Search

Defence mechanisms in plants have been naturally or artificially selected to cope with virus infection and/or insect colonization. This creates a range of host susceptibility to viruses and/or insects that can impact the epidemiology of insect‐borne viral diseases. Wheat dwarf disease (WDD), one of the most important viral diseases on small‐grain cereals, is caused by wheat dwarf virus (WDV), which is transmitted by the leafhopper Psammotettix alienus. In the current context of the unavailability of either WDV‐resistant/tolerant wheat cultivars or effective methods to control WDD in French cereal fields, the accurate characterization of WDV‐susceptible genotypes must be considered to improve management strategies against this viral disease. In this study, the impact of 12 wheat cultivars on epidemiological parameters related to the introduction (host selection and virus infection) and spread (insect performance and virus transmission) of WDD was evaluated. Results showed no differences between the tested cultivars for host selection made by P. alienus, whereas four tested cultivars (Complice, Filon, Hyking and Nemo) reduced survival and/or fecundity of the leafhopper. Characterization of virus–host interactions highlights the lower host and source quality of cv. Filon for WDV. Finally, multivariate analyses allowed the identification of cvs Filon, Boregar, Solindo CS, Complice and Hyking as less suitable hosts for WDV and/or P. alienus, suggesting that these cultivars could present interesting genetic resource(s) that should be considered for future breeding programmes against WDD. [ABSTRACT FROM AUTHOR]

Sweet potato symptomless virus 1 (SPSMV-1) is a single-stranded circular DNA virus, belonging to the genus Mastrevirus (family Geminiviridae) that was first identified on sweet potato plants in South Korea in 2012. Although SPSMV-1 does not induce distinct symptoms in sweet potato plants, its co-infection with different sweet potato viruses is highly prevalent, and thus threatens sweet potato production in South Korea. In this study, the complete genome sequence of a Korean isolate of SPSMV-1 was obtained by Sanger sequencing of polymerase chain reaction (PCR) amplicons from sweet potato plants collected in the field (Suwon). An infectious clone of SPSMV-1 (1.1-mer) was constructed, cloned into the plant expression vector pCAMBIA1303, and agro-inoculated into Nicotiana benthamiana using three Agrobacterium tumefaciens strains (GV3101, LBA4404, and EHA105). Although no visual differences were observed between the mock and infected groups, SPSMV-1 accumulation was detected in the roots, stems, and newly produced leaves through PCR. The A. tumefaciens strain LBA4404 was the most effective at transferring the SPSMV-1 genome to N. benthamiana. We confirmed the viral replication in N. benthamiana samples through strand-specific amplification using virion-sense- and complementary-sense-specific primer sets.

Wheat dwarf disease (WDD) is an important disease of monocotyledonous species, including economically important cereals. The causative pathogen, wheat dwarf virus (WDV), is persistently transmitted mainly by the leafhopper Psammotettix alienus and can lead to high yield losses. Due to climate change, the periods of vector activity increased, and the vectors have spread to new habitats, leading to an increased importance of WDV in large parts of Europe. In the light of integrated pest management, cultivation practices and the use of resistant/tolerant host plants are currently the only effective methods to control WDV. However, knowledge of the pathosystem and epidemiology of WDD is limited, and the few known sources of genetic tolerance indicate that further research is needed. Considering the economic importance of WDD and its likely increasing relevance in the coming decades, this study provides a comprehensive compilation of knowledge on the most important aspects with information on the causal virus, its vector, symptoms, host range, and control strategies. In addition, the current status of genetic and breeding efforts to control and manage this disease in wheat will be discussed, as this is crucial to effectively manage the disease under changing environmental conditions and minimize impending yield losses. [ABSTRACT FROM AUTHOR]

Abstract Background Maize-infecting viruses are known to inflict significant agronomic yield loss throughout the world annually. Identification of known or novel causal agents of disease prior to outbreak is imperative to preserve food security via future crop protection efforts. Toward this goal, a large-scale metagenomic approach utilizing high throughput sequencing (HTS) was employed to identify novel viruses with the potential to contribute to yield loss of graminaceous species, particularly maize, in North America. Results Here we present four novel viruses discovered by HTS and individually validated by Sanger sequencing. Three of these viruses are RNA viruses belonging to either the Betaflexiviridae or Tombusviridae families. Additionally, a novel DNA virus belonging to the Geminiviridae family was discovered, the first Mastrevirus identified in North American maize. Conclusions Metagenomic studies of crop and crop-related species such as this may be useful for the identification and surveillance of known and novel viral pathogens of crops. Monitoring related species may prove useful in identifying viruses capable of infecting crops due to overlapping insect vectors and viral host-range to protect food security.

Mastreviruses are an emerging group of viruses transmitted by leafhoppers and infect both monocot and dicot plants. Chickpea chlorotic dwarf virus (CpCDV), a mastrevirus, is increasingly becoming important in many parts of the world. Various gRNA constructs targeting conserved genomic regions were used singly or in tandem (three constructs together) in CRISPR/Cas9-based approach for triggering resistance against CpCDV. Following inoculation with the infectious clone and each of the constructs, Nicotiana benthamiana was tested for the relative accumulation of the viral DNA through qPCR. Out of five uniplex and three multiplex, one multiplex construct consisting of three genomic regions (LIR, Rep and RepA) showed a significant decrease in viral titre when 2^-∆∆Ct was compared at 7 days after inoculation (dai), 14 dai and 21 dai. When this multiplex construct was agroinfiltrated into the tomato, the qPCR for the viral titre was 0.266 ± 0.06 at 7 dai and 0.069 ± 0.034 when compared with the CpCDV positive control. The expression of gRNA and Cas9 decreased from 7.08 ± 1.24 to 5.22 ± 0.36 and 111.2 ± 5.19 to 75.2 ± 5.26 from 4 to 7 dai, respectively. Positive control plants infiltrated with an infectious clone showed chlorotic leaves, thickened veins and stunted growth at 7 dai, whereas plants infiltrated with the multiplex construct showed mild leaf yellowing and thickened veins and ultimately recovered from the symptoms at 21 dai stage. CRISPR/Cas9-based multiplex of three sgRNAs significantly reduced the viral titre; however, other triplex constructs of sgRNA and individual sgRNA failed to produce consistent results. Our study shows the potential of Cas9-based genome editing technique to generate resistance to CpCDV. [ABSTRACT FROM AUTHOR]

Background: Maize-infecting viruses are known to inflict significant agronomic yield loss throughout the world annually. Identification of known or novel causal agents of disease prior to outbreak is imperative to preserve food security via future crop protection efforts. Toward this goal, a large-scale metagenomic approach utilizing high throughput sequencing (HTS) was employed to identify novel viruses with the potential to contribute to yield loss of graminaceous species, particularly maize, in North America. Results: Here we present four novel viruses discovered by HTS and individually validated by Sanger sequencing. Three of these viruses are RNA viruses belonging to either the Betaflexiviridae or Tombusviridae families. Additionally, a novel DNA virus belonging to the Geminiviridae family was discovered, the first Mastrevirus identified in North American maize. Conclusions: Metagenomic studies of crop and crop-related species such as this may be useful for the identification and surveillance of known and novel viral pathogens of crops. Monitoring related species may prove useful in identifying viruses capable of infecting crops due to overlapping insect vectors and viral host-range to protect food security. [ABSTRACT FROM AUTHOR]

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 Mastrevirus (family Geminiviridae) is established. Reliable detection and identification methods are available. The pathogen is not included in the EU Commission Implementing Regulation 2019/2072. CpCDV has been reported in Africa, Asia and Oceania. It has not been reported in the EU. CpCDV infects plant species in the family Fabaceae and several species of other families (Amaranthaceae, Brassicaceae, Caricaceae, Cucurbitaceae, Malvaceae and Solanaceae), including weeds. It may induce symptoms on its hosts, causing severe yield reduction. The virus is transmitted in a persistent, circulative and non‐propagative manner by the leafhopper species Orosius orientalis and O. albicinctus, which are not regulated. O. orientalis is known to be present in some EU member states. Plants for planting (other than seeds), parts of plants and cut flowers of CpCDV hosts and viruliferous leafhoppers were identified as the most relevant pathways for the entry of CpCDV into the EU. Cultivated and wild hosts of CpCDV are distributed across the EU. Would the pest enter and establish in the EU territory, impact on the production of cultivated hosts is expected. Phytosanitary measures are available to prevent entry and spread of the virus in the EU. CpCDV fulfils the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest. [ABSTRACT FROM AUTHOR]

Wheat dwarf disease (WDD) is an important disease of monocotyledonous species, including economically important cereals. The causative pathogen, wheat dwarf virus (WDV), is persistently transmitted mainly by the leafhopper Psammotettix alienus and can lead to high yield losses. Due to climate change, the periods of vector activity increased, and the vectors have spread to new habitats, leading to an increased importance of WDV in large parts of Europe. In the light of integrated pest management, cultivation practices and the use of resistant/tolerant host plants are currently the only effective methods to control WDV. However, knowledge of the pathosystem and epidemiology of WDD is limited, and the few known sources of genetic tolerance indicate that further research is needed. Considering the economic importance of WDD and its likely increasing relevance in the coming decades, this study provides a comprehensive compilation of knowledge on the most important aspects with information on the causal virus, its vector, symptoms, host range, and control strategies. In addition, the current status of genetic and breeding efforts to control and manage this disease in wheat will be discussed, as this is crucial to effectively manage the disease under changing environmental conditions and minimize impending yield losses.

Abstract 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 Mastrevirus (family Geminiviridae) is established. Reliable detection and identification methods are available. The pathogen is not included in the EU Commission Implementing Regulation 2019/2072. CpCDV has been reported in Africa, Asia and Oceania. It has not been reported in the EU. CpCDV infects plant species in the family Fabaceae and several species of other families (Amaranthaceae, Brassicaceae, Caricaceae, Cucurbitaceae, Malvaceae and Solanaceae), including weeds. It may induce symptoms on its hosts, causing severe yield reduction. The virus is transmitted in a persistent, circulative and non‐propagative manner by the leafhopper species Orosius orientalis and O. albicinctus, which are not regulated. O. orientalis is known to be present in some EU member states. Plants for planting (other than seeds), parts of plants and cut flowers of CpCDV hosts and viruliferous leafhoppers were identified as the most relevant pathways for the entry of CpCDV into the EU. Cultivated and wild hosts of CpCDV are distributed across the EU. Would the pest enter and establish in the EU territory, impact on the production of cultivated hosts is expected. Phytosanitary measures are available to prevent entry and spread of the virus in the EU. CpCDV fulfils the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

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. [ABSTRACT FROM AUTHOR]

The maize streak virus belongs in the genus Mastrevirus, in the family Geminiviridae. The A-strain of the virus (MSV-A) is recognised as the principal causative agent of the most severe manifestation of maize streak disease (MSD). This disease continues to be a persistent limitation on maize output across sub-Saharan Africa and the nearby Indian Ocean islands. Irrespective of the causes behind the spread of MSV-A, we can determine the paths and speeds with which MSV-A spreads by analysing MSV genome sequence data along with information on when and where samples were taken. This information is valuable for identifying the geographical origins of viral strains that cause sporadic MSD epidemics in specific places and the geographical regions where viruses remain in reservoirs and contribute to prolonged epidemics during outbreaks. Our aim is to utilise these analyses to estimate the timing and origin of the MSV-A that arrived on the island of Madagascar in the Indian Ocean. Specifically, we employ model-based phylogeographic analyses on 524 complete MSV-A genome sequences, which consist of 56 newly obtained genomes from infected maize plants collected in Madagascar. These studies allow us to reconstruct the most likely paths of MSV-A to Madagascar. We found strong evidence for the existence of at least four separate movements of MSV-A variants from East and southern Africa to Madagascar. These movements took place between roughly 1979 (with a 95% highest probability density interval [HPD] ranging from 1976 to 1982) and 2003 (with a 95% HPD ranging from 2002 to 2003). While we inferred that MSV-A variants are spreading at an average rate of 38.9 km/year (with a 95% highest posterior density interval of 34.0-44.4) across their geographical range. Since their arrival in Madagascar, MSV-A variants have been migrating at an average rate of 47.6 km/year (with a 95% highest posterior density interval of 36.05-61.70). Human influences are likely significant contributors to both sporadic long-range movements of MSV-A between mainland Africa and Madagascar, as well as shorter to medium range movements within the island., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

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. [ABSTRACT FROM AUTHOR]

Gemini virus coat protein (CP) is an important element of vector specificity and mandatory for insect transmission as well regardless of the type of gemini virus. This study was planned to conduct virus acquisition and transmission experiments using screen cages in an insectary for the period of one month. For this purpose non-viruliferous whiteflies (B cryptic species) were reared and used to acquire the viruses for 48-72 h from the agroinfiltered symptomatic tobacco (Nicotiana benthamiana Domin.) and tomato (Solanum lycopersicum L.) plants and these were liberated to healthy plants for transmission of viruses. It was evident from the results that the whiteflies were incapable to acquire and transmit chickpea chlorotic dwarf virus (CpCDV)-a mastrevirus and mastrebegomo chimeric virus (MCV) from the symptomatic tobacco and tomato plants to healthy plants. Whiteflies also failed to acquire and transmit the cotton leaf curl Kokhran virus-Burewala strain (CLCuKoV-Bu)-a begomovirus from infected to healthy tobacco plants due to the inability of whiteflies to feed on Nicotiana benthamiana Domin. leaves. Although whitefly successfully acquired and transmitted the CLCuKoV-Bu from symptomatic tomato leaves to healthy one whose presence later confirmed by DNA extraction from whiteflies and symptomatic plants followed by PCR amplification of CP gene and full length genome of viruses for authentication of results. So, it has been confirmed that whiteflies were not responsible for transmission of CpCDV and MCV from diseased to healthy plants. [ABSTRACT FROM AUTHOR]

Non‐crop plants such as grasses and volunteer plants are an inseparable part of the flora of crop fields and can influence virus incidence in crop plants. The presence of grasses as virus reservoirs can lead to a higher probability of virus incidence in crop plants. However, the role of reservoirs as an inoculum source in agricultural fields has not been well studied for many viral diseases of crops. Grasses have been found to constitute potential reservoirs for cereal‐infecting viruses in different parts of the world. This study revealed that cereal‐infecting viruses such as wheat dwarf virus (WDV), barley yellow dwarf viruses (BYDVs), and cereal yellow dwarf virus‐RPV (CYDV‐RPV) can be found among ryegrass growing in or around winter wheat fields. Phylogenetic analysis showed that a WDV isolate from ryegrass was a typical WDV‐E isolate that infects wheat. Similarly, a ryegrass isolate of barley yellow dwarf virus‐PAV (BYDV‐PAV) grouped in a clade together with other BYDV‐PAV isolates. Inoculation experiments under greenhouse conditions confirmed that annual ryegrass of various genotypes can be infected with WDV to a very low titre. Moreover, leafhoppers were able to acquire WDV from infected ryegrass plants, despite the low titre, and transmit the virus to wheat, resulting in symptoms. Information from the grass reservoir may contribute to improving strategies for controlling plant virus outbreaks in the field. Knowledge of the likely levels of virus in potential reservoir plants can be used to inform decisions on insect vector control strategies and may help to prevent virus disease outbreaks in the future. [ABSTRACT FROM AUTHOR]

Chickpea chlorotic dwarf virus (CpCDV) (Mastrevirus, Geminiviridae) has a wide natural host range. Despite of possessing the potential loss, until now the virus has not been studied in eastern and southern Iran. In this research, natural leguminous hosts of CpCDV in Kerman, Razavi Khorasan and Fars provinces were studied and the full-length genome of a chickpea isolate from Rabor (Kerman province) was characterized. Samples were collected from leguminous plants in different regions of the three aforementioned provinces and the CpCDV infection was tested in PCR. Results showed that leguminous plants including pulse, vegetables, foliage and wild species have been infected with the virus. The full-length genome of the Rabor isolate of CpCDV was sequenced and the resulted sequence was compared with the sequences of similar isolates available in the GenBank. Furthermore, the infectious clone of CpCDV was constructed and agroinoculated into some plants. Thus, the pathogenesis of the virus was demonstrated. Collectively, the results of this study indicated that CpCDV has a wide natural host range in the family Fabaceae. Fenugreek, common sainfoin, alfalfa and sophora are reported as the new hosts of the virus in Iran. [ABSTRACT FROM AUTHOR]

The chickpea chlorotic dwarf virus (CpCDV) (from the genus Mastrevirus and the family Geminiviridae) and tomato leaf curl New Delhi virus (ToLCNDV) (from the genus Begomovirus and the family Geminiviridae) represent an important threat to different crops worldwide, as they are emerging viruses in the Asian continent, were introduced to the Mediterranean region in 2012, and were then reported in Morocco in 2017 and 2018. The present study addresses the dispersion of the CpCDV and the ToLCNDV and evaluates the genetic diversity of the Moroccan isolates of both viruses. A total of 1333 symptomatic leaf plant samples were analyzed by PCR. The study has reported the detection of the ToLCNDV in melon and tomato, as well as the CpCDV in squash crops for the first time in Morocco. Blast analysis of selected representative isolates showed a 97–99% nucleotide identity with the ToLCNDV and the CpCDV infecting different crops in the Mediterranean region. Phylogenetic analysis showed low variability among the Moroccan isolates for the ToLCNDV compared to the Spanish and Italian isolates, whereas the CpCDV strains were variable regarding strains reported in Tunisia and Egypt. Recombination analysis showed the presence of the ToLCNDV recombinant strains with variable parents. The spread of both geminiviruses represents a threat to different crop production, requiring the development of crop protection and management strategies. To prevent viral outbreaks, restrictive phytosanitary measures and the development of resistance strategies are also necessary.

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.

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.

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. [ABSTRACT FROM AUTHOR]

Chickpea chlorotic dwarf virus (CpCDV; genus Mastrevirus, family Geminiviridae) is one of the most important legume‐infecting viruses with a wide host range and geographic distribution in Africa and Asia. In Iran, CpCDV is common in chickpea (Cicer arietinum), but there is limited information about diversity and infections in plants of other legume species. In the current study, a total of 1671 leaf samples from different pulse crops with symptoms were collected in nine provinces of Iran, and the CpCDV infection status was tested by PCR and/or rolling circle amplification (RCA), resulting in the detection of CpCDV in samples of chickpea, lentil (Lens culinaris) and faba bean (Vicia faba) from different regions. Sequence analysis of complete genomes of 18 isolates recovered by digestion of RCA products revealed infection with isolates of the strains CpCDV‐A and CpCDV‐F in chickpea, lentil and faba bean. Phylogenetic analysis showed that the Iranian isolates of CpCDV were closely related to previously sequenced isolates of CpCDV‐A and CpCDV‐F. To the authors' knowledge, this is the first report of CpCDV‐F in Iran. Using agroinoculation with infectious clones for one isolate each of CpCDV‐A and CpCDV‐F, infectivity was confirmed in both faba bean and chickpea, with plants developing leaf curling and/or yellowing. Both infectious clones also successfully infected Nicotiana benthamiana resulting in mild yellowing and intensive leaf curling for CpCDV‐A, and dark‐green mosaic, dwarfing and mild leaf curling for CpCDV‐F. [ABSTRACT FROM AUTHOR]

Abstract Background In Africa and Asia, sugarcane is the host of at least seven different virus species in the genus Mastrevirus of the family Geminiviridae. However, with the exception of Sugarcane white streak virus in Barbados, no other sugarcane-infecting mastrevirus has been reported in the New World. Conservation and exchange of sugarcane germplasm using stalk cuttings facilitates the spread of sugarcane-infecting viruses. Methods A virion-associated nucleic acids (VANA)-based metagenomics approach was used to detect mastrevirus sequences in 717 sugarcane samples from Florida (USA), Guadeloupe (French West Indies), and Réunion (Mascarene Islands). Contig assembly was performed using CAP3 and sequence searches using BLASTn and BLASTx. Mastrevirus full genomes were enriched from total DNA by rolling circle amplification, cloned and sequenced. Nucleotide and amino acid sequence identities were determined using SDT v1.2. Phylogenetic analyses were conducted using MEGA6 and PHYML3. Results We identified a new sugarcane-infecting mastrevirus in six plants sampled from germplasm collections in Florida and Guadeloupe. Full genome sequences were determined and analyzed for three virus isolates from Florida, and three from Guadeloupe. These six genomes share >88% genome-wide pairwise identity with one another and between 89 and 97% identity with a recently identified mastrevirus (KR150789) from a sugarcane plant sampled in China. Sequences similar to these were also identified in sugarcane plants in Réunion. Conclusions As these virus isolates share

Maize striate mosaic virus (MSMV; genus Mastrevirus) has been previously reported in association with maize in Brazil. Here, we recovered the complete genome of a novel MSMV isolate from sugarcane via high-throughput sequencing. PCR assays with MSMV specific-primers confirmed the presence of this virus in sugarcane. To our knowledge, this is the first worldwide report of MSMV on sugarcane. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 (< 64%) with sequences of mastreviruses described elsewhere. Our analysis suggests a novel virus species, which is tentatively named maize streak dwarfing virus (MSDV). The pairwise comparison of capsid protein and replication-associated protein (Rep) of the novel species revealed a limited identity of 63% and 68% with the respective protein sequences of MSRV. The incidence of the virus species in the maize regions of Ethiopia was studied across 89 samples collected during four growing seasons. PCR analysis with general and specific mastrevirus primers showed that MSV is the most incident virus (39.3%) followed by MSRV (14.6%) and MSDV (12.4%). Identification of three different mastrevirus species in a confined geographical location on the same host, maize, is unprecedented, and suggests that Ethiopia may be one of the potential hot spots for diversity of maize-infecting mastreviruses. [ABSTRACT FROM AUTHOR]

Alfalfa plants in the field can display a range of virus-like symptoms, especially when grown over many years for seed production. Most known alfalfa viruses have RNA genomes, some of which can be detected using diagnostic assays, but many viruses of alfalfa are not well characterized. This study aims to identify the RNA and DNA virus complexes associated with alfalfa plants in Australia. To maximize the detection of RNA viruses, we purified double-stranded RNA (dsRNA) for high throughput sequencing and characterized the viromes of ten alfalfa samples that showed diverse virus-like symptoms. Using Illumina sequencing of tagged cDNA libraries from immune-captured dsRNA, we identified sequences of the single-stranded RNA viruses, alfalfa mosaic virus (AMV), bean leafroll virus, a new emaravirus tentatively named alfalfa ringspot-associated virus, and persistent dsRNA viruses belonging to the families Amalgaviridae and Partitiviridae. Furthermore, rolling circle amplification and restriction enzyme digestion revealed the complete genome of chickpea chlorosis Australia virus, a mastrevirus (family Geminiviridae) previously reported only from chickpea and French bean that was 97% identical to the chickpea isolate. The sequence data also enabled the assembly of the first complete genome (RNAs 1−3) of an Australian AMV isolate from alfalfa.

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.

Highlights • A dicot infecting mastrevirus (Chickpea chlorotic dwarf virus) was found infecting spinach (Spinacia oleracea) in Pakistan. • CpCDV association with cotton leaf curl Multan betasatellite (CLCuMB) shown. • CpCDV association with cotton leaf curl Multan alphasatellite (CLCuMA) shown. • Infectivity assay have shown that chickpea chlorotic dwarf virus (CpCDV) can transreplicate CLCuMB. • First report of association of CpCDV with CLCuMB and CLCuMA in dicot host i.e. spinach. Abstract 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. [ABSTRACT FROM AUTHOR]

In the Czech Republic, Barley yellow dwarf virus (BYDV) and Wheat dwarf virus (WDV) are the prevailing viral species that can cause significant yield losses in cereal stands. Another virus, which has been on the increase in the Czech Republic and whose impact is expected to increase, is Wheat streak mosaic virus (WSMV). In this study, a TaqMan Multiplex Real-Time (qPCR) assay for simultaneous detection of BYDV (species PAV, PAS and MAV),WDV and WSMV was developed. Furthermore, additional assays for the viruses' quantification in wheat and barley were developed. The assay was optimised and used to identify possible synergistic or antagonistic relations between the viruses in wheat and barley which would be characterised by increases or decreases of the titre of the individual viruses. For this, a greenhouse experiment with artificial inoculations of mixed and single infections of BYDV-PAV, WDV and WSMV was carried out, and field samples from the wheat and barley stands with mixed and single infections of BYDV and WDV were collected. No trend of increasing or decreasing titre was recorded for any of the viruses apart from WSMV titre which was decreased approximately five times in mixed infections with BYDV orWDVcompared with the singleWSMV infection. Further analyses are needed to expand the idea of possible interactions between WSMV and WDV or BYDV. [ABSTRACT FROM AUTHOR]

Maize streak virus (MSV, genus Mastrevirus , family Geminiviridae ), vectored by the leafhoppers ( Cicadulina sp.), is the most economically important viral disease of maize endemic to Sub-Saharan Africa and its offshore islands. Yield losses due to MSV are mainly controlled through use of resistant varieties. ‘Recovery’ (ability of plants to reduce symptom severity), is one of the types of resistance being used to develop MSV resistant cultivars through breeding. This study was conducted to map Quantitative Trait Loci (QTLs) associated with recovery resistance to MSV in a mapping population comprising 250 S1 lines derived from a cross between two MSV resistant lines. The population was genotyped using single nucleotide polymorphism (SNP) markers at 269 loci. A genetic map of 11 linkage groups was constructed comprising 230 SNP markers. Four QTLs, two putative QTLs with significant effect on chromosome 3 and two other QTLs with reduced effect on chromosomes 7 and 9, were identified from the population. The two QTLs on chromosome 3 together accounted for 47 to 51% of the total phenotypic variance while the other two QTLs accounted for 28 to 32% of the total variation. These QTLs originated from the two parents of the mapping population had both additive and dominance effects but interaction among the four loci was not significant. Further validation of these QTLs associated with recovery resistance in other diverse populations will lead to the development of new genomic resources to enhance breeding for MSV resistant maize. [ABSTRACT FROM AUTHOR]

Chickpea chlorotic dwarf virus (CpCDV), a polyphagous mastrevirus, family Geminiviridae, has been recently linked to the onset of the "hard fruit syndrome" of watermelon, first described in Tunisia, that makes fruits unmarketable due to the presence of white hard portions in the flesh, chlorotic mottling on the rind, and an unpleasant taste. To investigate the etiological agent of this disease, total RNA extracted from symptomatic watermelon fruits was subjected to small RNA sequencing through next generation sequencing (NGS) techniques. Data obtained showed the presence of CpCDV and two other viral species. However, following validation through polymerase chain reaction (PCR), CpCDV was the only viral species consistently detected in all samples. Watermelon seedlings were then challenged by an agroinfectious CpCDV clone; several plants proved to be CpCDV-infected, and were able to produce fruits. CpCDV infected and replicated in watermelon fruits and leaves, leading to abnormality in fruits and in seed production, similar to those described in field. These results indicate that CpCDV is the etiological agent of the "hard fruit syndrome" of watermelon. [ABSTRACT FROM AUTHOR]

Cotton leaf curl disease in the Indian subcontinent is associated with several distinct begomoviruses that interact with a disease-specific DNA satellite named Cotton leaf curl Multan betasatellite (CLCuMB). However, we isolated the distinct strain (L) of leafhopper transmitted chickpea chlorotic dwarf virus, CpCDV-L (genus Mastrevirus, family Geminiviridae) from cotton plants affected by leaf curl disease in a small number of plants. The question as to whether CpCDV-L contributes to the development of disease symptoms such as leaf curling and enations remains to be answered. Standard methods were used to produce partial direct and tandem repeat constructs of CpCDVL for Agrobacterium-mediated inoculation in the binary vector pBIN19. The role of CpCDV-L in the induction of typical disease symptoms was studied by Agrobacteriummediated inoculation of the partial repeat construct into Nicotiana benthamiana. CpCDV-L induced downward leaf curling leading to cupping in N. benthamiana. [ABSTRACT FROM AUTHOR]

Chickpea stunt disease (CSD), caused by Chickpea chlorotic dwarf virus (CpCDV) is a threat to chickpea production leading to yield losses of 75–95%. Chickpea chlorotic dwarf virus is a monopartite, single-stranded circular DNA virus in the genus Mastrevirus and family Geminiviridae. It is transmitted by Orosius albicinctus in a circulative (persistent) and nonpropagative manner. Symptoms of CSD include very small leaves, intense discoloration (yellowing (kabuli type) and reddening (desi type)), and bushy stunted appearance of the plant. Presently, CpCDVs occurs in Africa, Asia, Australia, and the Middle East, causing extensive losses on economically important crops in in the families Fabaceae, Asteraceae, Amaranthaceae, Brassicaceae, Cucurbitaceae, Caricaceae, Chenopodiaceae, Leguminosae, Malvaceae, Pedaliaceae, and Solanaceae. High frequency of recombinations has played a significant role in the wide host range, diversification, and rapid evolution of CpCDVs. This review highlights the extensive research on the CpCDV genome diversity, host range, plant–virus–insect interactions, and RNA interference-based resistance of CpCDV, providing new insights into the host adaptation and virus evolution.

Background: In Africa and Asia, sugarcane is the host of at least seven different virus species in the genus Mastrevirus of the family Geminiviridae. However, with the exception of Sugarcane white streak virus in Barbados, no other sugarcane-infecting mastrevirus has been reported in the New World. Conservation and exchange of sugarcane germplasm using stalk cuttings facilitates the spread of sugarcane-infecting viruses. Methods: A virion-associated nucleic acids (VANA)-based metagenomics approach was used to detect mastrevirus sequences in 717 sugarcane samples from Florida (USA), Guadeloupe (French West Indies), and Réunion (Mascarene Islands). Contig assembly was performed using CAP3 and sequence searches using BLASTn and BLASTx. Mastrevirus full genomes were enriched from total DNA by rolling circle amplification, cloned and sequenced. Nucleotide and amino acid sequence identities were determined using SDT v1.2. Phylogenetic analyses were conducted using MEGA6 and PHYML3. Results: We identified a new sugarcane-infecting mastrevirus in six plants sampled from germplasm collections in Florida and Guadeloupe. Full genome sequences were determined and analyzed for three virus isolates from Florida, and three from Guadeloupe. These six genomes share >88% genome-wide pairwise identity with one another and between 89 and 97% identity with a recently identified mastrevirus (KR150789) from a sugarcane plant sampled in China. Sequences similar to these were also identified in sugarcane plants in Réunion. Conclusions: As these virus isolates share <64% genome-wide identity with all other known mastreviruses, we propose classifying them within a new mastrevirus species named Sugarcane striate virus. This is the first report of sugarcane striate virus (SCStV) in the Western Hemisphere, a virus that most likely originated in Asia. The distribution, vector, and impact of SCStV on sugarcane production remains to be determined. [ABSTRACT FROM AUTHOR]

Maize streak virus (MSV), an important pathogen of maize in Africa, is the most extensively studied member of the Mastrevirus genus in the family Geminiviridae . Comparatively little is known about other monocot-infecting African mastreviruses, most of which infect uncultivated grasses. Here we determine the complete sequences of 134 full African mastrevirus genomes from predominantly uncultivated Poaceae species. Based on established taxonomic guidelines for the genus Mastrevirus , these genomes could be classified as belonging to the species Maize streak virus , Eragrostis minor streak virus , Maize streak Reunion virus , Panicum streak virus , Sugarcane streak Reunion virus and Sugarcane streak virus . Together with all other publicly available African monocot-infecting mastreviruses, the 134 new isolates extend the known geographical distributions of many of these species, including MSV which we found infecting Digitaria sp. on the island of Grand Canaria: the first definitive discovery of any African monocot-infecting mastreviruses north-west of the Saharan desert. These new isolates also extend the known host ranges of both African mastrevirus species and the strains within these. Most notable was the discovery of MSV-C isolates infecting maize which suggests that this MSV strain, which had previously only ever been found infecting uncultivated species, may be in the process of becoming adapted to this important staple crop. [ABSTRACT FROM AUTHOR]

Sweet potato symptomless virus 1 (SPSMV-1) is a single-stranded circular DNA virus, belonging to the genus Mastrevirus (family Geminiviridae) that was first identified on sweet potato plants in South Korea in 2012. Although SPSMV-1 does not induce distinct symptoms in sweet potato plants, its co-infection with different sweet potato viruses is highly prevalent, and thus threatens sweet potato production in South Korea. In this study, the complete genome sequence of a Korean isolate of SPSMV-1 was obtained by Sanger sequencing of polymerase chain reaction (PCR) amplicons from sweet potato plants collected in the field (Suwon). An infectious clone of SPSMV-1 (1.1-mer) was constructed, cloned into the plant expression vector pCAMBIA1303, and agro-inoculated into Nicotiana benthamiana using three Agrobacterium tumefaciens strains (GV3101, LBA4404, and EHA105). Although no visual differences were observed between the mock and infected groups, SPSMV-1 accumulation was detected in the roots, stems, and newly produced leaves through PCR. The A. tumefaciens strain LBA4404 was the most effective at transferring the SPSMV-1 genome to N. benthamiana. We confirmed the viral replication in N. benthamiana samples through strand-specific amplification using virion-sense- and complementary-sense-specific primer sets.

During the last decade, the leafhopper transmitted Wheat dwarf virus (WDV) has become a serious problem both in northwestern China and Hungary. In order to study the molecular diversity and population structure of WDV in these two countries, 39 Chinese isolates and 16 Hungarian isolates were collected from different regions of China and Hungary, and their genomes were sequenced. All isolates belonged to the wheat strain of WDV and showed limited genetic diversity. The highest and lowest nucleotide sequence identities among isolates from China and Hungary were 99.9 and 90%, respectively. In all isolates, the lowest nucleotide sequence identity was 89.5% between MO10-1 and KP10-5, which were collected from Martonvásár and Kompolt, Hungary. Phylogenetic analyses showed the genome sequences of 55 WDV isolates belong to two big clades, but no clear correlation to geographical location. Population difference analyses indicated that the Chinese and Hungarian WDV populations have no significant difference. The regions in WDV genome with relatively low nucleotide diversities represented protein coding regions suggested that these regions evolved under negative selection, and might be one of the causes restricting the number of genetic variants.