs of unidentified viruses which are often neglected during diversity studies. Ornamental plants may allow the spread and transmission of Geminiviruses back to crop plants when the cropping season returns, which enhances the host range of these viruses. Thus, there is a pressing need for additional information on the diversity and distribution of Geminiviruses in ornamental plants.

This study aims to identifying and characterizing some molecular properties of geminiviruses co-infection in squash field crop cultivated in Egypt. Squash crops observed to be heavily infected with several insect vectors, also severe chlorosis and stunting was observed. Electron microscopic analysis has revealed geminate capsid particles which indicate the infection of Geminiviruses, especially SqLCV which represent an economic problem to squash filed crop in Egypt. We have investigated possible mixed infections with different plant viruses associated with chlorotic stunt diseases and or other genus groups of geminiviruses. The main objective of this study is to investigate the recombination events, possible recombinants and variants among these genera in the same family differing in vector transmission. This is the first report of the molecular characterization, phylogenetic analysis and putative recombination events of the full length genome of the Chickpea Chlorotic Dwarf Mastrevirus in Egypt. And the first report of co-infection with another begomovirus infecting squash plants. A full length clone of both viruses were isolated and characterized at the molecular level. The complete nucleotide sequence of DNA-A was determined (2,572 bp) and submitted to the genbank under accession no. KF692356. The isolate from Egypt has about 97.8 % homology with the Chickpea chlorotic dwarf virus (CpCDV) isolate from Syria DNA-A isolate FR687959, a 83.2 % homology with the Sudan isolate AM933134 and a 82.7 % homology with Pakistan isolate FR687960. To best of our knowledge this is the first report of complete genome of CpCDV that infect squash plants in Egypt and worldwide.

Although members of five distinct viral species in the genus Mastrevirus (family Geminiviridae) infect dicotyledonous plants in Australia, in the remainder of the world, only a single dicot-infecting mastrevirus, chickpea chlorotic dwarf virus (CpCDV) has ever been identified. This virus has been found infecting leguminous hosts in Africa, the Middle East and the Indian subcontinent. To further explore the diversity of CpCDV in Pakistan, ten full mastrevirus genome sequences from chickpea and lentil plants were determined. Eight of these genomes were from previously described CpCDV strains and included the first reported strain D and H isolates in Pakistan. Two other genomes derived from infected chickpea plants are more closely related to dicot-infecting mastreviruses found in Australia than they are to CpCDV. These two divergent genomes shared less than 75 % genome-wide nucleotide sequence identity with other characterised mastreviruses and therefore are likely to belong to a second species of dicot-infecting mastreviruses outside of Australia. We propose naming this species Chickpea yellow dwarf virus. We discuss how the presence of chickpea yellow dwarf virus (CpYDV) in Pakistan weakens the hypothesis that Australia is the geographical origin of the dicot-infecting mastreviruses.

The genus Mastrevirus (family Geminiviridae) is composed of single-stranded DNA viruses that infect mono- and dicotyledonous plants and are transmitted by leafhoppers. In South America, there have been only two previous reports of mastreviruses, both identified in sweet potatoes (from Peru and Uruguay). As part of a general viral surveillance program, we used a vector-enabled metagenomics (VEM) approach and sampled leafhoppers (Dalbulus maidis) in Itumbiara (State of Goiás), Brazil. High-throughput sequencing of viral DNA purified from the leafhopper sample revealed mastrevirus-like contigs. Using a set of abutting primers, a 2746-nt circular genome was recovered. The circular genome has a typical mastrevirus genome organization and shares63% pairwise identity with other mastrevirus isolates from around the world. Therefore, the new mastrevirus was tentatively named "maize striate mosaic virus". Seventeen maize leaf samples were collected in the same field as the leafhoppers, and ten samples were found to be positive for this mastrevirus. Furthermore, the ten genomes recovered from the maize samples share99% pairwise identity with the one from the leafhopper. This is the first report of a maize-infecting mastrevirus in the Americas, the first identified in a non-vegetatively propagated mastrevirus host in South America, and the first mastrevirus to be identified in Brazil.

Most known mastreviruses (family Geminiviridae) infect members of the grass family, Poaceae. Although the greatest number of grass-infecting mastrevirus species have been discovered in Africa, it is apparent that the ten grass-infecting mastrevirus species that have so far only been discovered in south-east Queensland have a degree of diversity that rivals that observed in Africa. In this study, we have used a deep sequencing approach to identify two new mastrevirus species, tentatively named rice latent virus 1 and 2 (RLV 1 and 2), from two, undescribed wild rice species (Oryza AA genome group) in Cape York Peninsula, Queensland. The sequences of these new viruses had less than 70% identity with any previously identified mastrevirus, and therefore their discovery vastly expands the known diversity of monocot-infecting mastreviruses in Australia. This study also highlights the potential risks of novel crop pathogens emerging from uncultivated grass species, as the wild rice hosts are very closely related to domesticated rice.

Members of the genus, Mastrevirus (family, Gemniviridae) transmitted by leafhopper vectors infect monocotyledonous or dicotyledonous plants, and infection of agricultural crops results in reduced yield and quality. During 2012, a study was undertaken in the Punjab and Sindh Provinces in Pakistan to determine the identity of suspect geminiviruses associated with symptomatic cotton and vegetable plants exhibiting foliar enations, leaf curling, mosaic, and stunting reminiscent of geminivirus infection. To determine suspect geminiviral identity, fifteen apparently full-length mastrevirus genome (~ 2600 base pairs) were amplified by rolling-circle amplification, digested, cloned into the plasmid vector, pGEM-3Zf+, and sequenced from cucumber, Gossypium arboreum L., Gossypium hirsutum L., okra and tomato. The mastrevirus full-length genome sequences obtained shared their highest pairwise nucleotide sequence identity, at 97.3–98.6%, with previously reported C and L strains of Chickpea chlorotic dwarf virus (CpCDV) from chickpea and cotton in Pakistan, respectively. However, CpCDV has not been previously identified from cucumber, G. arboreum, okra, or tomato. The association of CpCDV with four previously unreported plant hosts suggests that CpCDV strains C and strain L have a broader than expected host range, and therefore may be found to negatively affect vegetable crops, particularly, when grown in proximity to cotton. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13337-018-0454-4) contains supplementary material, which is available to authorized users.

Complete genomic sequences of nine isolates of sweet potato symptomless virus 1 (SPSMV-1), a virus of the genus Mastrevirus in the family Geminiviridae, were determined from sweet potato accessions from different countries and found to be 2,559-2,602 nucleotides in length. These isolates shared 97-100% genome sequence identity and had an unusual nonanucleotide sequence (TAAGATTCC) in a large intergenic region as well as an additional open reading frame, C3, which is conserved in dicot-infecting mastreviruses.

BackgroundGeminiviruses (familyGeminiviridae) are prevalent plant viruses that imperil agriculture globally, causing serious damage to the livelihood of farmers, particularly in developing countries. The virus evolves rapidly, attributing to its single-stranded genome propensity, resulting in worldwide circulation of diverse and viable genomes. Genomics is a prominent approach taken by researchers in elucidating the infectious mechanism of the virus. Currently, the NCBI Viral Genome website is a popular repository of viral genomes that conveniently provides researchers a centralized data source of genomic information. However, unlike the genome of living organisms, viral genomes most often maintain peculiar characteristics that fit into no single genome architecture. By imposing a unified annotation scheme on the myriad of viral genomes may downplay their hallmark features. For example, the viron of begomoviruses prevailing in America encapsulates two similar-sized circular DNA components and both are required for systemic infection of plants. However, the bipartite components are kept separately in NCBI as individual genomes with no explicit association in linking them. Thus, our goal is to build a comprehensiveGeminivirusgenomics database, namely gb4gv, that not only preserves genomic characteristics of the virus, but also supplements biologically relevant annotations that help to interrogate this virus, for example, the targeted host, putative iterons, siRNA targets, etc.MethodsWe have employed manual and automatic methods to curate 508 genomes from four major genera ofGeminiviridae, and 161 associated satellites obtained from NCBI RefSeq and PubMed databases.ResultsThese data are available for free access without registration from our website. Besides genomic content, our website provides visualization capability inherited from UCSC Genome Browser.DiscussionWith the genomic information readily accessible, we hope that our database will inspire researchers in gaining a better understanding of the incredible degree of diversity of these viruses, and of the complex relationships within and between the different genera in theGeminiviridae.Availability and ImplementationThe database can be found at:http://gb4gv.lafayette.edu.

Mastreviruses (family Geminiviridae) are generally known to infect monocotyledon plants and are transmitted by leafhopper. Compared to begomoviruses, number of mastreviruses characterized are far less in India. Only two mastreviruses, chickpea chlorotic dwarf virus infecting dicot plant and wheat dwarf India virus (WDIV) infecting wheat have recently been identified in India. Both the viruses have been characterised at genomic level and infectivity of the cloned DNAs has been demonstrated. Interestingly, WDIV is associated with two alphasatellites and one betasatellite. The satellites contribute to viral pathogenicity and suppress the RNA silencing of the host.

Begomoviruses are plant pathogenic viruses belonging to family Geminiviridae. Based upon their host ranges, genome organizations, and insect vectors, geminiviruses are classified into nine genera: Begomovirus, Mastrevirus, Curtovirus, Becurtovirus, Topocuvirus, Turncurtovirus, Capulavirus, Grablovirus, and Eragrovirus. Most of the economically important geminiviruses belongs to genus Begomovirus and infect important cash crops of several families including Malvaceae (cotton, okra), Cucurbitaceae (melon, watermelon, squash, and gourds), Euphorbiaceae (cassava), Solanaceae (tobacco, tomato, potato, petunia, and pepper), and Fabaceae (soybean, cowpea, common bean, mung bean, and lima bean) in different regions of the world.

Begomoviruses are economically important viruses with ssDNA containing monopartite or bipartite genomes, encapsulated in twinned particles belonging to family Geminiviridae. Currently, a total seven genera are known in the family Geminiviridae, and they are designated as Mastrevirus, Curtovirus, Begomovirus, Topocuvirus, Eragrovirus, Turncurtovirus, and Becurtovirus. They are transmitted by the vector whitefly (Bemisia tabaci). Begomoviruses are known to have satellite molecules known as betasatellites and alphasatellites. The plant virology in Saudi Arabia is new and at infancy stage. Currently, very little information is available at the molecular level about the begomoviruses infecting cultivated and weed crops. The begomovirus infection and disease spread on new hosts as well as new geographic regions are significantly increasing in many new regions in the kingdom, and currently begomovirus-associated disease on multiple crops like Amaranthus plant, beans, Corchorus plant, cucumber, okra, ridge gourd, squash, and tomato has been reported from Saudi Arabia. There is an urgent need to perform more research on the disease spread, epidemiology, as well as molecular characterization of begomoviruses to identify the currently circulating virus isolates as well as possible emergence of new strains with their extended host characteristics in Saudi Arabia. This article provides the current status of major developments on the begomovirus research and future prospects in Saudi Arabia.

The family Geminiviridae primarily constitutes an important family of circular single-stranded DNA (ssDNA) plant-infecting viruses, which pose severe constraints in agricultural production globally and serious threat to food security in sub-Saharan Africa. There are seven known genera, Mastrevirus, Begomovirus, Curtovirus, Becurtovirus, Eragrovirus, and Turncurtovirus of viruses belonging to the family Geminiviridae. Of these, the best characterized economically important species belong to the genus Begomovirus. Begomovirus species are either monopartite (possessing only DNA-A) or bipartite (having both DNA-A and DNA-B components). Majority of the monopartite begomoviruses also have subviral ssDNA satellite components, called DNA α or DNA β. In some cases, defective interfering DNAs can be found in the helper virus due to deletions of some genomic parts associated with bipartite and monopartite begomoviruses. New begomoviral species and their associated subviral components continue to emerge globally, thereby, constituting a formidable challenge to the profitable production of vegetables and other crops. Key begomoviruses associated with major crops in Nigeria are documented in this review.

Wheat dwarf virus (WDV) is an economically important and widespread single-stranded DNA virus in the genus Mastrevirus, family Geminiviridae. So far, an RNA silencing suppressor in the genus Mastrevirus has not been reported. In this study, the viral replication-associated proteins of WDV, Rep and RepA proteins, were demonstrated to have RNA silencing suppressor activities when expressed in agro-infiltrated leaves of Nicotiana benthamiana line 16c, by their ability to inhibit posttranscriptional gene silencing (PTGS) of green fluorescent protein (GFP). On the basis of the analysis of GFP expression and siRNA accumulation, we concluded that both Rep and RepA proteins suppressed local silencing induced by either single-stranded GFP (ssGFP) or inverted repeat GFP (dsGFP) constructs, although their activity can be characterized as relatively weak in comparison to HC-Pro of tobacco etch virus.

Small interfering RNA deep sequencing (SRDS) was used to detect viruses in 23 sweetpotato plants, collected from various locations in Tanzania. Alignment of small RNA reads using a MAQ program recovered genomes of viruses from five families, namely Geminiviridae (2), Closteroviridae (1), Betaflexiviridae (1), Caulimoviridae (1) and Potyviridae (1). This was in agreement with the variation of symptoms observed on sweetpotato plants in fields and screen house, which included leaf curl, vein yellowing, chlorosis, stunted growth and brown blotches. PCR was also used to confirm the occurrence of viruses associated with leaf curl and symptomless infections. A complete genome (2768 nucleotides) was obtained for a sweepovirus that was 89.9% identical to the strain of Sweet potato leaf curl Sao Paulo virus (SPLCSPV; Begomovirus) reported in South Africa. Sweepoviruses are known to undergo frequent recombinations and evidence for this was found in the SPLCSPV sequence studied. The SRDS-based results indicated occurrence of the poorly studied Sweet potato badnavirus B (SPBV-B) and Sweet potato badnavirus A (collectively known as Sweet potato pakakuy virus; SPPV; Caulimoviridae) in sweetpotato plants in Tanzania. A 5′-end partial sequence (3065 nucleotides), encoding hypothetical, movement and coat proteins, was obtained and found to be 86.3% and 73.1% identical to SPBV-B and SPBV-A, respectively. A survey for the distribution of SPPV and Sweet potato symptomless mastrevirus 1 (SPSMV-1) showed that these viruses were wide spread and co-infecting sweetpotato plants in Tanzania. The importance of East Africa as a hot spot for the diversity and evolution of sweet potato viruses is discussed.

This is the first description of full genome sequences of chickpea chlorotic dwarf virus (CpCDV; genus Mastrevirus; family Geminiviridae) identified in papaya and tomato plants sampled in Burkina Faso. The CpCDV full genome sequences from papaya and tomato share the highest pairwise sequence identity (84% and 93.5%) with Sudanese isolates of the CpCDV-K and CpCDV-M strains, respectively. Based on the strain demarcation threshold (>94% identity) for mastreviruses, we propose two new strains, CpCDV-Q and CpCDV-R, identified in papaya and tomato, respectively. Phylogenetic analysis confirmed that the sequences belong to a distinct clade of the highly diverse population of CpCDVs. Evidence of inter-strain recombination provided more support for the important role of recombination in CpCDV evolution. The discovery of CpCDV on papaya, a previously unsuspected host, raises many questions about the natural and potential host range of this dicot-infecting mastrevirus species that is reported to be emerging worldwide.

Maize (Zea mays L.) is host for more than 50 virus species worldwide with Maize streak virus (MSV) (genus Mastrevirus) causing significant yield losses in Africa. A survey for viruses infecting maize was conducted in major growing regions of Ethiopia. To test for DNA viruses, in particular mastreviruses, rolling circle amplification was performed for the analysis of virus composition in assayed samples. Following the analysis of the entire virus genomes, three genetic groups, each representing distinct virus species, were identified. The first group was almost identical with the A-strain of MSV. The next sequence-cluster shared 96–98% identity with isolates of Maize streak reunion virus (MSRV) confirming the presence of this virus also in continental East Africa. Sequence analysis of additional virus genomes (each 2846 nt) in length revealed only a limited 70–71% nt identity with MSRV isolates and an even lower identity (

"Watermelon (Citrullus lanatus) is one of the most important cucurbit crops in the world, with a total production of c. 118 million tons (FAO, 2017). It is a popular fruit in many Mediterranean countries and is widely cultivated. In Morocco an area of 16,680 ha is grown annually with a production of 619,322 tonnes in 2017. During 2015 watermelon plants with fruits showing cracking, yellowing and brown areas in the flesh were observed in some areas in Morocco. During 2017, similar symptoms were again observed in the regions of Marrakech, Tifelt and Zagoura. The symptoms observed (Fig. 1) were similar to those caused by Chickpea chlorotic dwarf virus (CpCDV, genus Mastrevirus, family Geminiviridae) which was recently reported affecting watermelon in Tunisia inducing ""hard fruit syndrome"" (Zaagueri et al., 2017a). Seventeen samples of watermelon leaves from symptomatic plants were collected (six from Marrakech, four from Tifelt and seven from Zagoura) and were subjected to total nucleic acid extraction by the TLES bufferbased method (50 mM Tris-HCl, pH 9, 150 mM LiCl, 5 mM EDTA, and 5% SDS), according to Noris et al. (1996). CpCDV infection was detected by dot-blot hybridization, using a digoxigenin-labeled probe targeting the coat protein gene (Zaagueri et al., 2017b) and was confirmed by PCR using a novel primer pair CpCDV-SEQ2 (5'-CGACACATAAGGTTCAGGTTG-3') and CpCDV-Tu-1145-R (5'-AGGCAACCCTTGGGAGTCA-3'), amplifying a 544 bp fragment in the Rep gene. Four samples out of fifteen collected in 2017 (samples 11, 12, 14 and 15) and one sample out of two collected in 2015 (Sample 'R') were positive for CpCDV by PCR (Fig. 2, upper panel). All five infected samples were collected in the Zagoura area, south-eastern Morocco. Infection in three of five of the samples was confirmed by dot-blotting (Fig. 2, lower panel). To further confirm CpCDV detection, three positive samples collected in 2017 were amplified by PCR using the CP-targeting primer pair CpCDV-CP-F/R (Zaagueri et al., 2017b) and the 501 bp products were sequenced on both strands. The three sequences (GenBank Accession Nos. MH500777 - MH500779) were almost identical except for four mismatches. BLAST analysis identified a CpCDV isolate from squash in Egypt (KF692356) as the best match in the NCBI database. These results constitute the first record of CpCDV infecting watermelon in Morocco and indicate that the virus has been present in the country since at least 2015. In the Mediterranean region, CpCDV has only been previously reported in Egypt (Fahmy et al., 2015) and Tunisia (Zaagueri et al., 2017b), and this report indicates that the virus may be more widely distributed than indicated by published records."

Viruses of the genus Mastrevirus (family Geminiviridae) are transmitted by leafhoppers and infect either mono- or dicotyledonous plants. Here we have determined the full length sequences of 49 dicot-infecting mastrevirus isolates sampled in Australia, Eritrea, India, Iran, Pakistan, Syria, Turkey and Yemen. Comprehensive analysis of all available dicot-infecting mastrevirus sequences showed the diversity of these viruses in Australia to be greater than in the rest of their known range, consistent with earlier studies, and that, in contrast with the situation in monocot-infecting mastreviruses, detected inter-species recombination events outnumbered intra-species recombination events. Consistent with Australia having the greatest diversity of known dicot-infecting mastreviruses phylogeographic analyses indicating the most plausible scheme for the spread of these viruses to their present locations, suggest that most recent common ancestor of these viruses is likely nearer Australia than it is to the other regions investigated.

Chickpea stunt disease caused by Chickpea chlorotic dwarf virus (CpCDV) (genus Mastrevirus, family Geminiviridae) is the most important biotic stress affecting chickpea crops worldwide. A survey conducted on the incidence of stunt disease clearly revealed high incidence of the disease with severe symptom expression in both indigenous and imported genotypes. To manage the disease in a sustainable way, resistant genotypes need to be bred by adopting objective and precise assessment of the disease response of chickpea genotypes. At present, evaluation of CpCDV resistance is conducted on the basis of natural infection in the field, which is bound to be erroneous due to vagaries in vector population. To circumvent the above problems, we devised an agroinoculation technique that involves the delivery of viral genomic DNA through Agrobacterium tumefaciens. An objective scoring system assigning quantitative value to different symptoms has been evolved to assess the response of chickpea genotypes to CpCDV inoculation. Using the inoculation and scoring techniques, we screened 70 genotypes, which helped in differentiating field resistance that is more due to resistance to vector feeding than resistance to the virus.