Phytoplasma Prunorum Research Articles

A Draft Genome Resource for ‘Candidatus Phytoplasma prunorum’, the Agent Associated with European Stone Fruit Yellows Disease

‘Candidatus Phytoplasma prunorum’ is associated with European stone fruit yellows disease, affecting wild and cultivated species of Prunus at different degrees of susceptibility, so far being mainly restricted to Europe. Here, we report draft genome sequences for ‘Ca. Phytoplasma prunorum’ strains ESFY1 and LNS1, which represent the first available for this species. Strain ESFY1 is the causal agent of the European stone fruit yellows disease of Prunus persica in Germany and LNS1, leptonecrosis disease of Prunus salicina in Italy. Their draft genomes consist of 480,123 and 490,930 bases, assembled into 28 and 16 contigs, respectively, with an average GC content of 21.1% and 20.7%, respectively. Analysis of average nucleotide identity values between genomes further supported the delineation of ‘Ca. Phytoplasma prunorum’ as a species distinct from ‘Ca. Phytoplasma mali’, in agreement with previous phylogenetic data.

Molecular Characterization of 'Candidatus Phytoplasma prunorum' in the Czech Republic and Susceptibility of Apricot Rootstocks to the Two Most Abundant Haplotypes.

'Candidatus Phytoplasma prunorum' is one of the most destructive pathogens of Prunus species, where susceptible species render unproductive several years after infection. In epidemiology, the molecular characterization of phytoplasmas is based on sequence analysis of variable nonribosomal genes. In this study aceF, pnp, imp and secY genes were used for characterization of the 'Ca. P. prunorum' genotypes present in the Czech Republic. In total, 56 plant and 33 vector (Cacopsylla pruni) samples positive to 'Ca. P. prunorum' collected in seven localities were used in the study. Based on sequence analysis, four aceF, two pnp, six imp, and three secY genotypes were identified in analyzed samples. The most abundant in both plant and insect samples were the A6, P2, I4, and S2 genotypes. Most of the Czech 'Ca. P. prunorum' haplotypes clustered together in the haplotype network analysis. Next, two isolates representing the two most abundant Czech haplotypes (A6-P2-I4-S2 and A5-P2-I4-S2) were used in the susceptibility test of three apricot rootstock types (St. Julien A, M-VA-1, GF-305). Susceptibility was analyzed by phytoplasma quantification using quantitative real-time PCR and evaluation of symptom manifestation. Based on the results, the influence of the rootstock type on the phytoplasma titer and symptom manifestation was greater than of the phytoplasma isolate, while the year of analysis had no influence on the results. The results also showed that the phytoplasma titer is increasing in plant tissues during the vegetation period.

Detection of ‘Candidatus Phythoplasma prunorum’ in Apricot Trees and its Associated Psyllid Samples

‘Candidatus Phytoplasma prunorum’ is causing ever increasing economic losses through the decline of apricot trees in European countries, e.g., Hungary. In this study, the pathogen was identified from plant tissues and insects by nested-PCR. The insect species were identified via morphology and molecular methods. The incidence of the pathogen was 29.6% in randomly selected apricot trees. Most of the infected trees with symptoms died within a year. These results show that phytoplasma is significantly present and causes damage in the investigated plantations. The only known insect vector of this phytoplasma is the plum psyllid, Cacopsylla pruni, which was regularly encountered in the sampled apricot orchards and in their surroundings. In a two-year study, several adults among the sampled specimens were observed to be infected by the pathogen. This observation further confirms the role of the plum psyllid in vectoring the phytoplasma. All the sampled plum psyllid adults belonged to the ‘B’ biotype. Besides C. pruni, Cacopsylla crataegi was abundant in the samples. Several adults of the latter species were also infected by the pathogen ‘Ca. Phytoplasma prunorum’. The rates of occurrence of this phytoplasma in male and female adults of the two psyllid species appeared to be similar. The examined C. crataegi individuals showed genetic differences from each other and from specimens included in a previous investigation.

Detection and molecular characterization of ‘Candidatus Phytoplasma prunorum’ in apricot and plum orchards of Nigde, Turkey

Detection and molecular characterization of ‘Candidatus Phytoplasma prunorum’ in apricot and plum orchards of Nigde, Turkey

A survey of jumping plant-lice (Hemiptera: Psylloidea) overwintering on conifers in Hungary

AbstractSome jumping plant-lice species are economically important due to their capacity as vectors of phytopathogenic bacteria, for example phytoplasmas. Previous studies have identified 80 jumping plant-louse species from Hungary; however, little is known about their occurrence during winter. To extend our knowledge of overwintering sites of jumping plant-lice in Hungary, we sampled them from conifers in various regions of the country. One of our main objectives was to find Cacopsylla pruni (Scopoli, 1763), the vector of ‘Candidatus Phytoplasma prunorum' during winter.The period of this study extended from 2014 to 2020 in the winter months. Insects were collected at 18 sampling sites from Borsod-Abaúj-Zemplén county to Somogy county, located at Alsótekeres, Balatonvilágos, Boldogkőváralja, Budakeszi, Fenyőfő, Gyöngyöspata, Kecskemét, Martonvásár, Mátra Mountain, Nagykovácsi, Nagyszakácsi, Páty, Piliscsaba, Somogytúr, Soroksár, Sóskút and Verpelét.A total of 1,600 jumping plant-louse specimens belonging to 20 species and three families (Psyllidae, Aphalaridae and Triozidae) were collected and identified during the study. In the case of plum psyllid (C. pruni) four shelter sites were identified as new records for Hungary.The most common species were Trioza remota, Cacopsylla melanoneura, Trioza urticae, Bactericera albiventris, C. pruni and Cacopsylla crataegi.

Quantification of 'Candidatus Phytoplasma prunorum' in apricot trees exhibiting uneven European stone fruit yellows symptoms

This study focused on quantification of 'Candidatus Phytoplasma prunorum' in apricot trees exhibiting uneven symptoms of European stone fruit yellows. For the research, 17 trees showing early leaf bud break in one part of the crown were selected in winter season, and 13 trees showing leafroll in older part of the shoots and no symptoms in younger part of the same shoots were selected in summer season. Absolute quantification of phytoplasmas was performed by real-time PCR in samples collected from asymptomatic and symptomatic parts. The results showed, that phytoplasma could not be always detected in asymptomatic parts, where 2 out of 17 samples from asymptomatic parts from winter season were negative while in summer season 6 out of 13 samples from asymptomatic parts were negative. Comparison of phytoplasma quantities between symptomatic and asymptomatic plant parts then showed significantly higher quantities in symptomatic parts from samples collected in summer season and no quantity difference in samples collected in winter season.

Presence and seed transmission of phytoplasmas in tomato fields in Italy

Tomatoes are the second most consumed vegetable, quite often severely affected by phytoplasma-associated diseases worldwide. The identification and confirmation that the phytoplasmas associated with the disease in Southern Italy are also transmitted through seeds was achieved. DNA extractions from mother plants collected in 2020 and 2021 and the seedlings from these plants, tested at different times, allowed the detection of phytoplasmas in both mother plants and seedlings grown under an insect-proof greenhouse. Phytoplasmas enclosed in groups 16SrX-B (‘Candidatus Phytoplasma prunorum’) and 16SrV-A (‘Ca. P. ulmi’) were identified in 2020 samples, and the same phytoplasma groups were identified in the seedlings. Phytoplasmas enclosed in groups 16SrI and 16SrXII were identified in mother plants collected in 2021 and were also identified in the seedlings. Moreover, a difference in germination percentage was observed. The 16SrXII-A group phytoplasmas detected in the mother plants and were identified as variants St5 for the stamp gene, tuf-b1 for the tuf gene and Vm44 for the vmp1 gene. This research is a significant confirmation of previous laboratory results on transmission of phytoplasmas through seeds from several diseased plant species. The epidemiological role of phytoplasma seed transmission is an essential knowledge for efficient management strategy planning for a seed production aimed at reducing the impact of phytoplasma-associated diseases in horticultural relevant crops such as tomatoes.

Identification of 16SrXXX-A Phytoplasma Associated with Salt cedar (Tamarix chinensis Lour.) witches'-broom (SCWB) in Southern Xinjiang of China.

Salt cedar is an ornamental shrub/moderate tree species native to Asia and East Europe, and grows in salt-alkali soil, desert and other dry areas, which plays an important role in wind prevention and sand fixation as well as maintaining ecological balance. Salt cedar witches'-broom (SCWB), which was extremely pernicious to Salt cedar. It was first observed and reported in Xi'an, China in 2005 (Zhao et al.2005). Witches' broom symptoms were observed on 20 out of 150 (13.3%) salt plants surveyed from the Alar region and 10 out of 86 (11.6%) plants from the Akesu region in southern of Xinjiang in May 2020. The damaged plants compared with asymptomatic plants (Fig.1A), the major symptoms included branches clustered, intersegment shorten and coarsen, giving rise to the formation of clusters (Fig.1B). Total plant DNA was extracted from phloem tissues with asymptomatic symptoms and phloem tissues with witches'-broom symptoms by a CTAB-based DNA extraction method (Green et al.1999). The 16S rRNA gene and the phytoplasma universal primers P1/P7 and rpF1/rpR1 of the rp (ribosomal protein) gene were used for Polymerase chain reaction (PCR) amplification by using the extracted plant total DNA as the template. The PCR product was used as the template and the R16F2n/R16R2 prmer was used for nested PCR amplification of the 16S rRNA gene after the amplification was completed. The results show that no product was obtained in asymptomatic plants. When DNA samples from witches'-broom symptomatic plants were used as templates, fragments with lengths 1219 bp and 1174 bp, corresponding to 16S rRNA gene and rp gene, were obtained. 16S rRNA gene was sequenced and deposited in GenBank under accession number MW447513. BLAST analysis revealed that the partial 16S rRNA sequence of the phytoplasma associated with P. aphylla witches' broom showed highest sequence identity (99.67%) to salt cedar witches' broom phytoplasma, 'Candidatus Phytoplasma tamaricis' (Accession Number: FJ432664). Phylogenetic and molecular evolutionary analyses were conducted using MEGA-X (Kumar et al., 2018). Results showed taht the SCWB and 16S rXXX group's'Candidatus Phytoplasma tamaricis', (GenBank accession: FJ432664) have the highest affinity (Fig.2A). A virtual restriction fragment length polymorphism(RFLP) was done to determinethe subgroup ( Zhao et al. 2009). The 16S rDNA sequence from the Tamarix chinensis plant showed 99.3% similarity with that of the "Candidatus Phytoplasma tamaricis" reference strain (GenBank accession: FJ432664), suggesting that the phytoplasma in this study belongs to "Candidatus Phytoplasma tamaricis"-related strain. Therefore, it can be stated that SCWB belongs to the 16S rXXX group. The partial rp sequences only shared 84.74% sequence similarity with that of 'Candidatus Phytoplasma prunorum' (MG383523) of Apple proliferation group, a known subgroup 16S rX. Blast analysis based on the partial rp sequences showed that it shares less than 90% similarity with that of any known phytoplasma (Fig 2B), we suspect that this is due to a lack of sequenced rp gene sequences for the 16S rXXX group. To our knowledge, this is the first report of Salt Cedar Witches' Broom phytoplasma in Xinjiang province, China. As a consequence, we guess the SCWB phytoplasma rp gene belongs to 16S rXXX-rp group, which is also the first report about the 16SrXXX-rp group. Because SCWB1 is the only strain in the 16S rXXX group, and it is the representative strain of the 16S rXXX-A subgroup (Zhao et al. 2009). So, the SCWB disease we found in southern Xinjiang belongs to the 16S rXXX-A subgroup.

Occurrence data for the two cryptic species of Cacopsylla pruni (Hemiptera: Psylloidea).

BackgroundCacopsylla pruni is a psyllid that has been known since 1998 as the vector of the bacterium ‘Candidatus Phytoplasma prunorum’, responsible for the European stone fruit yellows (ESFY), a disease that affects species of Prunus. This disease is one of the major limiting factors for the production of stone fruits, most notably apricot (Prunus armeniaca) and Japanese plum (P. salicina), in all EU stone fruit-growing areas. The psyllid vector is widespread in the Western Palearctic and evidence for the presence of the phytoplasma that it transmits to species of Prunus has been found in 15 of the 27 EU countries.Recent studies showed that C. pruni is actually composed of two cryptic species that can be differentiated by molecular markers. A literature review on the distribution of C. pruni was published in 2012, but it only provided presence or absence information at the country level and without distinction between the two cryptic species.Since 2012, numerous new records of the vector in several European countries have been published. We ourselves have acquired a large amount of data from sampling in France and other European countries. We have also carried out a thorough systematic literature review to find additional records, including all the original sources mentioning C. pruni (or its synonyms) since the first description by Scopoli in 1763. Our aim was to create an exhaustive georeferenced occurrence catalogue, in particular in countries that are occasionally mentioned in literature with little detail. Finally, for countries that seem suitable for the proliferation of C. pruni (USA, Canada, Japan, China etc.), we dug deeper into literature and reliable sources (e.g. published checklists) to better substantiate its current absence from those regions.Information on the distribution ranges of these vector psyllids is of crucial interest in order to best predict the vulnerability of stone fruit producing countries to the ESFY threat in the foreseeable future.New informationWe give free access to a unique file of 1975 records of all occurrence data in our possession concerning C. pruni, that we have gathered through more than twenty years of sampling efforts in Europe or through intensive text mining.We have made every effort to retrieve the source information for the records extracted from literature (1201 records). Thus, we always give the title of the original reference, together with the page(s) citing C. pruni and, if possible, the year of sampling. To make the results of this survey publicly available, we give a URL to access the literature sources. In most cases, this link allows free downloads of a PDF file.We also give access to information extracted from GBIF (162 exploitable data points on 245 occurrences found in the database), which we thoroughly checked and often supplemented to make the information more easily exploitable.We give access to our own unpublished georeferenced and genotyped records from 612 samples taken over the last 20 years in several European countries (Switzerland, Belgium, Netherlands, Spain etc.). These include two countries (Portugal and North Macedonia), for which the presence of C. pruni had not been reported before. As our specimens have been genotyped (74 sites with species A solely, 202 with species B solely and 310 with species A+B), our new data enable a better overview of the geographical distribution of the two cryptic species at the Palaearctic scale.

Molecular detection of phytoplasmas in potato psyllids in ecuador

Since the potato purple top appeared and the potato psyllid was reported in Ecuador, crop losses have been significant. So far, phytoplasmas enclosed in two ribosomal groups (16SrI-F, 16SrII) and Candidatus Liberibacter solanacearum’ were molecularly identified in symptomatic potato plants. Later, Bactericera cockerelli, a potato psyllid, was also first reported and correlated to the potato purple top disease. Molecular identification of the pathogens involved in this disease has been quite elusive. Samples of potato psyllids were analyzed in this study resulting in the identification of phytoplasmas enclosed in group 16SrXI, and others related to Candidatus Phytoplasma prunorum’ and Ca. P. solani’. Potato purple top in Ecuador is a complex disease that constitutes a severe threat for the potato production in the region.

Multi-scale spatial genetic structure of the vector-borne pathogen \u2018Candidatus Phytoplasma prunorum\u2019 in orchards and in wild habitats

Inferring the dispersal processes of vector-borne plant pathogens is a great challenge because the plausible epidemiological scenarios often involve complex spread patterns at multiple scales. The spatial genetic structure of ‘Candidatus Phytoplasma prunorum’, responsible for European stone fruit yellows disease, was investigated by the application of a combination of statistical approaches to genotype data of the pathogen sampled from cultivated and wild compartments in three French Prunus-growing regions. This work revealed that the prevalence of the different genotypes is highly uneven both between regions and compartments. In addition, we identified a significant clustering of similar genotypes within a radius of 50 km or less, but not between nearby wild and cultivated Prunus. We also provide evidence that infected plants are transferred between production areas, and that both species of the Cacopsylla pruni complex can spread the pathogen. Altogether, this work supports a main epidemiological scenario where ‘Ca. P. prunorum’ is endemic in — and generally acquired from — wild Prunus by its immature psyllid vectors. The latter then migrate to shelter plants that epidemiologically connect sites less than 50 km apart by later providing infectious mature psyllids to their “migration basins”. Such multi-scale studies could be useful for other pathosystems.

Phloem Metabolites of Prunus Sp. Rather than Infection with Candidatus Phytoplasma Prunorum Influence Feeding Behavior of Cacopsylla pruni Nymphs

Phytoplasmas are specialized small bacteria restricted to the phloem tissue and spread by hemipterans feeding on plant sieve tube elements. As for many other plant pathogens, it is known that phytoplasmas alter the chemistry of their hosts. Most research on phytoplasma-plant interactions focused on the induction of plant volatiles and phytohormones. Little is known about the influence of phytoplasma infections on the nutritional composition of phloem and consequences on vector behavior and development. The plum psyllid Cacopsylla pruni transmits ‘Candidatus Phytoplasma prunorum’, the causing agent of European Stone Fruit Yellows (ESFY). While several Prunus species are susceptible for psyllid feeding, they show different responses to the pathogen. We studied the possible modulation of plant-insect interactions by bacteria-induced changes in phloem sap chemistry. Therefore, we sampled phloem sap from phytoplasma-infected and non-infected Prunus persica and Prunus insititia plants, which differ in their susceptibility to ESFY and psyllid feeding. Furthermore, the feeding behavior and development of C. pruni nymphs was compared on infected and non-infected P. persica and P. insititia plants. Phytoplasma infection did not affect phloem consumption by C. pruni nymphs nor their development time. In contrast, the study revealed significant differences between P. insititia and P. persica in terms of both phloem chemistry and feeding behavior of C. pruni nymphs. Phloem feeding phases were four times longer on P. insititia than on P. persica, resulting in a decreased development time and higher mortality of vector insects on P. persica plants. These findings explain the low infestation rates of peach cultivars with plum psyllids commonly found in field surveys.

First report of Candidatus Phytoplasma prunorum, the European stone fruit yellows phytoplasma on peach trees on the territory of Canton of Geneva, Switzerland

In recent years, ‘Ca. P. prunorum’, the agent of ESFY was reported from several apricot orchards of Canton of Wallis, the main apricot production region in Switzerland (Genini and Ramel, 2004). The psyllid vector Cacopsylla pruni was also found in several locations in the Lake Geneva area (Ackermann et al., 2006). The presence of the disease and of its proven vector C. pruni at the eastern part of the Lake Geneva area, as well as the existing risk of dissemination of ESFY to other stone fruit orchards along the Lake Geneva are the reasons for which ESFY needs to be studied further. ESFY and its possible dissemination through C. pruni on the territory of Canton of Geneva, bordering France, has never been yet studied. In 2016, visual observations were conducted in several stone fruit orchards near Geneva. Plant material was obtained from peach trees, displaying some of the typical symptoms such premature leaf colouration, leaf-roll, tree decline (Sabaté et al., 2015), in the autumn, when the concentration of the phytoplasma in the upper parts of the trees is the highest. Phloem was prepared from branches and was extracted with a CTAB-based adapted protocol (Lefort and Douglas, 1999). PCR amplification of phytoplasma DNA was achieved with the universal primers: fP1/rP7 (Deng and Hiruki, 1991; Schneider et al., 1995). All positive samples were tested with the ESFY-specific non-ribosomal primers ECA1/ECA2 (Jarausch et al., 1998). Typical symptoms of ESFY, like premature leaf colouration, leaf yellowing with reddish edges, leaf-roll, severe chlorosis, die-back of top branches and partial or, complete decline of the trees (Figure 1) were found in a peach orchard (GPS coordinates: 46°15'17.4"N 6°12'40.7"E) located in the area of Collonge-Bellerive, close to Geneva city. Ten trees were sampled in this orchard. The presence of ‘Ca. P. prunorum’ was confirmed in two of them (Figure 2 and Figure 3). At the beginning of spring 2017, the monitoring of the ESFY symptoms in the infested orchard was resumed. Early bud break was found on the two infected trees and the infection was confirmed again by PCR (Figure 4 and Figure 5). The same symptoms were observed in many trees of this orchard, which correlated with the previous autumn observations. Trapping confirmed the presence of the insect vector Cacopsylla pruni (Bodnár et al., 2018) in the infected area. In order to understand more about the origin and the diversity of ESFY phytoplasma in this area, additional plant and insect samples will be analyzed. The correlation between symptoms and infected plants will be studied further. We report here for the first time on the occurrence of ‘Candidatus Phytoplasma prunorum’ (‘Ca. P. prunorum’) the agent of ESFY on the territory of Canton of Geneva.

Epidemiological and molecular study on ‘Candidatus Phytoplasma prunorum’ in Austria and Hungary

AbstractThe epidemiology of ‘Candidatus Phytoplasma prunorum’ was studied in Austria and Hungary from 2014 to 2018. Testing of root samples showed average infections rates of 61 and 40% of the Austrian Prunus spinosa and Prunus domestica spp. insititia samples, respectively. In Hungary, on average 21% of the P. spinosa and 13% of the feral Prunus cerasifera samples were infected. The pathogen was found in 18 out of 19 apricot orchards and PCR positive Cacopsylla pruni were observed at 11 out of 17 sampling locations in both countries. In cage experiments with C. pruni remigrants successful pathogen transmission to Prunus armeniaca, P. domestica and P. spinosa seedlings in budding and foliated developmental stages was recorded, an inoculation access period of 4 hr was sufficient for transmission. A field experiment with ungrafted apricot seedlings planted in 2012 and 2014 indicated a prominent role of the insect vectors for disease spread. In 2017, 40 and 28% of the trees planted in 2012 and 2014, respectively, were infected. Molecular characterisation based on the genes aceF and imp allowed the discrimination between 10 phytoplasma types in apricots. Around 70% of the phytoplasma types in apricots were also common in P. spinosa, in P. domestica spp. insititia and in remigrant C. pruni pointing to a possible pathogen exchange by insects between wild and cultivated Prunus spp. For disease control, vector management over the entire flight period of the remigrants seems necessary; when selecting active compounds, the short inoculation access period of not more than 4 hr should be considered.

Host plant preferences and detection of host plant volatiles of the migrating psyllid species Cacopsylla pruni, the vector of European Stone Fruit Yellows

Plant-emitted volatile organic compounds play an important role in plant–insect interactions. Thanks to plant-emitted volatiles, herbivores are able to find suitable hosts. Recognition and location of host plants are a key challenge for successful survival and reproduction of migrating insects, such as the plum psyllid Cacopsylla pruni. This psyllid migrates between Prunus spp. for reproduction and conifers for overwintering. C. pruni also is the only known vector of ‘Candidatus Phytoplasma prunorum’, a plant pathogen causing the European Stone Fruit Yellows, a severe plant disease. The preference of C. pruni for different Prunus species was monitored in the field. The sampling revealed a high abundance of C. pruni on Prunus spinosa, the natural host, as well as on different Prunus rootstock suckers. To investigate the influence of volatile profiles from different plants on the host preferences of C. pruni, the volatiles of two reproduction hosts and one overwintering host were sampled and analyzed by gas chromatography and mass spectrometry. The volatile compositions were compared, and important components that lead to the differentiation between plant species and growth stages were identified. Antennal responses of C. pruni females were elicited by eleven plant species and growth stage-specific volatiles, detected by electroantennography. The role of host plant volatiles on the migration behavior and the use of synthetic components in alternative control strategies are discussed.

Türkiye’de yumuşak ve sert çekirdekli meyvelerde ‘Candidatus Phytoplasma’ türlerinin moleküler çeşitliliği

Apple, pear and apricot trees showing phytoplasma associated symptoms from Ankara and Isparta provinces were sampled and investigated to verify the presence of phytoplasma-associated diseases. Totally 31 samples were tested with phytoplasma universal and group specific primers and the PCR products were restricted using Tru1I, RsaI and SspI endonucleases. Different RFLP profiles were obtained and selected samples were directly sequenced. The apple samples were found infected with 16SrX-A (‘Candidatus Phytoplasma mali’), while the majority of the pear samples were infected with 16SrX-A and 16SrX-C subgroup phytoplasmas in mixed infection. The 16SrX-B (‘Candidatus Phytoplasma prunorum’), 16SrX-C (‘Candidatus Phytoplasma pyri’) and mixed infection of 16SrX-A/16SrX-C and 16SrX-C/16SrI (aster yellows) were detected in the apricot samples. In this study the 16SrI phytoplasmas in apricot and the mixed phytoplasma infections in pear and apricot trees were detected in Turkey for the first time.

Examination of the plum psyllid (Cacopsylla pruni Scopoli), a vector of European Stone Fruit Yellows (ESFY) phytoplasma in the countryside of Boldogkőváralja (Hungary)

European Stone Fruit Yellows(ESFY) phytoplasma disease on apricot was identified by molecular methods for the first time in 1992 in Hungary. Currently, the pathogen is known as’ Ca. Phytoplasma prunorum’. Since, the pathogen become wide-spreaded and manyof the apricot-plantations had to be eliminated. In 2009 and 2010 in the countryside of Boldogkőváralja the infection of the apricot-plantations was about 77%. As the disease spreading and causing large damages, we studied the roleo fpossible vector,the plum psyllid (Cacopsylla pruni Scopoli) in the areas of Boldogkőváralja, North-East-Hungary. Studies were done in the year of 2016, monitoring the behaviour of the psyllids in four different areas, and caught 41 them for further examination. We collected plant samples from those apricot trees, on which the plum psyllids were caught.

Epidemiology of European stone fruit yellows in Germany: the role of wild Prunus spinosa

A nationwide monitoring with regard to the presence and distribution of ‘Candidatus Phytoplasma prunorum’ and its vector, Cacopsylla pruni, has been carried out in Germany between 2013 and 2017. In total, 286 sites with cultivated and wild Prunus species were surveyed. 806 plant samples covering 94 administrative districts in all 13 federal area states and one city-state were analysed by PCR. Furthermore, 3108 C. pruni were caught in 63 districts and tested for ‘Ca. P. prunorum’. European stone fruit yellows was found mainly in symptomatic apricot, plum, almond and peach but also for the first time in Germany in sweet cherry. Non-symptomatic infections were detected in 437 randomly sampled P. spinosa at 104 sites without any stone fruit growing nearby representing a natural infection rate of 14%. The vector C. pruni was found on all P. spinosa plants at 62 sites spread across Germany. The infection rate of C. pruni was 1–2% regardless whether the insects were caught in stone fruit growing areas or at wild habitats. Our results strongly indicate that ‘Ca. P. prunorum’ is widespread in all natural habitats in Germany and that wild P. spinosa represent a major source of infection in stone fruit orchards. A representative sample of 1164 individuals of C. pruni captured at 100 sites was molecularly typed: all but one insect were of B-type, the one which is the proven vector of ‘Ca. P. prunorum’. C. pruni A-type was detected for the first time in Germany near the French border.

Preliminary results of auxin and brassinosteroid application on ‘Candidatus Phytoplasma prunorum’ infected plants

Preliminary results of auxin and brassinosteroid application on ‘<i>Candidatus</i> Phytoplasma prunorum’ infected plants

A study on the epidemiology and the vector transmission of ‘Candidatus Phytoplasma prunorum’

A study on the epidemiology and the vector transmission of ‘<i>Candidatus</i> Phytoplasma prunorum’