Susceptibility of apricot cultivars to artificial inoculation with plum pox potyvirus and use of ELISA for its evaluation1

The susceptibility to plum pox potyvirus (PPV) of 13 apricot cultivars and two hybrids was studied under isolated conditions in the experimental orchard of the Research Breeding Station at Vesele from 1989 to 1993 after artificial inoculation of the trees. The plants were inoculated in the nursery in 1988 by chip-budding with a local source of virus and then planted into the field trial. First symptoms of plum pox appeared on the leaves in 1990. Reinoculation of symptomless trees was done in summer 1991. By 1993, plum pox had totally invaded some apricot trees of the most susceptible cultivars (Madarska, Velkopavlovicka, Kisinevskij rannij, Ligeti orias, Bergeron, Vesna and Vestar). Uninoculated control trees remained symptomless despite the proximity of diseased trees and the fact that the orchard was not sprayed with insecticides during the period of experiment. Cvs Julskij, Veecot, Vegama and Veharda remained free from plum pox symptoms on leaves and fruits. In 1993-05/06, the trees were assayed for the presence of the PPV antigen by ELISA. Leaf samples from 33 trees showing symptoms were positive. Samples prepared from the healthy tissues of leaves with symptoms were negative. Other trees (indexed by ELISA) growing in the neighbourhood of diseased trees in the period of 5 years were visually and ELISA negative.     

Susceptibility of some North American and Yugoslav plum cultivars to plum pox potyvirus in Poland1

All North American plum cultivars investigated in Poland for their reaction to plum pox potyvirus appeared to be susceptible, showing severe symptoms on the leaves. Fruits of cvs Valor and Empress were also heavily damaged. Of the Yugoslav cultivars evaluated, Cacanska Najbolja was most tolerant whereas Cacanska Rodna appeared to be most sensitive to PPV.     

Evaluation of peach and nectarine cultivars in Bulgaria for their resistance to plum pox potyvirus

In spring and summer 1989, it was established that plum pox potyvirus (PPV) was present in certain peach cultivars in Bulgaria. At the same time, we started to investigate the distribution of PPV in naturally infected 4–5 year-old peach and nectarine cultivars and hybrids in order to optimize PPV detection. Over 160 peach and nectarine cultivars and hybrids were evaluated. In about 40% of the genotypes, typical plum pox symptoms were observed. The latter were estimated and divided into groups depending on their susceptibility to PPV. Observations were made on the population density of seven aphid species established in the peach orchards. Five proved to be vectors of the virus. Myzus persicae was the vector that played the main role in spreading the virus on peach.     

Comparison of four techniques for plum pox virus detection

Journal of Plant Diseases and Protection - 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...     

Plum pox situation in Europe

The EPPO Conference on plum pox organized at Bordeaux (FR) in 1993–10 included a round-table session at which scientists from research and plant protection services of EPPO Member Governments reviewed the current national status of the disease. These reports have been summarized and compared here. They show that plum pox is the most serious disease of stone fruit in Europe and that nearly all countries which produce stone fruits are affected to a greater or lesser extent. Broadly, Europe can be divided into three zones: (1) the central and eastern countries in which plum pox spread relatively early and levels are generally high; (2) the northern and western countries in which plum pox levels are very heterogeneous (sometimes fairly widespread as in Germany, sometimes very restricted as in France, sometimes absent as in Netherlands); (3) Mediterranean countries in which spread is relatively recent and there is high risk of further spread.     

Recent results on resistance to plum pox potyvirus in plum in Romania,and on the epidemiology of the disease1

Of 50 plum cultivars investigated for infection by plum pox potyvirus (PPV), three had the virus in the latent state (Mansan, Twilight and Frontier), 19 showed very slight or slight symptoms on leaves, 16 showed moderate symptoms and 12 severe symptoms. No symptoms were seen on fruits of cvs Diana, Ialomita, Abundance, Silvia, Mont Royal, Red Glow, Locale de Turt, Krikon and Blue Free. Slight symptoms present only on the fruit skin were noted on cvs Gras ameliorat, Seneca, Rosior de Zalau, Prun protuberat, Anna Späth, Early Rivers, LU, Pitestean, Pamiat Timiriazeva, Dunarea Albastra (Blue Danube), Gras romanesc and others. Few plum cultivars had sensitive or very sensitive fruit. Most hybrids obtained in Romania are tolerant in terms of symptoms on fruits. Of the rootstocks, Red Dwarf Myrobalan, Buburuz, Marianna and P. besseyi showed no or very slight symptoms. Plum plantations located close to a PPV infection source for 6–9 years were 13.2–45.5% infected. Trees planted in an infected orchard were up to 74% infected in 6 years.     

Inclusion bodies in plants infected with sharka (plum pox) virus

Sharka virus was found to give rise to the formation of inclusion bodies in nucleus and cytoplasm of host cells, as is known for several other viruses of the potato virus Y group. In inoculatedNicotiana clevelandii needle-shaped inclusion bodies were found loosely distributed in the nucleus 10 days after the first external symptoms appeared. In the cytoplasm, bundles of needles and granular inclusions arose 14 and 18 days, respectively, after external symptoms became visible. The intranuclear needles disappeared shortly before or after the first appearance of granular cytoplasmic inclusions. Inclusion bodies abound in parenchyma cells of fruits from sharka-diseased plum trees, but they did not occur in fruits from sharka-free trees, with or without pseudo-pox symptoms. Thus, inclusion bodies can be of value in the diagnosis of sharka and be of great help in differentiating between plum pox and pseudo-pox.     

Cross reactions of an antiserum to plum pox potyvirus1

In the early spring of 1992, plum pox-like viruses (PPLVs) were detected by standard ELISA in some Prunus species. The isolates reacted positively with plum pox potyvirus (PPV) antisera in immunosorbent electron microscopy and Western blot analysis. In Western blot analyses, bands associated with the coat protein subunits of the PPLVs were 48–56 kDa, whereas bands associated with the coat protein subunits of known PPV isolates were 32–37 kDa in size. Also, the PPLVs differed from known PPV isolates in their symptoms on woody and herbaceous indicators, and in their herbaceous host range. None of these PPLVs appears to be an isolate of PPV.     

李痘病毒及其2个主要流行株系的分子鉴定

通过分析李痘病毒及其2个不同株系核酸的保守序列,设计出3对引物,即1对通用引物和2对株系特异性引物对李痘病毒进行RT-PCR检测,结果显示通用引物可以同时检测该病毒的2个最主要的流行株系,即D株系和M株系,而D株系引物只能检测出D株系病毒,M株系只能检测出M株系病毒,为口岸对进境种子、苗木及果实等中的李痘病毒准确快速的检测提供了一个有效的方法。     

Breeding for resistance to plum pox potyvirus in the Czech Republic1

Breeding for plum cultivars resistant to plum pox potyvirus (PPV) is in progress in the Czech Republic, while projects for apricot and peach have started in 1991. The aim is to create an assortment of apricot and peach cultivars for northern regions of Europe in which PPV is widely distributed.     

Plum pox potyvirus on sour cherry in Moldova

Plum pox potyvirus (PPV) was identified in six cultivars of sour cherry in the collection orchard of the Moldavian Horticultural Research Institute. Study of biological properties of the sour cherry isolate in herbaceous indicators showed its similarity or identity with the PPV isolate of Van Oosten and a significant difference from isolates widespread in Moldova. A purified viral preparation was used to develop antiserum with a working titre of 1:1024. Comparative serological examination of the sour cherry and conventional plum PPV isolates using ELISA, ISEM and SDS-PAGE of the protein capsid could not differentiate these isolates. The sour cherry isolate was transferred to plum resulting in weak but distinctive PPV symptoms in susceptible cv. Sopernitsa.     

First report of Plum pox virus on plum in Finland

In July 2014, leaves showing symptoms of a viral infection were collected from a plum tree serving as a mother tree in a Finnish nursery and found to be infected by Plum pox virus (PPV). A subsequent survey revealed additional infected trees originating from the infected mother tree. This paper provides the first report of PPV, the causal agent of the most destructive viral disease of Prunus, in Finland.     

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

Journal of Plant Diseases and Protection - 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...     

Detection of prunus viruses by print-capture PCR 1

A very sensitive and simple procedure has been developed for the preparation of plant samples before PCR amplification using direct tissue printing. This technique was successfully used for the detection of plum pox potyvirus, apple chlorotic leaf spot trichovirus, prunus necrotic ringspot ilarvirus and apple mosaic ilarvirus, in different stone-fruit material (peach, apricot, plum and almond). The results demonstrate the general applicability of this technique.     

Resistance to plum pox potyvirus in apricots1

The susceptibility of 115 apricot cultivars to plum pox potyvirus (PPV) has been examined, since 1981, in the experimental plots of the Pomology Institute at Naoussa and Skydra, Makedonia (GR). Inoculation was assured by aphids, transmitting strain PPV-M (Marcus) from naturally infected trees in adjacent peach orchards. For each cultivar, four to six trees were examined for at least 4 years. Observations on symptoms were made on leaves early in May and on fruits at maturity. Most cultivars expressed severe disease symptoms. Those without symptoms were inoculated by grafting onto heavily infected old apricot trees. The grafted shoots were tested for PPV in the following year by ELISA and on the woody indicator GF305. The cultivars which were rated as resistant after artificial inoculation and ELISA came from North America: Early Orange, Stella, NJA2, Sunglo, Veecot, Harlayne, Goldrich and Henderson. Most of these have been crossed with quality cultivars for the creation of resistant hybrids. The PPV resistance of large numbers of these apricot hybrids is now under investigation.     

Detection of plum pox virus in Spain

Until recently, plum pox (sharka) virus (PPV) was never detected in Spain on any of the material analysed by the enzyme-linked immunosorbent assay (ELISA). It was only in June 1984 that the virus was first detected by two different antiscra in Japanese plum trees ( Prunus salicina ), cv. Red Beaut, showing typical symptoms of the disease. The detection was later confirmed by graft-transmission to GF-305 peach seedlings, and also by immunoelectron microscopy. The PPV was experimentally transmitted from GF-305 to GF-305 by aphids and from GF-305 to herbaceous plants by mechanical inoculation. Thus far (January 1985), PPV has been detected basically in Japanese plum trees in Sevilla, Murcia, Valencia and Castellón, in apricot in Castellón, and in peach trees in Sevilla and Lérida.
De nombreuses analyses par la méthode ELISA n'ont, pendant longtemps, pas permis de détecter le plum pox virus (agent de la sharka) en Espagne. Ce n'est qu'en juin 1984 que la présence du virus a été confirmée, par l'utilisation de deux antiséra différents, chez des pruniers japonais ( Prunus salicina ) cv. Red Beaut qui manifestaient des symptôines typiques de la maladie. La détection a été confirmée par greffage sur des plants du pêcher GF-305, ainsi que par microscopie immuno-électronique. La transmission du PPV de GF-305 à GF-305 a été réalisée à l'aide de pucerons et de GF-305 à des plantes herbacées mécaniquement. A cette date (janvier 1985). le PPV n'a été détecté quc dans des prunicrs japonais dans, les provinces de Sevilla, Murcia, Valencia et Castellón, ainsi que dans des abricotiers en Castellón et dans des pêchers en Sevilla et en Lérida.     

Production of plants of Nicotiana benthamiana and Prunus domestica transgenic for plum pox potyvirus coat protein,and demonstration of PPV resistance in transformed N. benthamiana1

Leaf discs of Nicotiana benthamiana plants were transformed with Agrobacterium tumefaciens and transgenic plants expressing plum pox potyvirus (PPV) coat protein (CP) were generated. Homozygous R₂ progeny from these plants were inoculated with PPV. Plants were scored for the appearance of symptoms and tested for infection by DAS-ELISA. Various levels of resistance were obtained after an initial stage in which PPV was able to multiply in all the transgenic plants. Within 2–3 weeks after inoculation, the transgenic resistant plants fully recovered from virus infection. Conversely, control and susceptible transgenic lines developed severe symptoms and high virus titres. Prunus domestica (plum) was transformed by inoculating hypocotyl slices with A. tumefaciens containing a binary plasmid which included the NPTII, GUS, and PPV CP genes within its T-DNA region. Transgenic shoots were rooted and established in the glasshouse. Analysis of selected transformants by PCR showed that the engineered foreign genes had been integrated, including that for PPV CP. Histological assays on young leaves of these putative transformants gave a positive reaction. This suggests that all genes transferred are expressed in these transformed plums.     

Sensitivity of the detection of plum pox potyvirus by molecular assays1

Recently, plum pox potyvirus (PPV) has been found in Basilicata, southern Italy, on plum, apricot and peach. In 1992-09, we started a large-scale survey to verify the effectiveness of diagnostic methods used during seasons when it is difficult to reveal any presence of the virus. The assays were carried out by dot-blot hybridization on stone-fruit cultivars normally planted in this area. The virus was found, by dot-blot hybridization, to be present in seven cultivars of peach, four of apricot and one of plum. All plants were 8–10 years old and, except for two apricot cultivars, were not displaying any apparent symptoms in spring 1992. Five peach cultivars, intended for use as primary sources of propagation material, were then selected for further study, and assayed in 1992–11 by ELISA and RT-PCR. ELISA tests on these selected peach cultivars were consistently negative, while PCR tests were consistently positive. However ELISA tests gave positive results when repeated in 1993–05. These results not only suggest that primary propagation material should be tested by techniques more sensitive than ELISA, but also question the usefulness of carrying out tests during any phenological phases of the plant.