Plum Pox Research Articles

Where biotic and abiotic stress responses converge: Common patterns in response to salinity and Plum pox virus infection in pea and peach plants

AbstractHerbaceous 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.

Plum pox virus infection level in Prunus species growing along roadsides or in backyards in Vojvodina province

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 Becej, 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.

Značaj i simptomatologija virusa šarke šljive

The plum pox virus was discovered in Bulgaria between 1915 and 1918, hence the name "plum pox". Despite strict quarantine measures, as early as 1980s, this virus was widespread in whole Europe, but its presence was also confirmed in South and North America, Africa and Asia. The only continent where the infection with this virus has not been described yet is Australia. The presence of strains PPV-D, PPV-M and PPV-Rec has been confirmed in Serbia. The PPV-M strain spreads very quickly naturally, and it is considered as very dangerous for stone fruit trees. Trees infected with the plum pox virus do not decay, but bear fruit of poorer quality. Poorer quality of fruits reduces their market value, which leads to significant economic damage.

REAL TIME PCR METHOD FOR PPV DIAGNOSTIC ON PLUMS AND APRICOT IN THE REPUBLIC OF NORTH MACEDONIA

Real-time PCR (Polymerase Chain Reaction) or qPCR is a method by which the amount of the PCR product can be determined in real-time, and is very useful for investigating gene expression. The main advantages of qPCR are that it provides fast and high-throughput detection and quantification of target DNA sequences in different matrices. The lower time of amplification is facilitated by the simultaneous amplification and visualization of newly formed DNA amplicons. The development and application of molecular methods for the detection of pathogens has significantly changed the diagnosis and control of plant diseases, various environmental samples, including hosts tissues, soil, water and air. With real time PCR method, it is possible not only to identify and detect the presence or absence of the target pathogen, but it is also possible to quantify the amount present in the sample allowing the quantitative assessment of the number of the pathogen in the sample. Detection and accurate identification of plant pathogens is one of the most important strategies for controlling plant diseases to initiate preventive or curative measures. Plum pox virus (PPV), the agent of Sharka, is the most devastating virus infecting stone fruits. The PPV control is mainly based on prevention, and its quick and reliable detection is considered crucial in this strategy. In this study DAS-ELISA and real-time PCR were compared for evaluating their potentialities and limits for large scale surveys. Plum hosts (Prunus domestica) and apricot samples (Prunus armeniaca) from several different place are included for laboratory test analyzes, plant organs (phloem, buds, flowers, leaves and fruits) and parts of them, different periods of the year (spring, summer and winter period 2017/20), the presence or absence of symptoms were considered for comparison. Using DAS-ELISA tests, and use a universal set of antibodies (BIOREBA), has proved the presence of virus of Plum pox in all examined samples, especially from samples collected in summer, but also in checking virus status in winter and early spring season. Testing found high concentrations of viral antigens in plant samples (OD 2.912-2.752, for 30 min / 405 nm). Real time PCR show amplification plot for positive PPV samples on plums and apricot.

Defining the \u2018HoneySweet\u2019 insertion event utilizing NextGen sequencing and a de novo genome assembly of plum (Prunus domestica)

‘HoneySweet’ plum (Prunus domestica) is resistant to Plum pox potyvirus, through an RNAi-triggered mechanism. Determining the precise nature of the transgene insertion event has been complicated due to the hexaploid genome of plum. DNA blots previously indicated an unintended hairpin arrangement of the Plum pox potyvirus coat protein gene as well as a multicopy insertion event. To confirm the transgene arrangement of the insertion event, ‘HoneySweet’ DNA was subjected to whole genome sequencing using Illumina short-read technology. Results indicated two different insertion events, one containing seven partial copies flanked by putative plum DNA sequence and a second with the predicted inverted repeat of the coat protein gene driven by a double 35S promoter on each side, flanked by plum DNA. To determine the locations of the two transgene insertions, a phased plum genome assembly was developed from the commercial plum ‘Improved French’. A subset of the scaffolds (2447) that were >10 kb in length and representing, >95% of the genome were annotated and used for alignment against the ‘HoneySweet’ transgene reads. Four of eight matching scaffolds spanned both insertion sites ranging from 157,704 to 654,883 bp apart, however we were unable to identify which scaffold(s) represented the actual location of the insertion sites due to potential sequence differences between the two plum cultivars. Regardless, there was no evidence of any gene(s) being interrupted as a result of the insertions. Furthermore, RNA-seq data verified that the insertions created no new transcriptional units and no dramatic expression changes of neighboring genes.

Zdravstvena selekcija višnje Maraske (Prunus cerasus var. Marasca) u najvećoj Hrvatskoj plantaži “Vlačine”

Sour cherry cv. Marasca is considered a native Croatian variety with the best fruit quality in the Northern Dalmatia region. The current production is not sufficient to cover the demand, therefore new orchards should be established with pathogen-tested planting material. To select virus- and bacteria-free mother trees, a survey was conducted in the largest Croatian Marasca plantation "Vlačine". ELISA on 205 trees (51 elite, 103 average, 51 below average) confirmed the presence of prunus necrotic ringspot virus (PNRSV) on 101 trees (49.3%); petunia asteroid mosaic virus (PeAMV) and prune dwarf virus (PDV) on 10 trees each (4.9%); raspberry ringspot virus (RpRSV) on 7 trees (3.4%); cherry leafroll virus (CLRV), arabis mosaic virus (ArMV) and plum pox virus (PPV) on 3 trees each (1.5%); and apple mosaic virus (ApMV) on 1 tree (0.5%). For PNRSV, significant ELISA detection sensitivity was found, with twigs in dormant period as more reliable virus source compared to leaves during the growing season. In addition, six trees were positive on little cherry virus 2 (LChV-2) by RT-PCR. Along with very frequent latent infections, following symptoms were observed during pre-harvest period: yellow spots on leaves (ApMV); yellowing, stunted growth, leafless twigs with leaves only at the tip (PDV), bark splitting (PeAMV), reduced leaf size (RpRSV), chlorotic/necrotic ring spots (PNRSV), and uneven fruit ripening (LChV-2). Eleven trees were free of all viruses and bacteria defined by EPPO cherry certification scheme, including PPV. The selected virus- and bacteria-free elite trees represent a valuable genetic source for propagation and further clonal selection.

Determination and partial molecular characterization of Plum pox virus in Bolu province

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.

Comparison of Nanopore Sequencing Protocols and Real-Time Analysis for Phytopathogen Diagnostics

Next-generation sequencing technologies have aided molecular detection and diagnosis of plant pathogens. Short read sequencing technologies can be expensive, time consuming, and lack portability. The Oxford Nanopore Technologies (ONT) MinION sequencer offers plant diagnosticians an alternative for whole-genome and transcriptome sequencing with the advantages of portability, rapid results and access to sequences generated, and relatively low cost. Although this company offers multiple sequencing products, most previous articles focused on comparing this technology with other sequencing technology (Sanger, Illumina) and not comparing ONT product performance. In this project, we explored the potential of using ONT’s kits without modifications for the sequencing of plant pathogens. We compared the performance of DNA library preparation protocols (1D versus 1D2 versus Rapid) and RNA library preparation protocols (cDNA PCR Sequencing versus Direct RNA) on the MinION sequencer and examined different data analysis approaches for two well-characterized plant pathogens of agricultural concern, Ralstonia solanacearum and plum pox virus. For bacterial DNA sequencing, the Rapid Sequencing kit had the lowest throughput but offered the shortest sample-to-sequence turnaround time. The cDNA PCR Sequencing kit was better suited for plant RNA viruses than the Direct RNA. Whole-genome assemblies using all tested kits provided accurate identification of the target pathogen when pure cultures or infected plant material was used. This technology offers a shorter sample-to-sequence timeline than previous technologies for both DNA and RNA samples. Data analysis can still be time- and resource-consuming, but we found that 1 h of data generation was sufficient for accurate identification of the target pathogens, which can alleviate computing resources because a full 48-h run of sequencing data is not required. With the decreasing costs of flow cells, MinION is now an additional tool to be considered by plant diagnosticians for whole-genome and transcriptome-based diagnostics.

First Report of Plum Pox Virus on Plum in Uzbekistan

Apricot, sweet cherry, plum, and peach are economically important stone fruit crops in Uzbekistan. Plum pox virus from the genus Potyvirus in the family Potyviridae is the causal agent of sharka disease. Plum pox virus (PPV) is the most destructive viral pathogen of stone fruit trees. No information is available on PPV occurrence in Uzbekistan. In 2019, plum (Prunus domestica) trees exhibiting foliar pale green rings and spots were observed in a 21-year-old orchard of the local cultivar ‘Ispanskiy’ in the Tashkent region of Uzbekistan. One symptomatic leaf was taken from each of four trees growing at the corners of this orchard. The samples were tested for PPV by double antibody sandwich ELISA using reagent set SRA 31505/0500 (Agdia, U.S.A.) and immunocapture RT-PCR using the coating antibody CAB 31505/0500 (Agdia) and PPV-specific P1/P2 primers (Wetzel et al. 1992). PPV was readily detected in each sample by both methods. PCR products of the expected size (198 bp) were generated by RT-PCR using P1/PD strain-specific primers (Olmos et al. 1997), indicating that the isolates belonged to the strain D. No positive reaction was observed with primers specific to the PPV strains M, W, and C, indicating no mixed infection. All four isolates were recognized by triple antibody sandwich ELISA using PPV-D-specific antibody 4DG5 (K-12B kit, Agritest, Italy), thus confirming the results of the strain-specific RT-PCR. The 3′-terminal genomic sequences encompassing the coat protein (CP) gene and flanking sequences of the NIb gene and 3′-noncoding region were amplified using NIbF/4CPR1 primers (Chirkov et al. 2016), and the PCR products of about 1.3 kb were sequenced using the Sanger method. The sequence of isolates Uz2 and Uz4 was identical, and isolates Uz1, Uz2, and Uz3 shared 99.1 to 99.6% and 99.0 to 99.3% identity at the nucleotide and amino acid levels, respectively. The low genetic diversity of Uzbek isolates suggests their common origin. The ¹¹DAG¹³ motif responsible for aphid transmission, the PPV-D-specific ⁵⁵QPATKP⁶⁰ epitope, and the universal ⁹⁴DRDV(I)DAG¹⁰⁰ epitope (Candresse et al. 2011) were found in the deduced N-terminal sequence of the CP of all the isolates. The 3′-terminal genomic sequences of the Uz1, Uz2, and Uz3 isolates were deposited in GenBank under accession numbers MT038048 to MT038050. Phylogenetic analysis of the CP gene assigned Uz1, Uz2, and Uz3 to the cluster of PPV strain D isolates (LT600779 to LT600782) detected in a Prunus germplasm collection from neighboring Kazakhstan (James et al. 2017) and the isolate BIII/2 (GU461890) from Slovakia. According to BLASTn, the Uzbek isolates were most closely related to the Kazakh isolate P7R1 from plum (LT600780) (99.2 to 99.5% nucleotide identity). To the best of our knowledge, this is the first report of PPV from Uzbekistan. This finding expands the geographical distribution of the virus and encourages further studies on PPV prevalence, host range, and genetic variability to reduce its impact on the fruit-growing industry.

Molecular epidemiology of Plum pox virus in Turkey

Molecular epidemiology of <i>Plum pox virus</i> in Turkey

The apricot as a source of self-compatibility and Plum pox virus resistance in the generation of interspecific hybrids Prunus salicina Lindl. × Prunus armeniaca L. (plumcots)

The apricot as a source of self-compatibility and <i>Plum pox virus</i> resistance in the generation of interspecific hybrids <i>Prunus salicina</i> Lindl. × <i>Prunus armeniaca</i> L. (plumcots)

Determination of Plum pox virus resistance and self-incompatibility using molecular markers in the local apricot (Prunus armeniaca) populations in Turkey

Determination of <i>Plum pox virus</i> resistance and self-incompatibility using molecular markers in the local apricot (<i>Prunus armeniaca</i>) populations in Turkey

Cost-Effective and Time-Efficient Molecular Assisted Selection for PPV Resistance in Apricot Based on ParPMC2 Allele-Specific PCR

Plum pox virus (PPV) is the most important limiting factor for apricot (Prunus armeniaca L.) production worldwide, and development of resistant cultivars has been proven to be the best solution in the long-term. However, just like in other woody species, apricot breeding is highly time and space demanding, and this is particularly true for PPV resistance phenotyping. Therefore, marker-assisted selection (MAS) may be very helpful to speed up breeding programs. Tightly linked ParPMC1 and ParPMC2, meprin and TRAF-C homology (MATH)-domain-containing genes have been proposed as host susceptibility genes required for PPV infection. Contribution of additional genes to PPV resistance cannot be discarded, but all available studies undoubtedly show a strong correlation between ParPMC2-resistant alleles (ParPMC2res) and PPV resistance. The ParPMC2res allele was shown to carry a 5-bp deletion (ParPMC2-del) within the second exon that has been characterized as a molecular marker suitable for MAS (PMC2). Based on this finding, we propose here a method for PPV resistance selection in apricot by combining high-throughput DNA extraction of 384 samples in 2 working days and the allele-specific genotyping of PMC2 on agarose gel. Moreover, the PMC2 genotype has been determined by PCR or by using whole-genome sequences (WGS) in 175 apricot accessions. These results were complemented with phenotypic and/or genotypic data available in the literature to reach a total of 325 apricot accessions. As a whole, we conclude that this is a time-efficient, cost-effective and straightforward method for PPV resistance screening that can be highly useful for apricot breeding programs.

Statistical model for Plum pox virus prediction in Prunus nursery blocks using vector and virus incidence data in four different European ecological areas

AbstractPlum pox virus (PPV) is the causal agent of sharka, the most devastating virus disease of Prunus species. PPV is transmitted by vegetative propagation, particularly by grafting, as well as by aphid species in a nonpersistent manner. The objective of this paper was to evaluate the prevalence and diversity of PPV‐vector aphid species in representative European areas of prunus cultivation. Four experimental nursery plots were established in Skierniewice (Poland), Liria (Spain), Plovdiv (Bulgaria) and Bistrita (Romania). Aphid population was weekly monitored using the sticky shoot method in spring and/or autumn in each nursery plot. Furthermore, we estimated the relative efficiency factor for the main PPV‐vector aphid species using bibliographic and reference data. Aphid diversity in each nursery plot was assessed using the Shannon index and the number of estimated aphid species was calculated by the rarefaction method. The highest diversity of aphid species population was reported in Plovdiv in spring while the lowest diversity was found in Liria in spring. A cluster analysis based on Morisita–Horn similarity index was performed to study the differences in species composition between the four nursery plots and seasons. Aphid population was clearly grouped by location and season. Results showed Aphis spiraecola and Hyalopterus pruni complex were typically spring aphid species, while Anoecia corni and Rhopalosiphum padi dominated autumn catch. Regarding PPV‐vector aphid species present in nursery plots, A. spiraecola was the most prevalent PPV‐vector aphid species in Liria and in Bistrita, showing a high relative efficiency factor of PPV transmission (0.91). Consequently, A. spiraecola should be considered a key actor in the spread of PPV in these regions. Hyalopterus pruni complex was the most prevalent PPV‐vector aphid species in Skierniewice and Plovdiv, showing a very low relative efficiency factor of PPV transmission (0.09). Therefore, the role of H. pruni complex in spread of PPV in these regions can be considered negligible. Furthermore, we statistically demonstrated that the presence of specific PPV‐vector aphid species is associated with the spread of the disease, whereas the biodiversity of aphid species population does not affect the spread of PPV. Finally, the advantages of the use of vector pressure index in the management of sharka disease are discussed.

Development of a novel polyprobe for simultaneous detection of six viruses infecting stone and pome fruits

A biotin-labeled, non-isotopic, novel polyprobe was developed for the simultaneous detection of six viruses viz. apple chlorotic leaf spot virus (ACLSV), apple mosaic virus (ApMV), apple stem grooving virus (ASGV), cherry virus A (CVA), prunus necrotic ringspot virus (PNRSV) and plum pox virus (PPV) infecting stone and pome fruit trees through dot-blot hybridization assay. The sensitivity of the polyprobe was checked by serial dilutions of total RNA extracted from the tissues of infected trees. ACLSV was detected up to a dilution of 5-5, whereas ApMV, ASGV, CVA, PPV and PNRSV up to 5-4. The developed assay was validated following testing a total of 45 symptomatic leaf samples collected from different geographical regions of Jammu and Kashmir (India), and the presence of the viruses was further confirmed by RT-PCR and sequencing. The polyprobe, designed for performing molecular hybridization assay can be developed quickly and avoid the tedious transformation and cloning procedures. Apart from simultaneously detecting viruses in stone and pome fruit trees, it holds great potential for virus indexing programmes to ascertain the supply of virus-free plant materials to the growers.

Abscisic Acid Connects Phytohormone Signaling with RNA Metabolic Pathways and Promotes an Antiviral Response that Is Evaded by a Self-Controlled RNA Virus

A complex network of cellular receptors, RNA targeting pathways, and small-molecule signaling provides robust plant immunity and tolerance to viruses. To maximize their fitness, viruses must evolve control mechanisms to balance host immune evasion and plant-damaging effects. The genus Potyvirus comprises plant viruses characterized by RNA genomes that encode large polyproteins led by the P1 protease. A P1 autoinhibitory domain controls polyprotein processing, the release of a downstream functional RNA-silencing suppressor, and viral replication. Here, we show that P1Pro, a plum pox virus clone that lacks the P1 autoinhibitory domain, triggers complex reprogramming of the host transcriptome and high levels of abscisic acid (ABA) accumulation. A meta-analysis highlighted ABA connections with host pathways known to control RNA stability, turnover, maturation, and translation. Transcriptomic changes triggered by P1Pro infection or ABA showed similarities in host RNA abundance and diversity. Genetic and hormone treatment assays showed that ABA promotes plant resistance to potyviral infection. Finally, quantitative mathematical modeling of viral replication in the presence of defense pathways supported self-control of polyprotein processing kinetics as a viral mechanism that attenuates the magnitude of the host antiviral response. Overall, our findings indicate that ABA is an active player in plant antiviral immunity, which is nonetheless evaded by a self-controlled RNA virus.

Dynamic changes impact the plum pox virus population structure during leaf and bud development

Plum pox virus (PPV) is a worldwide threat to stone fruit production. Its woody perennial hosts provide a dynamic environment for virus evolution over multiple growing seasons. To investigate the impact seasonal host development plays in PPV population structure, next generation sequencing of ribosome associated viral genomes, termed translatome, was used to assess PPV variants derived from phloem or whole leaf tissues over a range of plum leaf and bud developmental stages. Results show that translatome PPV variants occur at proportionately higher levels in bud and newly developing leaf tissues that have low infection levels while more mature tissues with high infection levels display proportionately lower numbers of viral variants. Additional variant analysis identified distinct groups based on population frequency as well as sets of phloem and whole tissue specific variants. Combined, these results indicate PPV population dynamics are impacted by the tissue type and developmental stage of their host.

Termal olmayan plazma tedavisi ile mikro çoğaltılmış erik bitkilerinde Plum pox virus inaktivasyonu çalışmaları

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.

Development of three duplex real-time RT-PCR assays for the sensitive and rapid detection of a phytoplasma and five viral pathogens affecting stone fruit trees

Three duplex real-time reverse-transcription polymerase chain reaction (real-time RT-PCR) assays based on TaqMan chemistry, were developed for the simultaneous detection and specific quantification of apple chlorotic leafspot virus (ACLSV), plum pox virus (PPV), prunus necrotic ringspot virus (PNRSV), prune dwarf virus (PDV), peach latent mosaic viroid (PLMVd) and the European stone fruit yellows (ESFY) phytoplasma, which are considered among the most important pathogens affecting stone fruit trees. The quantitative RT-PCR (RT-qPCR) assays were optimized using RNA transcripts (linearized plasmid was used for the assay optimization of the ESFY phytoplasma) of known concentrations. No differences in sensitivity were recorded between the duplex and singleplex RT-qPCR assays. The amplification efficiency of the duplex assays reached 91.1–95.8%, while the linear range of quantification was from 20 to 2 × 107 RNA/linearized plasmid transcripts for PLMVd and ESFY phytoplasma, 40 to 4 × 107 RNA transcripts for ACLSV, PPV and PDV, and 102 to 108 RNA transcripts for PNRSV, respectively. The duplex RT-qPCR assays, which were validated using both characterized isolates from all pathogens and field samples from Prunus species in Northern Greece, exhibited a broad detection range. Overall, the developed methods comprise useful tools that could be applied for the simultaneous and reliable detection of graft-transmissible pathogens in certification programs of Prunus spp.

Comparative Evaluation of Eurytoma schreineri Schr. Attack Frequency on Transgenic and Two Conventional Plum Varieties

The plum seed wasp (Eurytoma schreineri Schr.) is a polyphagous pest that can cause significant damages to the plum crop. A transgenic plum variety, resistant to Plum pox virus, was evaluated to the attack frequency of E. schreineri in the context of reduced number of insecticide treatments against aphids, in comparison with two conventional plum varieties. The most affected variety by plum seed wasp, for two consecutive years, was ‘Stanley’, followed by ‘Reine Claude d’Althan’, and then ‘HoneySweet’ transgenic plum. The differences between variants were statistically assured.