Plum Pox Virus Symptoms Research Articles

Are D and Rec strains of Plum pox virus similar or different in terms of competitiveness and symptomatology?

Plum pox virus (PPV) is considered the most detrimental viral pathogen of stone fruits, causing important economic losses. Exhaustive studies revealed that D, M and Rec are the prevalent strains of PPV in Europe. While different experimental reports revealed that PPV-M is more aggressive than PPV-D, limited information is available about the competitiveness of PPV-Rec under field conditions. Also, symptoms developed by PPV-Rec infection are scarcely documented. To increase this knowledge, we selected and monitored an experimental plum orchard already contaminated by both PPV-D and PPV-Rec. The disease spread was monitored by visual observation and ELISA testing each year along five consecutive vegetative periods. The dynamic of single and mixed infections was assessed by molecular strain typing (IC-RT-PCR) of all newly and single-infected trees. While the disease prevalence increased almost linearly, the number of single PPV infected trees (either by PPV-Rec or by PPV-D) remained relatively stable during the five-year period of monitoring, which is explainable by the continual increase of the number of trees infected with both strains together. No significant difference in the progression rate between D and Rec strains was found when considering their presence in both single and mixed infections. Although the types of PPV symptoms developed on leaves and fruits varied among cultivars, no clear-cut D or Rec strain-specific symptoms were developed within the same cultivar. Overall results revealed that PPV-D and PPV-Rec strains had similar behaviour in terms of competitiveness and symptoms developed under our experimental field conditions.

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.

Reaction of transgenic plum cv. HoneySweet to the Plum pox virus after a severe infection of Monilinia sp. - short communication

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.

First Report of Plum pox virus Strain M in Japan

Plum pox virus (PPV) is a causal agent of plum pox (sharka), the most serious viral disease for the stone fruit crops (Prunus spp.) (Garcia et al. 2014). Nine PPV strains are known, out of which strains D and M are the most widespread and economically important. In 2009, PPV-D was detected from Japanese apricots (Prunus mume) in Japan (Maejima et al. 2011). A nationwide survey was then started, followed by an eradication program. In the program, the collected samples were tested by a PPV immunochromatographic assay kit (NIPPON GENE, Japan), and only those with positive results were further tested by reverse transcription loop-mediated isothermal amplification method (RT-LAMP) using a PPV detection kit (NIPPON GENE). In June 2016, some Japanese apricots and apricot (P. armeniaca) trees were found with typical PPV symptoms such as ringspot and mottle on leaves, and some peach (P. persica) trees with mild mottle on leaves in Yokohama, Japan. These trees were distributed in a small area in Yokohama city. Most...

Experimental transmission efficiency of Plum pox virus T by Myzus persicae Sulzer (Homoptera: Aphididae)

Plum pox virus (PPV), which is a major threat to stone fruit trees, is transmitted by various aphid species. Of the nine PPV strains, PPV-T is a unique strain found only in Turkey. In this study, PPV-T was experimentally transmitted to Nicotiana benthamiana Domin by using Myzus persicae with the unrestricted probing method (UPM) and the controlled acquisition access period (CAAP) method. Three weeks after aphid inoculation, PPV symptoms were observed on some inoculated tobacco plants. When test plants were analysed by DAS-ELISA and real-time RT-PCR, only the symptomatic plants were found positive for PPV, and the infection rate was found to be 14.29% for both methods by using UPM, whereas it was 5.40% in CAAP only by real-time RT-PCR. Furthermore, it was revealed that PPV-T was transmitted more efficiently to N. benthamiana by M. persicae by using the UPM method.

Development and improvement of detection technologies to control sharka disease

First reported in Bulgaria in 1933, Plum pox virus (PPV), the causal agent of sharka disease, has spread throughout Europe, despite its classification as a quarantine pest. In recent years, PPV has reached North Africa, America, and Japan. Sharka disease causes severe yield losses to the stone-fruit industry. As is typical for plant virus diseases, there is neither cure nor effective treatment of infected trees. Detection and quarantine measures are relied upon to delay or halt virus spread. PPV detection has led to the harmonization of preventive measures such as spring season surveys of nurseries and orchards, the use of certified virus-free plants, removal of infected trees, and creation of quarantine zones. In summer, while a majority of susceptible cultivars exhibit PPV symptoms, some tolerant cultivars are symptomless, and infected fruits become marketable. This situation led us to analyze fruits through RT-PCR to evaluate levels of PPV in these symptomless marketed fruits. Because evidence of PPV infection was previously found in some fruit samples, this study may have implications for the export and marketing of fruits from PPV-tolerant plum cultivars.

Transgenic plum Prunus domestica L., clone C5 (cv. HoneySweet) for protection against sharka disease

Sharka caused by Plum pox virus (PPV) is the most harmful disease of stone fruits in Europe and elsewhere in the world. There is no highly PPV resistant cultivar of plum. Biotech approach has led to the development of resistance through genetic engineering. In this study, we evaluated a transgenic plum Prunus domestica L., clone C5 (cv. HoneySweet), where the PPV resistance is based on RNA interference (RNAi). Resistance in C5 plums has been evaluated for PPV, Prune dwarf virus (PDV), and Apple chlorotic leaf spot virus (ACLSV) in a regulated field trial in the Czech Republic for 12 years (2002–2013). Even under high and permanent infection pressure introduced through graft inoculation of the viruses, PPV has been detected in C5 trees only in several leaves situated close to the point of inoculum grafting in the first nine years. Mild symptoms of PPV disappeared year by year. No PPV symptoms were observed in the last three years and results of ELISA detection were negative. Similar results were obtained, when RT-PCR was used for PPV detection. No natural infection of PPV by aphids was recorded in C5 plums, even if PPV infected plants were growing in the same experimental field in close vicinity. Co-infections of PPV with PDV and/or ACLSV had practically no influence on stability of resistance in C5 trees. Twelve years of field testing in the Czech Republic clearly demonstrated the high level of resistance of C5 either to PPV infection by graft inoculation or natural infection through aphid vectors.

Comparison of four techniques for plum pox virus detection

Twenty-four stone fruit trees showing typical symptoms of plum pox virus (PPV) were tested for PPV using ELISA, RT-PCR, real-time RT-PCR and RT-LAMP. The isolates were obtained from various regions in the Czech Republic. PPV was detected in all tested plants. Part of the coding region of the coat protein gene and adjacent non-coding region were sequenced. PPV strains of individual isolates were classified according to the obtained sequences. This study provides comprehensive evaluation of the sensitivity of four techniques used for PPV detection. Five PPV strains (D, M, W, Rec and An) were observed according to analyses of obtained sequences. The results showed that the degree of sensitivity for each detection technique varied across the four chosen methods, with the RT-LAMP technique providing very sensitive results.

PRESENCE OF SHARKA DISEASE IN THE NORTH-HUNGARIAN COUNTIES

In the concerned region, such as Hungary Plum pox virus (PPV) causes the most serious yield loss in the stone fruit orchards. A survey of sharka disease was conducted in the north-Hungarian border region from 2010 to 2012. The main goals of the survey were to isolate the virus, to map the spreading and the actual status, to identify the PPV strains and inform the orchard owners and manufacturers about the results of the study. This survey was a part of the Hungary-Slovakia Cross-Border Co-operation Programme 2007-2012. Nearly 250 leaf samples were taken from 51 different settlements of the northern counties from stone fruit orchards, home gardens and natural environment, showing the symptoms of PPV. The surveyed species were plum, apricot, peach, sweet and sour cherry, and blackthorn. To identify the strains the following molecular methods were used: conventional RT-PCR with strain-specific primers, RT-PCR followed by RFLP analysis using EcoRI, DdeI and EcoRV restriction enzymes in the 3’P3-6K1-5’CI genomic region and RT-PCR followed by sequence analysis in the formerly mentioned region. The results show that the dominant strains were PPV-Rec in the central and PPV-D in the eastern region, but PPV-M was also identified. The apricot and peach orchards were less infected than plum orchards in the northern counties of Hungary. A suspected triple-mixed infection (M, D and Rec) is under further studies. After the survey a map was prepared, the dominant isolates, the infection rate, the host plants and the type of the sample collection places were marked. From the results a bilingual booklet was also published with the great help of the Slovak partners, for producers and orchard owners including all important knowledge about the virus and the disease prevention.

Assessment of antioxidant activity and total polyphenolic compounds of peach varieties infected with the Plum pox virus

Just like in other stone fruits, also in peach trees, the Plum pox virus is commonly known to be the cause of lower yields, worse quality and smaller size of fruits and it also affects the contained substances. The fruits of peach trees infected with the Plum pox virus (PPV) were subjected to various analyses to determine the content of antioxidant activity and overall polyphenolic compounds. The evaluation took place from 2011 to 2012. To conduct this experiment, two cultivars that had been infected by PPV naturally were selected – ‘Royal Glory’ and ‘Symphony’. Antioxidant activity was established using five principally different methods (DPPH, ABTS, FRAP, DMPD and Free Radicals). The content of total polyphenolic compounds was established using the Folin-Ciocalteu method. The results of these analyses are expressed as the equivalent of gallic acid (GAE) in mg·kg−1. Furthermore, in the period from April to October the intensity of PPV symptoms in blossoms, leaves and fruits was also assessed.It was discovered that as a result of the PPV infection, the content of antioxidant activity as well as of total polyphenols had increased. Average reading of antioxidant activity in the PPV infected fruits had increased by 13.2 % (DPPH), 26.7 % (FRAP), 27.6 % (ABTS), 28.1 % (DMPD), 39.2 % (Free Radicals) and the content of polyphenolic compounds had gone up by about 30.4 % in comparison with the control varieties.

Biological evidence for practical immunity of apricot cultivar Harlayne to Plum pox virus

Ten-year results of the practical immunity investigation of apricot cv. Harlayne are presented. Two-year-old trees of cv. Harlayne were inoculated by chip-budding with six different strains and isolates of Plum pox virus (PPV). PPV inoculated trees grew in the field and were evaluated from 2001 to 2011. No PPV symptoms appeared in the leaves of cv. Harlayne within ten years (2002–2011), and within eight years (2004–2011) in the fruits and stones. None of the six isolates of three different PPV strains was detected in the leaves and fruits by ELISA. Suckers of the rootstock Prunus myrobalana developed around cv. Harlayne trees in 2005–2011 were symptomless and ELISA was negative within seven years. New trees of cv. Harlayne obtained from tested trees by budding on PPV susceptible apricot rootstock MVA-2 in 2007 were PPV free from 2008 through 2011. The presence of PPV was proved by ELISA neither in leaves of cv. Harlayne nor in rootstock MVA-2.

TESTS OF PLUM HYBRIDS FOR RESISTANCE TO PLUM POX VIRUS

The investigation included four plum (Prunus domestica L.) hybrids, which were selected on the base of visual inspection in natural infection background and serological analyses. Two of the hybrids were obtained from hybridization of ‘Pasific’ × ‘Serdika’ (21-3 and 21-47) and another two were the result from crossing of ‘Pasific’ × ‘Stanley’ (21-55 and 21-67). The tests for resistance to Plum pox virus (PPV) combined biological indexing and field trial. In the biological indexing the hybrids were inoculated artificially by chip budding under greenhouse conditions, with isolates representing PPV-M, PPV-D and PPV-Rec strains of the virus. Up to now the data of the biological indexing showed that the hybrid 21-47 did not manifest symptoms of PPV and ELISA results were negative. The other three hybrids were infected by PPV isolates used. Simultaneously, the studied hybrids were propagated and planted under natural PPV infection pressure, without chemical protection against aphids. The results of the field trial after 5 years growing showed that hybrid 21-47 remained symptomless and reacted negatively with an antiserum to PPV, while in the other three hybrids 21-3, 21-55 and 21-67, the virus was detected respectively in 7.7, 23.5 and 42.1% of tested plants. At that stage of the study on the base of the summarized data, it could be accepted that the hybrid 21-47 possesses a high level of resistance to PPV.

EVALUATION OF PPV SYMPTOMS IN PLUM GERMPLASM AFTER ARTIFICIAL INFECTION

Plum pox virus (PPV) is one of the most economically important diseases of stone fruit in the Czech Republic. PPV is currently widespread on the whole territory of the Czech Republic. Therefore, spatially isolated plantation of a broad assortment of plum cultivars (207) was established in 1990. One-year-old plant material (2 trees/cultivar) at a spacing of 6 x 4 m on myrobalan rootstock was used. The collection was planted at an altitude of 320 m. Mean annual temperature is 8.1°C and precipitation 654.7 mm. Weed-free strips are maintained under the bushes with herbicide applications. Regularly cut grass is established between the rows. After artificial infection, the PPV was detected by ELISA in 77.1% of inoculated trees. After PPV reinfection in 1996, the percentage of infected trees increased to 92.9% in 1998. The virus spread only slightly in the following years. PPV was detected in 94.2% of trees in 2000-2005 and in 95.2% of trees since 2006. Symptoms of PPV on fruits were evaluated after the beginning of fruiting. Cultivars 'Italian prune' and its clones 'Albatros', 'Bonne de Bry', 'Centenar', 'Eliasova', 'Konigsbacher Fruhzwetsche', 'Lutzelsachser', 'Vengerka Kodrinskaja', 'Zimmers Friihzwetsche' developed the most visible symptoms on fruits. Commercially important cultivars 'Anna Spath', 'Cacanska lepotica', 'Cacanska najbolja', 'Elena', 'Gabrovska', 'Hamanova', 'Hanita', 'Chrudimer', 'Opal', 'Veeblue', 'Verity' and 'Voyageur' were without symptoms of PPV on fruits.

BEHAVIOUR OF TRANSGENIC PLUM POX VIRUS-RESISTANT PRUNUS DOMESTICA L. CLONE C5 GROWN IN THE OPEN FIELD UNDER A HIGH AND PERMANENT INFECTION PRESSURE OF THE PPV-REC STRAIN

Transgenic plum (Prunus domestica L.) clone C5 was grafted on virus-free St. Julien rootstocks and inoculated by bud grafting with the recombinant strain (PPVRec) of the Plum pox virus (PPV). Non inoculated C5 plums were used as controls. Transgenic plums infected with PPV-Rec and control plants were evaluated for six years in the open field. PPV symptoms, mild diffuse spots and rings, appeared on the basal leaves the second year after inoculation. The presence of PPV was confirmed by DAS-ELISA, ISEM, and RT-PCR. Severe PPV symptoms appeared in the leaves of shoots grown from non-transgenic inoculum buds. A reduction of symptoms and a decrease of the relative PPV concentration, as determined by DAS-ELISA in transgenic C5 plants, were observed from the third to the fifth year after virus inoculation. Very mild symptoms in older leaves of the basal branches of trees subsided by the end of the vegetative period, and were difficult to observe. The level of PPV detection by DAS-ELISA dropped from June to August together with a reduction of symptoms. PPV was undetectable by DAS-ELISA in more than half of the trees by the end of August. PPV-Rec was detected by RT-PCR in the basal and middle parts of the C5 scions. The upper leaves did not contain a detectable level of the virus. These results show the high level and stability of PPV resistance in graft-inoculated C5 trees.

Discovery and characterization of Plum pox virus isolates in Montenegro

In 2006, twenty extensive and intensive plum orchards, surrounding Nik s i C in Montenegro, were screened for the presence of symptoms of Plum pox virus (PPV) infection. Mild to severe symptoms were found in 15 orchards, usually only on some trees. In total 19 samples were collected and 17 proved to be positive by DAS-ELISA (Bioreba). Of these positives, 16 were selected for molecular identification. PPV isolates have been assigned to two major (PPV-D and PPV-M) and two minor (PPV-EA, PPVC) groups. Recently, a fifth group (PPV-REC) has been established, which corresponds to naturally-occurring recombinants between PPV-M and PPV-D isolates. All PPV-REC isolates share the same recombination breakpoint on the NIb polymerase gene and therefore conventional CP gene-based molecular and serological methods are not able to discriminate between PPV-M and PPV-REC isolates. Subgroup characterization was performed using two different PCR systems: one positioned downstream of the recombinant crossover (using the PPV-M and -D specific primer pairs P4/P3-M and P4/P3-D respectively; Dallot et al. , in press); and the other upstream of the recombination breakpoint (using the primer pairs CIf/CI-M (PPV-M specific) and CIf/CI-D (PPV-D specific); Glasa et al. , 2002). The results showed the presence of PPV-D type isolates in 4 samples. These samples were also negative for PPV-M when tested by TAS-ELISA (Agritest). The remaining 12 samples were PPV-M positive by TAS-ELISA. Of these, seven proved to be of PPV-REC type by RT-PCR. However, the isolate type could not be determined for the remaining five samples using the previously described method. Therefore they were further analyzed using primer pairs mM5/mM3, mD5/mD3 and mD5/ mM3 ( P ubr et al. , 2004), situated around the recombination breakpoint. All samples gave a positive result only with primer pair mD/mM3 and were therefore also identified as the PPV-REC type. Although plum production is important in Montenegro, data about PPV infection is scarce. Sharka symptoms were observed by Miju s kovi C (2002), but until now the presence of PPV was never confirmed. As a result, this is the first report confirming PPV as being present in Montenegro.

Role of the 25–26 nt siRNA in the resistance of transgenic Prunus domestica graft inoculated with plum pox virus

The reaction of a genetically engineered plum clone (C5) resistant to plum pox virus (PPV) by graft inoculation with the virus was evaluated. The resistance in this clone has been demonstrated to be mediated through post-transcriptional gene silencing (PTGS). A single C5 plant out of 30 plants inoculated with PPV M strain by double chip-budding showed mild diffuse mosaic 'Sharka' symptom at the bottom section of the scion. The upper leaves of this PPV-infected C5 plant remained symptomless and the virus was not detected in them by either DAS-ELISA or RT-PCR. An RNA silencing associated small interfering RNA duplex, siRNA (21-26 nt), was detected in non-inoculated C5 plants and in the portions of inoculated C5 plant in which PPV could not be detected. In the PPV-infected portion of the C5 plant and in C6 PPV susceptible plants only the approximately 21-22 nt siRNAs was detected. Cytosine-methylation was confirmed in C5 plants both uninfected and showing PPV symptoms. The 25-26 nt siRNA normally present in C5 was absent in PPV-infected C5 tissues confirming the critical role of this siRNA in the resistance of clone C5 to PPV infection. We also show that this PPV infection was limited and transient. It was only detected in one plant at one of four post-dormancy sampling dates and did not appear to affect the overall PPV resistance of the C5 clone.

Breeding for resistance: breeding for Plum pox virus resistant plums (Prunus domestica L.) in Germany

In German plum breeding programmes new varieties tolerant to Plum pox virus (PPV) were initially obtained by selecting hybrids originating from crossings between tolerant old varieties while, later on, sharka tolerant varieties bred in Čačak, Serbia were used as crossing partners. Varieties released from these programmes replaced the sensitive ones in all sharka infected regions in Germany. While all the new tolerant varieties can be infected by the virus, PPV symptoms on the fruits are acceptable. However, environmental factors can weaken the plant, causing them to suffer more from PPV infections and to display worse symptoms on fruits, as did occur during some recent very dry and warm years. A breeding programme at the University of Hohenheim is tackling this problem with genotypes that show a hypersensitive response after infection. These genotypes are completely field resistant to PPV, remaining virus free in the field since they cannot be infected via aphid transmission. They are able to isolate the virus after infection. The first hypersensitive variety was ‘Jojo’. Many seedlings originating from crossings with at least one hypersensitive parent are under evaluation. Since the inheritance of the trait ‘hypersensitivity against PPV’ is very good, combining hypersensitivity with excellent fruit quality and good cropping capacity will be possible soon. In 2005, a breeding programme for hypersensitive Prunus genotypes began at the Technical University of Munich.

Hosts and symptoms of Plum pox virus: woody species other than fruit and ornamental species of Prunus

The presence of Plum pox virus (PPV) in woody hosts other than in fruit and ornamental Prunus species was evaluated. PPV symptoms, and their variability and intensity, are described in leaves and fruits of Prunus cerasifera, Prunus spinosa, Ligustrum vulgare and Euonymus europaea. Juglans regia is not confirmed as a new host of PPV.

Oxidative stress induced by long‐term plum pox virus infection in peach (Prunus persica)

In this study, the effect of long‐term plum pox virus (PPV) infection on the response of certain antioxidant enzymes at the subcellular level was studied in peach plants (Prunus persica (L.) Batch) (cv. GF305), which are characterized by great susceptibility to the virus. In infected plants, a decrease in the efficiency of excitation energy capture by PSII (Fv′/Fm′) was observed, which was accompanied by a decrease in non‐photochemical quenching (NPQ). p‐Hydroxy‐mercury benzoic acid (pHMB)‐insensitive ascorbate peroxidase (APX) activity (class III peroxidase) was detected in both chloroplast and soluble fractions. In soluble fractions from inoculated peaches, a significant increase in pHMB‐sensitive APX activity and a significant decrease in superoxide dismutase (SOD) activity were observed. These changes were correlated with the observations in isolated chloroplasts, where an increase in both pHMB‐sensitive and pHMB‐insensitive APX activities was observed, whereas significant decreases in SOD, monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR) activities were produced. According to these results, as a consequence of PPV infection, an oxidative stress, indicated by an increase in lipid peroxidation and protein oxidation, was produced in peach leaves, which was monitored by the diaminobenzidine (DAB) peroxidase‐coupled H2O2 probe. PPV infection produced an alteration in chloroplast ultrastructure, giving rise to dilated thylakoid membranes. PPV‐infected peach leaves showed a decreased amount of starch in chloroplasts from palisade parenchyma, as well as an increase in the number and size of plastoglobuli, in relation to control plants. The results suggest that long‐term PPV infection produces an oxidative stress, and that an antioxidative metabolism imbalance may be related to the progress of PPV infection and symptoms in peach plants.

Resistance to Plum Pox Virus (Dideron Isolate RB3.30) in a Group of California Almonds and Transfer of Resistance to Peach

Sharka [(plum pox virus (PPV)] mainly affects Prunus species, including apricot (Prunus armeniaca L.), peach (Prunus persica L.), plum (Prunus salicina Lindl., Prunus domestica L.), and, to a lesser degree, sweet (Prunus avium L.) and sour cherry (Prunus cerasus L.). Level of resistance to a Dideron isolate of PPV in seven California almond [P. dulcis (Miller) D.A. Webb], five processing peach cultivars, and two peach rootstocks was evaluated. In addition, almond and peach selections resulting from interspecific almond × peach hybridization and subsequent gene introgression were tested. Evaluations were conducted in controlled facilities after grafting the test genotypes onto inoculated GF305 peach rootstocks. Leaves were evaluated for PPV symptoms during three consecutive cycles of growth. ELISA-DASI and RT-PCR analysis were also employed to verify the presence or absence of PPV. Peach cultivars and rootstocks showed sharka symptoms and were ELISA-DASI or RT-PCR positive for some growth cycles, indicating their susceptibility to PPV. Almond cultivars and almond × peach hybrids did not show symptoms and were ELISA-DASI and RT-PCR negative, demonstrating resistance to PPV. Two (almond × peach) F2 selections as well as two of three backcrossed peach selections also showed a resistant behavior against the PPV-D isolate. Results demonstrate a high level of resistance in almond and indicate potential for PPV resistance transfer to commercial peach cultivars.