Leafroll Research Articles

Occurrence of Grapevine Viruses in Different Cultivars and Regions Within Michigan

Viral diseases are widespread in vineyards throughout the world. Vineyard viruses are mostly disseminated via vegetative propagation, although insect and nematode vectors can also be involved in the spread. Michigan faces challenges with grapevine viruses due to the following: 1) multiple Vitis sp. (Vitis vinifera, Vitis labrusca, and Vitis interspecific hybrids) being cultivated within the state, 2) vineyards that vary in age, and 3) plant material being sourced from a variety of locations throughout the United States. Determining the distribution of grapevine viruses in Michigan is the first step in developing mitigation strategies. In this study we utilized real-time RT-PCR to test for a variety of grapevine viruses that are known to occur in other regions. Vineyards were sampled for grapevine leaf tissue (n = 429) across the northwest, southwest, mid, and southeast regions of the lower peninsula of Michigan and screened for a panel of viruses. Across all samples, grapevine rupestris stem pitting-associated virus (GRSPaV) was the most abundant. Other viruses found in relatively high abundance included grapevine leafroll-associated virus 3 (GLRaV3), grapevine fleck virus (GFkV), and tobacco ringspot virus (TRSV). Interestingly, this study identified grapevine red blotch virus (GRBV) and grapevine Pinot gris virus (GPGV), for the first time within the state. This survey gives researchers and growers an awareness of the distribution of viruses in Michigan vineyards that can aid management recommendations and encourage the use of virus tested material from reputable sources when planting new vineyards.

Artificial Intelligence Techniques in Grapevine Research: A Comparative Study with an Extensive Review of Datasets, Diseases, and Techniques Evaluation.

In the last few years, the agricultural field has undergone a digital transformation, incorporating artificial intelligence systems to make good employment of the growing volume of data from various sources and derive value from it. Within artificial intelligence, Machine Learning is a powerful tool for confronting the numerous challenges of developing knowledge-based farming systems. This study aims to comprehensively review the current scientific literature from 2017 to 2023, emphasizing Machine Learning in agriculture, especially viticulture, to detect and predict grape infections. Most of these studies (88%) were conducted within the last five years. A variety of Machine Learning algorithms were used, with those belonging to the Neural Networks (especially Convolutional Neural Networks) standing out as having the best results most of the time. Out of the list of diseases, the ones most researched were Grapevine Yellow, Flavescence Dorée, Esca, Downy mildew, Leafroll, Pierce's, and Root Rot. Also, some other fields were studied, namely Water Management, plant deficiencies, and classification. Because of the difficulty of the topic, we collected all datasets that were available about grapevines, and we described each dataset with the type of data (e.g., statistical, images, type of images), along with the number of images where they were mentioned. This work provides a unique source of information for a general audience comprising AI researchers, agricultural scientists, wine grape growers, and policymakers. Among others, its outcomes could be effective in curbing diseases in viticulture, which in turn will drive sustainable gains and boost success. Additionally, it could help build resilience in related farming industries such as winemaking.

A novel RAV transcription factor from pear interacts with viral RNA-silencing suppressors to inhibit viral infection.

In plants, RNA silencing constitutes a strong defense against viral infection, which viruses counteract with RNA-silencing suppressors (RSSs). Understanding the interactions between viral RSSs and host factors is crucial for elucidating the molecular arms race between viruses and host plants. We report that the helicase motif (Hel) of the replicase encoded by apple stem grooving virus (ASGV)-the main virus affecting pear trees in China-is an RSS that can inhibit both local and systemic RNA silencing, possibly by binding double-stranded (ds) siRNA. The transcription factor related to ABSCISIC ACID INSENSITIVE3/VIVIPAROUS1 from pear (PbRAV1) enters the cytoplasm and binds Hel through its C terminus, thereby attenuating its RSS activity by reducing its binding affinity to 21- and 24-nt ds siRNA, and suppressing ASGV infection. PbRAV1 can also target p24, an RSS encoded by grapevine leafroll-associated virus 2 (GLRaV-2), with similar negative effects on p24's suppressive function and inhibition of GLRaV-2 infection. Moreover, like the positive role of the PbRAV1 homolog from grapevine (VvRAV1) in p24's previously reported RSS activity, ASGV Hel can also hijack VvRAV1 and employ the protein to sequester 21-nt ds siRNA, thereby enhancing its own RSS activity and promoting ASGV infection. Furthermore, PbRAV1 neither interacts with CP, an RSS encoded by grapevine inner necrosis virus, nor has any obvious effect on CP's RSS activity. Our results identify an RSS encoded by ASGV and demonstrate that PbRAV1, representing a novel type of RAV transcription factor, plays a defensive role against viral infection by targeting viral RSSs.

Characterization of Genetic Diversity in the Capsid Protein Gene of Grapevine Fleck Virus and Development of a New Real-Time RT-PCR Assay.

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.

Development of simplex and quintuplex RT-PCR for simultaneous detection of soybean viruses

Five simplex and a multiplex-RT-PCR (m-RT-PCR) protocols were developed for detection and differentiation of bean pod mottle virus (BPMV), cherry leaf roll virus (CLRV), raspberry ringspot virus (RpRSV), soybean mosaic virus (SMV) and tomato ringspot virus (ToRSV) infecting soybean. The simplex RT-PCR protocols produced virus-specific amplicons of 538 bp for BPMV, 139 bp for CLRV, 298 bp for RpRSV, 403 bp for SMV, and 282 bp for ToRSV, with sensitivity down to 10−4 diluted cDNA. Further, to detect all the five viruses simultaneously in a single tube a quintuplex RT-PCR protocol was optimized with as low as 10−3 diluted cDNA and 0.05 µM primer. To validate the reliability of the simplex RT-PCR protocol, imported soybean samples were tested by ELISA as well as RT-PCR. The results revealed that the developed protocol could detect the viruses in imported soybean, and found to be efficient than ELISA in resolving ambiguity in detection of seed borne viruses. The developed simplex and quintuplex RT-PCR protocol will be quite helpful for the diagnosis of soybean germplasm co-infected with viruses during the quarantine processing for ensuring virus free long term seed conservation in the National Gene Bank as well as for quarantine certification.

Understanding the dissemination of viruses and viroids identified through virome analysis of major grapevine rootstocks and RPA-based detection of prevalent grapevine virus B

Grapevine stocks are generally vegetatively propagated for the commercial cultivation. The propagation is predominantly done on rootstocks with >90 % of plant stocks propagated on Dogridge rootstock alone in India. Three additional rootstocks i.e. Paulsen, SO4 and Ramsey are also used for grapevine propagation on a limited scale. However, no information is available on the health status of these rootstocks being used by nurserymen and growers. Therefore, these rootstocks were collected from nurseries of five different locations and subjected to high-throughput sequencing (HTS) to determine the spectrum of viruses and viroids. The de novo assembly of unaligned reads revealed the presence of genome sequences of nine viruses viz. grapevine rupestris stem pitting-associated virus (GRSPaV), grapevine leafroll-associated virus 3 (GLRaV-3), grapevine leafroll-associated virus 4 (GLRaV-4), grapevine virus A (GVA), grapevine virus B (GVB), grapevine virus D (GVD), grapevine virus F (GVF), grapevine virus L (GVL), grapevine fleck virus (GFkV) and five viroids viz. hopstunt viroid (HSVd), grapevine yellow speckle viroid 1 and 2 (GYSVd-1 and GYSVd-2), Australian grapevine viroid (AGVd) and grapevine latent viroid (GLVd). The identified viruses and viroids were further confirmed through RT-PCR and Sanger sequencing. Indexing for the presence of these graft-transmissible pathogens in 43 rootstocks and 23 scion samples collected through field surveys indicated that infected rootstocks are the probable source for dissemination of these viruses and viroids in grapevine scions. As GVB was the most prevalent virus in all the rootstocks and scions as observed in RT-PCR testing, a simplified crude sap-based recombinase polymerase amplification (RPA) assay was optimized for its rapid detection. The present study highlights that grapevine rootstocks are reservoir of viruses and viroids and source for their dissemination in grapevine vineyards. Findings of the study including the optimized simplified cost-effective isothermal nucleic acid-based detection technique for GVB will be highly useful for production of certified clean rootstocks of grapevine in India.

Elucidating the Subcellular Localization of GLRaV-3 Proteins Encoded by the Unique Gene Block in N. benthamiana Suggests Implications on Plant Host Suppression.

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.

Evidence of Grapevine enamovirus 1 Infecting Grapevine (Vitis vinifera L.) in Canada.

Grapevine enamovirus 1 (GEV1) belongs to the genus Enamovirus, in the family Solemoviridae. It has been reported from several countries infecting grapevines including Brazil (Silva et al. 2017), China (Ren et al. 2021) and France (Hily et al. 2022). To assess the prevalence and diversity of economically important grapevine viruses in nine Canadian vineyards, total RNA and double-stranded RNA (dsRNA) (Fall et al. 2020) were extracted from 30 and 100 composite samples respectively, with each consisting of five vines of the same cultivars. The cultivars included in this study are Frontenac noir (n=34), Vidal (n=32), Marquette (n=33), Riesling (n=31), and Pinot noir (n=31). The total RNA and dsRNA samples were subsequently multiplexed and diagnosed by high-throughput sequencing (HTS) on NovaSeq (600 S4 PE100) and MiSeq (2 × 250 cycle PE) respectively. From NovaSeq and MiSeq sequencing, an average of 410,000 to 1.3 million reads/sample were obtained, respectively, with mapped viral reads representing 10.92% to 12.48% of the total reads. After sequence quality was verified using Trimmomatic v.0.40 (Bolger et al. 2014), the clean sequences were screened against all possible viruses in the databases using the Virtool (Rott et al. 2017) and VirFind virus detection pipelines (Ho and Tzanetakis 2014). GEV1 was detected in clean sequences from two, three, and two leaf samples of cultivars 'Marquette' 'Riesling' and 'Frontenac noir' respectively. Six of the seven HTS-assembled GEV1 genomes were partial, ranging from 4,523 to 6,000 nucleotide (nt) with genome coverage varying from 71% to 89%. Only one 6,314 nt long assembled contig (Accession No. OR021829), represented a nearly complete genome, being only 53 and 3 nt shorter than Sd-CG (MT536978) at 5' and 3' untranslated regions (UTR), respectively. Isolate 3- Riesling-CAN (OR021829) shares 90.56 to 94.19% nt identities with several GEV1isolates at 96-99% of query coverage. Phylogenetically, OR021829 is closer to GEV1 isolates from France and China (Figure S1). To validate the HTS results, the developed primer pair SetF and Set1R (Silva et al., 2017) was used for RT-PCR detection. The amplicons from all seven HTS-positive samples were sequenced using Sanger sequencing, confirming the presence of GEV-1 in three studied grape cultivars in Canadian vineyards. Symptoms associated with the specific GEV1-infected vines could not be explained as composite samples were used. Each of the combined samples HTS library also tested positive for at least one of the known grape virus/viroids, namely grapevine leafroll associated-virus -3, grapevine pinot gris virus, grapevine rupestris stem pitting-associated virus, Marafivirus syrahense grapevine Syrah virus-1 and hop stunt viroid. To our knowledge, this is the first report of GEV1 being detected in grapevines in Canada, or in any North American vineyard. GEV1 is a relatively new virus, and its biology remains largely unknown. Based on this sequence new GEV1 primers can be developed to know the genetic variability among GEV-1 and improve the detection of this virus in vineyards.

Оздоровление растений винограда сорта Красностоп АЗОС от вируса скручивания листьев -1, -2 и -3 (grapevine leafroll-associated viruses -1, -2 and -3) методом термотерапии

Abstract. The grapevine leafroll-associated virus is one of the most harmful and economically significant. It is known from scientific literature sources that in the vineyards of the Krasnodar region this virus is spread over an area of 50 %. The problem of increasing the phytosanitary stability of grape plantations necessitates the constant improvement of protection systems, in which methods of improving planting material are of great importance. To date, there are several methods for inactivating viral particles and freeing individual plant organs from viral infection – in vitro, thermo- and chemotherapy. Thermotherapy is one of the widely used methods that involves growing and disinfecting vines at temperatures that can delete or inactivate viruses. This method focuses on inactivating viruses rather than completely removing them. Thermotherapy has been tested in the process of obtaining initial healthy grape plants from the grapevine leafroll-associated virus GLRaV-1, GLRaV-2 и GLRaV-3. The objectives of the research are the selection of thermotherapy regimens for the release of grape cuttings from the grapevine leafroll-associated virus (GLRaV-1, GLRaV2 и GLRaV-3). As a result of the research, it was found that the use of thermotherapy of 35 ℃ and 40 ℃ for 20, 30, 40, 50 minutes did not affect the elimination of the grapevine leafroll-associated virus, the yield of diseased plants after treatment was 100 %. A positive result in the healing of plants from the grapevine leafroll-associated virus is achieved at a temperature of 45 ℃ and 50 ℃ (exposure time is 20, 30, 40, 50 minutes). The number of virus-free plants ranges from 45.4 % to 59.8 %. The inclusion of thermotherapy in the process of phytosanitary breeding, as well as in the cultivation of seedlings for mother grape plantations, will significantly increase the guarantee of laying industrial grape plantations with planting material free from phytoplasmic, viral, bacterial and fungal infections. Keywords: grapes, cuttings, grapevine leafroll-associated virus GLRaV-1, GLRaV-2 and GLRaV-3, thermotherapy, thermal stability, elimination, healthy planting material Financing source: The research was carried out within the framework of the Federal project "Development of large-scale scientific and scientific-technological projects in priority research areas" of the national project "Science and Universities"

Survey on the Occurrence of Five Grapevine Viruses in Korean Vineyards in 2021

In this study, a total of 217 samples were collected from five grapevine cultivars in Chungcheongbuk-do and Gyeongsangbuk-do in 2021. These samples were tested for the presence of five grapevine viruses using specific primers through polymerase chain reaction. The results indicated that grapevine fleck virus was confirmed in 126 samples (58.06%), grapevine leafroll-associated virus (GLRaV)-3 in 112 samples (51.61%) and GLRaV-1 in four samples (1.84%). The infection rate was high in Shine Muscat and Alexandria cultivars, and by region, the Gyeongbuk region showed a high infection rate. However, the presence of grapevine red blotch associated virus and grapevine berry inner necrosis virus were not detected.

First Report of Grapevine Leafroll-Associated Virus 4 Infecting Grapevine in Hungary

First Report of Grapevine Leafroll-Associated Virus 4 Infecting Grapevine in Hungary

Molecular evidence of cherry leaf roll virus isolate from the phylogenetic group D1 infecting black elderberry (Sambucus nigra) in Ukraine

Molecular evidence of cherry leaf roll virus isolate from the phylogenetic group D1 infecting black elderberry (Sambucus nigra) in Ukraine

Identification of unique electromagnetic signatures from GLRaV-3 infected grapevine leaves in different stages of virus development.

Grapevine leafroll associated virus 3 (GLRaV-3) is one of the most common viruses that adversely affect grape production quality around the world. Grapevine virus is usually detected by polymerase chain reaction (PCR) tests, but the main diagnostic challenges with the PCR are uneven distribution of symptoms, low virus titers in early stage, and the tests are time consuming and expensive. In the absence of effective control and treatment for grapevine virus, the recommendation is to remove infected vines before they become a source of transmission and a rapid and early detection method for viruses is urgently needed. This study investigated how GLRaV-3 infection affects spectral behavior of grapevine leaves and the use of remote sensing tools to identify changes caused by the biotic stress. A Real-Time RT-qPCR test was performed to select representative vines with healthy and GLRaV-3 infection, and changes in electromagnetic (EM) spectrum of leaves were observed with a portable hyperspectral spectrometer and a multispectral sensor on a remotely piloted aircraft system (RPAS). The results of this study suggest that foliar EM reflectance may differ depending on the presence or absence of visible symptoms of infected leaves and different stages of virus infection progress could be indicated by changes in the relative rate of reflectance around 700 nm. This research also confirmed that the development of a narrow-band hyperspectral index for the detection of grapevine virus is feasible, further research is recommended in a much more comprehensive investigation including a combination of hyperspectral sensor and chlorophyll fluorescence sensors, interpolation of suspect wavebands into ratios or indices, larger sample sizes and a more controlled study environment.

Simultaneous Detection of Grapevine Viruses via Multiplex Reverse Transcription Polymerase Chain Reaction: An Academic Approach

Grapevine viruses pose a significant threat to the viticulture industry, resulting in reduced grape yield, poor fruit quality, and economic loss. Accurate and timely detection of multiple viruses are essential for effective disease management and the implementation of appropriate control measures. The aim of this study was to assess the presence of grapevine fanleaf virus (GFLV), grapevine fleck virus (GFkV), grapevine leafroll-associated virus‑1 (GLRaV-1), arabis mosaic virus (ArMV), and grapevine virus A (GVA) in 320 plant samples collected from the Aegean region of Turkey using the powerful technique of multiplex reverse transcription-polymerase chain reaction (RT-PCR). Through comprehensive analysis, 119 of the 320 infected samples were identified using PCR. The distribution of the detected viruses revealed the presence of 28 GFLV, 31 GLRaV‑1, 12 GFkV, 21 GVA, and 27 ArMV. By comprehensively analyzing the samples, the researchers were able to simultaneously detect and identify the target viruses using a single, cost-effective assay. These results reveal the prevalence and distribution of these viruses in the Aegean region, providing valuable insights into the viral landscape of grapevines in this important viticultural area. The high detection rates of these viruses highlight the urgent need for improved disease management strategies to safeguard vine health and productivity.

Present Status of Viral Diseases of Grapevine (<i>Vitis Vinifera</i> L.) and their Management Strategies in India

Grapevine is an important fruit crop cultivated in temperate, subtropical and tropical conditions in India. The maximum share in area, production, and productivity of grapes is governed by four states viz. Maharashtra, Karnataka, Tamil Nadu and Andhra Pradesh. The sudden and drastic changes in climatic conditions and the emergence of diseases have made grapevine cultivation more challenging. Fungal and bacterial diseases are the major constraints in the grapevine production. Besides, some viral diseases like Grapevine Leafroll Disease (GLD) and Rupestris Stem Pitting Associated Diseases (RSPD) are reported in Indian vineyards. Although the presence of Grapevine Leafroll-Associated Viruses (GLRaVs) viz., GLRaV-1, GLRaV-3, and GLRaV-4 are known the impact on yield and quality of the grapes is not yet studied. Similarly, the Rupestris Stem Pitting Associated Virus (RSPaV) is known to infect the Indian vineyards of different locations but a complete understanding of their overall impact on vineyards is lacking. Therefore, it is presumed that fewer or no losses occur due to GLD and RSPD diseases. There is a strong need for hours to study the impact of known viruses on physiological and yield contributing parameters. In addition to this, robust, rapid and reliable diagnostic techniques are required for the detection of known and unknown viruses. The presence of new and emerging viruses in the Indian vineyards cannot be overlooked. Further, for the management of the viruses and avoiding their spread, the availability of Disease-Free Quality Planting Material (DFQPM) is a prerequisite. To produce DFQPM, various tissue culture techniques need to be standardized for the elimination of the virus/es from the diseased vines. The Tissue Culture-Raised Quality Planting Material (TCQPM) needs to be further tested for genetic purity (true-to-type) and virus indexing to confirm DFQPM. By considering the importance of DFQPM, recently, the National Horticulture Board (NHB), Govt. of India in association with the Asian Development Bank (ADB) has initiated a National Mission on Clean Plant Programme. The implementation of this initiative is more challenging and expected to open different avenues of research and development in the production of DFQPM for the growers. This is an important and timely beginning of the production of DFQPM.

Variation in Viral Tolerance of 21 Grapevine Rootstocks

Grapevine is one of the most economically important fruit crops cultivated worldwide. However, grapevine is highly susceptible to virus infections and exposed to the most diverse forms of viral diseases compared to other fruit crops, and virus-induced incompatibility affects plant growth to different degrees ranging from decline to death. The influence of virus-induced incompatibility could be mitigated to an acceptable level by using appropriate rootstocks. However, the viral tolerance of various grapevine rootstocks with diverse genetic backgrounds remains unclear, along with the identification of the specific viral tolerance factors. In this study, the viral tolerance of 21 grapevine rootstocks was evaluated in a green grafting system. Cabernet Franc varieties infected with a single virus [grapevine leafroll associated virus-1 (GLRaV-1)], a co-infection of two viruses (GLRaV-1 plus grapevine virus A—GVA), and no infection were used as the scions, respectively. The vegetative growth and photosynthetic function of the grafts were analyzed 4 months after grafting. The results indicated that some rootstocks could alleviate the influence of the virus infection, with vegetative growth and photosynthetic function sustained at a normal level, whereas other rootstocks were susceptible to the virus infection, resulting in a decline in the growth and photosynthetic function of the grafts. Our research provides evidence for the existence and diversity of viral tolerance among grapevine rootstocks, offering important information for appropriate rootstock selection in the establishment of new vineyards and in the breeding of grapevine rootstocks with enhanced viral tolerance.

Novel insights into hotspots of insect vectors of GLRaV-3: Dynamics and global distribution

Grapevine leafroll-associated virus 3 (GLRaV-3) is the most prevalent and economically damaging virus in grapevines and is found on nearly all continents, except Antarctica. Ten mealybugs act as vector insects transmitting the GLRaV-3. Understanding the potential distribution range of vector insects under climate change is crucial for preventing and managing vector insects and controlling and delaying the spread of GLRaV-3. This study investigated the potential geographical range of insect vectors of GLRaV-3 worldwide using MaxEnt (maximum entropy) based on occurrence data under environmental variables. The potential distributions of these insects were projected for the 2030s, 2050s, 2070s, and 2090s under the three climate change scenarios. The results showed that the potential distribution range of most vector insects is concentrated in Southeastern North America, Europe, Asia, and Southeast Australia. Most vector insects contract their potential distribution ranges under climate-change conditions. The stacked model suggested that potential distribution hotspots of vector insects were present in Southeastern North America, Europe, Southeast Asia, and Southeast Australia. The potential distribution range of hotspots would shrink with climate change. These results provide important information for governmental decision-makers and farmers in developing control and management strategies against vector insects of GLRaV-3. They can also serve as references for studies on other insect vectors.

Influence of mixed and single infection of grapevine leafroll-associated viruses and viral load on berry quality.

Grapevine leafroll disease is a viral disease that affects grapevines (Vitis vinifera L.) and has a severe economic impact on viticulture. In this study, the effect of grapevine leafroll-associated viruses (GLRaV) on berry quality was investigated in clones of cultivar cv. Crimson Seedless table grapes infected with GLRaV. RT-PCR confirmed the identity of the clones: clone 3236, infected only with GLRaV-3 (termed single); clone 3215, infected with GLRaV-3, GLRaV-4 strain 9 and grapevine virus A (termed mixed); and a viral free clone of the same genetic background of the infected clones (termed control). The berry quality indices of size, sugar, acidity and anthocyanin content were measured at harvest maturity. RT-qPCR was used to determine the viral load. The study was repeated over 2year. A two-way, multivariate analysis of variance was applied with clone and year as independent variables and the measured berry quality parameters as a dependent variable. All dependent variables were significantly affected by viral infection (Wilks, λ, (2,33)=0.033895, P-value<0.001), while only titratable acidity was affected by year. The average berry dry mass decreased (P-value<0.001). The water content of both infected clones was greater than that of the control (P-value<0.001). Both infected clones displayed reduced sugar content as a fraction of the berry dry mass (P-value<0.001). The anthocyanin and the phenol content of the infected clones were significantly reduced compared with the control clone (P<0.001, P<0.05, clone 3236 and clone 3215, respectively). Finally, the viral load was highly variable, and no quantitative relationship between viral load and berry composition was found.

Landscape‐scale patterns and predictors of potato viruses in Scotland

AbstractVirus diseases represent important economic threats to seed potato production worldwide, yet relatively little is known of their epidemiology at the landscape‐scale. In this study, data was compiled from the Scottish national seed potato classification scheme on the incidence of 10 different potato viruses for the years 2009–2022. A co‐occurrence analysis identified that 12 virus species pairs occurred together more often than expected by chance, and potato blackleg was positively associated with eight potato viruses. ArcGIS was used to investigate spatial and spatiotemporal variation in incidence rates of the three most prevalent viruses (potato virus Y, potato leaf roll virus and potato virus A), and this revealed prominent geographic differences in long‐term disease outcomes. Focusing on potato virus Y as the most commonly occurring single infection, interpretable machine‐learning techniques were used to investigate the influence of key crop, management and environmental factors on patterns of incidence in space and time. The results showed that health characteristics of seed stocks were among the most important predictors of incidence, along with blackleg infection, several management features, cultivar resistance, distance to the nearest seed and ware crop, temperature variables and several soil features. This approach provides a comprehensive overview of potato viruses in Scotland, a deeper understanding of epidemiological risk factors at the landscape‐scale and a forecast model that could serve as the basis of a decision support tool for improved management of potato virus Y.

First report of cherry leaf roll virus from Juglans regia in Ukraine

First report of cherry leaf roll virus from Juglans regia in Ukraine