Search

The prevalence of cotton leaf curl disease (CLCuD) has significantly hampered chili (Capsicum spp.) production, presenting a formidable challenge in Pakistan. During a chili field survey in 2018, distinct symptoms, including stunted growth, yellowing, and severe leaf curling, were observed on several plants. Subsequently, a comprehensive sampling effort was undertaken, collecting a total of 39 symptomatic samples from diverse locations across Multan, Punjab. The DNA extraction from these samples was conducted at the plant virology laboratory at Bahauddin Zakariya University, Multan, marking a crucial step in the investigation of this debilitating disease and its impact on chili production in the region. Molecular analysis with PCR using Av/Ac Core, Beta 01/02, and CLCuMuBF11/R33 primers confirmed begomovirus infection in chili plants. Positive amplification demonstrated a 71.79% infection rate, with 579 bp, 1.4 kb, and 481 bp amplicons for Av/Ac Core, Beta 01/02, and CLCuMuBF11/R33, respectively. Sequencing identified cotton leaf curl Multan beta-satellite (MT668934) infecting the chili plant. Effectively managing these begomoviruses is crucial to curbing their multiplication and protecting vital crops like chili. Addressing the distributions of beta-satellites in agricultural fields, particularly chili, is imperative to prevent further viral spread.

The diversity of Geminiviridae and Alphasatellitidae species in tomatoes was assessed via high-throughput sequencing of 154 symptomatic foliar samples collected from 2002 to 2017 across seven Brazilian biomes. The first pool (BP1) comprised 73 samples from the North (13), Northeast (36), and South (24) regions. Sixteen begomoviruses and one Topilevirus were detected in BP1. Four begomovirus-like contigs were identified as putative novel species (NS). NS#1 was reported in the semi-arid (Northeast) region and NS#2 and NS#4 in mild subtropical climates (South region), whereas NS#3 was detected in the warm and humid (North) region. The second pool (BP2) comprised 81 samples from Southeast (39) and Central–West (42) regions. Fourteen viruses and subviral agents were detected in BP2, including two topileviruses, a putative novel begomovirus (NS#5), and two alphasatellites occurring in continental highland areas. The five putative novel begomoviruses displayed strict endemic distributions. Conversely, tomato mottle leaf curl virus (a monopartite species) displayed the most widespread distribution occurring across the seven sampled biomes. The overall diversity and frequency of mixed infections were higher in susceptible (16 viruses + alphasatellites) in comparison to tolerant (carrying the Ty–1 or Ty–3 introgressions) samples, which displayed 9 viruses. This complex panorama reinforces the notion that the tomato-associated Geminiviridae diversity is yet underestimated in Neotropical regions. [ABSTRACT FROM AUTHOR]

Ridge gourd (Luffa acutangula L. Roxb.) is one of the most important vegetable crops in India. It belongs to the family Cucurbitaceae; like any other crop, it is also highly susceptible to biotic and abiotic stresses. Among the biotic stresses, tomato leaf curl New Delhi Virus (ToLCNDV) is becoming a major constraint in cultivation of ridge gourd. ToLCNDV is naturally transmitted through whitefly in a circulative and persistent manner and causes the yield loss to the tune of 40–100% (Patil et al. in Virus Dis 28(2):146–155, 2017. https://doi.org/10.1007/s13337-017-0376-6). In present investigation, coat protein gene of ToLCNDV was used to construct a phylogenetic tree showing no host-specificity in the population studied. Further, for in vitro expression studies, the coat protein gene was cloned into pET28a and successfully overexpressed in E. coli BL21 (DE3) cells. The expression of recombinant coat protein varied with different induction time and the highest expression was recorded in 4 h of induction period, incubated with 1-mM IPTG at 37 °C. Overexpressed protein was further purified using Ni–NTA column and confirmed through SDS-PAGE analysis. The present study will help to develop ELISA-based detection tools to diagnose the disease as well as to take up immediate management practices. [ABSTRACT FROM AUTHOR]

Using a bioinformatics approach to identify binding pockets between proteins is a preferable method before modifying the genome to delineate host interactions with viruses. Based on extensive proteomics data in numerous databases, several interaction prediction methods are available to identify binding sites between viruses and hosts at the individual residue level, but little is known about the interaction prediction strategy for plant viruses. Begomoviruses, belonging to the family Geminiviridae, constitute a group of circular single-stranded (ss) DNA viruses that encode multifunctional proteins responsible for viral replication, causing severe diseases in multiple host plants. These viruses usually escape through plant defense mechanism overcoming physical and chemical barriers to trigger the infection with all possible combinations of interaction in the target host protein partners. Here, we have applied our computational approach for plant virus interaction at domain level. Previous study showed that myristoylation-like motif in Begomovirus cotton leaf curl Multan associated betasatellite protein βC1 (CLCuMB- βC1) played an important role in interaction with ubiquitin conjugating enzyme protein (UBC3) in tomato. This kind of binding at residue level has been validated using in vivo and in vitro molecular approach. Here, an in silico approach was utilized which is a combinatorial source of previous and recent protein prediction methods to determine all possible identified interface sites between βC1 and UBC3. This molecular interaction of CLCuMB- βC1 was further verified in the actual host i.e. cotton using a bimolecular fluorescence complementation system and yeast two-hybrid assay. This computational and molecular data will help to identify the interaction between virus and host before using any expensive and time-consuming molecular techniques. [ABSTRACT FROM AUTHOR]

Background: The family Geminiviridae contains plant viruses commonly referred to as geminiviruses, which cause diseases in numerous important plants. Geminiviridae is one of the most important family of plant-infecting viruses that has been divided into fourteen recognized genera. Amongst these, the genus Begomovirus is the largest and economically most important one, viruses of the genus are further categorized into bipartite (two genomic components called DNA-A and DNA-B) and monopartite (single genomic component or DNA-A) begomoviruses. Method: The genomic DNA was extracted from symptomatic plant samples and both the DNA-(B and A) components of a bipartite begomovirus were amplified via rolling circular amplification (RCA) and PCR. The amplified DNA-A and DNA-B were cloned and sequenced by Primer walking, Sanger sequencing, and Illumina sequencing methods. The phylogenetic and biogeographic analyses of both components were performed by various bioinformatics tools. Results: DNA-A (accession number MW722701) and DNA-B (accession number MW722782) of begomoviruses that were sequenced shared >95% sequence similarity with the bipartite begomovirus known as Tomato Leaf Curl New Delhi virus (TLCuNDV). Phylogenetic and biogeographic analyses proposed several possible ancestors, and multiple dispersal and vicariance events may be involved in the evolution of this virus. Conclusions: This is the first time a bipartite begomovirus has been found to infect a plant in the study area (District Swat, Pakistan). The existence of ToLCNDV may pose a major danger to other important crops in the region. [ABSTRACT FROM AUTHOR]

Members of the Geminviridae family are circular single-stranded DNA plant-infecting viruses, some of which impact global food production. Geminiviruses are vectored by sap-feeding insects such as leafhoppers, treehoppers, aphids, and whiteflies. Additionally, geminivirus sequences have also been identified in other insects such as dragonflies, mosquitoes, and stingless bees. As part of a viral metagenomics study on honeybees and solitary bees (Nomia sp.), two geminivirus genomes were identified. These represent a novel citlodavirus (from honeybees collected from Westmoreland, Jamaica) and a mastrevirus-like genome (from a solitary bee collected from Tempe, Arizona, USA). The novel honeybee-derived citlodavirus genome shares ~61 to 69% genome-wide nucleotide pairwise identity with other citlodavirus genome sequences and is most closely related to the passion fruit chlorotic mottle virus identified in Brazil. Whereas the novel solitary bee-derived mastrevirus-like genome shares ~55 to 61% genome-wide nucleotide identity with other mastreviruses and is most closely related to tobacco yellow dwarf virus identified in Australia, based on pairwise identity scores of the full genome, replication-associated protein, and capsid protein sequences. Previously, two geminiviruses in the Begomovirus genus were identified in samples of stingless bee (Trigona spp.) samples. Here, we identify viruses that represent two new species of geminiviruses from a honeybee and a solitary bee, which continues to demonstrate that plant pollinators can be utilized for the identification of plant-infecting DNA viruses in ecosystems. [ABSTRACT FROM AUTHOR]

The prevalence of cotton leaf curl disease (CLCuD) has significantly hampered chili (Capsicum spp.) production, presenting a formidable challenge in Pakistan. During a chili field survey in 2018, distinct symptoms, including stunted growth, yellowing, and severe leaf curling, were observed on several plants. Subsequently, a comprehensive sampling effort was undertaken, collecting a total of 39 symptomatic samples from diverse locations across Multan, Punjab. The DNA extraction from these samples was conducted at the plant virology laboratory at Bahauddin Zakariya University, Multan, marking a crucial step in the investigation of this debilitating disease and its impact on chili production in the region. Molecular analysis with PCR using Av/Ac Core, Beta 01/02, and CLCuMuBF11/R33 primers confirmed begomovirus infection in chili plants. Positive amplification demonstrated a 71.79% infection rate, with 579 bp, 1.4 kb, and 481 bp amplicons for Av/Ac Core, Beta 01/02, and CLCuMuBF11/R33, respectively. Sequencing identified cotton leaf curl Multan beta-satellite (MT668934) infecting the chili plant. Effectively managing these begomoviruses is crucial to curbing their multiplication and protecting vital crops like chili. Addressing the distributions of beta-satellites in agricultural fields, particularly chili, is imperative to prevent further viral spread. [ABSTRACT FROM AUTHOR]

Grapevine red blotch virus (GRBV) is a recently identified virus. Previous research indicates primarily a substantial impact on berry ripening in all varieties studied. The current study analyzed grapes' primary and secondary metabolism across grapevine genotypes and seasons to reveal both conserved and variable impacts to GRBV infection. Vitis vinifera cv. Cabernet Sauvignon (CS) grapevines grafted on two different rootstocks (110R and 420A) were analyzed in 2016 and 2017. Metabolite profiling revealed a considerable impact on amino acid and malate acid levels, volatile aroma compounds derived from the lipoxygenase pathway, and anthocyanins synthesized in the phenylpropanoid pathway. Conserved transcriptional responses to GRBV showed induction of auxin-mediated pathways and photosynthesis with inhibition of transcription and translation processes mainly at harvest. There was an induction of plant-pathogen interactions at pre-veraison, for all genotypes and seasons, except for CS 110R in 2017. Lastly, differential co-expression analysis revealed a transcriptional shift from metabolic synthesis and energy metabolism to transcription and translation processes associated with a virus-induced gene silencing transcript. This plant-derived defense response transcript was only significantly upregulated at veraison for all genotypes and seasons, suggesting a phenological association with disease expression and plant immune responses.

Mosaic disease causes a serious epidemic of cucumber plants in Iraq. To investigate causal agents of such symptoms, whole genome and metatrancriptomic sequencing data were collected from pathogenic cucumber leaves. The result shows that Tomato leaf curl Palampur virus DNA-A and B were existed with 2,756 and 2,719 bp sequences that deposited under acc. numbers ON229618 and ON229620 respectively, and the isolate named Babylon1. Further, Squash vein yellowing virus was found with 9,832 bp sequence that deposited under acc. number ON229619, and the isolate called Iraq. Mixed infection reported here for the first time in cucumber in Iraq, highlighting the impact of such infection that threat the cucumber fields. [ABSTRACT FROM AUTHOR]

Radish (Raphanus sativus) leaf curl disease (RLCD) characterized by yellowing, color breaking, and mosaic symptoms were observed in a garden at Chitwan, Southern Nepal. Polymerase chain reaction using Taq DNA polymerase followed by rolling circle amplification using φ29 polymerase identified an Old World begomovirus complex linked with the RLCD. Pairwise sequence identity with SDT (Sequence Demarcation Tool) analysis coupled with phylogenetic analysis confirmed an Ageratum yellow vein virus (AYVV) and Tomato leaf curl Java betasatellite (ToLCJaB) was responsible for causing RLCD. This study provided initial evidence that radish plants were naturally infected with AYVV and ToLCuJaB in southern Nepal. [ABSTRACT FROM AUTHOR]

Ridge gourd is cultivated in tropical, subtropical and few varieties like Pusa Nasdar and Satputia temperate regions across the world. It is a rich source of essential vitamins and minerals around the world. However, the production of ridge gourd has been severely affected by diseases among which viral diseases have major impact on its production. The viral disease caused by tomato leaf curl New Delhi virus (ToLCNDV), a member of the genus Begomovirus, family Geminiviridae-an economically important virus affecting the ridge gourd yield. It is transmitted by the whiteflies [Bemisia tabaci (Gennadius)] and causes ridge gourd yellow mosaic disease (RgYMD) in ridge gourds. The present study mainly aimed at the process of development of Agrobacterium coat protein gene construct and in silico analysis of CP. The total DNA from infected leaves of ridge gourd with ToLCNDV was amplified using CP specific primers with amplicon size of 771bp. The purified CP. gene was successfully cloned to the TA cloning vector. The CP gene was further moved into plant expression binary vector pBI121. The gene construct of the plant expression vector was transformed into Agrobacterium tumefaciens. In-silico analysis of the coat protein revealed that the protein contains nuclear export factors BR1 family. BLAST results analysis of coat protein with respect to the other coat proteins of ToLCNDV depicted 80-90 per cent resemblance. Phylogenetic tree revealed the common origin of this protein. [ABSTRACT FROM AUTHOR]

Mosaic disease causes a serious epidemic of cucumber plants in Iraq. To investigate causal agents of such symptoms, whole genome and metatrancriptomic sequencing data were collected from pathogenic cucumber leaves. The result shows that Tomato leaf curl Palampur virus DNA-A and B were existed with 2,756 and 2,719 bp sequences that deposited under acc. numbers ON229618 and ON229620 respectively, and the isolate named Babylon1. Further, Squash vein yellowing virus was found with 9,832 bp sequence that deposited under acc. number ON229619, and the isolate called Iraq. Mixed infection reported here for the first time in cucumber in Iraq, highlighting the impact of such infection that threat the cucumber fields.

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]

Circular single-stranded DNA viruses of the family Geminiviridae encode replication-associated protein (Rep), which is a multifunctional protein involved in virus DNA replication, transcription of virus genes, and suppression of host defense responses. Geminivirus genomes are replicated through the interaction between virus Rep and several host proteins. The Rep also interacts with itself and the virus replication enhancer protein (REn), which is another essential component of the geminivirus replicase complex that interacts with host DNA polymerases α and δ. Recent studies revealed the structural and functional complexities of geminivirus Rep, which is believed to have evolved from plasmids containing a signature domain (HUH) for single-stranded DNA binding with nuclease activity. The Rep coding sequence encompasses the entire coding sequence for AC4, which is intricately embedded within it, and performs several overlapping functions like Rep, supporting virus infection. This review investigated the structural and functional diversity of the geminivirus Rep. [ABSTRACT FROM AUTHOR]

Simple Summary: Two distinct genetic groupings of the treehopper, Spissistilus festinus i.e., California (CA) and Southeastern (SE), have been described but it is unknown whether they are reproducibly compatible. In addition, the CA genotype transmits grapevine red blotch virus (GRBV), but no information is available on the transmission capacity of the SE genotype. In this study, F1 offspring of mixed mating CA/SE S. festinus pairs exhibited varied physical characteristics compared to the offspring of the parental genotypes but acquired GRBV at similar rates. Likewise, the CA and SE parental genotypes acquired GRBV at similar rates, though the viral load in the salivary glands was significantly higher for SE than CA individuals and the transmission rate was significantly higher for the SE than the CA genotype. This is the first report of distinct GRBV transmission abilities of the two sexually compatible S. festinus populations, underscoring the need to study GRBV spread in the Southeastern United States. Two phenotypically similar but genetically distinct genotypes of Spissistilus festinus (Say, 1830) (Hemiptera: Membracidae), a pest of legume crops in Southern United States and a vector of grapevine red blotch virus (GRBV) in California vineyards, exist. No information is available on whether the two S. festinus genotypes, i.e., California (CA) and Southeastern (SE), are sexually compatible or whether the SE genotype can transmit GRBV. In this study, we established mixed mating S. festinus pairs for which the F1 offspring varied phenotypically compared with the offspring of same genotype pairs but acquired GRBV isolate NY175 at similar rates (p = 0.96) and with a similar viral genome copy number (p = 0.34). Likewise, rates of GRBV acquisition were alike for the two parental CA (58%, 61/105) and SE (61%, 65/106) genotypes (p = 0.74), though the GRBV copy number in the salivary glands was overall significantly higher for SE than CA individuals (p = 0.02). Furthermore, the GRBV transmission rate was significantly higher for the SE genotype (89%, 16/18) than the CA genotype (50%, 8/16) (p = 0.04). These results revealed the existence of two sexually compatible S. festinus genotypes with distinct GRBV transmission abilities, suggesting the need to study GRBV ecology in Southeastern United States and areas where the two genotypes might co-exist. [ABSTRACT FROM AUTHOR]

There is widespread evidence of plant viruses manipulating behavior of their insect vectors as a strategy to maximize infection of plants. Often, plant viruses and their insect vectors have multiple potential host plant species, and these may not overlap entirely. Moreover, insect vectors may not prefer plant species to which plant viruses are well-adapted. In such cases, can plant viruses manipulate their insect vectors to preferentially feed and oviposit on plant species, which are suitable for viral propagation but less suitable for themselves? To address this question, we conducted dual- and no-choice feeding studies (number and duration of probing events) and oviposition studies with non-viruliferous and viruliferous [carrying beet curly top virus (BCTV)] beet leafhoppers [Circulifer tenellus (Baker)] on three plant species: barley (Hordeum vulgare L.), ribwort plantain (Plantago lanceolata L.), and tomato (Solanum lycopersicum L.). Barley is not a host of BCTV, whereas ribwort plantain and tomato are susceptible to BCTV infection and develop a symptomless infection and severe curly top symptoms, respectively. Ribwort plantain plants can be used to maintain beet leafhopper colonies for multiple generations (suitable), whereas tomato plants cannot be used to maintain beet leafhopper colonies (unsuitable). Based on dual- and no-choice experiments, we demonstrated that BCTV appears to manipulate probing preference and behavior by beet leafhoppers, whereas there was no significant difference in oviposition preference. Simulation modeling predicted that BCTV infection rates would to be higher in tomato fields with barley compared with ribwort plantain as a trap crop. Simulation model results supported the hypothesis that manipulation of probing preference and behavior may increase BCTV infection in tomato fields. Results presented were based on the BCTV-beet leafhopper pathosystem, but the approach taken (combination of experimental studies with complementary simulation modeling) is widely applicable and relevant to other insect-vectored plant pathogen systems involving multiple plant species.

During routine virus screening, grapevine red blotch virus (GRBV; genus Grablovirus, family Geminiviridae) was detected in several samples of a recently released interspecific hybrid wine grapevine cultivar, Blanc du Soleil (BdS, US PP 34,483 P2, 2022). Molecular characterization of the BdS GRBV isolates revealed the presence of distinct complete genomes in nine isolates, with atypical lengths of 3,181 to 3,183 nucleotides (nt) relative to the expected 3,205 to 3,208 nt reported for GRBV isolates characterized to date globally. The difference in length was mainly due to deletions in the long intergenic region of the BdS GRBV isolates. In a phylogenetic reconstruction, the BdS GRBV isolates formed a monophyletic subclade basal to the clade II isolates to which they were more phylogenetically related than the clade I isolates. On average, complete genomes of these new isolates are 98.75% identical to each other, 96.66% identical to clade II isolates, and 92.02% identical to clade I isolates. Evolutionary analysis also revealed the occurrence of recombination in the history of these new isolates. [Graphic: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Members of the Geminviridae family are circular single-stranded DNA plant-infecting viruses, some of which impact global food production. Geminiviruses are vectored by sap-feeding insects such as leafhoppers, treehoppers, aphids, and whiteflies. Additionally, geminivirus sequences have also been identified in other insects such as dragonflies, mosquitoes, and stingless bees. As part of a viral metagenomics study on honeybees and solitary bees (Nomia sp.), two geminivirus genomes were identified. These represent a novel citlodavirus (from honeybees collected from Westmoreland, Jamaica) and a mastrevirus-like genome (from a solitary bee collected from Tempe, Arizona, USA). The novel honeybee-derived citlodavirus genome shares ~61 to 69% genome-wide nucleotide pairwise identity with other citlodavirus genome sequences and is most closely related to the passion fruit chlorotic mottle virus identified in Brazil. Whereas the novel solitary bee-derived mastrevirus-like genome shares ~55 to 61% genome-wide nucleotide identity with other mastreviruses and is most closely related to tobacco yellow dwarf virus identified in Australia, based on pairwise identity scores of the full genome, replication-associated protein, and capsid protein sequences. Previously, two geminiviruses in the Begomovirus genus were identified in samples of stingless bee (Trigona spp.) samples. Here, we identify viruses that represent two new species of geminiviruses from a honeybee and a solitary bee, which continues to demonstrate that plant pollinators can be utilized for the identification of plant-infecting DNA viruses in ecosystems.

The family Geminiviridae with fourteen accepted genera and an increasing number of unassigned species is currently identified as the largest family of plant‐infecting viruses. Their twinned icosahedral particles contain single-stranded genomic DNAs that are naturally transmitted by Hemiptera insects including whitefly (Bemisia tabaci), several species of leafhoppers, treehoppers and one species of aphid in a wide range of host plants. Also, some geminiviruses are transmitted by seeds in certain hosts. In addition to climate changes, industrial cultivations, and the development of global trade, the genetic flexibility of geminiviruses has led to an increase in the rate of their distribution. Diseases caused by geminiviruses constitute a serious constraint to tropical and sub-tropical agroecosystems worldwide. The economic losses caused by geminivirus infections have grown especially in open fields and greenhouses in Iran during the last years. Defining two distinct genera by having unique molecular and biological characteristics, Becurtovirus and Turncurtovirus, and the presence of different species and strains of other geminiviruses introduces Iran as a putative origin of diversification for old-world monopartite geminiviruses. This review presents the occurrence and diversity of the members of Geminiviridae in Iran. Moreover, some applicable control measures have been proposed based on compatibility with the Iran agroecosystem which would also be recommended for other tropical and subtropical regions of the world. [ABSTRACT FROM AUTHOR]

Tomato yellow leaf curl virus (TYLCV) is a monopartite DNA virus with a genome size of ~ 2,800 base pairs. The virus belongs to the genus Begomovirus within the family Geminiviridae. Extant TYLCV strains are differentiated based on an established threshold of 94% genome-wide pairwise nucleotide identity. The phylogenetic relationships, diversification mechanisms, including recombination, and extent of spread within and from the center of origin for TYLCV have been reported in previous studies. However, the evolutionary relationships among strains, strains' distribution and genomic diversification, and genetic mechanisms shaping TYLCV strains' evolution have not been reevaluated to consider globally representative genome sequences in publicly available sequence database, including herein newly sequenced genomes from the U.S. and Middle East, respectively. In this study, full-length genome sequences for the extant strains and isolates of TYLCV (n=818) were downloaded from the GenBank database. All previously published genome sequences, and newly sequenced TYLCV genomes of TYLCV isolates from Kuwait and USA, determined herein (n=834), were subjected to recombination analysis. To remove the 'phylogenetic noise' imparted by interspecific recombination, the recombinant genomes were removed from the data set, and the remaining non-recombinant genome sequences (n=423) were subjected to population genetics and Bayesian analyses. Results of the phylogeographical analysis indicated that the type strain, TYLCV-Israel, and TYLCV-Mild strain, were globally distributed, spanning Africa, America, Asia, Australia/Oceania, Europe, and New Caledonia, while the other TYLCV strains were prevalent only throughout the Middle East. The results of Bayesian evolutionary (ancestral) analysis predicted that TYLCV-Israel represents the oldest, most recent common ancestor (MRCA) (41,795 years), followed by TYLCV-Mild at 39,808 years. These were closely followed by two Iranian strains viz., TYLCV-Kerman and TYLCV-Iran at 37,529 and 36,420 years, respectively. In contrast, the most recently evolving strains were TYLCV-Kuwait and TYLCV-Kahnooj at 12,445 and 298 years, respectively. Results of the neutrality test indicated that TYLCV-Israel and TYLCV-Mild populations are undergoing purifying selection and/or population expansion, although statistically significant selection was documented for only TYLCV-Israel, based on positive selection acting on five codons. [ABSTRACT FROM AUTHOR]

Tomato leaf curl New Delhi virus (ToLCNDV), a bipartite Begomovirus belonging to the family Geminiviridae, causes severe damage to many economically important crops worldwide. In the present study, pathogenicity of Asian (ToLCNDV-In from Pakistan) and Mediterranean isolates (ToLCNDV-ES from Italy) were examined using infectious clones in tomato plants. Only ToLCNDV-In could infect the three tomato cultivars, whereas ToLCNDV-ES could not. Genome-exchange of the two ToLCNDVs revealed the ToLCNDV DNA-A segment as the main factor for ToLCNDV infectivity in tomato. In addition, serial clones with chimeric ToLCNDV-In A and ToLCNDV-ES A genome segments were generated to identify the region determining viral infectivity in tomatoes. A chimeric clone carrying the ToLCNDV-In coat protein (CP) exhibited pathogenic adaptation in tomatoes, indicating that the CP of ToLCNDV is essential for its infectivity. Analyses of infectious clones carrying a single amino acid substitution revealed that amino acid at position 143 of the CP is critical for ToLCNDV infectivity in tomatoes. To better understand the molecular basis whereby CP function in pathogenicity, a yeast two-hybrid screen of a tomato cDNA library was performed using CPs as bait. The hybrid results showed different interactions between the two CPs and Ring finger protein 44-like in the tomato genome. The relative expression levels of upstream and downstream genes and Ring finger 44-like genes were measured using quantitative reverse transcription PCR (RT-qPCR) and compared to those of control plants. This is the first study to compare the biological features of the two ToLCNDV strains related to viral pathogenicity in the same host plant. Our results provide a foundation for elucidating the molecular mechanisms underlying ToLCNDV infection in tomatoes. [ABSTRACT FROM AUTHOR]

BackgroundGeminiviruses are circular, single-stranded viruses responsible for enormous crop loss worldwide. Rapid expansion of geminivirus diversity outweighs the continuous effort to control its spread. Geminiviruses channelize the host cell machinery in their favour by manipulating the gene expression, cell signalling, protein turnover, and metabolic reprogramming of plants. As a response to viral infection, plants have evolved to deploy various strategies to subvert the virus invasion and reinstate cellular homeostasis.Main bodyNumerous reports exploring various aspects of plant-geminivirus interaction portray the subtlety and flexibility of the host-pathogen dynamics. To leverage this pool of knowledge towards raising antiviral resistance in host plants, a comprehensive account of plant's defence response against geminiviruses is required. This review discusses the current knowledge of plant's antiviral responses exerted to geminivirus in the light of resistance mechanisms and the innate genetic factors contributing to the defence. We have revisited the defence pathways involving transcriptional and post-transcriptional gene silencing, ubiquitin-proteasomal degradation pathway, protein kinase signalling cascades, autophagy, and hypersensitive responses. In addition, geminivirus-induced phytohormonal fluctuations, the subsequent alterations in primary and secondary metabolites, and their impact on pathogenesis along with the recent advancements of CRISPR-Cas9 technique in generating the geminivirus resistance in plants have been discussed.ConclusionsConsidering the rapid development in the field of plant-virus interaction, this review provides a timely and comprehensive account of molecular nuances that define the course of geminivirus infection and can be exploited in generating virus-resistant plants to control global agricultural damage.

Flowering plants and mammals contain imprinted genes that are primarily expressed in the endosperm and placenta in a parent-of-origin manner. In this study, we show that early activation of the geminivirus genes C2 and C3 in Arabidopsis (Arabidopsis thaliana) plants, encoding a viral suppressor of RNA interference and a replication enhancer protein, respectively, is correlated with the transient vegetative expression of VARIANT IN METHYLATION5 (VIM5), an endosperm imprinted gene that is conserved in diverse plant species. VIM5 is a ubiquitin E3 ligase that directly targets the DNA methyltransferases MET1 and CMT3 for degradation by the ubiquitin-26S proteasome proteolytic pathway. Infection with Beet severe curly top virus induced VIM5 expression in rosette leaf tissues, possibly via the expression of the viral replication initiator protein, leading to the early activation of C2 and C3 coupled with reduced symmetric methylation in the C2-3 promoter and the onset of disease symptoms. These findings demonstrate how this small DNA virus recruits a host imprinted gene for the epigenetic activation of viral gene transcription. Our findings reveal a distinct strategy used by plant pathogens to exploit the host machinery in order to inhibit methylation-mediated defense responses when establishing infection.

Tomato yellow leaf curl virus (TYLCV) is a monopartite DNA virus with a genome size of ~ 2,800 base pairs. The virus belongs to the genus Begomovirus within the family Geminiviridae. Extant TYLCV strains are differentiated based on an established threshold of 94% genome-wide pairwise nucleotide identity. The phylogenetic relationships, diversification mechanisms, including recombination, and extent of spread within and from the center of origin for TYLCV have been reported in previous studies. However, the evolutionary relationships among strains, strains’ distribution and genomic diversification, and genetic mechanisms shaping TYLCV strains’ evolution have not been re-evaluated to consider globally representative genome sequences in publicly available sequence database, including herein newly sequenced genomes from the U.S. and Middle East, respectively. In this study, full-length genome sequences for the extant strains and isolates of TYLCV (n=818) were downloaded from the GenBank database. All previously published genome sequences, and newly sequenced TYLCV genomes of TYLCV isolates from Kuwait and USA, determined herein (n=834), were subjected to recombination analysis. To remove the ‘phylogenetic noise’ imparted by interspecific recombination, the recombinant genomes were removed from the data set, and the remaining non-recombinant genome sequences (n=423) were subjected to population genetics and Bayesian analyses. Results of the phylogeographical analysis indicated that the type strain, TYLCV-Israel, and TYLCV-Mild strain, were globally distributed, spanning Africa, America, Asia, Australia/Oceania, Europe, and New Caledonia, while the other TYLCV strains were prevalent only throughout the Middle East. The results of Bayesian evolutionary (ancestral) analysis predicted that TYLCV-Israel represents the oldest, most recent common ancestor (MRCA) (41,795 years), followed by TYLCV-Mild at 39,808 years. These were closely followed by two Iranian strains viz., TYLCV-Kerman and TYLCV-Iran at 37,529 and 36,420 years, respectively. In contrast, the most recently evolving strains were TYLCV-Kuwait and TYLCV-Kahnooj at 12,445 and 298 years, respectively. Results of the neutrality test indicated that TYLCV-Israel and TYLCV-Mild populations are undergoing purifying selection and/or population expansion, although statistically significant selection was documented for only TYLCV-Israel, based on positive selection acting on five codons.

Numerous, diverse plant viruses encode movement proteins (MPs) that aid the virus movement through plasmodesmata, the plant intercellular channels. MPs are essential for virus spread and propagation in distal tissues, and several unrelated MPs have been identified. The 30K superfamily of MPs (named after the molecular mass of tobacco mosaic virus (TMV) MP, the classical model of plant virology) is the largest and most diverse MP variety, represented in 16 virus families, but its evolutionary origin remained obscure. Here, we show that the core structural domain of the 30K MPs is homologous to the jelly-roll domain of the capsid proteins (CPs) of small RNA and DNA viruses, in particular, those infecting plants. The closest similarity was observed between the 30K MPs and the CPs of the viruses in the families Bromoviridae and Geminiviridae. We hypothesize that the MPs evolved via duplication or horizontal acquisition of the CP gene in a virus that infected an ancestor of vascular plants, followed by neofunctionalization of one of the paralogous CPs, potentially through the acquisition of unique N- and C-terminal regions. During the subsequent coevolution of viruses with diversifying vascular plants, the 30K MP genes underwent explosive horizontal spread among emergent RNA and DNA viruses, likely permitting viruses of insects and fungi that coinfected plants to expand their host ranges, molding the contemporary plant virome. Movement proteins, a signature of plant RNA and DNA viruses, enable cell-to-cell movement of the virus via plasmodesmata channels. This study shows that the most common movement proteins of the 30K superfamily originated from jelly-roll capsid proteins of plant viruses, emphasizing the key role of exaptation in virus evolution. [ABSTRACT FROM AUTHOR]

The Begomovirus genus of the family Geminiviridae comprises the largest group of geminiviruses. Begomoviruses are transmitted by the whitefly complex (Bemisia tabaci) and infect dicotyledonous plants in tropical and subtropical regions. The list of begomoviruses is continuously increasing as a result of improvements in the methods for identification, especially from weed plants, which are considered a source of new viruses and reservoirs of economically important viruses but are often neglected during diversity studies. Lathyrus aphaca L. weed plants (yellow-flowered pea) with varicose veins and discoloration of the leaves were found. Amplified genomic DNA through rolling circular amplification was subjected to PCR analysis for the detection of the viral genome and associated DNA-satellites (alphasatellites and betasatellites). A full-length sequence (2.8 kb) of a monopartite begomovirus clone was determined; however, we could not find any associated DNA satellites. The amplified full-length clone of Rose leaf curl virus (RoLCuV) reserved all the characteristics and features of an Old World (OW) monopartite begomovirus. Furthermore, it is the first time it has been reported from a new weed host, yellow-flowered pea. Rolling circle amplification and polymerase chain reaction analysis of associated DNA satellites, alphasatellite, and betasatellite, were frequently accomplished but unable to amplify from the begomovirus-infected samples, indicating the presence of only monopartite Old World begomovirus. It is observed that RoLCuV has the capability to infect different hosts individually without the assistance of any DNA satellite component. Recombination in viruses is also a source of begomovirus infection in different hosts. [ABSTRACT FROM AUTHOR]

Grapevine red blotch virus (GRBV) causes red blotch disease and is transmitted by the three-cornered alfalfa hopper, Spissistilus festinus. GRBV isolates belong to a minor phylogenetic clade 1 and a predominant clade 2. Spatiotemporal disease dynamics were monitored in a 1-hectare 'Merlot' vineyard planted in California in 2015. Annual surveys first revealed disease onset in 2018 and a 1.6% disease incidence in 2022. Ordinary runs and phylogenetic analyses documented significant aggregation of vines infected with GRBV clade 1 isolates in one corner of the vineyard (Z = −4.99), despite being surrounded by clade 2 isolates. This aggregation of vines harboring isolates from a non-prevalent clade is likely due to infected rootstock material at planting. GRBV clade 1 isolates were predominant in 2018–2019 but displaced by clade 2 isolates in 2021–2022, suggesting an influx of the latter isolates from outside sources. This study is the first report of red blotch disease progress immediately after vineyard establishment. A nearby 1.5-hectare 'Cabernet Sauvignon' vineyard planted in 2008 with clone 4 (CS4) and 169 (CS169) vines was also surveyed. Most CS4 vines that exhibited disease symptoms one-year post-planting, likely due to infected scion material, were aggregated (Z = −1.73). GRBV isolates of both clades were found in the CS4 vines. Disease incidence was only 1.4% in non-infected CS169 vines in 2022 with sporadic infections of isolates from both clades occurring via secondary spread. Through disentangling GRBV infections due to the planting material and S. festinus-mediated transmission, this study illustrated how the primary virus source influences epidemiological dynamics of red blotch disease. [ABSTRACT FROM AUTHOR]

Spissistilus festinus (Hemiptera: Membracidae) transmit grapevine red blotch virus (GRBV, Grablovirus, Geminiviridae) in greenhouse settings; however, their role as a vector of GRBV in vineyards is unknown. Following controlled exposures of aviruliferous S. festinus for two weeks on infected, asymptomatic vines in a California vineyard in June and a 48 h gut clearing on alfalfa, a nonhost of GRBV, approximately half of the released insects tested positive for GRBV (45%, 46 of 102), including in the salivary glands of dissected individuals (11%, 3 of 27), indicating acquisition. Following controlled exposures of viruliferous S. festinus for two to six weeks on GRBV-negative vines in vineyards in California and New York in June, transmission of GRBV was detected when two S. festinus were restricted to a single leaf (3%, 2 of 62 in California; 10%, 5 of 50 in New York) but not with cohorts of 10–20 specimens on entire or half shoots. This work was consistent with greenhouse assays in which transmission was most successful with S. festinus exposed to a single leaf (42%, 5 of 12), but rarely occurred on half shoots (8%, 1 of 13), and never on entire shoots (0%, 0 of 18), documenting that the transmission of GRBV is facilitated through the feeding of fewer S. festinus on a restricted area of grapevine tissue. This work demonstrates S. festinus is a GRBV vector of epidemiological importance in vineyards. [ABSTRACT FROM AUTHOR]

Simple Summary: Begomoviruses constitute a successful group of emerging plant viruses threatening vegetable, root and fiber crops worldwide that are transmitted in nature by whiteflies of the Bemisia tabaci complex. Tomato leaf curl New Delhi virus is a paradigmatic example of a begomovirus that has recently emerged in Mediterranean countries after movement from its original location in the Indian subcontinent. The Mediterranean isolates of this virus belong to a novel strain, named "Spain strain", which infects zucchini and other cucurbits but is poorly adapted to tomato. This work aimed to clarify some aspects of the whitefly transmission of tomato leaf curl New Delhi virus. It was shown that contrary to a recent study reporting the transmission of an Indian isolate of the virus by the greenhouse whitefly (Trialeurodes vaporariorum), the Mediterranean isolate is not transmitted by this insect. In addition, the most prevalent Bemisia tabaci species, Mediterranean, is not an efficient vector of this begomovirus between zucchini plants and the wild cucurbit Ecballium elaterium. These results suggest that this wild plant, although frequently infected, may not play a relevant role as a reservoir in the epidemiology of the disease caused by tomato leaf curl New Delhi virus Spain strain. Tomato leaf curl New Delhi virus (ToLCNDV) is a bipartite begomovirus (genus Begomovirus, family Geminiviridae) persistently transmitted, as with all other begomoviruses, by whiteflies (Hemiptera: Aleyrodidae) of the Bemisia tabaci cryptic species complex. The virus, originally from the Indian subcontinent, was recently introduced in the Mediterranean basin, where it is currently a major concern for protected and open-field horticulture. The Mediterranean ToLCNDV isolates belong to a novel strain named "Spain strain" (ToLCNDV-ES), which infects zucchini and other cucurbit crops but is poorly adapted to tomato. Recently, it has been reported that another whitefly, Trialeurodes vaporariorum, is able to transmit an isolate of ToLCNDV from India which infects the chayote plant, a cucurbit. The present work aimed to clarify some aspects of whitefly transmission of ToLCNDV-ES. It was shown that T. vaporariorum is not able to transmit ToLCNDV-ES between zucchini plants. In addition, Ecballium elaterium may not act as a relevant reservoir for this virus strain in the Mediterranean basin, as B. tabaci Mediterranean (MED), the most prevalent species of the complex in the region, is not an efficient vector of this begomovirus between cultivated zucchini and wild E. elaterium plants. [ABSTRACT FROM AUTHOR]

Background: Geminiviruses are among the most threatening emerging plant viruses, accountable for a huge loss to agricultural production worldwide. These viruses have been responsible for some serious outbreaks during the last few decades across different parts of the world. Sincere efforts have been made to regulate the disease incidence by incorporating a multi-dimensional approach, and this process has been facilitated greatly by the advent of molecular techniques. But, the mixed infection due to the polyphagous nature of vectors results in viral recombination followed by the emergence of novel viral strains which thus renders the existing mitigation strategies ineffective. Hence, a multifaceted insight into the molecular mechanism of the disease is really needed to understand the regulatory points; much has been done in this direction during the last few years. The present review aims to explore all the latest developments made so far and to organize the information in a comprehensive manner so that some novel hypotheses for controlling the disease may be generated. Methods and Results: Starting with the background information, diverse genera of geminiviruses are listed along with their pathological and economic impacts. A comprehensive and detailed mechanism of infection is elaborated to study the interactions between vector, host, and virus at different stages in the life cycle of geminiviruses. Finally, an effort isalso made to analyze the progress made at the molecular level for the development of various mitigation strategies and suggest more effective and better approaches for controlling the disease. Conclusion: The study has provided a thorough understanding of molecular mechanism of geminivirus infection. [ABSTRACT FROM AUTHOR]

Simple Summary: Whiteflies (Bemisia tabaci) 'B mitotype' represent an insect pest of fruit, vegetable, ornamental and weed plants. B. tabaci is a cryptic species comprising at least eight endemic haplotypes, of which haplotypes 6 and/or 8 are recognized invasives. The objective of this study was to identify the prevalence and relationships among putative native and exotic begomoviruses and North Africa–Middle East haplotypes in Oman. Several begomoviral species were identified from B. tabaci adults collected from infested plant species, with 67% and 33% representing native and exotic species, respectively. Logistic regression and correspondence analyses predicted 'strong' and 'close' virus–vector associations involving haplotypes 5 and 2 and the exotic chili leaf curl virus and endemic tomato yellow leaf curl virus-OM, respectively. Irrigated agriculture and global trade expansion have facilitated diversification and spread of begomoviruses (Geminiviridae), transmitted by the Bemisia tabaci (Gennadius) cryptic species. Oman is situated on major crossroads between Africa and South Asia, where endemic/native and introduced/exotic begomoviruses occur in agroecosystems. The B. tabaci 'B mitotype' belongs to the North Africa–Middle East (NAFME) cryptic species, comprising at least eight endemic haplotypes, of which haplotypes 6 and/or 8 are recognized invasives. Prevalence and associations among native and exotic begomoviruses and NAFME haplotypes in Oman were investigated. Nine begomoviral species were identified from B. tabaci infesting crop or wild plant species, with 67% and 33% representing native and exotic species, respectively. Haplotypes 2, 3, and 5 represented 31%, 3%, and 66% of the B. tabaci population, respectively. Logistic regression and correspondence analyses predicted 'strong'- and 'close' virus–vector associations involving haplotypes 5 and 2 and the exotic chili leaf curl virus (ChiLCV) and endemic tomato yellow leaf curl virus-OM, respectively. Patterns favor a hypothesis of relaxed virus–vector specificity between an endemic haplotype and the introduced ChiLCV, whereas the endemic co-evolved TYLCV-OM and haplotype 2 virus–vector relationship was reinforced. Thus, in Oman, at least one native haplotype can facilitate the spread of endemic and introduced begomoviruses. [ABSTRACT FROM AUTHOR]

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]

The incidence and severity of begomovirus diseases have been increasing around the world recently, and the ridge gourd [Luffa acutangula (Roxb.) L.] is the latest example of a crop that has become highly susceptible to the outbreak of the tomato leaf curl New Delhi virus (ToLCNDV, genus Begomovirus) in India. Accurate diagnosis of causal agents is important in designing disease management strategies. In this study the coat protein (CP) gene from a ToLCNDV-Rg ridge gourd isolate was used to produce polyclonal antibodies (ToLCNDV-Rg-CP-PAb) in a rabbit. The antibodies successfully detected a 30.5 kDa ToLCNDV-Rg-CP in extracts of symptomatic ridge gourd leaf samples by several assays, such as Western Blotting (WB), Dot Immuno Binding Assay (DIBA), Direct Antigen Coating Enzyme Linked Immuno Sorbent Assay (DAC-ELISA), Immuno Capture Polymerase Chain Reaction (IC-PCR), and Immuno Capture Loop-Mediated Isothermal Amplification (IC-LAMP) assays. However, none of the negative samples tested positive in either of the detection methods. Among all the methods tested, the immunocapture assay, IC-LAMP, was the most sensitive in detecting ToLCNDV-Rg. Furthermore, antibodies generated in this study also detected other commonly occurring begomoviruses in South India, such as tomato leaf curl Palampur virus and squash leaf curl China virus in cucurbits. Together, ToLCNDV-Rg-CP-PAb can be used for detecting at least three species of begomoviruses infecting cucurbits. The obtained antibodies will contribute to monitoring disease outbreaks in multiple crops. [ABSTRACT FROM AUTHOR]

Betasatellites, single-stranded circular DNAs, are multifunctional agents associated with monopartite begomoviruses (family Geminiviridae), that act as symptoms determinant. Begomoviruses are replicated by species-specific interactions between the viral replicationassociated protein (Rep) and iteron motifs at the upstream of the origin of replication (ori). In contrast, promiscuous replication of betasatellites could be supported by different geminiviruses. In this study, the interaction of Cotton leaf curl Multan virus (CLCuMuV, genus Begomovirus) and Beet curly top virus (BCTV, genus Curtovirus) encoded Rep proteins with the iteron-like sequence of betasatellite, 5́-GAGGACC-3́, was investigated using in silico approaches. Nucleotide sequences of two Rep-encoding genes were obtained from the GenBank database, NCBI. Physicochemical characteristics of Rep proteins and their secondary and tertiary structures were predicted using the SOMPA tool and I-TASSER servers, respectively. The binding affinity of the best-predicted models of both proteins toward betasatellite iteron-like sequence was assessed using Docking simulations. The results represented reliable tertiary structures and showed structural similarity for Rep of different analyzed geminiviruses. Cluster analysis of HADDOCK revealed more total binding energy for CLCuMuV Rep toward the iteron-like sequence than BCTV complex. These in silico results confirmed the more trans-replication activity for relative geminiviruses in replication of betasatellite genomes. They emphasized the role of iteron-like sequences in interactions with the Rep of helper geminiviruses. Furthermore, targeting of identified activate sites within Rep protein structures to interact with betasatellite genomes could be considered as a control measure for begomovirus/betasatellite complexes. [ABSTRACT FROM AUTHOR]

Apple geminivirus 1 (AGV) in the genus Maldovirus of the family Geminiviridae was first identified infecting apple trees in the year 2015 in China. In this work, we characterized three isolates of the AGV in the Chinese pearleaf crabapple (Malus asiatica) in Inner Mongolia Autonomous Region. The viruses were detected by Illumina sequencing and its existence was confirmed by reverse transcription-polymerase chain reaction (RT-PCR) amplification of an AGV fragment. Between the three AGV isolates and the initially characterized AGV isolate PL2015, the nucleotide sequence identities of the complete genome ranged from 91.2 to 91.7%, of the coat protein gene (V1) ranged from 95.4% to 97.3%, and of the replicase gene (C1) ranged from 87.3% to 88.0%. Phylogenetic analysis indicated that the three isolates formed a monophyletic group together with the AGV, separated from the current genera in the family Geminiviridae. This is the first description of the AGV infecting crabapples. [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.

Two phenotypically similar but genetically distinct genotypes of Spissistilus festinus (Say, 1830) (Hemiptera: Membracidae), a pest of legume crops in Southern United States and a vector of grapevine red blotch virus (GRBV) in California vineyards, exist. No information is available on whether the two S. festinus genotypes, i.e., California (CA) and Southeastern (SE), are sexually compatible or whether the SE genotype can transmit GRBV. In this study, we established mixed mating S. festinus pairs for which the F1 offspring varied phenotypically compared with the offspring of same genotype pairs but acquired GRBV isolate NY175 at similar rates (p = 0.96) and with a similar viral genome copy number (p = 0.34). Likewise, rates of GRBV acquisition were alike for the two parental CA (58%, 61/105) and SE (61%, 65/106) genotypes (p = 0.74), though the GRBV copy number in the salivary glands was overall significantly higher for SE than CA individuals (p = 0.02). Furthermore, the GRBV transmission rate was significantly higher for the SE genotype (89%, 16/18) than the CA genotype (50%, 8/16) (p = 0.04). These results revealed the existence of two sexually compatible S. festinus genotypes with distinct GRBV transmission abilities, suggesting the need to study GRBV ecology in Southeastern United States and areas where the two genotypes might co-exist.

Begomoviruses have emerged as a group of plant pathogens that cause devastating diseases in a wide range of crops in tropical and subtropical regions of the world. Betasatellites, the circular single-stranded DNA molecules with the size of almost half of that of the associated helper begomoviruses, are often essential for the production of typical disease symptoms in several virus-host systems. Association of betasatellites with begomoviruses results in more severe symptoms in the plants and affects the yield of numerous crops leading to huge agroeconomic losses. βC1, the only protein encoded by betasatellites, plays a multifaceted role in the successful establishment of infection. This protein counteracts the innate defence mechanisms of the host, like RNA silencing, ubiquitin-proteasome system and defence responsive hormones. In the last two decades, the molecular aspect of betasatellite pathogenesis has attracted much attention from the researchers worldwide, and reports have shown that βC1 protein aggravates the helper begomovirus disease complex by modulating specific host factors. This review discusses the molecular aspects of the pathogenesis of betasatellites, including various βC1-host factor interactions and their effects on the suppression of defence responses of the plants.

Abstract Background Bhendi or okra (Abelmoschus esculentus) is an important crop widely cultivated in the Indian subcontinent. The production of okra in tropical regions is constrained by several abiotic and biotic factors. Among biotic stresses, yellow vein mosaic disease (YVMD), transmitted by the whitefly (Bemisia tabaci Genn.), causes significant production losses. Results Leaves showing symptoms of YVMD were collected from okra plants in the district of Mardan, Pakistan, from which the total nucleic acid was extracted. It was found that the viral genome was 2739 bp in the length and had seven conserved open reading frames, comparable to those of monopartite begomovirus species from the Old World. Nucleotide sequence comparison revealed that the genome has 97.7% identity with bhendi yellow vein mosaic virus (BYVMV). Additionally, alpha- and betasatellite DNA components were amplified and sequenced. The alpha- and betasatellite DNA sequences were 1367 and 1346 nt in length, respectively. Sequence analysis revealed that the alpha- and betasatellite sequences shared 97.9 and 98.7% similarity with cotton leaf curl Multan alphasatellite DNA (CLCuMuA) and croton yellow vein mosaic betasatellite DNA (CroYVMB), respectively. Conclusions Based on the prevailing classification system, the isolate was identified as a variant of BYVMV, CLCuMuA, and CroYVB. Alphasatellite presence in the begomovirus betasatellite complex detected in the present study indicated a recent mobilization into the viral complex infecting okra in this region. The study findings may facilitate the design of new management strategies to protect this valuable crop against begomovirus infection.

Two newly described viruses belonging to distinct families, Rhabdo-viridae and Geminiviridae, were discovered co-infecting Hyptis pectinata from a tropical dry forest of Ecuador. The negative-sense RNA genome of the rhabdovirus, tentatively named Hyptis latent virus (HpLV), comprises 13,765 nucleotides with seven open reading frames separated by the conserved intergenic region 3'-AAUUAUUUUGAU-5'. Sequence analyses showed identities as high as 56% for the polymerase and 38% for the nucleocapsid to members of the genus Cytorhabdovirus. Efficient transmission of HpLV was mediated by the pea aphid (Acyrthosiphon pisum) in a persistent replicative manner. The single-stranded DNA genome of the virus tentatively named Hyptis golden mosaic virus (HpGMV) shared homology with members of the genus Begomovirus with bipartite genomes. The DNA-A component consists of 2,716 nucleotides (nt), whereas the DNA-B component contains 2,666 nt. Pairwise alignments using the complete genomic sequence of DNA-A of HpGMV and closest relatives showed identities below the cutoff (<91 % shared nt) established by the ICTV as species demarcation, indicating that HpGMV should be classified in a distinct begomovirus species. Transmission experiments confirmed that the whitefly Bemisia tabaci Middle East-Asia Minor I (MEAM1) is a vector of HpGMV. [ABSTRACT FROM AUTHOR]

Grapevine red blotch virus (GRBV) is a DNA virus in the family Geminiviridae. This pathogen is the causal agent of grapevine red blotch disease, which affects cultivated grapevines and leads to negative effects on crop quality and yield. GRBV is present in commercial vineyards across North America, indicating that spread might have been largely human mediated. That said, recent surveys have demonstrated that there appears to be secondary transmission, most likely by an insect vector. In this study, vineyard insects and plants were surveyed to identify potential candidate vectors and noncrop plants that could act as reservoirs for this pathogen. Results reconfirm that GRBV is limited to Vitis spp., including both cultivated and wild grapevines. Eleven insect genera or species, field collected in vineyards, tested positive for GRBV using quantitative polymerase chain reaction. These insect taxa include unknown Aphididae, the cicadellids Aceratagallia spp., Acinopterus angulatus, Caladonus coquilleti, Colladonus montanus reductus, Colladonus sp., Empoasca spp., Erythroneura elegantula, and Scaphytopius graneticus, along with the membracid Spissistilus festinus and an unknown delphacid. Of these organisms, S. festinus is already known to be capable of transmitting GRBV, and Scaphytopius graneticus may merit closer evaluation as a candidate vector. [Graphic: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

• In this study, we analyzed RNAseq data from different saffron cultivars to explore its virome. • We found 17 broadly distributed viruses, some not previously described. • This analysis provides a tool for future studies for saffron phytosanitary improvement. Saffron (Crocus sativus L.), a historically significant crop valued for its nutraceutical properties, has been poorly explored from a phytosanitary perspective. This study conducted a thorough examination of viruses affecting saffron samples from Spanish cultivars, using high-throughput sequencing alongside a systematic survey of transcriptomic datasets from Crocus sativus at the Sequence Read Archive. Our analysis unveiled a broad diversity and abundance, identifying 17 viruses across the 52 analyzed libraries, some of which were highly prevalent. This includes known saffron-infecting viruses and previously unreported ones. In addition, we discovered 7 novel viruses from the Alphaflexiviridae, Betaflexiviridae, Potyviridae, Solemoviridae , and Geminiviridae families, with some present in libraries from various locations. These findings indicate that the saffron-associated virome is more complex than previously reported, emphasizing the potential of phytosanitary analysis to enhance saffron productivity. [ABSTRACT FROM AUTHOR]

Asystasia gangetica (A. gangetica) leaves exhibiting yellow mosaic symptoms were tested for the presence of begomovirus infection. The putative full-length of a bipartite begomovirus components A and B molecules, respectively were amplified, sequenced, and analyzed. This represents a distinct begomovirus species infecting Asystasia in Benin Republic in West Africa. [ABSTRACT FROM AUTHOR]

Tomato yellow leaf curl virus (TYLCV) is the most devastating and globally spreading begomovirus (family Geminiviridae). Interestingly, until recently, it has not been reported from South Asia. In the current study, for the first time, we identified a novel strain of TYLCV and associated betasatellite infecting eggplant in Pakistan. [ABSTRACT FROM AUTHOR]

Begomoviruses are members of the family Geminiviridae, a large and diverse group of plant viruses characterized by a small circular single-stranded DNA genome encapsidated in twinned quasi-icosahedral virions. Cultivated tomato (Solanum lycopersicum L.) is particularly susceptible and is infected by .100 bipartite and monopartite begomoviruses worldwide. In Brazil, 25 tomato-infecting begomoviruses have been described, most of which are bipartite. Tomato mottle leaf curl virus (ToMoLCV) is one of the most important of these and was first described in the late 1990s but has not been fully characterized. Here, we show that ToMoLCV is a monopartite begomovirus with a genomic DNA similar in size and genome organization to those of DNA-A components of New World (NW) begomoviruses. Tomato plants agroinoculated with the cloned ToMoLCV genomic DNA developed typical tomato mottle leaf curl disease symptoms, thereby fulfilling Koch's postulates and confirming the monopartite nature of the ToMoLCV genome. We further show that ToMoLCV is transmitted by whiteflies, but not mechanically. Phylogenetic analyses placed ToMoLCV in a distinct and strongly supported clade with other begomoviruses from northeastern Brazil, designated the ToMoLCV lineage. Genetic analyses of the complete sequences of 87 ToMoLCV isolates revealed substantial genetic diversity, including five strain groups and seven subpopulations, consistent with a long evolutionary history. Phylogeographic models generated with partial or complete sequences predicted that the ToMoLCV emerged in northeastern Brazil .700 years ago, diversifying locally and then spreading widely in the country. Thus, ToMoLCV emerged well before the introduction of MEAM1 whiteflies, suggesting that the evolution of NW monopartite begomoviruses was facilitated by local whitefly populations and the highly susceptible tomato host. [ABSTRACT FROM AUTHOR]