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The study of Potyvirus plumpoxi (plum pox virus, PPV) has a long history, beginning with its foundational description by Atanassof in 1932 in Bulgaria. Interest in the virus has significantly increased over the past decades, as evidenced by a rise in published articles, highlighting its importance in plant pathology. Research on PPV offers broader insights into the biology and pathology of the extensive Potyviridae virus family to which it belongs. The virus's large strain diversity and wide host range make it a key subject for research into plant–virus interactions, host adaptation and virus evolution. PPV causes sharka, the most damaging disease affecting stone fruit trees. Economic losses from sharka disease have recently been estimated at over €2.4 thousand million for the last 28 years. The significance of this disease is further amplified by the ease of aphid‐mediated transmission from infected plant material and the virus's ability to establish and spread to new regions, making it a global agricultural challenge. This review aims to provide a comprehensive overview of the various biological traits of PPV and will form the basis of an updated version on the Association of Applied Biologists Description of Plant Viruses for PPV. [ABSTRACT FROM AUTHOR]

During seasonal inspections and a need for detection of fruit tree pathogens, diagnostic laboratories often have to deal with situations where a large number of samples have to be analyzed in a short time. We therefore focused on the development of a faster and more efficient diagnostic procedure for the detection of Plum pox virus (PPV). A relatively cheap and simple serological method, the double antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA), is usually used to detect PPV in plant material. The standard detection time for the DAS-ELISA kit sold by Bioreba AG is 32 hours. The optimization of the method involved reducing the incubation times and increasing the incubation temperature. At the same time, it was necessary to increase the antibody concentration to maintain the sensitivity of the method. Pathogen detection using a modified DAS-ELISA method from Bioreba AG can provide in one working day (8.5 h).

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Plum pox virus (PPV, genus Potyvirus) is one of the most economically important plant viruses. The PPV M strain (PPV-M) was first isolated in Japan in 2016. While a broad host range of the PPV M strain from trees to weeds has been widely reported, host range and the contribution of weeds to the PPV infection cycle in Japan remained unknown. In this study, we examined the host range of PPV-M in Japan within the Asteraceae weeds and explored its potential role as an intermediate host. By mechanically inoculating twelve herbaceous species belonging to Asteraceae (alternatively Compositae) in orchards with PPV-M, we found that all were susceptible to the virus. Of those, Hemisteptia lyrata showed high infection rates on the upper leaves, typically favored by aphids. A subsequent survey of multiple aphid species feeding on H. lyrata showed a seasonal infection cycle in which the aphid Aphis fabae solanella likely transmitted PPV-M from Japanese apricot leaves to H. lyrata in the spring. Then, A. spiraecola, an efficient PPV vector known to shift between hosts in summer and autumn, transmitted the disease to healthy Japanese apricot seedlings from PPV-M infected H. lyrata in autumn. It is conceivable that PPV-M in Japanese apricot orchards follows a seasonal infection cycle, potentially involving an intermediate host (Asteraceae) and two aphid species. [ABSTRACT FROM AUTHOR]

Sharka, caused by plum pox virus (PPV), is by far the most harmful disease of stone fruits (genus Prunus). Although Italy is a major producer of stone fruits, and sharka has spread in most Italian regions since its first identification in the 1970s, information on the diffusion of the disease in Italy results still scattered and incomplete. To address this knowledge gap, the present review aimed to firstly provide a historical overview of sharka in Italy, summarizing outcomes on the disease achieved since the first identification of its causal agent PPV. Data retrieved from a variety of sources (i.e., published literature, official reports and personal communications) showed that (i) sharka spread across almost the whole Italian peninsula as only Liguria, Umbria and Aosta Valley regions officially result disease-free; (ii) the regions with higher rates of infected districts are not always those more dedicated to the production of stone fruits; (iii) only the three major PPV strains causing sharka, i.e., PPV-Dideron (D), PPV-Marcus (M), and PPV-Recombinant (Rec), have been reported in Italy; and (iv) only apricot, peach and plum (i.e., widespread and economically relevant species) are hosts of PPV, with different scenarios among regions. A focus on Tuscany (Central Italy) showed that, (i) sharka has been reported since the 1990s, but extensive PPV monitoring campaigns were run from 2013 to 2021, especially in nurseries; (ii) higher number of symptomatic and PPV positive samples were recorded in farms, mostly in the Arezzo and Florence districts; and (iii) only PPV-M and PPV-Rec strains seem still present. We believe that the present overview will benefit and encourage both researchers for future investigations on sharka and farmers that have to manage the disease. [ABSTRACT FROM AUTHOR]

Plant disease control is often implemented at the private property level, and problems of cooperation and coordination between landowners can lead to social inefficiencies. Drawing on the private management problem of sharka on Prunus trees, we analyse an epidemic game and its outcomes according to initial infection levels. We show that, depending on the infection level in each farm, the nature of strategic interactions changes drastically, and a wide range of games can occur, including games with multiple or without pure strategy equilibria and games with coordination or anti-coordination patterns. We characterise the epidemic conditions for which private management produces social inefficiency and analyse the properties of uniform and differentiated subsidy schemes to solve it. We conclude with a discussion of the policy implications of the ongoing deregulation of sharka management in France. [ABSTRACT FROM AUTHOR]

The conservation of plant species, especially those vital for agriculture, is crucial to responsibly use biological resources and prevent further losses in plant diversity. Preserving plant genetic resources ensures the adaptability of wild populations and cultivars for future sustainability in agriculture, supports biotechnology and commerce, and honors cultural significance. In Serbia, the European plum (Prunus domestica L.) faces challenges from climate change and persistent pathogen pressure, endangering valuable local plum genotypes. Biotechnology-based conservation methods, such as cryopreservation at ultra-low temperatures, provide important long-term solutions. Cryotherapy, a novel application, helps in eliminating pathogens from infected plant material, though its efficacy varies among genotypes. Considering that viral diseases pose a significant threat to agriculture, reducing yields and crop quality, two cryotherapy methods (D and V cryoplate) were assessed for plum pox virus (PPV) eradication from autochthonous plums (Crvena Ranka and Belošljiva). Cryopreservation successfully eliminated PPV from the Crvena Ranka variety, while neither method achieved PPV elimination in the Belošljiva variety despite the treatments applied. Given the prevalence of PPV in Serbia, cryotherapy shows promise for preserving endangered plum genotypes by eradicating viruses. [ABSTRACT FROM AUTHOR]

Sharka is a disease affecting stone fruit trees. It is caused by the Plum pox virus (PPV), with Myzus persicae being one of the most efficient aphid species in transmitting it within and among Prunus orchards. Other agricultural management strategies are also responsible for the spread of disease among trees, such as grafting and pruning. We present a mathematical model of impulsive differential equations to represent the dynamics of Sharka disease in the tree and vector population. We consider three transmission routes: grafting, pruning, and through aphid vectors. Grafting, pruning, and vector control occur as pulses at specific instants. Within the model, human risk perception towards disease influences these agricultural management strategies. Model results show that grafting with infected biological material has a significant impact on the spread of the disease. In addition, detecting infectious symptomatic and asymptomatic trees in the short term is critical to reduce disease spread. Furthermore, vector control to prevent aphid movement between trees is crucial for disease mitigation, as well as implementing awareness campaigns for Sharka disease in agricultural communities that provide a long-term impact on responsible pruning, grafting, and vector control. [ABSTRACT FROM AUTHOR]

Within the plum gene pool collection, where more than 150 genotypes of individual pomological groups were planted, a core collection was created taking into account the behaviour of the genotypes to the plum virus and their pomological groups. The infection was carry out on the base of field tolerance, without artificial infection in conditions of medium pressure of plum pox virus. Pomological groups were simplified and modified according to Hegi classification and the core collection was compiled based on the diversity of pomological groups and resistance to plum pox. Perspective genotypes were selected in each pomological group from the point of view of growing practice, breeding and processing.

Sharka is a disease of stone fruits, produced by the Plum Pox Virus and transmitted by aphids. It was detected for the first time in Argentina in 2004. In order to assess the aphid species that could act as a potential vector of this disease, we described the aphids community and seasonal fluctuation within two Prunus orchards affected by Sharka disease, located within two quarantine areas in Cuyo Region. Aphids were trapped weekly from October (spring) to April (autumn) during 2011-2012 and 2012-2013, by using yellow water traps (TAA), and identified using winged aphid's taxonomic keys. In total, 27 aphid species were identified. The most dominant species collected was Myzus persicae (Sulzer). Orchard-trapped population of this dominant aphid showed seasonal fluctuation with two peaks, November (spring) and March (autumn). [ABSTRACT FROM AUTHOR]

Plum pox virus (PPV) infects Prunus trees across the globe, causing the serious Sharka disease. Breeding programs in the past 20 years have been successful, generating plum varieties hypersensitive to PPV that show resistance in the field. Recently, a single tree displaying typical PPV symptoms was detected in an orchard of resistant plums. The tree was eradicated, and infected material was propagated under controlled conditions to study the new PPV isolate. Performing overlapping PCR analysis, the viral sequence was reconstructed, cloned and tested for infectivity in different 'Jojo'-based resistant plums. The results confirmed that the isolate, named PPV-D 'Herrenberg' (PPVD-H), was able to infect all these varieties. Analyses of chimeras between PPVD-H and a PPV-D standard isolate (PPVD) revealed that the NIa region of PPD-H, carrying three amino acid changes, was enough to break the resistance of these plums. Experiments with single and double mutants showed that all changes were essential to preserve the escaping phenotype. Additionally, one of the changes at the VPg-NIapro junction suggested the involvement of controlled endopeptidase cleavage in the viral response. Transient expression experiments in Nicotiana benthamiana confirmed that NIa cleavage in PPVD-H was reduced, compared to PPVD, linking the observed behavior to an NIa cleavage modulation. [ABSTRACT FROM AUTHOR]

Conservation of plant species, particularly of those important for agriculture, has now reached a very high importance in order to ensure sustainable utilization of biological resources by preventing further losses of plant diversity. The most advanced method for plant conservation is cryopreservation. Cryotherapy that relies on cryopreservation procedure, alone or in combination with other techniques, can be used for pathogen elimination from infected plants. Viral diseases pose a significant threat to the agriculture, decreasing yields and crop quality. In this work, two cryotherapy methods (D and V cryo-plate) were evaluated for plum pox virus (PPV) eradication from autochthonous plums (Prunus domestica L.) 'Crvena Ranka' and 'Belošljiva', widely present under different local names on the Balkan peninsula. Nine different cryo-plate treatments were performed per genotype. Cryopreservation was effective in PPV elimination from variety 'Crvena Ranka' in three cryo-treatments. PPV elimination was, however, not achieved in variety 'Belošljiva' by any of the two methods (D and V-cryoplate) and treatments applied. Key message: Eradication of plum pox virus from infected plums is possible by cryotherapy methods, but the efficiency is highly dependent on the treatment applied and the given genotype. [ABSTRACT FROM AUTHOR]

The genetic diversity and evolutionary history of the epidemic plum pox virus strain M (PPV‐M) have been poorly studied. We sequenced the genomes of 69 PPV‐M isolates selected from different Turkish regions. These new nearly full‐length genomic sequences were analysed together with 21 previously reported Turkish sequences of the PPV‐MIs clade and with 50 sequences of other PPV‐M isolates collected worldwide, including four sequences of Albanian isolates. Major genomic features were maintained in all new PPV‐M genomic sequences, with the highest divergence detected in the PIPO, P1 and CP proteins. Turkish PPV‐M isolates displayed a high genetic diversity and grouped into two sister clades, one formed by PPV‐MIs isolates only and a second clade consisting of the previously described PPV‐Ma and PPV‐Mb subclades. The combined diversity for PPV‐M isolates (Europe, Japan and Turkey) reached to 0.022 ± 0.001, which is slightly higher than the diversity of the globally distributed PPV‐D strain (0.017 ± 0.001). Likewise, the genetic diversity of PPV‐M (0.020 ± 0.001) in Turkey was found to be comparable to that observed for PPV‐M isolates from other countries (0.021 ± 0.001) and even marginally higher if considering partial genomic sequences that allow the inclusion of a much larger number of isolates and countries. Overall, the original distribution of PPV‐MIs, which seems to be almost specific to Turkey, and the high genetic diversity of PPV‐MIs and other Turkish PPV‐M isolates suggest a long evolutionary history of M isolates in Turkey and position this country as a centre of diversity of PPV‐M. [ABSTRACT FROM AUTHOR]

Plum pox virus (PPV) is a causal agent of the stone fruit tree sharka disease that often causes enormous economic losses. Due to its worldwide distribution and economic importance, rapid and reliable diagnostic technologies are becoming increasingly important for successful management of sharka disease. In this study, we have produced two super-sensitive and specific anti-PPV monoclonal antibodies (i.e., MAbs 13H4 and 4A11). Using these two MAbs, we have now developed a dot enzyme-linked immunosorbent assay (dot-ELISA) and a colloidal gold immunochromatographic strip (CGICS) assay. These two technologies can be used to quickly and reliably detect PPV. The results of these sensitivity assays confirmed that the dot-ELISA and CGICS assays could detect PPV infection in apricot tree leaf crude extracts diluted up to 1:5120 and 1:6400 (w/v), respectively. Further analyses using field-collected apricot tree leaf samples showed that the detection endpoint of the dot-ELISA was ~26 times above that obtained through RT-PCR, and the CGICS was as sensitive as RT-PCR. This present study is to broaden the knowledge about detection limits of dot-ELISA and CGICS for PPV monitoring. We consider that these newly developed dot-ELISA and CGICS are particularly useful for large scale PPV surveys in fields. [ABSTRACT FROM AUTHOR]

Sharka disease, caused by the Plum pox virus (PPV), is one of the most harmful, quarantine viral diseases that affect stone fruit crops. The absence of natural resistance to the virus in stone fruits has become a decisive factor for the use of genetic transformation methods to obtain stable forms. The eIF(iso)4G and eIF(iso)4E genes encode translation initiation factors used in the PPV life cycle. In the presented study, the effect of silencing these genes using the RNA interference method on the resistance of sour cherry rootstock 146-2 plants (Prunus pumila L. x Prunus tomentosa Thunb) to the sharka disease was studied. Two vectors have been created for the genetic transformation of plants, with self-complementary sequences of the eIF(iso)4G and eIF(iso)4E gene fragments. The hairpin expression cassette contains a strong promoter of the peach ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCo) gene, as well as an intron and terminator of the same gene. We used the pMF1 vector containing recombinase R and a codA-nptII gene which makes it possible to obtain intragenic marker-free plants. A successful genetic transformation was carried out by the AGL0 strain of A. tumefaciens. Whole leaves of shoots cultivated in vitro were used as a source of explants. Eight independent transgenic lines of rootstock 146-2 were obtained in experiments (sixlines with a hairpin to the eIF(iso)4G gene and two lines with a hairpin to the eIF(iso)4E gene). Their status was confirmed by the PCR and Southern blotting. The obtained plants were acclimatized in a greenhouse. The silencing of the eIF(iso)4G and eIF(iso)4E genes in transgenic plants was confirmed by the quantitative PCR. The presence of specific small interfering (si) RNAs was confirmed by the method of Northern blotting. Plants of all transgenic rootstock lines were infected with PPV by the method of grafting with infected buds. Resistance to the PPV infection of the obtained transgenic plants was carried out by using an enzyme immunoassay. The ELISA results showed that silencing the eIF(iso)4G gene did not lead to increased resistance while silencing the eIF(iso)4E factor gene led to increased resistance to the PPV, and the one line's plants showed no signs of infection for two years after infecting. The work demonstrates a (promising) approach in which the creation of stone cultures resistant to the plum pox virus can be achieved by suppressing the genes of translation initiation factors in clonal rootstocks. [ABSTRACT FROM AUTHOR]

Plum pox virus (PPV) is of the most important and harmful virus disease of plums, apricots, and peaches. Previous research has shown the non-transmissibility of PPV by aphids to genetically modified ’HoneySweet’ plum cultivar and to PK clone of BN4Kr myrobalan rootstock. In our experiments, the hypothesis was verified that non-transmissibility of PPV by aphids also exists in more resistant non-transgenic cultivars of plum or apricot. Therefore, relatively resistant cultivars of plum ’Gabrovská’, ’Anna Späth’, ’Althanova renklóda’ and apricot ’Harcot’, ’Hargrand’, ’Krajová raná’, grafted on the aphid transmission resistant myrobalan rootstock PK, were tested in pilot plantation conditions. None of the tested plum and apricot cultivars were naturally infected with PPV by aphid transmission. However, during monitoring in particular years, the successive die back of the ’Krajová’ and ’Hargrand’ apricot trees was noted, probably due to the poor affinity with PK myrobalan. Monitoring will continue in the following years.

Technology based on artificial small RNAs, including artificial microRNAs (amiRNAs), exploits natural RNA silencing mechanisms to achieve silencing of endogenous genes or pathogens. This technology has been successfully employed to generate resistance against different eukaryotic viruses. However, information about viral RNA molecules effectively targeted by these small RNAs is rather conflicting, and factors contributing to the selection of virus mutants escaping the antiviral activity of virus‐specific small RNAs have not been studied in detail. In this work, we transformed Nicotiana benthamiana plants with amiRNA constructs designed against the potyvirus plum pox virus (PPV), a positive‐sense RNA virus, and obtained lines highly resistant to PPV infection and others showing partial resistance. These lines have allowed us to verify that amiRNA directed against genomic RNA is more efficient than amiRNA targeting its complementary strand. However, we also provide evidence that the negative‐sense RNA strand is cleaved by the amiRNA‐guided RNA silencing machinery. Our results show that the selection pressure posed by the amiRNA action on both viral RNA strands causes an evolutionary explosion that results in the emergence of a broad range of virus variants, which can further expand in the presence, and even in the absence, of antiviral challenges. [ABSTRACT FROM AUTHOR]

This study was conducted in stone fruit orchards in five provinces of the East Mediterranean Region of Turkey between the years of 2009-2011. The aim of the study was to determine the potential aphid vectors of the quarantine pathogen PPV (plum pox virus, family Potyviridae) that causes serious yield losses. During the surveys, 542 orchard/nurseries were sampled and 6 aphid species (Hemiptera: Aphididae) [Brachycaudus persicae (Passerini,1860), B. helichrysi (Kaltenbach, 1843), B. cardui (Linnaeus, 1758), Hyalopterus pruni (Geoffroy, 1762), Myzus persicae (Sulzer, 1776) and M.cerasi (Fabricius, 1775)] from stone fruit trees and 4 aphid species [Aphis craccivora (Koch, 1854), A. fabae Scopoli 1763, A. gossypii Glover 1877, A. nasturtii Kaltenbach 1843)] from weeds that were known as the efficient vectors of PPV were detected in the stone fruit orchards. Stone fruit samples (flower, leaf, fruit), weed samples and aphid samples were tested by DAS-ELISA to determine the presence of PPV. PPV infected samples that resulted uncertain from DAS-ELISA were processed to conventional RT-PCR (Reverse Transcription Polymerase Chain Reaction) to finalize the decision of PPV presence. A total of 8 orchards were resulted as PPV-infected with both analyzing methods in the region. Three of these orchards were infected with aphids as well. B.cardui collected from the PPV-infected orchard in Hatay-Samandağ were also run to analyse for the presence of PPV and resulted virus positive.

Sharka is a disease affecting stone fruit trees. It is caused by the Plum pox virus (PPV), with Myzus persicae being one of the most efficient aphid species in transmitting it within and among Prunus orchards. Other agricultural management strategies are also responsible for the spread of disease among trees, such as grafting and pruning. We present a mathematical model of impulsive differential equations to represent the dynamics of Sharka disease in the tree and vector population. We consider three transmission routes: grafting, pruning, and through aphid vectors. Grafting, pruning, and vector control occur as pulses at specific instants. Within the model, human risk perception towards disease influences these agricultural management strategies. Model results show that grafting with infected biological material has a significant impact on the spread of the disease. In addition, detecting infectious symptomatic and asymptomatic trees in the short term is critical to reduce disease spread. Furthermore, vector control to prevent aphid movement between trees is crucial for disease mitigation, as well as implementing awareness campaigns for Sharka disease in agricultural communities that provide a long-term impact on responsible pruning, grafting, and vector control.

Plum pox virus (PPV) causes sharka disease in Prtillus trees. Peach persicat trees are severely affected by PPV, and no definitive source genetic resistance has been identified. However, previous results discovshowed that PPV-resistant 'Garrigues' almond (P. duk·is) was able to transfer its resistance to GF305' peach through grafting. reducing symptoins and viral load in PPV-infected plants. A recent study tried to idenantivitify genes responsible for this effect by studying messenger RNA colexpression through RNA sequencing in peach and almond plants, before and after grafting and before and after PPV infection. In this work. we used the same peach and almond samples but focused the high throughput analyses on small RNA (sRNA) expression. We studied massive sequencing data and found an interesting pattern of sRNA over-expression linked to antiviral defense genes that suggested activation of these genes followed by downregulation to basal levels. We also discovshowed ered that 'Garrigues' almond plants were infected by different plant viruses that were transferred to reach plants. The large amounts of viral sRNA found in grafted peaches indicated a strong RNA silencing antivitify ral response and led us to postulate that these plant viruses could be colexpression laborating in the observed "Garrigues effect. [ABSTRACT FROM AUTHOR]

In order to fill in a decade-long information gap regarding the biological, serological and molecular data for plum tree viruses in Bosnia and Herzegovina, a three-phase study combining symptom evaluation, and serological and molecular assays with high-throughput sequencing (HTS) technology was conducted. The most frequently observed symptoms were discolorations in the form of ring patterns, bands and irregular shapes, as well as vein banding. Sharka-associated symptoms in the form of ring patterns and semicircles were prevalent. A total of 468 plum tree samples were tested by ELISA for the presence of PPV, ApMV, PDV, PNRSV, PBNSPaV, ACLSV and MLRSV. An overall infection incidence of 51.9% was detected, with PPV being the most prevalent (48.7%), followed by PDV (2.99%), PNRSV (0.21%) and mixed infections of PPV+PDV (1.71%). RT-PCR-assisted strain typing in 45 samples revealed PPV-D as the most common strain (22.22%), followed by PPV-REC (6.66%). Mixed infections of PPV-D+PPV-REC were detected (6.66%). HTS enabled the recovery of a 9743 nts long sequence of PPV-D (PPV_O7/80, MW412433), which shared the highest nucleotide and amino acid identities with isolates S13 (LC375131) from Serbia, SVN1 (LC375132) from Slovenia and N9 (LC375129) from Bulgaria. The phylogenetic analysis of the whole genome placed the isolate of the D strain in a distinctive group with the Slovenian isolate SVN1 (LC375132). In addition, the (Cter)NIb/(Nter)CP fragment of a PPV-REC isolate (MW412434) obtained in this survey formed a separate group with previously known isolates from Bosnia and Herzegovina (BOS64Pl and BOS257Pl). [ABSTRACT FROM AUTHOR]

Abstract Objective To find mutations that may have recently occurred in Plum pox virus (PPV), we collected six PPV-infected plum/peach trees from the western part of Japan and one from the eastern part. After sequencing the full-length PPV genomic RNAs, we compared the amino acid sequences with representative isolates of each PPV strain. Results All new isolates were found to belong to the PPV-D strain: the six isolates collected from western Japan were identified as the West-Japan strain while the one collected from eastern Japan as the East-Japan strain. Amino acid sequence analysis of these seven isolates suggested that the 1407th and 1529th amino acid residues are characteristic of the West-Japan and the East-Japan strains, respectively. Comparing them with the corresponding amino acid residues of the 47 non-Japanese PPV-D isolates revealed that these amino acid residues are undoubtedly unique. A further examination of the relevant amino acid residues of the other 210 PPV-D isolates collected in Japan generated a new hypothesis regarding the invasion route from overseas and the subsequent diffusion route within Japan: a PPV-D strain might have invaded the western part of Japan from overseas and spread throughout Japan.

Plum pox virus (PPV) infects Prunus trees across the globe, causing the serious Sharka disease. Breeding programs in the past 20 years have been successful, generating plum varieties hypersensitive to PPV that show resistance in the field. Recently, a single tree displaying typical PPV symptoms was detected in an orchard of resistant plums. The tree was eradicated, and infected material was propagated under controlled conditions to study the new PPV isolate. Performing overlapping PCR analysis, the viral sequence was reconstructed, cloned and tested for infectivity in different ‘Jojo’-based resistant plums. The results confirmed that the isolate, named PPV-D ‘Herrenberg’ (PPVD-H), was able to infect all these varieties. Analyses of chimeras between PPVD-H and a PPV-D standard isolate (PPVD) revealed that the NIa region of PPD-H, carrying three amino acid changes, was enough to break the resistance of these plums. Experiments with single and double mutants showed that all changes were essential to preserve the escaping phenotype. Additionally, one of the changes at the VPg-NIapro junction suggested the involvement of controlled endopeptidase cleavage in the viral response. Transient expression experiments in Nicotiana benthamiana confirmed that NIa cleavage in PPVD-H was reduced, compared to PPVD, linking the observed behavior to an NIa cleavage modulation.

The present study was conducted on 106 leaf samples of Prunus species (44 plum, 47 myrobalan plum, 10 apricot, 3 peach, 1 blackthorn, and 1 sour cherry) collected from the Vojvodina province of Serbia and assessed for the presence of Plum pox virus (PPV) with the aim of establishing whether trees growing along roadsides and in backyards could be sources of PPV infection in commercial orchards. Analyses confirmed PPV infection in 68.2%, 38.6%, and 20% of plum, myrobalan plum and apricot samples, respectively. The infection level varied considerably across locations, with 80% noted in Uljma, followed by 69% in Sremska Kamenica, 60% in Bečej, 50% in Temerin, 50% in Senta, 40% in Petrovaradin, 31% in Novi Sad, 30% in Susek, and 20% in Subotica. As no difference in infection rates was noted between young and older plum trees, the infections seemed to have occurred in their early life stage. Trees growing along roadsides were infected to a higher extent (89.6%) than those in backyards (66.6%). In some cases, symptomless trees were also proven to be PPV positive, indicating that they are a potentially important source of further virus infections. Due to the widespread presence of the virus, tolerant or hypersensitive cultivars are recommended for planting new orchards.

The NIa protease of potyviruses is a chymotrypsin-like cysteine protease related to the picornavirus 3C protease. It is also a multifunctional protein known to play multiple roles during virus infection. Picornavirus 3C proteases cleave hundreds of host proteins to facilitate virus infection. However, whether or not potyvirus NIa proteases cleave plant proteins has so far not been tested. Regular expression search using the cleavage site consensus sequence [EQN]xVxH[QE]/[SGTA] for the plum pox virus (PPV) protease identified 90 to 94 putative cleavage events in the proteomes of Prunus persica (a crop severely affected by PPV), Arabidopsis thaliana, and Nicotiana benthamiana (two experimental hosts). In vitro processing assays confirmed cleavage of six A. thaliana and five P. persica proteins by the PPV protease. These proteins were also cleaved in vitro by the protease of turnip mosaic virus (TuMV), which has a similar specificity. We confirmed in vivo cleavage of a transiently expressed tagged version of AtEML2, an EMSY-like protein belonging to a family of nuclear histone readers known to be involved in pathogen resistance. Cleavage of AtEML2 was efficient and was observed in plants that coexpressed the PPV or TuMV NIa proteases or in plants that were infected with TuMV. We also showed partial in vivo cleavage of AtDUF707, a membrane protein annotated as lysine ketoglutarate reductase trans-splicing protein. Although cleavage of the corresponding endogenous plant proteins remains to be confirmed, the results show that a plant virus protease can cleave host proteins during virus infection and highlight a new layer of plant-virus interactions. [ABSTRACT FROM AUTHOR]

Plum pox virus (PPV) is a causal agent of the stone fruit tree sharka disease that often causes enormous economic losses. Due to its worldwide distribution and economic importance, rapid and reliable diagnostic technologies are becoming increasingly important for successful management of sharka disease. In this study, we have produced two super-sensitive and specific anti-PPV monoclonal antibodies (i.e., MAbs 13H4 and 4A11). Using these two MAbs, we have now developed a dot enzyme-linked immunosorbent assay (dot-ELISA) and a colloidal gold immunochromatographic strip (CGICS) assay. These two technologies can be used to quickly and reliably detect PPV. The results of these sensitivity assays confirmed that the dot-ELISA and CGICS assays could detect PPV infection in apricot tree leaf crude extracts diluted up to 1:5120 and 1:6400 (w/v), respectively. Further analyses using field-collected apricot tree leaf samples showed that the detection endpoint of the dot-ELISA was ~26 times above that obtained through RT-PCR, and the CGICS was as sensitive as RT-PCR. This present study is to broaden the knowledge about detection limits of dot-ELISA and CGICS for PPV monitoring. We consider that these newly developed dot-ELISA and CGICS are particularly useful for large scale PPV surveys in fields.

Peach (Prunus persica) is a deciduous, edible, stone fruit producing plant, belonging to the family Rosaceae. The plant is prone to various pathogens and one of them is the plum pox virus (PPV). This is a lethal virus of peach plant causing pox disease of plum. Its attack results in 83%-100% yield loss in highly susceptible varieties of peach plant. The complete genome of PPV is 9791 base pairs with positive-sense single strand. The full-length genome of PPV encodes a large polyprotein initially, which cleaves proteolytically into ten mature proteins - coat protein, helper component proteinase, P1, P3, viral genome-linked protein, 6K1, 6K2, cylindrical inclusion protein, cylindrical inclusion protein b and NIa-pro-proteins. The objective of this study is to identify such sites in the PPV genome which can be targeted by PPV-derived miRNAs through target prediction computational tools/algorithms. A total of 214 mature miRNAs were chosen from the miRNA database to check their complementarity with the PPV genome. Minimum free energy, folding energy, seed pairing, target-site accessibility, pattern recognition and multiple target sites were the parameters considered for target prediction algorithms. Two out of 214 miRNAs were predicted as potential against plum pox virus by three of four tools used for target prediction. Thus, the results encourage generating transgenic, PPV-resistant peach plants by expression of predicted miRNAs. [ABSTRACT FROM AUTHOR]

Peach cultivars (’Elberta’, ‘Red Top’, and ’Dixie Red’) were studied for their in vitro adoptability and performance in producing virus-free plantlets. The thermotherapy method with increasing temperatures (25 °C to 37 °C) was applied for the elimination of famous peach infecting plum pox viruses (PPVs) and prunus necrotic ringspot virus (PNRSV), and the DS-ELISA test and RT-PCR technique were performed to confirm the production of virus-free microshoots. The application of 30 mg L−1 of Fe-EDDHA treatment resulted in the best performance for culture establishment of all cultivars, where the best subsequent morphological performance in terms of branch and leaf numbers was recorded for the ’Dixie Red’ cultivar in MS medium, supplemented with 0.5 mgL−1 of gibberellic acid (GA3) and 0.5 mg L−1 of 6-Benzylaminopurine (BAP). At the regeneration stage, the highest (26.96 mm) and lowest (18.43 mm) shoot lengths were obtained from the ’Dixie Red’ cultivar treated with GA3 (2 mg L−1) + thidiazuron (TDZ) (2.5 mg L−1) and the ’Red Top’ cultivar treated with GA3 (1 mg L−1) + TDZ (1 mg L−1), respectively. The leaf numbers were affected by the application of growth regulators, where the ’Elberta’ cultivar under GA3 (2 mg L−1) + TDZ (2.5 mg L−1) treatment showed the highest numbers and the ’Red Top’ cultivar under GA3 (1 mg L−1) + TDZ (1 mg L−1) showed the lowest mean values. The thermotherapy treatment and micropropagation of shoot tips resulted in 100% virus-free plantlets, as confirmed by both applied diagnostic methods. The result of the application of the rooting stage with growth regulators on ’Elberta’ plantlets showed the best performance (90%) in ½ MS medium supplemented with 0.5–1 mg L−1 of IBA, which was significantly higher than the same treatment in MS medium. The obtained results should constitute the basis for further optimization of the multiplication and rooting of virus-free peach plantlets to be served for nurseries and planation orchards.

Plum pox virus (PPV) is a plant virus (genus Potyvirus, family Potyviridae) infecting stone fruit trees. Since the first report from Bulgaria in 1917, PPV has spread to Europe, Africa, America, and Asia. In 2015, the first identification of PPV in Korea was reported from symptomatic peaches (Prunus persica). Diagnosis of PPV is a significant issue in quarantining plants as well as in preventing disease spread. In this study, a duplex reverse transcription and polymerase chain reaction (RT-PCR) detection system was developed with two different target regions in the PPV genome. Peach trees showing variable detection efficiency for PPV were sampled over two years and analyzed with other peach trees that were confirmed as indicator plants for PPV. Based on the RT-PCR results, the highest viral accumulation of PPV was confirmed in spring and decreased with increasing temperature in summer; therefore, PPV was typically unable to be detected during summer. The inability of RT-PCR to detect the virus in summer was repeatedly observed. This study also diagnosed PPV from 9 of the 19 major weed species around PPV-infected peach trees and confirmed that Erigeron annuus is an important weed that can act as a host for the proliferation of aphids and the spread of the virus from the weed to the peach and other host crops. Therefore, performing PPV diagnosis in spring and the management of weeds such as E. annuus, which can be a host of both, the virus and the insect vector, are important ways to prevent the spread of the virus. [ABSTRACT FROM AUTHOR]

Objective: To find mutations that may have recently occurred in Plum pox virus (PPV), we collected six PPV-infected plum/peach trees from the western part of Japan and one from the eastern part. After sequencing the full-length PPV genomic RNAs, we compared the amino acid sequences with representative isolates of each PPV strain. Results: All new isolates were found to belong to the PPV-D strain: the six isolates collected from western Japan were identified as the West-Japan strain while the one collected from eastern Japan as the East-Japan strain. Amino acid sequence analysis of these seven isolates suggested that the 1407th and 1529th amino acid residues are characteristic of the West-Japan and the East-Japan strains, respectively. Comparing them with the corresponding amino acid residues of the 47 non-Japanese PPV-D isolates revealed that these amino acid residues are undoubtedly unique. A further examination of the relevant amino acid residues of the other 210 PPV-D isolates collected in Japan generated a new hypothesis regarding the invasion route from overseas and the subsequent diffusion route within Japan: a PPV-D strain might have invaded the western part of Japan from overseas and spread throughout Japan. [ABSTRACT FROM AUTHOR]

Plum pox virus (PPV) is a significant viral disease in Prunus spp. worldwide. A nationwide survey was started in Prunus spp. orchards, since PPV was first detected from peach in Korea, 2015. During 2016-2017, samples were collected from 30,333 trees in 1,985 orchards of stone fruits in 8 provinces and 4 cities, Korea and tested by reverse transcription polymerase chain reaction using specific PPV primer set. As a result, 21 trees including peach (9 trees), Japanese apricot (4 trees), plum (1 tree), apricot (7 trees) in 10 orchards were infected and controlled by eradication program. Amplicons of the expected size (547 bp) were obtained from total RNA of seven peach trees in 2016, and directly sequenced. BLAST analysis revealed the highest nucleotide (NT) identity (99%) with a PPV D isolates (LC331298, LT600782) in GenBank. The seven isolates from shared nt sequence identities of 98 to 100% with one another. Phylogenetic analysis showed the isolates in peach clustered closely with the PPV-D isolates from Korea, Japan, USA, and Canada. This is, to our knowledge, the first report of the presence of PPV in Prunus spp. orchards in Korea, 2016-2017, we hope that our results and efforts will contribute to effective measures for eradication of PPV.

In order to fill in a decade-long information gap regarding the biological, serological and molecular data for plum tree viruses in Bosnia and Herzegovina, a three-phase study combining symptom evaluation, and serological and molecular assays with high-throughput sequencing (HTS) technology was conducted. The most frequently observed symptoms were discolorations in the form of ring patterns, bands and irregular shapes, as well as vein banding. Sharka-associated symptoms in the form of ring patterns and semicircles were prevalent. A total of 468 plum tree samples were tested by ELISA for the presence of PPV, ApMV, PDV, PNRSV, PBNSPaV, ACLSV and MLRSV. An overall infection incidence of 51.9% was detected, with PPV being the most prevalent (48.7%), followed by PDV (2.99%), PNRSV (0.21%) and mixed infections of PPV+PDV (1.71%). RT-PCR-assisted strain typing in 45 samples revealed PPV-D as the most common strain (22.22%), followed by PPV-REC (6.66%). Mixed infections of PPV-D+PPV-REC were detected (6.66%). HTS enabled the recovery of a 9743 nts long sequence of PPV-D (PPV_O7/80, MW412433), which shared the highest nucleotide and amino acid identities with isolates S13 (LC375131) from Serbia, SVN1 (LC375132) from Slovenia and N9 (LC375129) from Bulgaria. The phylogenetic analysis of the whole genome placed the isolate of the D strain in a distinctive group with the Slovenian isolate SVN1 (LC375132). In addition, the (Cter)NIb/(Nter)CP fragment of a PPV-REC isolate (MW412434) obtained in this survey formed a separate group with previously known isolates from Bosnia and Herzegovina (BOS64Pl and BOS257Pl).

Plum pox virus (PPV) is one of the most destructive viral pathogens infecting stone fruit trees worldwide. As PPV causes a viral disease that requires plants to be quarantined, the development of a reliable method of PPV detection is essential for preventing the spread of the disease. In this study, an isothermal reverse transcription-recombinase polymerase amplification (RT-RPA) assay was developed for the detection of PPV in peaches. The major advantage of this RT-RPA assay is that it can be performed at 42 °C and can be completed in 10 min and has specificity for viruses that infect peaches. In addition, this assay was successfully performed using field-collected samples. This RT-RPA assay is a promising method with high efficiency for rapid PPV detection as part of quarantine inspection and certification program. [ABSTRACT FROM AUTHOR]

Plum pox virus (PPV) is the most dangerous viral agent of stone fruits. PPV can be transmitted by vector aphids and may cause serious damage on fruits, leaves and flowers of Prunus species, especially on plum, apricot, and peach. Eradication of infected plants is one of the most recommended control methods of PPV in the world. The main objective of this study is to evaluate the National PPV survey and eradication program carried by the National Plant Health Authority between 2013 and 2018. During the six years of study, approximately 60.000 trees in 96.26% of Turkey were screened for PPV symptoms and 21.394 samples were collected from suspected plants from seven different fruit species. The samples were tested by ELISA (Enzyme Linked Immunosorbent Assay), and then ELISA questionable samples were verified by RT-PCR (Reverse Transcription Polymerase Chain Reaction). Based on the six years results, 2.718 samples from 161 locations were determined as PPV positive and the infection rate was calculated as 12.70%. During this study, 78.868 trees were eradicated. By the help of intensive monitoring and eradication program, PPV infection rate decreased from 35.72% to 7.47%. On the other hand, PPV infection was firstly recorded and eradicated in seven provinces (Aydın, Bolu, Denizli, Erzincan, Kırıkkale, Sivas, Samsun) which have been known as PPV-free before. This study showed that eradication is a very effective way to suppress PPV infection and spread. In conclusion, the national survey and eradication program should be operated nationwide and concentrated in nurseries. [ABSTRACT FROM AUTHOR]

Herbaceous and woody plants display specific mechanisms allowing them to adapt and survive to a broad variety of environmental stresses. Nevertheless, all plant species share certain basic physiological and biochemical mechanisms. Under both abiotic and biotic challenges, the extent to which reactive oxygen species (ROS) accumulate relies on the antioxidative system, which is in charge to maintain cellular homeostasis and prevent ROS damage. Moreover, a tight control of ROS production is crucial so that they perform their signalling function. Thus, antioxidative metabolism and redox biology are key players in the physiological response to stress. However, little attention has been paid to the overlapping mechanisms and convergent pathways of antioxidant metabolism between abiotic and biotic stress responses. In the present review, the responses of an herbaceous plant (Pisum sativum L.) and a woody plant (Prunus persica L.) against two forms of stress—salinity and infection by Plum pox virus—were compared, placing emphasis on common response patterns. This information may serve to devise agronomic approaches conferring stress tolerance to many economically relevant crops. [ABSTRACT FROM AUTHOR]

In stone fruit trees, resistance to Plum pox virus (PPV) can be achieved through the specific degradation of viral RNA by the mechanism of RNA interference (RNAi). Transgenic virus-resistant plants, however, raise serious biosafety concerns due to the insertion and expression of hairpin constructs that usually contain various selective foreign genes. Since a mature stone tree represents a combination of scion and rootstock, grafting commercial varieties onto transgenic virus-tolerant rootstocks is a possible approach to mitigate biosafety problems. The present study was aimed at answering the following question: To what extent are molecular RNAi silencing signals transmitted across graft junctions in transgrafted plum trees and how much does it affect PPV resistance in genetically modified (GM)/non-transgenic (NT) counterparts? Two combinations, NT:GM and GM:NT (scion:rootstock), were studied, with an emphasis on the first transgrafting scenario. Viral inoculation was carried out on either the scion or the rootstock. The interspecific rootstock "Elita" [(Prunus pumila L. × P. salicina Lindl.) × (P. cerasifera Ehrh.)] was combined with cv. "Startovaya" (Prunus domestica L.) as a scion. Transgenic plum lines of both cultivars were transformed with a PPV-coat protein (CP)-derived intron-separate hairpin-RNA construct and displayed substantial viral resistance. High-throughput sequence data of small RNA (sRNA) pools indicated that the accumulation of construct-specific small interfering RNA (siRNA) in transgenic plum rootstock reached over 2%. The elevated siRNA level enabled the resistance to PPV and blocked the movement of the virus through the GM tissues into the NT partner when the transgenic tissues were inoculated. At the same time, the mobile siRNA signal was not moved from the GM rootstock to the target NT tissue to a level sufficient to trigger silencing of PPV transcripts and provide reliable viral resistance. The lack of mobility of transgene-derived siRNA molecules was accompanied by the transfer of various endogenous rootstock-specific sRNAs into the NT scion, indicating the exceptional transitivity failure of the studied RNAi signal. The results presented here indicate that transgrafting in woody fruit trees remains an unpredictable practice and needs further in-depth examination to deliver molecular silencing signals. [ABSTRACT FROM AUTHOR]

Although it is currently eradicated from the United States, Plum pox virus (PPV) poses an ongoing threat to U.S. stone fruit production. Although almond ( Prunus dulcis ) is known to be largely resistant to PPV, there is conflicting evidence about its potential to serve as an asymptomatic reservoir host for the virus and thus serve as a potential route of entry. Here, we demonstrate that both Tuono and Texas Mission cultivars can be infected by the U.S. isolate PPV Dideron (D) Penn4 and that Tuono is a transmission-competent host, capable of serving as a source of inoculum for aphid transmission of the virus. These findings have important implications for efforts to keep PPV out of the United States and highlight the need for additional research to test the susceptibility of almond to other PPV-D isolates., Competing Interests: The author(s) declare no conflict of interest.

Abstract Background Plum pox virus (PPV), causing Sharka disease, is one of the main limiting factors for Prunus production worldwide. In apricot (Prunus armeniaca L.) the major PPV resistance locus (PPVres), comprising ~ 196 kb, has been mapped to the upper part of linkage group 1. Within the PPVres, 68 genomic variants linked in coupling to PPV resistance were identified within 23 predicted transcripts according to peach genome annotation. Taking into account the predicted functions inferred from sequence homology, some members of a cluster of meprin and TRAF-C homology domain (MATHd)-containing genes were pointed as PPV resistance candidate genes. Results Here, we have characterized the global apricot transcriptome response to PPV-D infection identifying six PPVres locus genes (ParP-1 to ParP-6) differentially expressed in resistant/susceptible cultivars. Two of them (ParP-3 and ParP-4), that encode MATHd proteins, appear clearly down-regulated in resistant cultivars, as confirmed by qRT-PCR. Concurrently, variant calling was performed using whole-genome sequencing data of 24 apricot cultivars (10 PPV-resistant and 14 PPV-susceptible) and 2 wild relatives (PPV-susceptible). ParP-3 and ParP-4, named as P runus ar meniaca P PVres MATHd-containing genes (ParPMC), are the only 2 genes having allelic variants linked in coupling to PPV resistance. ParPMC1 has 1 nsSNP, while ParPMC2 has 15 variants, including a 5-bp deletion within the second exon that produces a frameshift mutation. ParPMC1 and ParPMC2 are adjacent and highly homologous (87.5% identity) suggesting they are paralogs originated from a tandem duplication. Cultivars carrying the ParPMC2 resistant (mutated) allele show lack of expression in both ParPMC2 and especially ParPMC1. Conclusions Accordingly, we hypothesize that ParPMC2 is a pseudogene that mediates down-regulation of its functional paralog ParPMC1 by silencing. As a whole, results strongly support ParPMC1 and/or ParPMC2 as host susceptibility genes required for PPV infection which silencing may confer PPV resistance trait. This finding may facilitate resistance breeding by marker-assisted selection and pave the way for gene edition approaches in Prunus.

A field trial with plum cv. HoneySweet was established in 2003 in an experimental plot near Crop Research Institute in Prague-Ruzyně, Czech Republic, on the basis of a permission issued by the Ministry of the Environment of the Czech Republic. In addition to the evaluation of resistance of plum cv. HoneySweet to Plum pox virus, the field trial was used to evaluate gene flow of the inserted transgene. Sampling of blackthorn and myrobalan trees outside the field test site occurred at distances ranging from 544 m to 845 m from the test site and showed no gene flow, testing both plants and seeds collected from blackthorns and myrobalans. Similarly, seeds from plums cv. Jojo growing directly at the field test place did not show any presence of the transgene after seven years of evaluation.

Plum pox virus (PPV), the causal agent of Sharka disease, causes yield, quality, and economic losses in stone fruits. PPV has been reported worldwide, especially in Europe. In studies to date, the presence of the virus has been identified as being restricted in different regions of Turkey. However, there is no record of PPV in Bolu province so far. Hence, surveys were carried out in Bolu province between 2016- 2019, and a total of 306 samples were collected. To determine the presence of PPV, the samples were first tested by DAS-ELISA, and only three peach samples were found to be infected. DAS-ELISA results of infected samples were confirmed by RT-PCR using universal primers (P1/P2), then infected samples were identified at the strain level using strain-specific primers. The samples were found to be infected with the PPV-M (Marcus) strain and 243-bp long nucleotide sequences containing the partial coat protein gene of three isolates were deposited to NCBI. Phylogenetic analysis (Neighbor-Joining) generated by 38 representative PPV sequences indicated that Bolu isolates were clustered with PPV-M isolates and separated from other strains, as in BLAST analysis. To our knowledge, this is the first report of PPV in Bolu. This study reveals the necessity to carry out more extensive surveys to prevent the PPV dissemination in Bolu and to identify the complete genomes of the obtained isolates to determine their genetic variation. All the PPV-infected trees were destroyed as a consequence. [ABSTRACT FROM AUTHOR]

Recently, cold atmospheric plasma (CAP) is under investigation for possibility to be applied for inactivation of pathogens in medicine, food technologies, water cleaning technologies and agriculture. The aim of the current study is to investigate the effect of CAP on microplants, propagated in vitro from plum tree (Prunus domestica L., cv. 'Kyustendilska sinya') naturally co-infected by M and D strains of Plum pox virus (PPV) and in that respect the possibility for CAP application for virus inactivation. In the present work, we have used two types of plasma sources for biological systems treatments: a surface-wave-sustained Argon plasma torch and an underwater diaphragm discharge. These enabled several variants of plasma treatment to be performed. Based on the data of IC-RT-PCR tests of the microplants on the third subculture after treatment, it was found the most effective variant was the reiterated plasma torch tip treatment to nodal segments without leaves in gas medium. The strain specific RT-PCR analysis results of PPV positive CAP-treated microplants showed that only PPV-M strain was identified after treatment, although the starting material was co-infected by both strains. The results obtained from IC-RT-PCR and strain specific RT-PCR of the acclimatized ex vitro plants have been in agreement with the data from molecular analyses of the microplants tested. These are the first experiments on CAP ability for inactivation of PPV from tissue of living woody plants even if in in vitro conditions. The completed estimation of this approach for obtaining of PPV-free plum plants will be made after more prolonged observation and testing of the ex vitro plants. [ABSTRACT FROM AUTHOR]

Plum pox virus (PPV) is one of the most important plant viruses causing serious economic losses. Thus far, strain typing based on the definition of 10 monophyletic strains with partially differentiable biological properties has been the sole approach used for epidemiological characterization of PPV. However, elucidating the genetic determinants underlying intra‐strain biological variation among populations or isolates remains a relevant but unexamined aspect of the epidemiology of the virus. In this study, based on complete nucleotide sequence information of 210 Japanese and 47 non‐Japanese isolates of the PPV‐Dideron (D) strain, we identified five positively selected sites in the PPV‐D genome. Among them, molecular studies showed that amino acid substitutions at position 2,635 in viral replicase correlate with viral titre and competitiveness at the systemic level, suggesting that amino acid position 2,635 is involved in aphid transmission efficiency and symptom severity. Estimation of ancestral genome sequences indicated that substitutions at amino acid position 2,635 were reversible and peculiar to one of two genetically distinct PPV‐D populations in Japan. The reversible amino acid evolution probably contributes to the dissemination of the virus population. This study provides the first genomic insight into the evolutionary epidemiology of PPV based on intra‐strain biological variation ascribed to positive selection. [ABSTRACT FROM AUTHOR]

Molecular analysis of new isolates of the plum pox virus (PPV) found in the gene pool collections of peach, apricot, and plum from the Nikitsky Botanical Garden (National Science Center, Russian Academy of Sciences), as well as on wild cherry plum trees in the surrounding area, has been carried out. Using the enzyme-linked immunosorbent assay and reverse transcription polymerase chain reaction, 19 new PPV isolates have been detected. Most of them belonged to the strain D; single isolates of the strains Rec and M were also found. The 3'-terminal sequences of genome of the new isolates were sequenced, including the coat protein (CP) gene and adjacent sequences of the NIb gene and the 3'-nontranslated region. Phylogenetic analysis of these sequences revealed the distribution of PPV-D isolates into several clusters or clades. An average divergence rate between sequences of Crimean PPV-D isolates was 2.0%. A relatively high level of genetic variation indicates a long-standing introduction of the ancestors of the current PPV-D isolates to Nikitsky Botanical Garden (NBG). Isolate H23, identified in the apricot collection, belonged to strain M. This is the first detection of PPV-M in Crimea. Isolate AL-Ch (strain Rec) was found on wild cherry plum. In the CP of isolate K87 (strain D), the K59T mutation was detected, which prevents its recognition by PPV-D-specific 4DG5 monoclonal antibodies. In CP of AL-Ch and previously characterized isolates K28 and Kisl-1pl (strain Rec), amino acid substitutions were detected at position 68, which did not affect the recognition of these isolates by AL monoclonal antibodies. Apparently, position 68 is outside the PPV-M/Rec-specific epitope. The results of the work show that PPV most likely entered the NBG with contaminated drupaceous fruit material as a result of several independent introductions from different regions of the world and spread over plantations by aphids. [ABSTRACT FROM AUTHOR]

Salicylic acid (SA) plays a central role in plant responses to environmental stresses. In a recent study, we suggested a third pathway for SA biosynthesis from mandelonitrile (MD) in peach plants. This pathway is an alternative to the phenylalanine ammonia‐lyase pathway and links SA biosynthesis and cyanogenesis. In the present work, using biochemical approaches, we studied the effect of salt stress and Plum pox virus (PPV) infection on this proposed SA biosynthetic pathway from MD.Peach plants were submitted to salt stress and Plum pox virus (PPV) infection. We studied the levels of SA and its intermediates/precursors (phenylalanine, MD, amygdalin and benzoic acid) in in vitro shoots. Moreover, in peach seedlings, we analysed the content of H2O2‐related enzymes, SA and the stress‐related hormones abscisic acid and jasmonic acid.We showed that the contribution of this SA biosynthetic pathway from MD to the total SA pool does not seem to be important under the stress conditions assayed. Nevertheless, MD treatment not only affected the SA content, but also had a pleiotropic effect on abscisic acid and jasmonic acid levels. Furthermore, MD modulates the antioxidative metabolism via SA‐dependent or ‐independent redox‐related signalling pathways.Even though the proposed SA biosynthetic pathway seems to be functional under stress conditions, MD, and hence cyanogenic glycosides, may be operating more broadly than by influencing SA pathways and signalling. Thus, the physiological function of the proposed SA biosynthetic pathway remains to be elucidated. [ABSTRACT FROM AUTHOR]

The most sensitive viral disease of the stone crops is Sharka, the causative agent of which is the plum pox virus (PPV, Plum Pox virus). PPV worldwide has a quarantine status. PPV is widespread in many regions of Ukraine and poses a serious problem to horticulture stone crops of our country. The purpose of our research was to analyze the distribution and the harmfulness of this pathogen, to describe the ways of transmission, to carry out research on the identification of aphids that were carriers of the disease and to characterize its molecular features and strains diversity in the territory of Ukraine. The samples were visually selected from the central and northern regions of Ukraine. Modern methods of molecular diagnostics were used such as: polymerase chain reaction with reverse transcription, sequencing. The phylogenetic analysis confirmed the identity of the strains and helped us made a comparative characterization of the samples to the already known strains. Depending on the strain, different kinds and varieties of plants could be damaged and crop losses could significantly vary. Therefore, it is important to determine the diversity of PPV strains and their similarities with other isolates. The result revealed high level of damage to stone crops in the territory of Ukraine, especially in Odessa and the Kiev region. Harmfulness and distribution of this disease increases every year. These researches are needed to find ways to fight this pathogen and stop the spread of a dangerous virus in Ukraine. [ABSTRACT FROM AUTHOR]

Sharka, caused by Plum pox virus (PPV), is considered one of the most serious viral diseases of stone fruits worldwide due to the great yield losses in orchards. In Rama Caída, Mendoza, a 5-year study (2007-2011) was conducted in a European plum cv D'agen orchard using samples from leaves and DAS-ELISA assay against PPV in order to determine incidence over time and spatial spread. Incidence significantly increased between 2007 and 2009, while for the next two years the increase was not statistically significant. Spatial point pattern of PPV at the plot was characterized by the occurrence of some heterogeneous clusters of infected trees located up to 65 m in the west-east direction of the rows over the five years. Point pattern and correlation type-approaches were undertaken using joint-count and Ripley's K function and showed that the detected infected plants had a disease aggregation pattern both in west-east and south-north directions, as well as within and between rows across the plot. This short-distance local dispersion would be associated with diverse factors, such as vector aphids, that were not evaluated in this study. Hence, this work can serve as a basis for further studies of sharka dispersion in Cuyo region. [ABSTRACT FROM AUTHOR]

'HoneySweet' is a transgenic plum protected against Plum pox virus (PPV). Its behaviour to natural PPV infection was the subject of different field trials undertaken in several endemic European countries. The first experiment in Romania was performed between 1996-2006 and no 'HoneySweet' tree was found infected under high natural PPV infection pressure. To further asses the durability of resistance to PPV of 'HoneySweet', a new field trial was established in 2013. As inoculum sources of PPV were used plants, previously artificially inoculated with D or Rec strains, grown in pots and placed inside of the blocks. Limited treatments with insecticides were made within the plot in order to stimulate the virus spread by aphids. The monitoring of PPV spreading was made by serological and molecular assays. Strains discrimination was made by RT-PCR. The temporal spread of PPV revealed a continual evolution of infection in conventional plums. No trees of transgenic plum 'HoneySweet' expressed PPV symptoms or were found infected, by serological and molecular assays, confirming its durable resistance to natural PPV infection with D or Rec strains. [ABSTRACT FROM AUTHOR]

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