Plum Pox Virus Isolates Research Articles

First molecular characterization of plum pox virus strains in stone fruits of Tuscany (Central Italy)

Plum pox virus (PPV) a potyvirus in the family Potyviridae, is the etiologic agent of sharka, the worldwide most important and detrimental viral disease of stone fruits (genus Prunus). Although PPV was identified in Italy already in the 1970s and it has been largely reported in almost all Italian regions, a broad investigation and genetic characterization of PPV isolates was lacking in most of them, including Tuscany (Central Italy). To address this knowledge gap, in 2020 and 2021, field surveys were carried out in 80 commercial Tuscany orchards and a total of 690 leaf samples were collected from different Prunus species. PPV was identified in 25 and 12 peach and plum samples, respectively (more than 5% of tested samples), whereas no positive samples were reported in apricot. Eighteen of the 37 PPV positive samples showed mixed infections with other viruses and viroids, mostly Prunus necrotic ringspot virus in plum and peach latent mosaic viroid in peach. Molecular typing of PPV infected samples generated NIb/CP amplicons corresponding to PPV-Marcus (M) or PPV-Recombinant (Rec) strains. Furthermore, starting from the identification of eight PPV nucleotide sequences (among which five and two new PPV-M and PPV-Rec isolates, respectively), this study firstly identified the PPV-Mb subgroup in Italy, which was even prevalent than PPV-Ma. Finally, PPV-Rec isolates resulted phylogenetically close to Italian and Turkish isolates previously detected. Overall, the results here presented represent an important step to fill knowledge gaps about PPV in Tuscany, and we believe it may encourage other similar research to achieve more accurate data on PPV populations at both national and international levels.

The Mechanism of Resistance of EUROPEAN Plum to Plum pox virus Mediated by Hypersensitive Response Is Linked to VIRAL NIa and Its Protease Activity.

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

New Cherry-Adapted Plum Pox Virus Phylogroups Discovered in Russia.

Plum pox virus (PPV) is the most pathogenic virus of stone fruit crops worldwide. Unusual PPV isolates were discovered on sour cherry (Prunus cerasus L.) and steppe cherry (P. fruticosa Pall.) in the Republic of Tatarstan and the Middle Ural region, Russia. They induced typical sharka symptoms and tested positive for PPV by ELISA and RT-PCR, but were not detected by PCR using known strain-specific primers. Their complete genomes were determined using high-throughput sequencing. Phylogenetic analysis allocated new isolates to four clearly distinguished lineages (SC, TAT, Y, Tat-26) within a cluster of PPV cherry-adapted strains. The phylogroups SC and TAT had 84.5 to 86.9% average nucleotide identity to each other and strain CR, with which they comprised a common subcluster. Isolates from the Middle Ural region (group Y) were closer to strain C, sharing 96.9% identity. The fourth lineage is represented by the isolate Tat-26, which was a recombinant of strain CR and C isolates as major and minor parents, respectively. These results show that the genetic diversity of PPV is higher than thought and may contribute to a better understanding of the origin and evolution of cherry-adapted strains of the virus. P. fruticosa was reported as a new natural PPV host for the first time.

Occurrence, Distribution, and Genomic Characteristics of Plum Pox Virus Isolates from Common Apricot (Prunus armeniaca) and Japanese Apricot (Prunus mume) in China.

Plum pox, or Sharka disease, caused by infection with plum pox virus (PPV), results in enormous economic losses to the stone fruit industry. However, the frequency and distribution of PPV remain unclear in China, the world's largest stone fruit producer. Systemic visual surveys were performed on stone fruit trees in China from 2008 to 2018, and the results suggest that plum pox disease is widely distributed on common apricots (Prunus armeniaca) and Japanese apricots (Prunus mume), with an average symptoms incidence rate >30% in the latter. In samples collected from Beijing, Nanjing, Shanghai, Wuhan, Wuxi, and Yuncheng, PPV was detected in 77% (85 of 110) of collected samples by immunochromatographic (IC) strip tests and reverse transcription PCR, and 96% (67 of 70) of samples showing Sharka symptoms were PPV positive. Transmission electron microscopy revealed filamentous particles of ∼640 × 12.5 nm (n = 19) in size and pinwheel inclusions in symptomatic plants but not in the asymptomatic and PPV-negative plants. Full-length genomes were determined for four isolates (three from Japanese apricot and one from common apricot), and phylogenetic analyses indicated that all four isolates belong to a clade PPV-D, despite slight differences in genome size. These findings not only highlight the widespread occurrence and distribution of PPV in China but also provide detailed information about the genomic characteristics and evolutionary position of PPV isolates in China.

Plum Pox Virus Strain C Isolates Can Reduce Sour Cherry Productivity.

The impact of plum pox virus (PPV) on sour cherry (Prunus cerasus L.) productivity has been studied by comparing the yield of PPV-infected and PPV-free fruit-bearing trees. A total of 152 16- to 17-year-old trees of nine cultivars and hybrids were surveyed in the production orchards (cultivar collection and hybrid testing plots) in the Republic of Tatarstan, Russia. Sixty trees tested positive for PPV using ELISA and RT-PCR. Among them, 58 PPV isolates belonged to the strain C and the other 2 isolates to the strain CV. For the cultivars Sevastyanovskaya, Shakirovskaya, hybrids 88-2 and 80-8, the average (2012 to 2019) productivity of infected trees was 38% to 45% lower than for PPV-free trees of the same cultivar or hybrid. No ilarviruses (prunus necrotic ringspot virus, prune dwarf virus, apple mosaic virus, American plum line pattern virus) were detected in PPV-infected trees, suggesting that reduced cherry productivity was attributed to the PPV infection. Thus, it was shown for the first time that PPV can reduce the productivity of at least some sour cherry cultivars and hybrids, and strain C isolates are responsible for crop losses.

First report of Plum pox virus on Tilia spp. in Turkey

The Tilia genus (linden, lime) comprises about 30 deciduous tree species native to North America, Europe, and Asia. They are often used along roads and in parks because of their aesthetic value in urban landscapes. During surveys in 2017–2018 in Istanbul, Turkey, typical viral disease symptoms such as foliar mosaics, mottling and chlorotic ringspots, and deformations were observed on Tilia spp. (Figs. 1-3). Forty-six leaf samples were collected from diseased and asymptomatic trees from 43 different recreation fields in Istanbul. All leaf samples were screened for Plum pox virus (PPV) by DAS-ELISA (PPV ELISA kit, Bioreba, Switzerland). Three leaf samples had positive ELISA test results with mean absorbance values (A405) ranging from 0.73 to 0.74 compared to 0.21 in the healthy control. To confirm the presence of PPV, total RNA was extracted from the diseased and the healthy leaf samples using a Qiagen RNeasy Plant Mini kit and subjected to RT-PCR using universal primers P1/P2 located at the C-terminus of the PPV coat protein (CP) gene as described by Wetzel et al. (1991). A 243 bp product was amplified from the three ELISA positive samples, confirming infection with PPV. The amplicon from one sample was cloned and sequenced, and the partial sequence was deposited in GenBank (Accession No. MF616012). Analysis of the obtained sequence revealed that it shares the highest (100%) nucleotide identity with PPV isolate AnMrPl540 (MG686887.1) from Turkey, and the lowest identity (86%) with PPV isolate Avang (KU359729.1) from Russia. Phylogenetic analysis by the neighbour-joining method using MEGA7 software (Kumar et al., 2016) indicated the Turkish Tilia isolate clustered closely with isolate AnMrPl540 (MG686887.1) (Fig. 4). The disease caused by PPV, known as Sharka, is particularly detrimental to apricots, peaches, and European and Japanese plums because it can seriously reduce yield and fruit quality. Losses in susceptible cultivars may reach 100% in some cases (Kegler & Hartmann, 1998; Németh, 1994). It has also been reported to infect several ornamental and wild Prunus species as natural and experimental hosts (Damsteegt et al., 2007). This is the first report of PPV on Tilia sp. as a natural host in the world. Further molecular studies will be conducted to obtain the full genome sequence of the Tilia isolate and understand its phylogenetic relationship with other published PPV sequences.

Spiraea sp. new natural host of Plum pox virus (Sharka)

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.

Molecular Analysis of New Crimean Isolates of the Plum Pox Virus

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

The effectiveness of hypersensitivity resistance of Prunus domestica ‘Jojo’ and P. domestica × P. cerasifera ‘Docera® 6’ against a broad range of Plum pox virus isolates

The effectiveness of hypersensitivity resistance of <i>Prunus domestica</i> ‘Jojo’ and <i>P. domestica</i> × <i>P. cerasifera</i> ‘Docera^® 6’ against a broad range of <i>Plum pox virus</i> isolates

Update on Distribution and Genetic Variability of Plum pox virus Strains in Bulgaria

Field surveys for Plum pox virus (PPV) infection were conducted in stone fruit orchards all over Bulgaria. In total, 1168 out of 3020 leaf samples from cultivated Prunus spp. and wildly growing P. cerasifera trees reacted positive for PPV in DASI-ELISA with the universal monoclonal antibody (MAb) 5B. Further ELISA analyses showed that 987 and 127 isolates belonged to PPV-M and PPV-D serotypes, respectively. The plum and P. cerasifera showed 82.0% and 50.5% levels of infection, respectively followed by the peach (40.0%) and the apricot (32.0%). Five hundred fifty one PPV isolates were further typed by IC-RT-PCR with PPV-Rec, -M and -D-specific primers, targeting (Cter)NIb-(Nter) CP genome region, as 125 isolates were sequenced. The results revealed the presence of PPV-Rec, PPV-M and PPV-D and mixed infections of these strains. PPV-Rec was the most prevalent strain (49.0%), followed by PPV-M (40.1%), while PPV-D was the less spread strain (8.2%). PPV-Rec was the most common strain in plums, including the eight “old-aged” trees from the region of the first Sharka discovery. PPV-M was the most prevalent strain in peach and apricot. Phylogenetic analyses on (Cter)NIb-(Nter)CP of the isolates were performed. PPV-Rec isolates formed a homogeneous group, while PPV-M isolates split into PPV-Ma and PPV-Mb subgroups. Five separated clades were formed by the analyzed PPV-D isolates. Nucleotide sequences of the partial CP coding region of the analyzed isolates revealed a slightly higher intra-strain genetic variability in PPV-Rec and PPV-M isolates, while that of PPV-D strain isolates was higher from the reported for these strains.

Genetic diversity, host range and transmissibility of CR isolates of Plum pox virus

The new strain of Plum pox virus (PPV), CR, was recently discovered on sour cherry (Prunus cerasus) in geographically distant Saratov/Samara and Moscow regions of European Russia. The full genomes of five Moscow PPV-CR isolates were sequenced using the 454 platform. In a phylogenetic analysis, isolates of the two geographic groups clustered separately within the CR branch. PPV-CR was transmitted to non-cherry hosts by in vitro grafting and induced systemic, generally symptomless infection in P. cerasifera and P. domestica. Seeds and black cherry aphid Myzus cerasi did not transmit the Moscow PPV-CR isolates.

Development of one-tube real-time RT-qPCR for the universal detection and quantification of Plum pox virus (PPV)

In this study a one-tube real-time RT-qPCR assay was developed using the TaqMan chemistry for the universal detection and quantification of PPV, one of the most important pathogens affecting stone fruit trees. In order to design appropriate primers and probe, nucleotide sequences from different PPV isolates originating from all known strains were recovered from the databases. Various genomic regions were screened and finally primers were selected from a conserved region of the 3′- terminal part of the CP gene amplifying a 146 bp DNA fragment while the probe was designed to bind within the amplicon. Ten-fold serial dilutions of in vitro synthesized RNA transcripts were applied for the construction of standard curve. The amplification efficiency of the assay was 93.8% and the linear range of quantification was from 40 up to 4 × 108 RNA copies. The real time RT-PCR was successfully tested with a collection of genetically diverse isolates with different geographical origin belonging to seven PPV strains. The present method is proposed as a useful tool for various basic or applied research studies of PPV as well as for routine testing of plant material during phytosanitary control or in certification schemes of Prunus species.

Molecular characterization of Plum pox virus Rec isolates from Russia suggests a new insight into evolution of the strain.

Field isolates of Plum pox virus (PPV), belonging to the strain Rec, have been found for the first time in Russia. Full-size genomes of the isolates K28 and Kisl-1pl from myrobalan and plum, respectively, were sequenced on the 454 platform. Analysis of all known PPV-Rec complete genomes using the Recombination Detection Program (RDP4) revealed yet another recombination event in the 5'-terminal region. This event was detected by seven algorithms, implemented in the RDP4, with statistically significant P values and supported by a phylogenetic analysis with the bootstrap value of 87%. A putative PPV-M-derived segment, encompassing the C-terminus of the P1 gene and approximately two-thirds of the HcPro gene, is bordered by breakpoints at positions 760-940 and 1838-1964, depending on the recombinant isolate. The predicted 5'-distal breakpoint for the isolate Valjevka is located at position 2804. The Dideron (strain D) and SK68 (strain M) isolates were inferred as major and minor parents, respectively. Finding of another recombination event suggests more complex evolutionary history of PPV-Rec than previously assumed. Perhaps the first recombination event led to the formation of a PPV-D variant harboring the PPV-M-derived fragment within the 5'-proximal part of the genome. Subsequent recombination of its descendant with PPV-M in the 3'-proximal genomic region resulted in the emergence of the evolutionary successful strain Rec.

First detection and complete genome characterization of a Cherry (C) strain isolate of plum pox virus from sour cherry (Prunus cerasus) in Germany

An isolate of plum pox virus (PPV) was detected in sour cherry (Prunus cerasus) in the Eastern region of Germany. Symptoms observed on infected sour cherry included leaf chlorosis, vein clearing, leaf abnormality and dark spots and rings on fruit. The complete genome sequence of this PPV isolate (GC27) was determined. The virus genome consists of 9795 nucleotides (nt), excluding the poly(A) tail at the 3′ terminus, with 5′ and 3′ untranslated regions (UTRs) of 146 and 217 nt, respectively. Phylogenetic analysis based on the complete genome, the nucleotide sequence of the coat protein and the deduced amino acid sequence of the PIPO protein indicate that PPV isolate GC27 is a member of the Cherry (C) strain of PPV. In pairwise comparisons, the complete genome (nt) of isolate GC27 is 98.2–99.7% identical to other C isolates; with much lower identities for isolates of other strains including approximately 83% identity for isolates of the strain Cherry Russian. This is the first detection of a strain C isolate of PPV in Germany.

In vitro micrografting of different Prunus species by cherry-adapted Plum pox virus isolate.

In vitro micrografting of different Prunus species by cherry-adapted Plum pox virus isolate.

Analysis of Genetic Diversity of Russian Sour Cherry Plum pox virus Isolates Provides Evidence of a New Strain.

Plum pox virus (PPV) exists as a complex of nine strains adapted to different Prunus hosts. Unusual PPV isolates that do not belong to the known cherry-adapted strains were discovered on sour cherry in Russia. Here, two complete genomes of isolates Tat-2 and Tat-4 were determined by sequencing on the Illumina HiSeq 2500 platform. Both were composed of 9,792 nucleotides, excluding the poly(A) tail, with the organization typical of PPV and had 99.4 and 99.7% identity between each other at the nucleotide and amino acid levels. The sequence identities between Tat-2/Tat-4 and known PPV strains ranged from 77.6 to 83.3% for genomic RNA and from 80.0 to 93.8% for polyprotein. Phylogenetic analysis placed Tat-2 and Tat-4 in a separate clade, distinct from the C and CR strains. Three more Tat-2/Tat-4-like isolates were detected in local cherry plantings using the newly developed, specific RT-PCR assay. Based on the phylogenetic analysis, sequence identities, and environmental distribution, Tat-2, Tat-4, and related isolates represent a new cherry-adapted PPV strain for which the name PPV-CV (Cherry Volga) is proposed.

Molecular analysis of the complete genomes of apricot and plum isolates ofPlum pox virusdetected in aPrunusgermplasm collection in Almaty’s Pomological Gardens, Kazakhstan

Partial molecular characterization of isolates of Plum pox virus (PPV) from Kazakhstan was described by Spiegel et al. (2004). The isolates were classified as members of the Dideron (D) strain based on: a) RFLP analysis of a 243-bp amplicon in the region of the C terminus of the coat protein (CP) fragment, b) RFLP analysis of an 836-bp amplicon in the P3-6K1 coding region and c) analysis of the CP coding region. The plum isolates were detected in plum trees maintained in the plum selection-orchard of the Pomological Garden, Almaty, Kazakhstan. The apricot isolates were detected in wild apricot seedlings obtained originally from Zailiyski Alatou at the northern edge of the Tien-Shan Mountains, but maintained in the Pomological Garden, Almaty, for about 15 years. Disease symptoms were observed on fruit from one of these infected apricot trees and on the leaves of the infected plum trees. PPV was never detected in any wild apricot plants growing in their natural habitat in Zailiyski Alatou. In this recent study, the virus genomes were sequenced completely and their analysis confirmed their identities as members of the D strain of PPV. Interestingly, in some cases, the genomes of the apricot and plum isolates were very similar, with identities of approximately 99.7% (nucleotide and amino acid sequence). Phylogenetic analyses seem to indicate a close relationship of the Kazakhstan apricot and plum isolates to each other, and to the PPV isolate BIII/2 (GenBank accession no. GU461890), a plum isolate from Slovakia. The Kazakhstan isolates and the Slovakia isolate are approximately 99% identical (nucleotide and amino acid sequence). The deletion event described by Spiegel et al. (2004) in the plum isolate P5R8 (KZPLa1) was confirmed.

Impact of Plum pox virus (PPV-D) infection on peach tree growth, productivity and bud cold hardiness

In 2000, the Dideron (D) strain of Plum pox virus (PPV) was detected in commercial peach and nectarine orchards in the Niagara region of Ontario where most of Canada’s stone fruit crops are produced. As part of a disease management research programme, peach (Prunus persica L. Batsch) trees in a commercial orchard at Niagara-on-the-Lake were assayed for PPV annually for 3 years. The orchard consisted of two blocks of the cultivars ‘Allstar’ and ‘Brighton’, of which 4 of 288 and 5 of 252 trees, respectively, were infected with PPV-D. The growth and health of these PPV-infected and non-infected trees were evaluated based on the annual growth rates, vigour (chlorophyll content) and bud winter hardiness. Comparative fruit quantity and quality index values were based on total yield and marketable yield per tree, fruit size and weight, fruit pH, titratable acidity, total soluble solids, flesh firmness, and fruit skin colour. Results from these preliminary studies showed that trees infected with this mild Ontario isolate of PPV produced slightly more fruit of smaller size that ripened earlier than non-infected trees. However, yield efficiencies based on weight of fruit relative to the trunk cross-sectional area did not differ statistically. Screenhouse studies on three graft-inoculated fresh market peach cultivars (‘Babygold’, ‘Catherina’, and ‘Garnet Beauty’) similarly did not demonstrate any differences in growth or fruit production in the second and third year post inoculation, but fruit on infected trees matured somewhat earlier.

New highly divergent Plum pox virus isolates infecting sour cherry in Russia

Unusual Plum pox virus (PPV) isolates (named Tat isolates) were discovered on sour cherry (Prunus cerasus) in Russia. They failed to be recognized by RT-PCR using commonly employed primers specific to the strains C or CR (the only ones that proved able to infect sour cherry) as well as to the strains M and W. Some of them can be detected by RT-PCR using the PPV-D-specific primers P1/PD or by TAS-ELISA with the PPV-C-specific monoclonal antibody AC. Phylogenetic analysis of the 3′-terminal genomic region assigned the Tat isolates into the cluster of cherry-adapted strains. However, they grouped separately from the C and CR strains and from each other as well. The sequence divergence of the Tat isolates is comparable to the differences between the known PPV strains. They may represent new group(s) of cherry-adapted isolates which do not seem to belong to any known strain of the virus.

FIRST REPORT OF PLUM POX VIRUS STRAIN PPV-T IN ALBANIA

In previous surveys for the presence of Plum pox virus (PPV) in Albania, PPV-M prevailed largely whereas PPV-D and PPV-Rec were less represented. Natural mixed infections of strains M and D were also found, more frequently than expected in varietal collections (Stamo and Myrta, 2006). In spring 2011, a new field survey was carried out to collect representative PPV isolates from different areas of the country and evaluate their diversity. A total of 11 PPV isolates were recovered from symptomatic plants in 10 orchards located at Kavaje, Elbasan, Pogradec and Korce. Samples were tested by DASI-ELISA using the monoclonal antibodies 5B (universal), 4DG5 (PPV-D specific) and AL (PPV-M specific), and two highly informative genome portions (P3-6K1 and NIb- CP) were sequenced to check for the presence of PPV-M, PPV-D PPV-Rec and other strains. Five of the tested Albanian isolates proved to be PPV-M, four were PPV-Rec, one was PPV-D and one PPV-T. Further comparative sequence analysis of the entire CP gene demonstrated that the isolate Al-08pl (from an European plum tree) diverged from the cluster of PPV-M isolates and was 99% identical to PPV-T (Serce et al., 2009). To our knowledge, this is the first report of PPV-T in Albania. To assess the importance of this new PPV strain in Albania, further work is needed. An interesting output of this study, is the fact that in a small collection of Albanian PPV isolates the biodiversity of this virus is very high (4 different strains in 11 isolates). This can be interpreted either as an indication of a long history of PPV presence in the country or as the consequence of frequent introduction events from outside.