Plum Pox Research Articles

Plum pox virus (sharka) resistance in peach by grafting ‘Garrigues’ almond as interstock

Sources of resistance to sharka (Plum pox virus, PPV) have not been identified among peach [Prunus persica (L) Batsch] cultivars to date. However, several studies have shown the possibility of inducing resistance to PPV by grafting with the ‘Garrigues’ almond [P. dulcis (Mill) D. A. Webb] cultivar. The so-called “Garrigues effect” progressively reduces the symptoms of the disease and the accumulation of the virus in ‘GF305’ peach plants highly infected with PPV Dideron after grafting ‘Garrigues’. In addition, grafting 'Garrigues' onto ‘GF305’ before inoculation completely prevents infection by the virus. In this work, the ‘Garrigues’ cultivar has been used as an interstock to prevent PPV infection in peach. We have evaluated a collection of peach cultivars representing red and yellow skin, white and yellow flesh, and free and cling stones, in addition to platycarpa peaches (‘Maya’, ‘Transvalia’, ‘Romea’, ‘Catherine’, ‘Astoria’, ‘Tirrenia’, ‘Maruja M13’, ‘Levante 30′, ‘Alisio 15′ and ‘Carioca’). The cultivars were grafted onto ‘Garrigues’ that was already growing on ‘GF305’, ‘GF677’ and ‘Garnem’ rootstocks. Once the assayed plants were ready and fully developed [rootstock + interstock (‘Garrigues’) + peach cultivars], we graft inoculated the rootstocks and the growing peach plants with PPV at least three times. We were not able to obtain symptoms or detect the virus by RT-PCR in any of the cases, despite the proven susceptibility of these cultivars. In view of the results, we can affirm that using the ‘Garrigues’ graft as interstock could act as a kind of "vaccine" against PPV-Dideron in peach that is ready to be used commercially.

Californian almond cultivar and rootstock behavior against Plum pox virus

Californian almond cultivar and rootstock behavior against <i>Plum pox virus</i>

Californian almond cultivar and rootstock behavior against Plum pox virus

Californian almond cultivar and rootstock behavior against <i>Plum pox virus</i>

Evaluation of susceptibility to Plum pox virus and European stone fruit yellows phytoplasma in Japanese plum and pluot cultivars

Evaluation of susceptibility to Plum pox virus and European stone fruit yellows phytoplasma in Japanese plum and pluot cultivars

Use of Bacterial Toxin-Antitoxin Systems as Biotechnological Tools in Plants.

Toxin-antitoxin (TA) systems in bacteria are key regulators of the cell cycle and can activate a death response under stress conditions. Like other bacterial elements, TA modules have been widely exploited for biotechnological purposes in diverse applications, such as molecular cloning and anti-cancer therapies. However, their use in plants has been limited, leaving room for the development of new approaches. In this study, we examined two TA systems previously tested in plants, MazEF and YefM-YoeB, and identified interesting differences between them, likely related to their modes of action. We engineered modifications to these specific modules to transform them into molecular switches that can be activated by a protease, inducing necrosis in the plant cells where they are expressed. Finally, we demonstrated the antiviral potential of the modified TA modules by using, as a proof-of-concept, the potyvirus plum pox virus as an activator of the death phenotype.

Effect of storage temperature on viral RNA accumulation in Plum pox virus-infected Red Lyon plum fruit from the Central Valley of Chile

Plum pox virus (PPV), the causative agent of Sharka disease, causes serious economic losses to the stone fruit industry. As PPV is not transmitted by seed, fruit from countries with Sharka present are considered low-risk for spreading the disease. However, there have been cases raising concerns about the safety of exporting fruit from countries with Sharka disease. Due to this, the generation of new scientific evidence becomes important to address these concerns. This study aimed to compare the relative accumulation of PPV viral titer between freshly harvested infected fruit with fruit subjected to cold storage, simulating transit conditions to export markets. During two consecutive seasons, the fruit was collected from a PPV-infected ’Red Lyon’ plum orchard, and divided into three treatments (T): freshly harvested fruit (T1); fruit exposed to cold (0 °C) for seven days (T2), and fruit exposed to cold (0 °C) for 15 days (T3). Semi-quantitative RT-PCR was used to estimate the viral titer; band density values obtained for products of amplification of a PPV genome fragment were normalized with the density values obtained from the constitutive gene nad5 and plotted relative to treatment T1, which served as a control for this purpose. The results showed a significant difference (p < 0.05) between T1 and other treatments. For the first season, the viral RNA reduction was of 50% in T2 and 61% in T3, compared to T1. For the second season, the corresponding RNA viral reductions were 45% in T2 and 56% in T3, compared to T1.

Cold Atmospheric Plasma (CAP) Treatment of In Vitro Cultivated Plum Plantlets—A Possible Way to Improve Growth and Inactivate Plum Pox Virus (PPV)

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

Adaptive substitutions at two amino acids of HCPro modify its functional properties to separately increase the virulence of a potyviral chimera.

We had previously reported that a plum pox virus (PPV)-based chimera that had its P1-HCPro bi-cistron replaced by a modified one from potato virus Y (PVY) increased its virulence in some Nicotiana benthamiana plants, after mechanical passages. This correlated with the natural acquisition of amino acid substitutions in several proteins, including in HCPro at either position 352 (Ile→Thr) or 454 (Leu→Arg), or of mutations in non-coding regions. Thr in position 352 is not found among natural potyviruses, while Arg in 454 is a reversion to the native PVY HCPro amino acid. We show here that both mutations separately contributed to the increased virulence observed in the passaged chimeras that acquired them, and that Thr in position 352 is no intragenic suppressor to a Leu in position 454, because their combined effects were cumulative. We demonstrate that Arg in position 454 improved HCPro autocatalytic cleavage, while Thr in position 352 increased its accumulation and the silencing suppression of a reporter in agropatch assays. We assessed infection by four cloned chimera variants expressing HCPro with none of the two substitutions, one of them or both, in wild-type versus DCL2/4-silenced transgenic plants. We found that during infection, the transgenic context of altered small RNAs affected the accumulation of the four HCPro variants differently and hence, also infection virulence.

A host range survey of the M strain of plum pox virus in native Asteraceae weeds in Japanese apricot orchards and a possible infection cycle

A host range survey of the M strain of plum pox virus in native Asteraceae weeds in Japanese apricot orchards and a possible infection cycle

Prevalence of stone fruit viruses in Russian regions and genetic analysis of PNRSV isolates

As part of monitoring works carried out by specialists of the All-Russian Plant Quarantine Center, samples of stone fruit crops collected in 20 Russian Federation subjects were tested by enzyme immunoassay for the presence of the following viruses: ACLSV, ApMV, APLPV, ArMV, CLRV, CRLV, PBNSPaV, PDV, PNRSV, PPV, PRMV, RpRSV, SLRSV, TBRV, ToRSV, and TRSV. The distribution of plum pox potyvirus (PPV), prunus necrotic ring spot ilarvirus (PNRSV), and prune dwarf ilarvirus (PDV) was determined across the area of 12, 12, and 8 Russian Federation subjects in 14.9 %, 11.9 %, and 1.7 % of test samples, respectively. The presence of these viruses was confirmed by polymerase chain reaction with subsequent sequencing of the amplification products obtained. The occurrence of these viruses was analyzed depending on the type of plantation, plant species, and region of distribution. The envelope protein gene region of 18 PNRSV isolates from five Russian Federation subjects was analyzed, which showed a significant genetic variability of this virus among the Russian population.

Development of an NLR-ID Toolkit and Identification of Novel Disease-Resistance Genes in Soybean.

The recognition of pathogen effectors through the nucleotide-binding leucine-rich repeat receptor (NLR) family is an important component of plant immunity. In addition to typical domains such as TIR, CC, NBS, and LRR, NLR proteins also contain some atypical integrated domains (IDs), the roles of which are rarely investigated. Here, we carefully screened the soybean (Glycine max) genome and identified the IDs that appeared in the soybean TNL-like proteins. Our results show that multiple IDs (36) are widely present in soybean TNL-like proteins. A total of 27 Gm-TNL-ID genes (soybean TNL-like gene encoding ID) were cloned and their antiviral activity towards the soybean mosaic virus (SMV)/tobacco mosaic virus (TMV) was verified. Two resistance (R) genes, SRA2 (SMV resistance gene contains AAA_22 domain) and SRZ4 (SMV resistance gene contains zf-RVT domain), were identified to possess broad-spectrum resistance characteristics towards six viruses including SMV, TMV, plum pox virus (PPV), cabbage leaf curl virus (CaLCuV), barley stripe mosaic virus (BSMV), and tobacco rattle virus (TRV). The effects of Gm-TNL-IDX (the domain of the Gm-TNL-ID gene after the TN domain) on the antiviral activity of a R protein SRC7TN (we previously reported the TN domain of the soybean broad-spectrum resistance gene SRC7) were validated, and most of Gm-TNL-IDX inhibits antiviral activity mediated by SRC7TN, possibly through intramolecular interactions. Yeast-two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays showed that seven Gm-TNL-IDX interacted with SMV-component proteins. Truncation analysis on a broad-spectrum antiviral protein SRZ4 indicated that SRZ4TIR is sufficient to mediate antiviral activity against SMV. Soybean cDNA library screening on SRZ4 identified 48 interacting proteins. In summary, our results indicate that the integration of IDs in soybean is widespread and frequent. The NLR-ID toolkit we provide is expected to be valuable for elucidating the functions of atypical NLR proteins in the plant immune system and lay the foundation for the development of engineering NLR for plant-disease control in the future.

Almond Can Be Infected by Plum Pox Virus-D Isolate Penn4 and Is a Transmission-Competent Host.

Although it is currently eradicated from the United States, Plum pox virus (PPV) poses an ongoing threat to U.S. stone fruit production. Although almond (Prunus dulcis) is known to be largely resistant to PPV, there is conflicting evidence about its potential to serve as an asymptomatic reservoir host for the virus and thus serve as a potential route of entry. Here, we demonstrate that both Tuono and Texas Mission cultivars can be infected by the U.S. isolate PPV Dideron (D) Penn4 and that Tuono is a transmission-competent host, capable of serving as a source of inoculum for aphid transmission of the virus. These findings have important implications for efforts to keep PPV out of the United States and highlight the need for additional research to test the susceptibility of almond to other PPV-D isolates.

Bazı yabancı otların Plum pox virüs T ile ilgili çalışmalarda indikatör bitki olarak kullanım potansiyelinin belirlenmesi

Determination of the potential of some weeds to be used as an indicator plant in studies on Plum pox virus-T&#x0D; &#x0D; ABSTRACT &#x0D; The plum pox virus (PPV) is the cause of sharka, the most destructive viral disease of Prunus species. A unique strain of PPV has so far been identified in Turkey and called as PPV-Turkey (PPV-T). Since viruses are obligate parasitic organisms, they cannot be cultured in artificial nutrient media. Weeds play a significant role in virus ecology and epidemiology as alternate hosts of plant viruses and as food plants for virus vectors. In this study, the potential of some weeds (such as Chenopodium album, Amaranthus retroflexus and Convolvulus arvensis) are indicators plants in experimental studies on PPV-T was investigated. C. album, A. retroflexus plants were inoculated by dusting three leaf on each 3-week-old plant. For each experiment, a homogeneous group of 10 plants grown singly in pots was inoculated PPV-T. Mock- and non-inoculated plants were used as negative controls. Inoculated plants were monitored dayl for symptom development. Following appearance of symptoms on PPV-T inoculated leaves tested by reverse transcription-polymerase chain reaction (RT-PCR). The results obtained from the indicator test showed that when mechanically inoculated of the two out of three plants tested species, C. album (6 out of 10 plants) and A. retroflexus (10 plants) reacted with infection. Initially, this indicator reacted with local symptoms, and later symptoms of systemic infection occurred.&#x0D; &#x0D; Keywords: Plum pox virus, PPV-Turkey, Herbaceous hosts, &#x0D; Indicator plant

On the possible impacts of a regulatory change on resource conservation: The case of the plumpox virus in France

Preserving natural resources in the context of global change includes looking at how to protect trees, whether in forests or for fruit production, from various epidemic diseases. A change in European regulation presently underway (EU 2016/2031; currently, in 2023, transitional measures are being implemented in France) transfers, from the public authorities to the profession (all the tree growers susceptible to be concerned), the responsibility for detecting plum pox virus, which has the potential to damage virtually all stone fruit orchards, and for eliminating the affected trees. Yet the disease is a viral one, transmitted by a vector (aphids) from tree to tree and from orchard to orchard. Within a few years, fruit from contaminated trees can no longer be marketed. We show here that, in the context of this new regulation, the heterogeneity of the tree growers (due to the size of the orchards, the diversification of the crops, the future of the farm...) can lead to a recrudescence of the disease throughout the stone fruit orchards. This would also imply all kind of negative effects on the economic (employment in the agricultural sector, national trade balance, processing and marketing sector activities...), social and environmental (landscapes...) levels. The results can easily be generalised to any problem of conservation of natural resources whose management is delegated to private stakeholders.

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.

TULPINI DE PLUM POX VIRUS IDENTIFICATE LA PIERSIC IN ZONA CENTRAL-SUDICĂ A BULGARIEI

Sharka disease, caused by plum pox virus (PPV), was detected on peach (Prunus persica (L.) Batsch.) for the first time in Bulgaria in 1989. Nowadays PPV is widespread in peach crops grown under varied agro-ecological conditions. The current study aimed to determinate the PPV strains spread in peach in six agro-ecological micro-regions located in three provinces (Plovdiv, Pazardzhik, Stara Zagora) of South Bulgaria. Altogether 70 PPV accessions, collected from 23 peach cultivars, were analysed by reverse transcription – polymerase chain reaction (RT-PCR) using primer pairs discriminating isolates of PPV-M, PPV-D and PPV-Rec strains. The summarized results revealed that PPV-M and PPV-D were identified in 85.7% and 8.6 % of the analysed samples, respectively. Both strains were detected at the highest infection rates in Pazardzhik province. Co-infection by both strains PPV-M and PPV-D was registered at the rate of 5.7 % of the tested accessions. PPV-Rec strain was not identified neither single nor in co-infection with the other strains. It has found differences in strain status in each of the studied orchards located in one and the same province. Likely the continuous increase of the PPV infection rate in peach is due to the prevalence of PPV-M strain, considered the epidemic form of the virus, and possible arising of higher virulent PPV-D variants. In that case, it should be applied all reasonable measures for containment of the virus spread and protection of the tree health.

PRUNUL TRANSGENIC HONEYSWEET ARE EFECT NEUTRAL ASUPRA DIVERSITĂȚII ȘI DINAMICII POPULAȚIILOR DE AFIDE ÎN CONDIȚII DE CLIMAT TEMPERAT- CONTINENTAL

‘HoneySweet’ is a genetically engineered plum resistant to Plum pox virus. Potential risks such as its impact on the diversity and dynamics of indigenous aphid populations was assessed. The study compared winged population of aphids visiting transgenic and conventional plums under continental temperate climatic conditions of Romania. The experimental analysis was conducted during three years (2016-2018) within an experimental plot containing transgenic (‘HoneySweet’) and conventional (‘Reine Claude d’Althan’ and ‘Stanley’) plums. This study revealed a similarity of both flight curves and the number and species of aphids landing on the two types of plum. Overall results showed no statistically differences between aphid species visiting the three cultivars, respectively the two types of plum. Consequently, our results support the hypothesis of the neutral effect of the transgenic plum on indigenous populations of aphids.

Bioengineering of horticultural crops in Russia and in the world

Modern bioengineering technologies make it possible to create fruit and berry crops with signs that are unattainable by traditional breeding methods, while significantly reducing the time of breeding work. A review of more than 90 scientific publications in the period from 1989 to 2020 with research work on the creation of transgenic fruit and berry crops using various bioengineering technologies, which showed a wide variety of methods for modifying and identifying the resulting plants.&#x0D; For example, the modification of the genome of an apple tree using genes that accelerate flowering, the so-called “Fast breeding” technology, allows you to speed up breeding work to create valuable varieties. The developed new varieties of transgenic apple trees are resistant to the fungi, bacteria, apple moth, and also reduced ability to browning fruits, with an increased content of sucrose, etc.&#x0D; Modern methods of genetic engineering make it possible to significantly accelerate the processes of creating highly productive varieties of fruit crops with increased or complete resistance to viruses. Transgenic papaya, expressing the gene for the envelope protein of the virus, made it possible to save plantations in Hawaii. The plum varieties created with the help of bioengineering were resistant to the plum pox virus (PPV), which poses a greater danger to perennial fruit crops.&#x0D; In Russia, clonal rootstocks of apple and pear trees resistant to herbicides, strawberries and pears with improved fruit taste, rootstocks and varieties of plums and cherries resistant to the Plum Pox Virus have been created and field tested, a technology for obtaining cisgenic plants has been developed and applied using the example of apple and tomato trees that do not contain viral and bacterial sequences. Methods of genomic editing and accelerated selection of fruit crops are being developed.

Aphid species populations and their seasonal fluctuation in Prunus orchards affected by Sharka disease within the quarantine areas of Argentina

Sharka is a disease of stone fruits, produced by the Plum Pox Virus and transmitted by aphids. It was detected for the first time in Argentina in 2004. In order to assess the aphid species that could act as a potential vector of this disease, we described the aphids community and seasonal fluctuation within two Prunus orchards affected by Sharka disease, located within two quarantine areas in Cuyo Region. Aphids were trapped weekly from October (spring) to April (autumn) during 2011-2012 and 2012-2013, by using yellow water traps (TAA), and identified using winged aphid’s taxonomic keys. In total, 27 aphid species were identified. The most dominant species collected was Myzus persicae (Sulzer). Orchard-trapped population of this dominant aphid showed seasonal fluctuation with two peaks, November (spring) and March (autumn).

Modeling the Impact of Agricultural Mitigation Measures on the Spread of Sharka Disease in Sweet Cherry Orchards.

Sharka is a disease affecting stone fruit trees. It is caused by the Plum pox virus (PPV), with Myzus persicae being one of the most efficient aphid species in transmitting it within and among Prunus orchards. Other agricultural management strategies are also responsible for the spread of disease among trees, such as grafting and pruning. We present a mathematical model of impulsive differential equations to represent the dynamics of Sharka disease in the tree and vector population. We consider three transmission routes: grafting, pruning, and through aphid vectors. Grafting, pruning, and vector control occur as pulses at specific instants. Within the model, human risk perception towards disease influences these agricultural management strategies. Model results show that grafting with infected biological material has a significant impact on the spread of the disease. In addition, detecting infectious symptomatic and asymptomatic trees in the short term is critical to reduce disease spread. Furthermore, vector control to prevent aphid movement between trees is crucial for disease mitigation, as well as implementing awareness campaigns for Sharka disease in agricultural communities that provide a long-term impact on responsible pruning, grafting, and vector control.