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Resistance to PPV and ESFY phytoplasma has been evaluated for Japanese plum ('Aphrodite', 'Black Amber', 'Crimson Glo', 'Santa Rosa') and pluot ('Dapple Supreme', 'Flav Queen', 'Flav Supreme') cultivars. Each cultivar was grafted by chip-budding on GF 305 peach rootstocks and infected with the virulent PPV-Rec or ESFY phytoplasma strain also by chip-budding. After bud break, cultivar evaluation consisted in observing presence or absence of symptoms on leaves, noting the symptom intensity on leaves and on the whole plant. Plants were studied in controlled conditions in a sealed screen-house for three consecutive growth periods. DAS-ELISA and RFLP-PCR analyses were also employed to verify the presence or absence of PPV, respectively ESFY phytoplasma. Results obtained in the context of this very severe biological test against PPV and ESFY phytoplasma confirm the high level of susceptibility of Japanese plum and pluot cultivars.

Plasma technology, relatively new in the fields of biomedicine, agriculture, and ecology, is the subject of intensive research as a prospective means of decontamination of various microorganisms (bacteria, viruses, and fungi). The objectives of the present study were to follow the effect of cold atmospheric plasma (CAP) treatment on in vitro grown plum plants (Prunus domestica L. 'Kyustendilska sinya' cv.) and the possibility of eradicating or inactivating plum pox virus (PPV) causing Sharka disease by CAP. The source tree is naturally co-infected by PPV (both M and D strains). In the experiments, two different plasma sources were used. First, a surface-wave-sustained Argon plasma torch and second, an underwater diaphragm discharge. For the treatments, nodal segments (10 mm in length) from in vitro cultured plum plants with or without one leaf were prepared. Apical shoots from treated plants (PPV-positive and negative clones as well non-treated controls) were cultivated in vitro for four passages. Then they were rooted and acclimatized to ex vitro conditions, and their virus status was observed periodically for more than 3 years after treatment for the appearance of Sharka symptoms. All plants, acclimatized to ex vitro conditions, were tested for PPV by immune capture–reverse transcription–polymerase chain reaction (IC-RT-PCR). As a first step in understanding the plasma treatment of living plants, a plasma treatment variant causing no damage must be established; this has been done in our previous works. Treatment of plants by plasma with parameters that have been carefully selected leads to better development than the non-treated plants. In the treated in vitro plants, no significant differences were found in the number and length of shoots compared to the control plantlets. In ex vitro acclimated plants, greater stem length was reported, but no differences in leaf number were observed. No significant differences in growth were recorded between the control and plants that were treated twice or three times. At this stage, 3 years after ex vitro cultivation in a greenhouse, Sharka symptoms were not registered on treated in vitro negative PPV plants, and the virus was not detected by IC-RT-PCR. Very mild symptoms were showing in CAP-treated PPV-positive plants. Development of typical Sharka symptoms on non-treated controls were observed. [ABSTRACT FROM AUTHOR]

Introduction: Trans-grafting could be a strategy to transfer virus resistance from a transgenic rootstock to a wild type scion. However contradictory results have been obtained in herbaceous and woody plants. This work was intended to determine if the resistance to sharka could be transferred from transgenic plum rootstocks to wild-type apricot scions grafted onto them. Methods: To this end, we conducted grafting experiments of wild-type apricots onto plum plants transformed with a construction codifying a hairpin RNA designed to silence the PPV virus and studied if the resistance was transmitted from the rootstock to the scion. Results: Our data support that the RNA-silencing-based PPV resistance can be transmitted from PPV-resistant plum rootstocks to non-transgenic apricot scions and that its efficiency is augmented after successive growth cycles. PPV resistance conferred by the rootstocks was robust, already occurring within the same growing cycle and maintained in successive evaluation cycles. The RNA silencing mechanism reduces the relative accumulation of the virus progressively eliminating the virus from the wild type scions grafted on the transgenic resistant PPV plants. There was a preferential accumulation of the 24nt siRNAs in the scions grafted onto resistant rootstocks that was not found in the scions grafted on the susceptible rootstock. This matched with a significantly lower relative accumulation of hpRNA in the resistant rootstocks compared with the susceptible or the tolerant ones. Discussion: Using transgenic rootstocks should mitigate public concerns about transgenes dispersion and eating transgenic food and allow conferring virus resistance to recalcitrant to transformation cultivars or species. [ABSTRACT FROM AUTHOR]

IntroductionTrans-grafting could be a strategy to transfer virus resistance from a transgenic rootstock to a wild type scion. However contradictory results have been obtained in herbaceous and woody plants. This work was intended to determine if the resistance to sharka could be transferred from transgenic plum rootstocks to wild-type apricot scions grafted onto them.MethodsTo this end, we conducted grafting experiments of wild- type apricots onto plum plants transformed with a construction codifying a hairpin RNA designed to silence the PPV virus and studied if the resistance was transmitted from the rootstock to the scion.ResultsOur data support that the RNA-silencing-based PPV resistance can be transmitted from PPV-resistant plum rootstocks to non-transgenic apricot scions and that its efficiency is augmented after successive growth cycles. PPV resistance conferred by the rootstocks was robust, already occurring within the same growing cycle and maintained in successive evaluation cycles. The RNA silencing mechanism reduces the relative accumulation of the virus progressively eliminating the virus from the wild type scions grafted on the transgenic resistant PPV plants. There was a preferential accumulation of the 24nt siRNAs in the scions grafted onto resistant rootstocks that was not found in the scions grafted on the susceptible rootstock. This matched with a significantly lower relative accumulation of hpRNA in the resistant rootstocks compared with the susceptible or the tolerant ones.DiscussionUsing transgenic rootstocks should mitigate public concerns about transgenes dispersion and eating transgenic food and allow conferring virus resistance to recalcitrant to transformation cultivars or species.

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]

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]

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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.

Aim of study: To investigate the changes in chemical composition of fresh plum fruits cv. ‘Čačanska Lepotica’ prompted by the presence of various strains of plum pox virus (PPV). Area of study: Serbia Material and methods: In an experimental orchard of ‘Čačanska Lepotica’ plum cultivar, fruits were picked from virus-free and PPV-infected trees (PPV-D and PPV-Rec strains) in four harvest stages in 2017 and 2018. Fruits were further analyzed on total phenolics, flavonoids, anthocyanins, antioxidant capacity and selected phenolics. Main results: The results indicate that virus infection causes chemical changes to a certain extent, but mostly in initial harvest stages, while the values are equal in later stages. In the last harvest stage, as the most utilizable in commercial purposes, only chlorogenic acid content was affected in 2017, while in 2018 contents of neochlorogenic acid and chrysanthemin were altered by the PPV infection. Total contents of flavonoids and phenolics revealed no influence of virus infection during both 2017 and 2018, while PPV-Rec infected samples were richer in anthocyanins under heavy rainfall during summer months of 2018. Given the number of identified compounds (10) and the vast experimental data, it might be concluded that influence of PPV infection on chemical composition of ‘Čačanska Lepotica’ plum fruits was quite limited. Research highlights: Plum cultivar ‘Čačanska Lepotica’ should be considered as highly tolerant cultivar to PPV, and can be grown in heavily infected environment with no risk. Therefore, it might be a great replacement for sensitive plum cultivars, such as ‘Požegača’ and ‘Čačanska Rodna’.

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.

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. [ABSTRACT FROM AUTHOR]

Abstract Background In plants, host factors encoded by susceptibility (S) genes are indispensable for viral infection. Resistance is achieved through the impairment or the absence of those susceptibility factors. Many S genes have been cloned from model and crop species and a majority of them are coding for members of the eukaryotic translation initiation complex, mainly eIF4E, eIF4G and their isoforms. The aim of this study was to investigate the role of those translation initiation factors in susceptibility of stone fruit species to sharka, a viral disease due to Plum pox virus (PPV). Results For this purpose, hairpin-inducing silencing constructs based on Prunus persica orthologs were used to generate Prunus salicina (Japanese plum) 4E and 4G silenced plants by Agrobacterium tumefaciens-mediated transformation and challenged with PPV. While down-regulated eIFiso4E transgenic Japanese plums were not regenerated in our conditions, eIFiso4G11-, but not the eIFiso4G10-, silenced plants displayed durable and stable resistance to PPV. We also investigated the alteration of the si- and mi-RNA profiles in transgenic and wild-type Japanese plums upon PPV infection and confirmed that the newly generated small interfering (si) RNAs, which are derived from the engineered inverted repeat construct, are the major contributor of resistance to sharka. Conclusions Our results indicate that S gene function of the translation initiation complex isoform is conserved in Prunus species. We discuss the possibilities of using RNAi silencing or loss-of-function mutations of the different isoforms of proteins involved in this complex to breed for resistance to sharka in fruit trees.

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.

Evaluation of the presence and concentration of PPV (Plum pox virus) in selected rootstocks was carried out in 2016–2017. For the purpose of the experiment we used rootstocks derived from crossbreeding of Prunus davidiana (Carr.) Franch, such as Cadaman and Barrier, and also a P. davidiana seedling. Peach seedling rootstock GF‑305 was used as a control. The rootstocks were inoculated artificially with PPV strain M (Marcus). Both the rootstock and the inoculum were tested for presence of the virus by a serological method – semiquantitative DAS‑ELISA test and molecular methods – RT‑PCR, real‑time RT‑PCR and RT‑LAMP. During the growing season the plants were evaluated for symptom intensity by using a scoring scale. The results show interdependency between symptom intensity and the amount of PPV in leaves, with DAS‑ELISA test giving less positive samples than RT‑PCR. The RT‑LAMP and real‑time RT‑PCR methods were capable of revealing low concentrations of the virus even in symptom‑free plants. The lowest PPV concentrations of all the four rootstocks were detected by real‑time RT‑PCR in P. davidiana. The highest PPV concentrations were detected in Barrier rootstock. In inocula, the lowest concentration was found in the inocula on Cadaman rootstock, whereas the highest PPV concentration was detected in the inocula inoculated on Barrier rootstock.

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]

Plum pox virus (PPV) was detected in Argentina for the first time in 2004. After eradication of the initial outbreaks, establishment of quarantine areas and strict control of nursery stock plants, no evidence of disease spread was recorded. During spring 2018, symptoms, consisting of chlorotic rings, were observed on leaves of an ornamental plant of the Rosaceae family "Bridal Crown" (Spiraea sp.) in the garden of a house within the PPV quarantine area in San Rafael, Mendoza province. Symptomatic leaves were analyzed for PPV by DAS-ELISA with positive results. The presence of the virus was confirmed by conventional and qRT-PCR and the use of "GF-305" biological indicator plants inoculated by T-bud grafting with buds from the Spiraea. A 243 bp PCR fragment amplified from the Spiraea samples, and corresponding to the carboxy-terminal region of PPV coat protein gene was isolated, sequenced, and deposited in GenBank (MN587037). It showed 99% identity to other PPV isolates. RT-qPCR, confirmed the virus as being an isolate of the PPV D strain previously found in the quarantine areas. Our results confirm PPV natural infection on a new ornamental host, "Bridal Crown", which does not belong to the genus Prunus, warning of the potential danger of the species as a host of, and a source of, inoculum for PPV. [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. Highlights Plum pox virus (PPV) positive trees were detected by DAS-ELISA showing an increasing number of diseased plants overtime in a European plum cv D’agen plot in Rama Caída, Mendoza, Argentina during five years. The incidence of overtime was higher at the beginning of the study instead of the following years, indicating that the PPV epidemic was at a very early stage. The spatial point pattern of PPV at the plot was characterized by some heterogeneous clusters of infected trees observed from initial focus (within the row) up to 65 m in the west-east direction of the rows. Heterogeneous aggregated spatial associations of PPV occurred close in space and time, which was confirmed by autocorrelation spatial analysis with Ripley's K function and Join-count. An aggregated point pattern of PPV had a positive correlation between the infected tree and the distance between each one showing a disease aggregation in both directions W-E and S-N, across the plot.

Resistance to Plum pox virus (PPV) in transgenic Prunus domestica L., clone C5 (cv. HoneySweet) was evaluated in a regulated field in the Czech Republic for fifteen years (2002-2016). PPV mild symptoms appeared in C5 trees only in several leaves situated close to the point of inoculum grafting up to 2010. No symptoms of PPV were observed in the years 2011-2013 and results of ELISA and RT-PCR detection tests were negative. In the twelfth year (2013), there was a severe unusual natural attack of plum trees by Monilinia sp. This Monilinia sp. attack occurred only one time - in 2013. There was no Monilinia sp. infection in 2002-2012 and in 2014-2016. Mild PPV symptoms reappeared in several leaves of transgenic plum trees in the next two years (2014-2015) and the presence of PPV was proved by DAS-ELISA and confirmed by RT-PCR.

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]

Plum pox virus (PPV) strain D is globally distributed and causes serious losses in stone fruits in over 40 countries. Here, full‐length genomic sequences were analysed for 44 PPV‐D isolates from all regions of Turkey, together with partial sequences for a larger number of isolates. PPV‐D isolates from Turkey are similar to other PPV‐D isolates in all major genomic features. However, the majority of Turkish PPV‐D isolates form separate phylogenetic clusters from all other isolates and show a geographical clustering tendency, suggestive of limited movement between regions. In particular, PPV‐D isolates from Thrace and Central Anatolia formed a monophyletic sister cluster to the cluster that includes all previously known PPV‐D isolates. Two isolates with strong evidence of recombination with the PPV‐T strain were identified, together with two isolates with weaker evidence for intra‐D strain recombination. The genetic diversity of PPV‐D was found to be particularly high in Turkey (0.017 ± 0.001%), close to that observed for PPV‐D world diversity once the over‐represented isolates from Japan, the USA and Canada have been excluded (0.020 ± 0.001%). Taken together, these results suggest a long and largely isolated evolutionary history of PPV‐D in Turkey and further extend knowledge of the diversity of this highly successful strain. The high diversity of PPV‐D in Turkey, together with the basal phylogenetic position of Turkish isolates, are compatible with a hypothesis making Turkey the centre of origin of the D strain. [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]

Plum pox virus (PPV) causes sharka — the most serious viral disease of stone fruit trees. PPV is wide spread in Europe and Mediterranean Basin, its incidence has been further approved in Asia and both Americas. Nine PPV strains have been recognized until now (PPV-D, PPV-M, PPV-Rec, PPV-EA, PPV-C, PPV-T, PPV-W, PPV-CR, and PPV-An), forming molecularly distinct entities, however, only partially differentiable by their biological or epidemiological properties. The most strict virus-host linkages under natural conditions have been detected for strains naturally infecting cherries (PPV-C and PPV-CR). However, although less stringent but still clear host preference is observed also for three epidemiologically most important strains (PPV-D/plum/apricot, PPV-M/peach, and PPV-Rec/plum). So far no genetic marker has been mapped in the PPV genome, which responsibility for the host specificity/preference could be explicitly demonstrated. In this review, we focus on the host preference of three major PPV strains as evidenced by analysis of an extensive dataset of PPV isolates of Slovak and world-wide origin. Together, we discuss several performed relevant experiments and further possible research procedures aimed to better understand the genetic determinants and mechanisms of the host preference of this potyvirus.

Research on the resistance to frost, susceptibility to sharka, flowering biology, fruit setting, yield, and ploidy levels of 36 Japanese plum cultivars (mostly hybrids of Prunus salicina with Prunus cerasifera) were carried out in 2015–2020 at the Experimental Orchard located in Dąbrowice near Skierniewice. Relatively mild winters with sporadic temperature drops to nearly −21 °C in January of 2017 and 2018 caused slight damage to several cultivars of Japanese plum insufficiently resistant to frost. The trees of most cultivars remained healthy, with no signs of damage. ‘Barkhatnaya’ and ‘Tatyana’ cultivars turned out to be very susceptible to sharka. ‘Herkules’ trees were the most vigorous. ‘Barkhatnaja’, ‘Blue Gigant’, ‘Shater’, and ‘Tatyana’ trees were characterized by weak growth. The trees of Japanese plum started flowering early, usually in the first or second decade of April. Most of the cultivars belonged to early season cultivars, the fruits of which ripened in July. Based on the assessment of tree productivity, ‘Barkhatnaya’, ‘Inese’, ‘Shater’, ‘Tatyana’, and ‘Vanier’ are the best for growing in the climate of Central Europe. ‘Tsernushka’, ‘Chuk’, ‘Dofi Sandra’, ‘Early Golden’, ‘Ewierch Rannyj’, ‘Yevraziya’, ‘Gek’, ‘General’, ‘Kometa’, ‘Kometa Late’, ‘Maschenka’, and ‘Naidyona’ trees also yielded well. ‘Blue Gigant’, ‘Black Amber’, and ‘Herkules’ had the largest fruits, and ‘Chuk’ and ‘Inese’ cultivars produced the smallest fruits. Among the assessed Japanese plum cultivars, those with round fruit, dark skin with various shades of purple, yellow flesh, and A cytometric analysis showed that almost all cultivars are diploid, except for ‘Herkules’ (possibly pentaploid) and ‘Yevraziya’ (possibly hexaploid or aneuploid).

Epidemiological models are increasingly used to predict epidemics and improve management strategies. However, they rarely consider landscape characteristics although such characteristics can influence the epidemic dynamics and, thus, the effectiveness of disease management strategies. Here, we present a generic in silico approach which assesses the influence of landscape aggregation on the costs associated with an epidemic and on improved management strategies. We apply this approach to sharka, one of the most damaging diseases of Primus trees, for which a management strategy is already applied in France. Epidemic simulations were carried out with a spatiotemporal stochastic model under various management strategies in landscapes differing in patch aggregation. Using sensitivity analyses, we highlight the impact of management parameters on the economic output of the model. We also show that the sensitivity analysis can be exploited to identify several strategies that are, according to the model, more profitable than the current French strategy. Some of these strategies are specific to a given aggregation level, which shows that management strategies should generally be tailored to each specific landscape. However, we also identified a strategy that is efficient for all levels of landscape aggregation. This one-size-fits-all strategy has important practical implications because of its simple applicability at a large scale. [ABSTRACT FROM AUTHOR]

Sharka (PPV) is one of the most dangerous viruses in fruit growing. More and more fruit growers are unsatisfied with the resistances or tolerance of plum varieties cultivated today. With the utilisation of the hypersensitive reaction to PPV in breeding we developed 'Jojo' as the first absolutely resistant cultivar in the field. Most interesting now is the development of new sharka-resistant cultivars, especially in three points: extension of ripening range, better fruit size, and high fruit quality. In a new breeding programme, we obtained many hypersensitive clones. After testing in different regions, some interesting resistant clones and cultivars were selected and are presented here. [ABSTRACT FROM AUTHOR]

Highlights • Irano-Caucasian apricots are not a source for PPV resistance. • Four new accessions possessing the PPVres loci were identified as resistant to PPV. • Two additional resistant accessions did not carry any of the PPVres resistance markers. • The molecular markers targeting the PPVres locus are not fully reliable. • PPV resistance in apricot is not probably strain-specific. Abstract Plum pox virus (PPV) is an important threat to apricot (Prunus armeniaca) production globally, including in Turkey and Iran, the world's leading producers of dried apricots. Although most apricot cultivars are susceptible and host resistance is the most promising approach to managing the disease. A few cultivars carrying the resistance locus PPVres have been used in breeding programs. Additional sources of resistance are highly desirable. The PPV susceptibility of cultivars in the Irano-Caucasian eco-geographical group, considered a secondary center of apricot diversity, has been little studied. We surveyed the response of 227 apricot accessions to PPV strain 'Turkey' (PPV-T) and, in parallel, scored molecular markers linked to PPVres. Four accessions ('Cebir', 'Lifos', 'Karum', and 'Zard') were identified as resistant to PPV-T and carried molecular markers for PPVres. Two additional accessions ('Kaniş', and Italian Cultivar 'Fracasso') were resistant but did not carry any of the PPVres resistance markers, indicating possible new sources of resistance. Their novelty was also supported by previously published molecular diversity analyses. The new resistance sources will be particularly useful for breeding new cultivars of apricot for drying. The marker ZP002 is more reliable and easy to use in selecting for the resistance allele at the PPVres locus. PPV resistance in apricot is not likely strain-specific. [ABSTRACT FROM AUTHOR]

Very limited information is available on the origin, diversity and evolution of Plum pox virus (PPV) 'Turkey' (T) strain. Phylogenetic analyses based on partial sequences of 421 isolates and complete genome sequences of 57 isolates, representing the geographical distribution of PPV‐T in Turkey, revealed the existence of several monophyletic and, in some cases, geographically limited groups within the PPV‐T strain (Ankara‐Konya1‐Kayseri, Ankara‐Balkan, Istanbul, Konya2 and Balkan). PPV‐T diversity (0.018%) was found to be greater than that of PPV strains D and Rec but lower than that of the M strain when including the newly described and divergent M‐Istanbul isolates, suggesting a long evolutionary history for PPV‐T. The European part of Turkey in the Balkans, close to Bulgaria where PPV was identified for the first time, appears as a likely centre of origin for PPV‐T isolates. The colonization of various parts of Turkey by diverse isolates from that region, followed by secondary local spread, is the most likely scenario for the diffusion of PPV‐T in Turkey. [ABSTRACT FROM AUTHOR]

Highlights • Plum genes associated with plant response to PPV infection have been identified. • Some genes were selected for further studies of plum defence reactions. • Some of genes are proposed as candidates for sharka resistance markers. Abstract The aim of the study was to identify plum genes which are associated with plant hypersensitive response to Sharka caused by Plum pox virus (PPV) and to explain the molecular mechanism of hypersensitive reaction (HR) in response to PPV infection in selected genotypes of plum and search for molecular markers related of hypersensitivity. To identify candidate genes whose expression is modified during PPV infection, cDNA-AFLP technique was used. The analyses were done using pools of RNA isolated from hypersensitive and sensitive plants, both healthy and infected. Products of selective amplification showing differential expression in PPV-infected and non-infected plants were re-amplified and sequenced. Analysis using Basic Local Alignment Search Tool (BLAST) revealed their homology to genes encoding proteins involved in defence and host-pathogen interaction, cellular stress, signal perception and transduction, transmembrane transport, regulation of transcription and translation and various enzymes involved in other metabolic pathways. Especially interesting for their potential function in plant defence reactions are genes which were overexpressed in infected plants, both hypersensitive and susceptible. Some of them are proposed as potential molecular markers of hypersensitive reaction to PPV infection, useful in early selection of hypersensitive genotypes in plum breeding. [ABSTRACT FROM AUTHOR]

Highlights • Plum Pox Virus affects stone fruit trees and causes severe economic damages. • The PPV biosensor is based on a Electrolyte-Gated Organic Field-Effect Transistor. • Sensitivity and dynamic range are comparable to those of commercially available platforms. Abstract Plum Pox Virus (PPV) is the pathogen responsible for Sharka, a highly infectious disease affecting stone fruit trees and causing severe economic damages, which can be only contained through early-detection and frequent monitoring. We propose a bioelectronic PPV biosensor, based on a electrolyte-gated organic field-effect transistor (EGOFET), for the specific detection of PPV in plant extracts with a sub ng/ml detection limit. The sensing unit of the biosensor is based on anti-PPV antibodies, uniformly oriented on the gold gate electrode by using a sub-monolayer of Protein G. The sensitivity and dynamic range of the EGOFET-based biosensor are comparable to those of commercially available platforms for detection of plant pathogens. This novel electronic immunosensor is compatible with low-cost fabrication procedures and can be easily reconfigured into a fully portable device to be operated in greenhouse and in the field orchards. [ABSTRACT FROM AUTHOR]

Evaluation of the presence and concentration of PPV (Plum pox virus) in selected rootstocks was carried out in 2016 - 2017. For the purpose of the experiment we used rootstocks derived from crossbreeding of Prunus davidiana (Carr.) Franch, such as Cadaman and Barrier, and also a P. davidiana seedling. Peach seedling rootstock GF-305 was used as a control. The rootstocks were inoculated artificially with PPV strain M (Marcus). Both the rootstock and the inoculum were tested for presence of the virus by a serological method - semiquantitative DAS-ELISA test and molecular methods - RT-PCR, real-time RT-PCR and RT-LAMP. During the growing season the plants were evaluated for symptom intensity by using a scoring scale. The results show interdependency between symptom intensity and the amount of PPV in leaves, with DAS-ELISA test giving less positive samples than RT-PCR. The RT-LAMP and real-time RT-PCR methods were capable of revealing low concentrations of the virus even in symptom-free plants. The lowest PPV concentrations of all the four rootstocks were detected by real-time RT-PCR in P. davidiana. The highest PPV concentrations were detected in Barrier rootstock. In inocula, the lowest concentration was found in the inocula on Cadaman rootstock, whereas the highest PPV concentration was detected in the inocula inoculated on Barrier rootstock. [ABSTRACT FROM AUTHOR]

Apricot (Prunus sp.) is an important fruit crop worldwide. Despite recent advances in apricot research, much is still to be done to improve its productivity and environmental adaptability. The availability of wild apricot germplasms with economically interesting traits is a strong incentive to increase research panels toward improving its economic, environmental and nutritional characteristics. New technologies and genomic studies have generated a large amount of raw data that the mining and exploitation can help decrypt the biology of apricot and enhance its agronomic values. Here, we outline recent findings in relation to apricot production, pomological and nutraceutical properties. In particular, we retrace its origin from central Asia and the path it took to attain Europe and other production areas around the Mediterranean basin while locating it in the rosaceae family and referring to its genetic diversities and new attempts of classification. The production, nutritional, and nutraceutical importance of apricot are recapped in an easy readable and comparable way. We also highlight and discuss the effects of late frost damages on apricot production over different growth stages, from swollen buds to green fruits formation. Issues related to the length of production season and biotic and abiotic environmental challenges are also discussed with future perspective on how to lengthen the production season without compromising the fruit quality and productivity. [ABSTRACT FROM AUTHOR]

Two hyperspectral remote sensing techniques, spectral reflectance and chlorophyll fluorescence, were used for the identification of biotic stress (sharka disease) in plum trees at an early stage without visible symptoms on the leaves. The research was focused on cultivars that are widely spread in Bulgaria: ‘Angelina’, ‘Black Diamond’ and ‘Mirabelle’. Hyperspectral reflectance and fluorescence data were collected by means of a portable multichannel fibre-optics spectrometer in the visible and near infrared spectral ranges (400-1000 nm). Statistical and deterministic analyses were applied for assessing the significance of the differences between the spectral data of healthy (control) and infected plum leaves. Comparative analyses were performed with complementary serological test DAS-ELISA, broadly implemented in plant virology. The strong relationship that was found between the results from the two remote sensing techniques and serological analysis indicates the applicability of hyperspectral reflectance and fluorescence techniques for conducting health condition assessments of vegetation easily and without damage before the appearance of visible symptoms.

Phosphorylation and O-GlcNAcylation are widespread post-translational modifications (PTMs), often sharing protein targets. Numerous studies have reported the phosphorylation of plant viral proteins. In plants, research on O-GlcNAcylation lags behind that of other eukaryotes, and information about O-GlcNAcylated plant viral proteins is extremely scarce. The potyvirus Plum pox virus (PPV) causes sharka disease in Prunus trees and also infects a wide range of experimental hosts. Capsid protein (CP) from virions of PPV-R isolate purified from herbaceous plants can be extensively modified by O-GlcNAcylation and phosphorylation. In this study, a combination of proteomics and biochemical approaches was employed to broaden knowledge of PPV CP PTMs. CP proved to be modified regardless of whether or not it was assembled into mature particles. PTMs of CP occurred in the natural host Prunus persica, similarly to what happens in herbaceous plants. Additionally, we observed that O-GlcNAcylation and phosphorylation were general features of different PPV strains, suggesting that these modifications contribute to general strategies deployed during plant-virus interactions. Interestingly, phosphorylation at a casein kinase II motif conserved among potyviral CPs exhibited strain specificity in PPV; however, it did not display the critical role attributed to the same modification in the CP of another potyvirus, Potato virus A.

Accurate assembly of viral particles in the potyvirus Plum pox virus (PPV) has been shown to depend on the contribution of the multifunctional viral protein HCPro. In this study, we show that other viral factors, in addition to the capsid protein (CP) and HCPro, are necessary for the formation of stable PPV virions. The CP produced in Nicotiana benthamiana leaves from a subviral RNA termed LONG, which expresses a truncated polyprotein that lacks P1 and HCPro, together with HCPro supplied in trans, was assembled into virus-like particles and remained stable after in vitro incubation. In contrast, deletions in multiple regions of the LONG coding sequence prevented the CP stabilization mediated by HCPro. In particular, we demonstrated that the first 178 amino acids of P3, but not a specific nucleotide sequence coding for them, are required for CP stability and proper assembly of PPV particles. Using a sequential coagroinfiltration assay, we observed that the subviral LONG RNA replicates and locally spreads in N. benthamiana leaves expressing an RNA silencing suppressor. The analysis of the effect of both point and deletion mutations affecting RNA replication in LONG and full-length PPV demonstrated that this process is essential for the assembly of stable viral particles. Interestingly, in spite of this requirement, the CP produced by a nonreplicating viral RNA can be stably assembled into virions as long as it is coexpressed with a replication-proficient RNA. Altogether, these results highlight the importance of coupling encapsidation to other viral processes to secure a successful infection. IMPORTANCE Viruses of the family Potyviridae are among the most dangerous threats for basically every important crop and such socioeconomical relevance has made them a subject of many research studies. In spite of this, very little is currently known about proteins and processes controlling viral genome encapsidation by the coat protein. In the case of Plum pox virus (genus Potyvirus), for instance, we have previously shown that the multitasking viral factor HCPro plays a role in the production of stable virions. Here, by using this potyvirus as a model, we move further to show that additional factors are also necessary for the efficient production of potyviral particles. More importantly, a comprehensive screening for such factors led us to the identification of a functional link between virus replication and packaging, unraveling a previously unknown connection of these two key events of the potyviral infection cycle. [ABSTRACT FROM AUTHOR]

This study was conducted in stone fruit trees in Antalya region in 2008-2011. In this respect, a survey was accomplished in stone fruit trees (apricot, plum, peach, cherry and nectarine) cultivated in Antalya city center, Aksu, Serik, Alanya, Manavgat, Gazipaşa, Korkuteli, Elmalı, Finike and Kaş districts to evaluate the situation of Plum pox potyvirus, the agent of sharka disease. Samplings were conducted in both orchards and individual stone fruit trees. In the study, a total of 426 leaf samples were tested by double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) serologic method. As a result of serologic tests, samples of nectarine trees obtained from a garden were only positive and these samples were sent to Ankara Plant Protection Central Research institute’s virology laboratory for verification by polymerase chain reaction (PCR). Positive samples by PCR tests were considered as PPV-infected.

BACKGROUND Plum pox virus ( PPV) causes severe economic losses in stone fruit production, but little is known about its effect on plum fruit composition. In this study, the influence of PPV on sugars and organic acids was evaluated in a susceptible plum ( Prunus domestica L.) cultivar. RESULTS PPV infection significantly affected the content and composition of sugars and organic acids. The composition of necrotic tissue was modified the most. A short-time infected tree yielded fruit with similar sugar composition to fruit from a healthy tree, but the decline of organic acids was faster. Prematurely ripened symptomatic fruit had reduced fruit weight and low sugar content. CONCLUSION Infected trees of the studied cultivar produce fruit of inferior quality. Fruits are not suitable for processing, especially when most of them exhibit visual symptoms of PPV infection. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Aim. During the spring of 2016 in three locations of Central Ukraine - Cherkasy, Kyiv and Yahotyn, we found plum and pear trees displaying foliar symptoms similar to those causing by an important quarantine pathogen Plum pox virus (PPV), and cherry trees showing symptoms typical for Apple mosaic virus (ApMV) - one of the most widespread viruses which can infect over 65 plants species of Rosaceae family. The aim of this study was to perform detection, identification and molecular analysis of viruses causing diseases symptoms found by us on fruit trees in Central Ukraine. Меthods. Total RNA extracted from leaves of infected and healthy plants was used to generate cDNA with known PCR primers as well as with own primers designed by «Primer3» software. The amplified DNAs of Cp gene fragments of ukrainian PPV isolates were sequenced by Sanger dideoxy sequencing method and were compared with those available in GeneBank. The comparison and molecular analysis of virus isolates were performed using BLAST, MultAline and MEGA 6 softwares, and a set of own a simple computer programs (utilities), tightly specialized for the solution of a narrow objectives of sequence analysis. Results. The primers have been developed for Plum pox virus detection proved to be effective for revealing and molecular diagnostic of PPV in three regions of the Central Ukraine. Using these primers three PPV-D isolates, named seq1, seq2, seq3, have been selected from pears in Cherkasy (seq1) and from plums in Yahotyn (seq2) and Kyiv (seq3). According to sequence comparison of 181-base Cp gene fragments, the plum isolates seq2 and seq3 turned out to be identical among themselves and have 95.6% sequence identity to pear isolate (seq1). Ukrainian isolates obtained have shown high identity (95 - 99.4%) with all of 33 PPV-D isolates from different countries and host plants tested in our study. The 181-base sequences of these isolates contain 30 nucleotide replacements concerning seq1 sequence. The vast majority of replacements (27 of 30) are synonymous and do not cause of amino acid substitutions in the viral coat proteins. PPV-D isolates form 6 groups of members with identical nucleotide replacements, which remind Vavilov's homologous series of heritable variation of morphological traits. Conclusion. The primers have been developed were successfully used for detection of PPV-D isolates from pear and plum trees in three regions of Central Ukraine. It is the first time the PPV has been reported in Cherkasy. Our studies provide information about spreading PPV isolates, that can be valuable in understanding the epidemiological role of this virus. Groups of identical nucleotide replacements, revealed by us in Cp gene sequence fragments of different PPV isolates, remind Vavilov's homologous series of heritable morphological traits, and are of interest for clarification of the molecular basis of hereditary variation and parallel mutations. [ABSTRACT FROM AUTHOR]

RNA silencing is a powerful technology for molecular characterization of gene functions in plants. A commonly used approach to the induction of RNA silencing is through genetic transformation. A potent alternative is to use a modified viral vector for virus-induced gene silencing (VIGS) to degrade RNA molecules sharing similar nucleotide sequence. Unfortunately, genomic studies in many allogamous woody perennials such as peach are severely hindered because they have a long juvenile period and are recalcitrant to genetic transformation. Here, we report the development of a viral vector derived from Prunus necrotic ringspot virus (PNRSV), a widespread fruit tree virus that is endemic in all Prunus fruit production countries and regions in the world. We show that the modified PNRSV vector, harbouring the sense-orientated target gene sequence of 100-200 bp in length in genomic RNA3, could efficiently trigger the silencing of a transgene or an endogenous gene in the model plant Nicotiana benthamiana. We further demonstrate that the PNRSV-based vector could be manipulated to silence endogenous genes in peach such as eukaryotic translation initiation factor 4E isoform ( eIF(iso)4E), a host factor of many potyviruses including Plum pox virus (PPV). Moreover, the eIF(iso)4E-knocked down peach plants were resistant to PPV. This work opens a potential avenue for the control of virus diseases in perennial trees via viral vector-mediated silencing of host factors, and the PNRSV vector may serve as a powerful molecular tool for functional genomic studies of Prunus fruit trees. [ABSTRACT FROM AUTHOR]

• ACLSV corroborated to be a very complex virus for works in artificial conditions. • We have obtained new apricots showing combined resistance to ACLSV and PPV. • There no interaction between both viruses, establishing independently. Spain is one of the most important producers of fresh apricots (Prunus armeniaca L.). Traditional production was based on several local cultivars with good quality and well adapted to the industry. However, most are susceptible to important viral diseases that affect fruit production and quality. The main viral diseases are sharka (Plum pox virus , PPV) and viruela (Apple chlorotic leaf spot virus , ACLSV). Using foreign resistance sources to PPV, new resistant cultivars have been released. More recently, two new resistance sources to ACLSV have been identified: the Spanish cultivar 'Mauricio' and the French cultivar 'Bergeron'. With the objective of obtaining new genotypes resistant to both diseases simultaneously, two crosses between the apricot selections '5–26' and '11–1' from CEBAS-CSIC (resistant to PPV) and ACLSV-resistant cultivars 'Mauricio' and 'Bergeron' were achieved, and the descendants were evaluated for resistance to these diseases. Molecular markers were also used to evaluate the genitors and descendants. Results showed that 100% and 75% of seedlings were resistant to PPV and ACLSV, respectively, and 70% were resistant to both diseases simultaneously. In general, no interaction between both viruses was detected, infecting the plant independently. For the first time, apricot plants resistant to PPV and ACLSV simultaneously have been obtained. [ABSTRACT FROM AUTHOR]

Susceptibility of plum cultivars: 'Katinka', 'Jubileum', 'Diana', 'Valjevka', 'Żółta Afaska', 'Elena', 'Jojo', 'President', 'Vision', and 'Węgierka Zwykła' (Pozegaca type, included as reference, highly susceptible cultivar) to aphid-vectored Plum pox virus (strain D), was evaluated. The trees were grown for 7-8 years in the field characterized with high infection pressure. 'Katinka' and 'President' showed susceptibility even higher than 'Węgierka Zwykła'. 'Vision' and 'Valjevka' showed relatively low susceptibility with less than 30% of trees becoming infected. All 'Jojo' trees remained free from ELISA-detectable amounts of PPV, although a high percentage of the fruit of this cultivar showed sharka-like symptoms on stones and fruit flesh. The reason for that phenomenon is not known.

Resistance to Plum pox virus (PPV) in transgenic Prunus domestica L., clone C5 (cv. HoneySweet) was evaluated in a regulated field in the Czech Republic for fifteen years (2002-2016). PPV mild symptoms appeared in C5 trees only in several leaves situated close to the point of inoculum grafting up to 2010. No symptoms of PPV were observed in the years 2011-2013 and results of ELISA and RT-PCR detection tests were negative. In the twelfth year (2013), there was a severe unusual natural attack of plum trees by Monilinia sp. This Monilinia sp. attack occurred only one time - in 2013. There was no Monilinia sp. infection in 2002-2012 and in 2014-2016. Mild PPV symptoms reappeared in several leaves of transgenic plum trees in the next two years (2014-2015) and the presence of PPV was proved by DAS-ELISA and confirmed by RT-PCR. [ABSTRACT FROM AUTHOR]

Members the Potyviridae family belong to a group of plant viruses that are causing devastating plant diseases with a significant impact on agronomy and economics. Plum pox virus (PPV), as a causative agent of sharka disease, is widely discussed. The understanding of the molecular biology of potyviruses including PPV and the function of individual proteins as products of genome expression are quite necessary for the proposal the new antiviral strategies. This review brings to view the members of Potyviridae family with respect to plum pox virus. The genome of potyviruses is discussed with respect to protein products of its expression and their function. Plum pox virus distribution, genome organization, transmission and biochemical changes in infected plants are introduced. In addition, techniques used in PPV detection are accentuated and discussed, especially with respect to new modern techniques of nucleic acids isolation, based on the nanotechnological approach. Finally, perspectives on the future of possibilities for nanotechnology application in PPV determination/identification are outlined.