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Grapevine cultivation has important threats, being viral disorders one of the most extended among the disorders of biotic origin. The Vitis genus hosts many viruses. Although most of them are largely unknown, the focus is placed on a few that produce significant effects in a global scenario. Those viruses are Arabis mosaic virus (ArMV), Grapevine fanleaf virus (GFLV), Grapevine fleck virus (GFkV), and Grapevine leafroll-associated viruses 1 and 3 (GLRaV-1 and -3), which cause the viral disorders arabis, fanleaf, fleck, and leafroll respectively. Due to their worldwide distribution and/or the economic impact they cause on the crop, they are included in different certification schemes. That consideration has motivated the development of many studies and the record of their effects. This chapter delves into the current understanding of those viral organisms and into the disorders they cause in the grapevine. It aims to bring together the current knowledge at the biological, genetic, and cytopathological levels, highlighting the deep knowledge achieved on some aspects as the further need for research into others. Additionally, it emphasizes the need for active research and legislation actualization due to the continuous emergence of new viral strains and species. [ABSTRACT FROM AUTHOR]

The grapevine fleck virus (GFkV) is a ubiquitous grapevine-infecting virus found worldwide, is associated with the grapevine fleck complex, and is often found in mixed infections with viruses of the grapevine leafroll complex and/or vitiviruses. Although GFkV has been studied for a long time, limited sequence information is available in the public databases. In this study, the GFkV sequence data available in GenBank and data generated at the Foundation Plant Services, University of California, Davis, were used to perform nucleotide sequence comparisons, construct a phylogenetic tree, and develop a new RT-qPCR assay. Sequence comparisons showed high genetic diversity among the GFkV isolates, and the phylogenetic analyses revealed a new group comprised of GFkV isolates identified in the present study. A new assay, referred to as GFkV-CP, was designed and validated using an existing GFkV positive control together with 11 samples known to be infected with combinations of different marafiviruses and maculaviruses but not GFkV. In addition, the newly designed assay was used in a field survey to screen grapevines from diverse geographical locations that are maintained at the United States Department of Agriculture (USDA) National Clonal Germplasm Repository (NCGR) in Winters, CA. [ABSTRACT FROM AUTHOR]

Shiraz disease (SD) is a highly destructive disease of grapevines that is associated with grapevine virus A (GVA) infection of vineyards in Australia and South Africa. However, little is known about the transcriptional modifications in grapevine phloem tissues induced by SD. In this study, we explored the viral diversity and transcriptional changes linked to SD. Vines symptomatic for SD exhibited higher viral abundance and were also shown to be co-infected with both GVA and grapevine leafroll-associated virus (GLRaV-4) strain 9. Differential gene (DE) expression analysis revealed physiological responses of Vitis vinifera to the infection. Similar to other plant pathogen infections, SD upregulated genes associated with the systemic acquired resistance (SAR) mechanism and downregulated genes related to vine immunity. Additionally, upregulated genes suggests that callose deposition and the blocking of phloem sieve elements are likely employed by V. vinifera as a defence strategy to limit the internal spread of SD viruses.

Grapevine leafroll-associated virus 3 (GLRaV-3) is a formidable threat to the stability of the global grape and wine industries. It is the primary etiological agent of grapevine leafroll disease (GLD) and significantly impairs vine health, fruit quality, and yield. GLRaV-3 is a member of the genus Ampelovirus, Closteroviridae family. Viral genes within the 3′ proximal unique gene blocks (UGB) remain highly variable and poorly understood. The UGBs of Closteroviridae viruses include diverse open reading frames (ORFs) that have been shown to contribute to viral functions such as the suppression of the host RNA silencing defense response and systemic viral spread. This study investigates the role of GLRaV-3 ORF8, ORF9, and ORF10, which encode the proteins p21, p20A, and p20B, respectively. These genes represent largely unexplored facets of the GLRaV-3 genome. Here, we visualize the subcellular localization of wildtype and mutagenized GLRaV-3 ORFs 8, 9, and 10, transiently expressed in Nicotiana benthamiana. Our results indicate that p21 localizes to the cytosol, p20A associates with microtubules, and p20B is trafficked into the nucleus to carry out the suppression of host RNA silencing. The findings presented herein provide a foundation for future research aimed at the characterization of the functions of these ORFs. In the long run, it would also facilitate the development of innovative strategies to understand GLRaV-3, mitigate its spread, and impacts on grapevines and the global wine industry. [ABSTRACT FROM AUTHOR]

This scientific note discusses the discovery of the silver fly species Leucopina bivittata feeding on the vine mealybug, Planococcus ficus, in Baja California Norte, Mexico. The vine mealybug is a threat to the local wine industry, and the presence of Leucopina bivittata adds to our understanding of the ecological dynamics of this pest. The article provides detailed information on the collection and identification of the specimens. Leucopina bivittata may be a potential biological control agent for the mealybug, as it can overcome bark obstacles to find its prey. The study acknowledges the support of field workers and reviewers. [Extracted from the article]

Viruses can adversely affect vines' vitality, longevity, quality, and quantity in single or mixed infections. In this work, to detect single and mixed viral infections of grapevine in two central viticulture regions of Azerbaijan, a total of 166 samples showing virus-like symptoms including yellows, reddening, fan leaf, mosaic, leaf rolling, and shortening of internodes were collected during the growing seasons of 2022-2023 from different vineyards and subjected to ELISA and RT-PCR analyses. Plant samples were initially assayed using the one-step assay AgriStrip based on lateral flow immunochromatography and DAS-ELISA with specific antisera for Grapevine fanleaf virus (GFLV), Grapevine leafroll-associated virus 1 (GLRaV-1), Grapevine leafroll-associated virus 2 (GLRaV-2), Grapevine leafroll-associated virus 3 (GLRaV-3), and Grapevine leafroll-associated virus 4 (GLRaV-4). Following serological tests, 65% (108 out of 166) of the examined samples exhibited a positive result for one or more of the specified viruses. Total RNA was extracted, and synthesized cDNA was used to amplify a part of the coat protein (CP) gene in RT-PCR using specific primers. Amplicons of the expected size of 1560 bp, 401 bp, 600 bp, 942 bp, 500 bp, and 272 bp were amplified for the mentioned viruses, respectively (but not from healthy samples). The result of this study can be used in the management strategies of these viruses in grapevine-producing areas of Azerbaijan. [ABSTRACT FROM AUTHOR]

This article reports the first detection of grapevine foveavirus A (GFVA) in France. Grapevine plants in a vineyard in the Alsace region showed symptoms of stunted growth and shortened internodes. High-throughput sequencing was used to assess the virome of the vines, revealing a complex mixture of grapevine-infecting viruses, including GFVA. The presence of multiple variants of other viruses may contribute to the observed symptoms. The study confirms the infection by GFVA using RT-PCR and detects the virus in additional plants in the following year. This finding expands the geographical range of GFVA and raises questions about its transmission. [Extracted from the article]

Grapevine (Vitis vinifera L.) is a globally significant agricultural crop affected by many viral diseases. Among these, grapevine fanleaf degeneration, leafroll, rugose wood, and fleck are the most harmful and widespread, contributing significantly to their economic impact worldwide. Grapevine cultivars Prokupac, Tamjanika, Jagoda, Vranac, and Bagrina were collected in 2023 in vineyards and nurseries at localities in central Serbia. A total of 70 leaf samples were analyzed for the presence of nine viruses: grapevine fanleaf virus (GFLV), grapevine leafroll-associated viruses 1, 2, and 3 (GLRaV-1, GLRaV-2, GLRaV-3), grapevine rupestris stem pitting associated virus (GRSPaV), grapevine virus A (GVA), grapevine virus B (GVB), grapevine fleck virus (GFkV) and arabis mosaic virus (ArMV). Multiplex reverse transcription polymerase chain reaction (mRTPCR) was employed to detect these viruses simultaneously, using different primer pairs for each virus in a single reaction. Obtained results showed that the most prevalent was GFkV which was confirmed in 37 samples, followed by GRSPaV (26), GLRaV-1 (12) and GFLV (5). The mRT-PCR proved to be a reliable and rapid method in detecting grapevine viruses from a large number of samples, as supported by this research. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the response of the grapevine variety 'Tribidrag' to virus infection over two vegetation seasons. Virus-free plants were greenhouse cultivated and green grafted with five different virus inocula composed of grapevine leafroll-associated virus 3 (GLRaV-3) singly or in coinfection with other most economically important grapevine viruses. Changes in nutrient status and photosynthesis-related parameters, along with symptom development, were measured. Using the quantitative PCR method, the relative concentration of five selected Vitis genes was determined. Cluster analysis and ANOVA revealed the reduction in phosphorus concentration (P) and photosynthesis-related parameters in infected plants in both seasons, even in the absence of symptom expression, indicating P and assimilation rate (Photo (A)) as stable markers of virus infection. Plants infected with inoculum Y composed of five different viruses provoked major significant changes in the first season while, in the second, fewer changes were measured. The sucrose synthase 3 gene was upregulated in infected plants confirming disturbed sugar metabolism related to virus-induced stress. This study showed that virus-induced changes in 'Tribidrag' plants even in the absence of symptoms are dependent on plant age, as well as on the composition of virus inocula. [ABSTRACT FROM AUTHOR]

The present study aimed to detect and eliminate Grapevine leafroll-associated viruses (GLRaVs) in commercially available Vitis varieties in order to produce appropriate clones for certification. A total of nine commercially available grapevine (Vitis vinifera L.) cultivars grown in the Lahore vineyards of Pakistan were selected. Real-time RT-PCR (TaqMan) assay was used before and after the regeneration of vine plants for the detection of GLRaVs. All nine cultivars were infected with two or more GLRaVs before apical meristem tip culture therapy. Apical meristem tip culture therapy was used as a mean to eliminate the GLRaVs from the optimum size (0.5 mm) of meristem tips. Out of 270 isolated meristems (30 each of nine cultivars), a total of 207 plants were regenerated with a 76.7% regeneration rate. The A7 cultivar demonstrated the highest regeneration rate (86.7%), while the A3 cultivar showed the lowest regeneration rate (66.7%). Screening after apical meristem tip culture therapy showed that the A1, A4, A5 & A8 cultivars demonstrated 100.0% elimination rate, while the A2, A3, A6, A7 & A9 cultivars demonstrated > 95.0% elimination rate, resulting in 97.5% overall elimination rate. The study concludes that apical meristem tip culture is an effective method for the elimination of GLRAVs infection from grapevine plants. [ABSTRACT FROM AUTHOR]

A comprehensive study on the whole spectrum of viruses and viroids in five Iranian grapevine cultivars was carried out using sRNA libraries prepared from phloem tissue. A comparison of two approaches to virus detection from sRNAome data indicated a significant difference in the results and performance of the aligners in viral genome reconstruction. The results showed a complex virome in terms of viral composition, abundance, and richness. Thirteen viruses and viroids were identified in five Iranian grapevine cultivars, among which the grapevine red blotch virus and grapevine satellite virus were detected for the first time in Iranian vineyards. Grapevine leafroll-associated virus 1 (GLRaV1) and grapevine fanleaf virus (GFLV) were highly dominant in the virome. However, their frequency and abundance were somewhat different among grapevine cultivars. The results revealed a mixed infection of GLRaV1/grapevine yellow speckle viroid 1 (GYSVd1) and GFLV/GYSVd1 in grapevines that exhibited yellows and vein banding. We also propose a threshold of 14% of complete reconstruction as an appropriate threshold for detection of grapevine viruses that can be used as indicators for reliable grapevine virome profiling or in quarantine stations and certification programs. [ABSTRACT FROM AUTHOR]

Planococcus ficus (Signoret) is a worldwide pest of grapevine. Mealybugs overwinter under bark and move into the grape canopy as the season progresses. Because crawlers are more active than later stages, mealybug movement behavior is likely to be stage specific. To quantify P. ficus demography and movement behavior, a series of laboratory experiments were conducted. First, P. ficus populations were monitored on grapevine seedlings to describe survival, change in size, timing of male pupation, and timing of oviposition over a 6-wk period. Subsequently, cohorts of mealybugs were generated by infesting grapevines with crawlers and holding infested grapevines for a specified duration of 0 (crawlers), 1, 2, 3, or 4 wk. Crawlers (0-wk) were more likely to move upwards and towards a light source, than all other age cohorts tested. Further, mealybugs from 4-wk-old cohorts were more likely to move downward than all other age cohorts tested. Results suggest that crawlers are more likely to move to the top of grapevines by moving upwards and orienting towards either the sun or the moon than all other age cohorts tested, whereas older gravid females are more likely to move downward. Passive movement of mealybugs on farm machinery or animals requires surviving a host free period.To quantify risk of passive movement, establishment rates and effects of starvation on each age cohort were quantified. Larger and older mealybugs were more likely to establish on grapevines than smaller and younger mealybugs. Further, mealybug longevity in absence of food was greater for older cohorts compared to younger cohorts. Crawlers survived an average of 2 days without food, whereas females from 4-wk-old cohorts survived for an average of 11 days without food. Further, 70% of starved females from 4-wk-old cohorts deposited fertile eggs. In the absence of food, some mealybugs from cohorts aged 2-, 3-, and 4-wk formed pupa with viable males emerging. Adult males from starved nymphs lived for an average of 3 days post-emergence. Results provide methods for producing cohorts of mealybugs of predictable size and stage and provides insight into P. ficus demography and movement behavior. [ABSTRACT FROM AUTHOR]

In this study, an analysis of the virome of 51 grapevines from the Don ampelographic collection named after Ya. I. Potapenko (Russia) was performed using high-throughput sequencing of total RNA. A total of 20 previously described grapevine viruses and 4 viroids were identified. The most detected were grapevine rupestris stem pitting-associated virus (98%), hop stunt viroid (98%), grapevine Pinot gris virus (96%), grapevine yellow speckle viroid 1 (94%), and grapevine fleck virus (GFkV, 80%). Among the economically significant viruses, the most present were grapevine leafroll-associated virus 3 (37%), grapevine virus A (24%), and grapevine leafroll-associated virus 1 (16%). For the first time in Russia, a grapevine-associated tymo-like virus (78%) was detected. After a bioinformatics analysis, 123 complete or nearly complete viral genomes and 64 complete viroid genomes were assembled. An analysis of the phylogenetic relationships with reported global isolates was performed. We discovered and characterized the genomes of five novel grapevine viruses: bipartite dsRNA grapevine alphapartitivirus (genus Alphapartitivirus, family Partitiviridae), bipartite (+) ssRNA grapevine secovirus (genus Fabavirus, family Secoviridae) and three (+) ssRNA grapevine umbra-like viruses 2, -3, -4 (which phylogenetically occupy an intermediate position between representatives of the genus Umbravirus and umbravirus-like associated RNAs). [ABSTRACT FROM AUTHOR]

To determine the occurrence and distribution of prevalent viruses in commercially important vineyards, a survey was carried out in all thirteen wine-growing regions in Germany. Results reveal that the recently emerged Grapevine pinot gris virus (GPGV) was the most abundant virus with a percentage of 18% prevalence, followed by 13% Grapevine fleck virus (GFkV), 9% Grapevine leafroll-associated virus 1 (GLRaV-1), 4% Grapevine fanleaf virus (GFLV), 2% Raspberry ringspot virus (RpRSV), 2% Arabis mosaic virus (ArMV) and 2% Grapevine leafroll-associated virus 3 (GLRaV-3). Distribution of some viruses varies greatly between individual regions, thus regional hotspots or gradients were detected. GPGV for example is mostly found in southeastern Germany, while its incidence decreases to the north along the river Rhine. The findings of this survey provide an overview of the allocation of the most prevalent grapevine viruses in Germany and can support regional virus management and national risk assessment especially GPGV. [ABSTRACT FROM AUTHOR]

Grapevine leafroll disease (GLRD) is the most globally prevalent and destructive disease complex responsible for significant reductions in grape yield and quality as well as wine production. GLRD is associated with several positive-strand RNA viruses of the family Closteroviridae, designated as grapevine leafroll-associated viruses (GLRaVs). However, the specific etiological role of any of these GLRaVs in GLRD has not been demonstrated. Even though GLRaV-3 is considered the chief GLRD agent, little is known about the molecular, cellular, and pathological properties of this virus. Such a knowledge gap is due to multiple factors, including the unavailability of biologically active virus cDNA clones and the lack of reliable experimental systems for launching grapevine infection using such clones. In this work, we tested four methods for inoculating tissue-cultured grapevine plantlets with cDNA clones of GLRaV-3: (i) vacuum agro-infiltration; (ii) agro-pricking; (iii) agro-drenching; and (iv) agro-injection. We showed that vacuum agro-infiltration was the most effective of these methods. Furthermore, we examined the impacts of different experimental conditions on the survival and infectivity rate of grapevines after infiltration. To verify the infectivity rate for different treatments, we used RT-PCR, RT-qPCR, and Western blotting. We found that humidity plays a critical role in the survival of plantlets after agro-infiltration and that the use of RNA silencing suppressor and dormancy treatment both had strong effects on the infection rates. To our knowledge, the experimental protocol reported herein is the most effective system for launching the infection of grapevine using cDNA clones of grapevine viruses featuring up to a 70% infection rate. This system has strong potential to facilitate grapevine virology research including the fulfillment of Koch's postulates for GLRD and other major virus diseases as well as identifying the molecular, cellular, and pathological properties of GLRaVs and, potentially, other important grapevine viruses. [ABSTRACT FROM AUTHOR]

Virus diseases in grapevine 'Shine Muscat', an economically significant table grape cultivar in China, have become a major concern for grapevine growers. To investigate which viruses are frequent in 'Shine Muscat' and screen for healthy propagation material for this cultivar, a total of 140 samples (dormant canes) of 'Shine Muscat' plants were collected from 45 vineyards in different viticultural areas in China. RT-PCR was conducted to detect the presence of grapevine leafroll-associated virus 1 (GLRaV-1), GLRaV-2, GLRaV-3, grapevine fanleaf virus (GFLV), grapevine fleck virus (GFkV), grapevine virus A (GVA), grapevine rupestris stem pitting-associated virus (GRSPaV), grapevine Pinot gris virus (GPGV) and grapevine berry inner necrosis virus (GINV). No virus-free cane was found and all samples were infected with a mixture of at least two viruses; double, triple and quadruple infections accounted for about 31%, 30%, and 22% of the infections, respectively. The most frequent viruses in 'Shine Muscat' plants were GPGV (67.86%), GVA (59.29%) and GRSPaV (55.0%), and GFLV and GLRaV-1 were not detected in any of the samples. In vitro-grown 'Shine Muscat' plantlets carrying GFkV/GINV/GVA/GRSPaV were subjected to thermotherapy or chemotherapy followed by shoot-tip culture. GINV, GFkV and GVA were easily eliminated from the cultivar by both sanitation methods, whereas the frequency of GRSPaV elimination was relatively low. The results presented here contribute to our understanding of virus diseases in grapevine cv. Shine Muscat and to improving the sanitary status of the cultivar's planting material. [ABSTRACT FROM AUTHOR]

Grapevine leafroll disease (GLD) is a globally important disease that affects the metabolic composition and biomass of grapes, leading to a reduction in grape yield and quality of wine produced. Grapevine leafroll-associated virus 3 (GLRaV-3) is the main causal agent for GLD. This study aimed to identify protein-protein interactions between GLRaV-3 and its host. A yeast two-hybrid (Y2H) library was constructed from litis vinifera mRNA and screened against GLRaV-3 open reading frames encoding structural proteins and those potentially involved in systemic spread and silencing of host defense mechanisms. Five interacting protein pairs were identified, three of which were demonstrated in planta. The minor coat protein of GLRaV-3 was shown to interact with 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase 02, a protein involved in primary carbohydrate metabolism and the biosynthesis of aromatic amino acids. Interactions were also identified between GLRaV-3 p20A and an 18.1 -kDa class I small heat shock protein, as well as MAP3K epsilon protein kinase 1. Both proteins are involved in the response of plants to various stressors, including pathogen infections. Two additional proteins, chlorophyll a-b binding protein CP26 and a SMAX1-LIKE 6 protein, were identified as interacting with p20A in yeast but these interactions could not be demonstrated in planta. The findings of this study advance our understanding of the functions of GLRaV-3-encoded proteins and how the interaction between these proteins and those of V. vinifera could lead to GLD. [ABSTRACT FROM AUTHOR]

We developed a NitroPure Nitrocellulose (NPN) membrane-based method for sampling and storing grapevine sap for grapevine virus detection. We devised an efficient nucleic acid extraction method for the NPN membrane, resulting in 100% amplification success for grapevine leafroll-associated virus 2 (GLRaV2) and 3 (GLRaV3), grapevine rupestris stem pitting-associated virus (GRSPaV), grapevine virus A, grapevine virus B, and grapevine red blotch virus (GRBV). This method also allowed the storage of recoverable nucleic acid for 18 months at room temperature. We created a sampling kit to survey GLRaV2, GLRaV3, and GRBV in Japanese vineyards. We tested the kits in the field in 2018 and then conducted mail-in surveys in 2020–2021. The results showed a substantial prevalence of GLRaV3, with 48.5% of 132 sampled vines being positive. On the other hand, only 3% of samples tested positive for GLRaV2 and none for GRBV. [ABSTRACT FROM AUTHOR]

Among other pathogens, more than 80 viruses infect grapevine. The aim of this work was to study the virome diversity of grapevine viruses and mycoviruses of a vineyard using high-throughput sequencing technologies. The grapevine virome was studied in symptomatic vines of the Rkatsiteli cultivar (V. vinifera) collected at the vineyards of the Krasnodar Krai in Russia. Ribosomal-depleted total RNA and isolated small RNAs were used for library preparation and high-throughput sequencing. Six grapevine-infecting viruses and two viroids were validated by RT-PCR and analyzed phylogenetically. We identified the presence of grapevine leafroll-associated virus 3, grapevine Pinot gris virus, grapevine virus T, grapevine rupestris stem-pitting-associated virus, grapevine fleck virus, and grapevine rupestris vein feathering virus, as well as two viroids, grapevine yellow speckle viroid 1 and hop stunt viroid. We also studied the mycovirome of the vineyard and identified nine viruses with single-stranded positive-sense RNA genomes: alternaria arborescens mitovirus 1, botrytis cinerea mitovirus 1, botrytis cinerea mitovirus 2, botrytis cinerea mitovirus 3, botrytis cinerea mitovirus 4, sclerotinia sclerotiorum mitovirus 3, botrytis cinerea hypovirus 1, grapevine-associated narnavirus 1, and botrytis virus F. In addition, we identified botrytis cinerea hypovirus 1 satellite-like RNA and two single-stranded negative-sense RNA viruses. This is the first study of grapevine mycoviruses in Russia. The obtained result will contribute to the development of biocontrol strategies in the future. [ABSTRACT FROM AUTHOR]

French-American hybrids and North American grape species play a significant role in Canada's grape and wine industry. Unfortunately, the occurrence of viruses and viral diseases among these locally important non-vinifera grapes remains understudied. We report here the results from a large-scale survey to assess the prevalence of 14 viruses among 533 composite samples representing 2665 vines from seven French-American hybrid wine grape cultivars, two North American juice grape cultivars (Concord and Niagara), and the table grape cultivar Sovereign coronation. Based on reverse transcription polymerase chain reaction (RT-PCR) assays, ten viruses were detected. Grapevine rupestris stem pitting-associated virus, grapevine leafroll-associated virus 3, grapevine Pinot gris virus and grapevine red blotch virus were detected with the highest frequency. As expected, mixed infections were common; 62% of the samples contained two or more viruses. Overall, hybrid wine grapes were infected with more viruses and a higher prevalence of individual viruses than juice and table grapes. To validate these findings and to refine the virome of these non-European grapes, high-throughput sequencing (HTS) analyses of five composite samples representing each category of grapevine cultivars was performed. Results from HTS agreed with those from RT-PCR. Importantly, Vidal, a widely grown white-wine grape with international recognition due to its use in the award-winning icewine, is host to 14 viruses, four of which comprise multiple and distinct genetic variants. This comprehensive survey represents the most extensive examination of viruses among French-American hybrids and North American grapes to date. [ABSTRACT FROM AUTHOR]

The U.S. wine and grape industry loses S3B annually due to viral diseases including grapevine leafroll-associated virus complex 3 (GLRaV-3). Current detection methods are labor-intensive and expensive. GLRaV-3 has a latent period in which the vines are infected but do not display visible symptoms, making it an ideal model to evaluate the scalability of imaging spectroscopy-based disease detection. The NASA Airborne Visible and Infrared Imaging Spectrometer Next Generation was deployed to detect GLRaV-3 in Cabernet Sauvignon grapevines in Lodi, CA in September 2020. Foliage was removed from the vines as part of mechanical harvest soon afterimage acquisition. In September of both 2020 and 2021, industry collaborators scouted 317 hectares on a vine-by-vine basis for visible viral symptoms and collected a subset for molecular confirmation testing. Symptomatic grapevines identified in 2021 were assumed to have been latently infected at the time of image acquisition. Random forest models were trained on a spectroscopic signal of noninfected and GLRaV-3 infected grapevines balanced with synthetic minority oversampling of noninfected and GLRaV-3 infected grapevines. The models were able to differentiate between noninfected and GLRaV-3 infected vines both pre- and postsymptomatically at 1 to 5 m resolution. The best-performing models had 87% accuracy distinguishing between noninfected and asymptomatic vines, and 85% accuracy distinguishing between noninfected and asymptomatic + symptomatic vines. The importance of nonvisible wavelengths suggests that this capacity is driven by disease-induced changes to plant physiology. The results lay a foundation for using the forthcoming hyperspectral satellite Surface Biology and Geology for regional disease monitoring in grapevine and other crop species. [ABSTRACT FROM AUTHOR]

This is the first viral metagenomic analysis of grapevine conducted in Mexico. During the summer of 2021, 48 plants displaying virus-like symptoms were sampled in Queretaro, an important grapevine-producing area of Mexico, and analyzed for the presence of viruses via high-throughput sequencing (HTS). The results of HTS were verified by real-time RT-PCR following a standardized testing scheme (Protocol 2010). Fourteen different viruses were identified, including grapevine asteroid mosaic-associated virus (GAMaV), grapevine Cabernet Sauvignon reovirus (GCSV), grapevine fanleaf virus (GFLV), grapevine fleck virus (GFkV), grapevine Pinot gris virus (GPGV), grapevine red globe virus (GRGV), grapevine rupestris stem pitting-associated virus (GRSPaV), grapevine rupestris vein feathering virus (GRVFV), grapevine Syrah virus 1 (GSyV-1), grapevine virus B (GVB), and grapevine leafroll-associated viruses 1, 2, 3, 4 (GLRaV1, 2, 3, 4). Additionally, divergent variants of GLRaV4 and GFkV, and a novel Enamovirus-like virus were discovered. This is the first report of GAMaV, GCSV, GLRaV4, GPGV, GRGV, GRVFV, and GSyV-1 infecting grapevines in Mexico; the impact of these pathogens on production is unknown. [ABSTRACT FROM AUTHOR]

Andalusia is a Spanish region that is home to numerous minority varieties due to its diversity and territorial extension, offering the local viticulture the possibility of diversifying its wine production. The genotypic characterization of 98 specimens from six areas with a winemaking tradition in Andalusia was carried out between the years 2020 and 2022, by means of thirteen microsatellite markers, including the nine recommended by the OIV. A total of 33 different genotypes were obtained, 20 of which corresponded to profiles of already described varieties (11 of them are of 6 minority cultivars in Andalusia: 'Rojal Tinto', 'Beba', 'Zurieles', 'Rome', 'Hebén', 'Mollar Cano', 'Listán Prieto', 'Listán del Condado', 'Jarrosuelto', 'Negra Dorada', and 'Mantúo de Pilas'), while the other 12 profiles did not match with previously identified varieties. These profiles were registered in the database of the IFAPA "Rancho de la Merced" Germplasm Bank. The eco-geographical groups of the new identified genotypes were determined through an analysis of genetic diversity. The presence of grapevine fanleaf virus, grapevine fleck virus, and grapevine leafroll-associated viruses was also determined due to the requirement of healthy clones of the new varieties for their potential interest to be authorized for cultivation in Spain. [ABSTRACT FROM AUTHOR]

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The second paper in this series [[2]] concerned an examination of two subgroups of the cytorhabdovirus lettuce necrotic yellows virus (LNYV), a virus apparently endemic to the Australia/New Zealand region. The Special Issue "State-of-the-Art Plant Virus Research in Australasia" in I Viruses i provided a fascinating snapshot of plant and fungus virus research being undertaken in Australasia during the final year of the official COVID-19 pandemic. In contrast to papers 2 and 3, where indigenous viruses were adapting to new hosts, in this paper, exotic viruses were shown to be evolving in exotic hosts under selection pressures present in their new geographical location of Tasmania. Paper seven [[7]] reported research into mycoviruses (viruses that infect fungi), not plant viruses as such, although in this case, the virus-infected fungus originated from inside the root of an Australian indigenous orchid. [Extracted from the article]

Developing actionable early detection and warning systems for agricultural stakeholders is crucial to reduce the annual $200B USD losses and environmental impacts associated with crop diseases. Agricultural stakeholders primarily rely on labor‐intensive, expensive scouting and molecular testing to detect disease. Spectroscopic imagery (SI) can improve plant disease management by offering decision‐makers accurate risk maps derived from Machine Learning (ML) models. However, training and deploying ML requires significant computation and storage capabilities. This challenge will become even greater as global‐scale data from the forthcoming Surface Biology & Geology satellite becomes available. This work presents a cloud‐hosted architecture to streamline plant disease detection with SI from NASA's AVIRIS‐NG platform, using grapevine leafroll‐associated virus complex 3 (GLRaV‐3) as a model system. Here, we showcase a pipeline for processing SI to produce plant disease detection models and demonstrate that the underlying principles of a cloud‐based disease detection system easily accommodate model improvements and shifting data modalities. Our goal is to make the insights derived from SI available to agricultural stakeholders via a platform designed with their needs and values in mind. The key outcome of this work is an innovative, responsive system foundation that can empower agricultural stakeholders to make data‐driven plant disease management decisions while serving as a framework for others pursuing use‐inspired application development for agriculture to follow that ensures social impact and reproducibility while preserving stakeholder privacy. Plain Language Summary: Agricultural decision‐makers need reliable access to accurate data to make sustainable crop management choices. This is especially important for decisions related to crop disease management, which can have major financial, environmental, and societal impacts. Forthcoming hyperspectral satellite systems such as Surface Biology & Geology will provide spectroscopic imagery (SI) that can be used in combination with machine learning (ML) for agricultural decision making at the global scale. However, deploying ML models trained on SI requires significant computation and storage resources, limiting non‐expert use. Additionally, agricultural stakeholders frequently have reservations and/or restrictions about how data can or cannot be shared with outside entities. Here, we overview a proof‐of‐concept, cloud system designed with agricultural users in mind that allows researchers to rapidly deploy ML models for plant disease detection using SI from AVIRIS‐NG without retaining confidential stakeholder information. We use grapevine leafroll virus‐complex 3 (GLRaV‐3) in California wine grapes, a virus that causes $3 billion in damages and losses to the US grape industry annually, as a case study. We provide a framework design that outlines how this system is implemented and could be made accessible to both growers and researchers, as well as discuss system limitations and opportunities for future work. Key Points: Cloud‐based plant disease detection system, easily accommodates model improvements and future data sourcesEmpower agricultural stakeholders to use hyperspectral data for decision support while preserving stakeholder data privacyOutline framework for researchers interested in designing geospatial/remote sensing applications for agricultural stakeholders to follow [ABSTRACT FROM AUTHOR]

Grapevine leafroll disease (GLD) is caused by one or more of the Grapevine leafroll-associated viruses (GLRaVs). GLD's symptoms are expected to be evident in indicator cultivars, regardless of the GLRaV(s) involved. In the present study, disease incidence (I) and severity (S), symptoms before veraison (Sy < V), a disease severity index (DSI) and an earliness index (EI) (2013–2022) were recorded in order to examine the factors affecting the evolution of GLD in Pinot noir graft inoculated with scions infected with GLRaV-3 that, in origin, showed a diversity of GLD symptoms. Strong correlations between I and S (r = 0.94) and between Sy < V and EI (r = 0.94) were observed; early symptoms proved good predictors of incidence and severity after veraison and of yield and sugar content of the must. The environmental conditions and time after infection did not modify the wide range of symptoms (I: 0–81.5%; S: 0.1–4) that corresponded with the variation in losses (<0–88% for yield and <0–24% for sugar content). With all other factors being constant, the significant differences between plants were mainly due to the GLRaVs present. Plants infected with some GLRaV-3 isolates always had mild symptoms or remained asymptomatic 10 years after grafting but remained a source of infection for GLRaV vectors. [ABSTRACT FROM AUTHOR]

Background and Aims. Shiraz disease (SD) is a viral disease associated with Grapevine virus A that causes significant yield loss in economically important grape cultivars in Australia such as Shiraz and Merlot. Current diagnostic methods are time-consuming and costly. This study evaluates an alternative methodology using visible remote sensing imagery to detect SD in Shiraz grapevines. Methods and Results. High-resolution visible remote sensing images were captured of Shiraz grapevines in two South Australian viticultural regions over two seasons. The projected leaf area (PLA) of individual grapevines was estimated from the images. Virus-infected vines had significantly lower PLA than healthy vines in the early season but fewer difference after veraison. The lower PLA was only observed in grapevines coinfected with grapevine leafroll-associated viruses (GLRaVs) and Grapevine virus A (GVA). Shiraz vines infected with either GLRaVs or GVA had similar PLA to healthy vines. Conclusions. High-resolution RGB remote sensing technology has the potential to rapidly estimate SD infection in Shiraz grapevines. Our observations of shoot devigouration only in coinfected vines calls into question the etiology of SD. Further validation of the PLA technique incorporating different regions, seasons, cultivars, and combinations of viruses is needed for improving the robustness of the method. Significance of the Study. This preliminary study presents a new rapid and low-cost surveillance method to estimate SD infections in Shiraz vineyards, which could significantly lower the cost for growers who conduct on-ground SD visual assessments or lab-based tissue testing at the vineyard scale. [ABSTRACT FROM AUTHOR]

Grapevine leafroll disease affects the health status of grapevines worldwide. Most studies in Australia have focused on grapevine leafroll-associated viruses 1 and 3, while little attention has been given to other leafroll virus types, in particular, grapevine leafroll-associated virus 2 (GLRaV-2). A chronological record of the temporal occurrence of GLRaV-2 in Australia since 2001 is reported. From a total of 11,257 samples, 313 tested positive, with an overall incidence of 2.7%. This virus has been detected in 18 grapevine varieties and Vitis rootstocks in different regions of Australia. Most varieties were symptomless on their own roots, while Chardonnay showed a decline in virus-sensitive rootstocks. An isolate of GLRaV-2, on own-rooted Vitis vinifera cv. Grenache, clone SA137, was associated with severe leafroll symptoms after veraison with abnormal leaf necrosis. The metagenomic sequencing results of the virus in two plants of this variety confirmed the presence of GLRaV-2, as well as two inert viruses, grapevine rupestris stem pitting-associated virus (GRSPaV) and grapevine rupestris vein feathering virus (GRVFV). No other leafroll-associated viruses were detected. Among the viroids, hop stunt viroid and grapevine yellow speckle viroid 1 were detected. Of the six phylogenetic groups identified in GLRaV-2, we report the presence of four groups in Australia. Three of these groups were detected in two plants of cv. Grenache, without finding any recombination event. The hypersensitive reaction of certain American hybrid rootstocks to GLRaV-2 is discussed. Due to the association of GLRaV-2 with graft incompatibility and vine decline, the risk from this virus in regions where hybrid Vitis rootstocks are used cannot be overlooked. [ABSTRACT FROM AUTHOR]

The negative effects of viruses and the positive effects of arbuscular mycorrhizal fungi (AMF) on grapevine performance are well reported, in contrast to the knowledge about their interactive effects in perennial plants, e.g., in grapevine. To elucidate the physiological consequences of grapevine–AMF–virus interactions, two different AMF inoculum (Rhizophagus irregularis and 'Mix AMF') were used on grapevine infected with grapevine rupestris stem pitting virus, grapevine leafroll associated virus 3 and/or grapevine pinot gris virus. Net photosynthesis rate (AN), leaf transpiration (E), intercellular CO2 concentration (Ci) and conductance to H2O (gs) were measured at three time points during one growing season. Furthermore, quantum efficiency in light (ΦPSII) and electron transport rate (ETR) were surveyed in leaves of different maturity, old (basal), mature (middle) and young (apical) leaf. Lastly, pigment concentration and growth parameters were analysed. Virus induced changes in grapevine were minimal in this early infection stage. However, the AMF induced changes of grapevine facing biotic stress were most evident in higher net photosynthesis rate, conductance to H2O, chlorophyll a concentration, total carotenoid concentration and dry matter content. The AMF presence in the grapevine roots seem to prevail over virus infection, with Rhizophagus irregularis inducing greater photosynthesis changes in solitary form rather than mixture. This study shows that AMF can be beneficial for grapevine facing viral infection, in the context of functional physiology. [ABSTRACT FROM AUTHOR]

Introduction: Grapevine leafroll-associated viruses (GLRaVs) and grapevine red blotch virus (GRBV) cause substantial economic losses and concern to North America's grape and wine industries. Fast and accurate identification of these two groups of viruses is key to informing disease management strategies and limiting their spread by insect vectors in the vineyard. Hyperspectral imaging offers new opportunities for virus disease scouting. Methods: Here we used two machine learning methods, i.e., Random Forest (RF) and 3D-Convolutional Neural Network (CNN), to identify and distinguish leaves from red blotch-infected vines, leafroll-infected vines, and vines co-infected with both viruses using spatiospectral information in the visible domain (510-710nm). We captured hyperspectral images of about 500 leaves from 250 vines at two sampling times during the growing season (a pre-symptomatic stage at veraison and a symptomatic stage at mid-ripening). Concurrently, viral infections were determined in leaf petioles by polymerase chain reaction (PCR) based assays using virus-specific primers and by visual assessment of disease symptoms. Results: When binarily classifying infected vs. non-infected leaves, the CNN model reaches an overall maximum accuracy of 87% versus 82.8% for the RF model. Using the symptomatic dataset lowers the rate of false negatives. Based on a multiclass categorization of leaves, the CNN and RF models had a maximum accuracy of 77.7% and 76.9% (averaged across both healthy and infected leaf categories). Both CNN and RF outperformed visual assessment of symptoms by experts when using RGB segmented images. Interpretation of the RF data showed that the most important wavelengths were in the green, orange, and red subregions. Discussion: While differentiation between plants co-infected with GLRaVs and GRBV proved to be relatively challenging, both models showed promising accuracies across infection categories. [ABSTRACT FROM AUTHOR]

Grapevine leafroll disease (GLD) is the most common and economically destructive grapevine viral disease in South African vineyards and throughout the world. There are many GLD-associated virus variants with Grapevine leafroll-associated virus 3 (GLRaV-3) being the main causative agent of GLD. The vine mealybug, Planococcus ficus, is the most widespread and problematic vector of GLRaV-3. Roguing, pesticides and sanitary measures are common control strategies used in South African vineyards. In this paper, we propose an age-structured mathematical model for the transmission of (GLRaV-3) by Planococcus ficus in the South African context. The model is investigated in terms of the transmission thresholds and control strategies. A simplified model is used to shed light into the qualitative dynamics of transmission and assess the effectiveness of roguing as the main control strategy for GLRaV-3 spread. [ABSTRACT FROM AUTHOR]

Worldwide, virus infections in grapevines are of concern due to the potential for economic loss. Although the grape industry in Mexico is relatively small and focused mainly on the local market, production dates back to the time of the Spanish colonization. This manuscript discusses the findings on grapevine viruses in Mexico. Nine viruses have been identified in the last fifty years, including grapevine red blotch virus (GRBV), grapevine leafroll-associated virus 3 (GLRaV-3), grapevine fanleaf virus (GFLV), and grapevine virus A (GVA). Important information is provided about these viruses and viral pathogens that have not yet been reported in Mexico, but represent an ongoing threat to plant health and grapevine production in other viticultural regions of the world. Strategies for virus control in vineyards are described. The information discussed here should be shared with growers and stakeholders to prevent future negative impacts on the Mexican grapevine industry and to save ancient grapevine accessions. [ABSTRACT FROM AUTHOR]

Shiraz disease (SD) is an economically important virus-associated disease that can significantly reduce yield in sensitive grapevine varieties and has so far only been reported in South Africa and Australia. In this study, RT-PCR and metagenomic high-throughput sequencing was used to study the virome of symptomatic and asymptomatic grapevines within vineyards affected by SD and located in South Australia. Results showed that grapevine virus A (GVA) phylogroup II variants were strongly associated with SD symptoms in Shiraz grapevines that also had mixed infections of viruses including combinations of grapevine leafroll-associated virus 3 (GLRaV-3) and grapevine leafroll-associated virus 4 strains 5, 6 and 9 (GLRaV-4/5, GLRaV-4/6, GLRaV-4/9). GVA phylogroup III variants, on the other hand, were present in both symptomatic and asymptomatic grapevines, suggesting no or decreased virulence of these strains. Similarly, only GVA phylogroup I variants were found in heritage Shiraz grapevines affected by mild leafroll disease, along with GLRaV-1, suggesting this phylogroup may not be associated with SD. [ABSTRACT FROM AUTHOR]

Grapevine (Vitis vinifera L.) is one of the most important crops in the world due to its economic and social impact. Like many other crops, grapevine is susceptible to different types of diseases caused by pathogenic microorganisms. Grapevine leafroll-associated virus 1 (GLRaV-1) is a virus associated with grapevine leafroll disease and it is considered at the national and European level as a pathogen that must be absent in propagative plant material. For this reason, the availability of specific, sensitive and reliable detection techniques to ascertain the sanitary status of the plants is of great importance. The objective of this research was the development of a new GLRaV-1 detection method based on a TaqMan quantitative real-time RT-PCR targeted to the coat protein genomic region and including a host internal control in a duplex reaction. To this end, three new GLRaV-1 full genomes were recovered by HTS and aligned with all sequences available in the databases. The method has been validated following EPPO standards and applied for the diagnosis of field plant material and transmission vectors. The new protocol designed has turned out to be highly sensitive as well as much more specific than the current available methods for the detection and absolute quantitation of GLRaV-1 viral titer. [ABSTRACT FROM AUTHOR]

In this work, we report the parametric optimization of surface acoustic wave (SAW) delay lines on Lithium niobate for environmental monitoring applications. First, we show that the device performance can be improved by acting opportunely on geometrical design parameters of the interdigital transducers such as the number of finger pairs, the finger overlap length and the distance between the emitter and the receiver. Then, the best-performing configuration is employed to realize SAW sensors. As aerosol particulate matter (PM) is a major threat, we first demonstrate a capability for the detection of polystyrene particles simulating nanoparticulates/nanoplastics, and achieve a limit of detection (LOD) of 0.3 ng, beyond the present state-of-the-art. Next, the SAW sensors were used for the first time to implement diagnostic tools able to detect Grapevine leafroll-associated virus 3 (GLRaV-3), one of the most widespread viruses in wine-growing areas, outperforming electrochemical impedance sensors thanks to a five-times better LOD. These two proofs of concept demonstrate the ability of miniaturized SAW sensors for carrying out on-field monitoring campaigns and their potential to replace the presently used heavy and expensive laboratory instrumentation. [ABSTRACT FROM AUTHOR]

Mealybugs are phloem-feeding insects found on many crops worldwide. In New Zealand vineyards, they transmit the economically important Grapevine leafroll-associated virus 3 (GLRaV-3). For some mealybug species, synthetic sex pheromones have been commercialised, and are used as monitoring tools. The mealybugs Pseudococcus longispinus and Pseudococcus calceolariae are major pests in many New Zealand vineyards. We present work on the development of a combined P. longispinus and P. calceolariae pheromone lure. The optimal dose for monitoring P. longispinus was found to be 10 µg of the (S)-(+)-enantiomer, either alone or in the racemic mixture. Addition of the corresponding alcohol did not improve trap catch of P. longispinus. Both the P. longispinus and the P. calceolariae pheromone lures remained active in the field for 90 days. Combining the 2 species' pheromones had no negative effects on male mealybug trap catch for either species. We conclude that the pheromone ester alone is the best lure for the male P. longispinus. Combining the two mealybug species' pheromones into a single lure provides the New Zealand viticultural industry with an efficient monitoring tool. Late-vintage deployment of baited lures will provide information on mealybug abundance and local distribution that will inform the scope of future insecticide programmes, to target areas based on need rather than an area-wide application by default. [ABSTRACT FROM AUTHOR]

With the aim to characterize changes caused by grapevine leafroll-associated virus 3 (GLRaV-3) singly or in coinfection with other viruses and to potentially determine genotype-specific or common markers of viral infection, thirty-six parameters, including nutrient status, oxidative stress parameters, and primary metabolism as well as symptoms incidence were investigated in 'Cabernet Franc,' 'Merlot,' 'Pinot Noir,' and 'Tribidrag' grapevine varieties. Host responses were characterized by changes in cellular redox state rather than disturbances in nutrient status and primary metabolic processes. Superoxide dismutase, hydrogen peroxide, and proteins were drastically affected regardless of the type of isolate, the host, and the duration of the infection, so they present cellular markers of viral infection. No clear biological pattern could be ascertained for each of the GLRaV-3 genotypes. There is a need to provide a greater understanding of virus epidemiology in viticulture due to the increasing natural disasters and climate change to provide for global food production security. Finding grape varieties that will be able to cope with those changes can aid in this task. Among the studied grapevine varieties, autochthonous 'Tribidrag' seems to be more tolerant to symptoms development despite numerous physiological changes caused by viruses. [ABSTRACT FROM AUTHOR]

The roles of proteins encoded by members of the genus Ampelovirus, family Closteroviridae are largely inferred by sequence homology or analogy to similarly located ORFs in related viruses. This study employed yeast two-hybrid and bimolecular fluorescence complementation assays to investigate interactions between proteins of grapevine leafroll-associated virus 3 (GLRaV-3). The p5 movement protein, HSP70 homolog, coat protein, and p20B of GLRaV-3 were all found to self-interact, however, the mechanism by which p5 interacts remains unknown due to the absence of a cysteine residue crucial for the dimerisation of the closterovirus homolog of this protein. Although HSP70h forms part of the virion head of closteroviruses, in GLRaV-3, it interacts with the coat protein that makes up the body of the virion. Silencing suppressor p20B has been shown to interact with HSP70h, as well as the major coat protein and the minor coat protein. The results of this study suggest that the virion assembly of a member of the genus Ampelovirus occurs in a similar but not identical manner to those of other genera in the family Closteroviridae. Identification of interactions of p20B with virus structural proteins provides an avenue for future research to explore the mechanisms behind the suppression of host silencing and suggests possible involvement in other aspects of the viral replication cycle. [ABSTRACT FROM AUTHOR]

Grapevine is a widely grown fruit crop that is seriously affected by different viruses, reducing grape yield and quality, as well as threatening profitability. Vineyard disease management requires accurate identification of viral infections. This study aimed to survey the presence of ten grapevine viruses in four geographic sites in the Mendoza province of Argentina. Two hundred twenty-three composite cane samples from 1060 plants of six cultivars were collected from 26 blocks distributed across 11 vineyards. The cane samples were screened by RT-PCR for the following viruses: grapevine leafroll-associated viruses 1–4 (GLRaV 1, 2, 3, and 4), grapevine fanleaf virus (GFLV), grapevine fleck virus (GFkV), grapevine virus A (GVA) and B (GVB), grapevine rupestris stem pitting associated virus (GRSPaV), and arabis mosaic virus (ArMV). The results showed an uneven occurrence of viruses through the sampled regions, with GRSPaV being prevalent (71.1%), followed by GFLV (28.9%), GFkV (20.6%), and GLRaV-2 (14.7%). GVB was not detected. This study revealed a moderate prevalence of viruses associated with economically impactful diseases in the vineyards surveyed. [ABSTRACT FROM AUTHOR]

This research studied serological relationships and genetic diversity of Argentinean isolates of grapevine leafroll-associated virus-4 (GLRaV-4). Phylogenetic analysis of coat protein (CP) sequences from 19 local isolates revealed clustering with the previously described GLRaV-4 strain 5, strain 6, and strain 9 groups. Evolutionary sequence analysis of the obtained and database-available sequences showed evidence of recombination events. Additionally, both CP N- and C-terminal regions appeared to be under purifying selection, but the N-terminal region presented seven sites under positive selection, with a dN/dS ratio 5-fold greater than that of the C-terminal region. Serological reactivity against monoclonal antibodies supports a higher occurrence probability for linear epitopes in the N-terminal region, as inferred by the sequence analysis. The obtained results reflect an unusual evolutionary behavior of the CP that, together with protein serological reactivity, suggests biological significance of the observed variability. [ABSTRACT FROM AUTHOR]

Grapevine virus G (GVG) and grapevine virus H (GVH) (genus Vitivirus) are recently discovered viruses. Analysis of 38 samples from Sardinian grapevine cultivars for the presence of GVG and GVH was carried out using RT-PCR. All samples were also tested for grapevine Pinot gris virus (GPGV) using RT-PCR, and for grapevine leafroll virus -1, -2 and -3, grapevine virus A (GVA) and B (GVB), arabis mosaic virus (ArMV), grapevine fanleaf virus (GFLV) and grapevine fleck virus (GFkV) using multiplex RT-PCR. GVG was confirmed in four vines, and GVH was detected in only one sample. In phylogenetic analyses of the coat protein (CP) region, the Sardinian GVG isolates clustered separately from isolates from Croatia and New Zealand. The Sardinian GVH isolate clustered with most sequences from other countries, but with greater affinity to isolates from California (USA) for the CP region, whereas it clustered with isolates from Croatia in the RNA-dependent RNA polymerase (RdRp) region. In addition to GVG and GVH, many samples were coinfected with GVA, viruses from the leafroll complex, and GPGV. This is the first record of GVG and GVH occurring in Italy. [ABSTRACT FROM AUTHOR]

Grapevine-infecting ampelo- and vitiviruses are transmitted by scale insects belonging to several species, among which is the European fruit lecanium, Parthenolecanium corni (Bouché) (Hemiptera Coccidae). Our objective was to characterize the transmission biology of grapevine leafroll-associated viruses (GLRaV) and grapevine virus A (GVA) by this soft scale species in order to evaluate its ability to spread these viruses. In transmission experiments with nymphs sampled from different vineyards infected with GLRaV 1, 2, 3 and GVA, P. corni transmitted only GLRaV 1 and GVA to healthy vines. GVA was predominantly transmitted along with GLRaV 1, whereas the latter could be transmitted alone from single or co-infected vines. Vineyard-sampled second instar nymphs were more efficient than first instars at transmitting GLRaV 1, whereas both instars displayed similar transmission rates for GVA. Short virus inoculation access periods and the absence of virus in eggs of females living on infected grapevines fulfilled the criteria of non-circulative semi-persistent transmission mode. [ABSTRACT FROM AUTHOR]

In this study, we analyzed the virome of 73 grape samples from two Dagestan ampelographic collections in Russia using high-throughput sequencing of total RNAs. Fourteen viruses and four viroids were identified, with one to eleven of them detected in each plant. For the first time in Russia, we identified grapevine leafroll-associated virus 7 and grapevine Kizil Sapak virus. A total of 206 genomes of viruses and viroids were obtained, and their phylogenetic analysis was carried out. The de novo assembly and tblastx analysis allowed us to obtain contigs of a novel (+) ssRNA genome of a plant virus from the genus Umbravirus, which was tentatively named grapevine umbra-like virus (GULV), as well as contigs of a novel dsDNA pararetrovirus from the genus Caulimovirus, which was tentatively named grapevine pararetrovirus (GPRV). Complete genomes of these viruses were obtained and used for Sequence Demarcation Tool (SDT) analysis and phylogeny studies. GULV and GPRV were detected in 16 and 33 germplasm samples from the Dagestan collections, respectively. [ABSTRACT FROM AUTHOR]

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Grapevine leafroll-associated virus 3 (GLRaV-3) is a graft-transmissible virus present in every viticultural region of the world and poses a large threat to grapevine production. Frequent coinfections with other viruses, the large number of grapevine varieties, the complexity of processes involved in plant response to virus infection, and the lack of studies on GLRaV-3 replication limit our knowledge of GLRaV-3 damaging effects and their background. In this study, five different inocula, one containing GLRaV-3 and others containing GLRaV-3 in combination with different grapevine viruses were green grafted to 52 different grapevine plants of four varieties to analyze the influence of the phenological stage and virus composition on GLRaV-3 replication. Relative concentration analysis by quantitative PCR conducted over a 16-month period revealed that other viruses as well as plant stage had a significant effect on GLRaV-3 replication and symptoms expression. The replication was most pronounced in the deep dormancy stage at the beginning of the infection, and the least at the exit of the dormancy stage. This study brings new insight into GLRaV-3 replication and discusses about viral interactions in one of the most economically important perennial plants, the grapevine. [ABSTRACT FROM AUTHOR]

Five grapevine viruses, including grapevine geminivirus A (GGVA), grapevine Syrah virus 1 (GSyV-1), grapevine Cabernet Sauvignon reovirus (GCSV), grapevine virus F (GVF) and grapevine Red Globe virus (GRGV) have been detected in four South Australian vineyards using metagenomic high throughput sequencing for the first time in Australia. Most of them were present in asymptomatic grapevines and some were present in grapevines with leafroll disease that were infected by several other viruses, including grapevine leafroll-associated viruses. Therefore, the association of GGVA, GSyV-1, GCSV, GVF and GRGV with disease in Australia is unknown. [ABSTRACT FROM AUTHOR]