Plum Pox Virus Symptoms Research Articles

Evaluation of American peach cultivars for resistance to Plum pox virus

Twenty-eight American peach cultivars were screened for their reaction to Plum pox virus (PPV). The cultivars were evaluated for the presence and intensity of PPV symptoms in leaves and fruits, and the relative concentration of PPV protein in flowers was determined by ELISA. The results allowed to divide the cultivars into four groups: cultivars Flame Prince, Cotender, Newhaven, Ruby Prince, Sun Prince, Jefferson, Camden and Jersey Queen were characterised as medium resistant to PPV; cultivars Loring, Blaze Prince, June Prince and Legend were classified as tolerant; cultivars Quachita Gold, O’Henry, Crest Haven, Biscos, Sentry, Fire Prince, Carogem, Carolina Belle, Redglobe and Harvester were rated as medium susceptible; and cultivars Bounty, Summer Prince, Gold Prince, Redhaven, Gala and Sunbrite were characterised as highly susceptible to PPV.

SEOPA-1 and GOLGI-2 Apricot Seedlings Are Resistant to Plum Pox Virus

SEOPA-1 and GOLGI-2 Apricot Seedlings Are Resistant to Plum Pox Virus

Localisation and movement of Plum pox virus in apricot stem tissues

SummaryLocalisation and movement of Plum pox virus (PPV), sharka disease, in stem tissues of susceptible and resistant apricot (Prunus armeniaca L.) cultivars was studied. Two different assays were performed. In the first assay, apricot cultivars were grafted on to a non‐inoculated GF305 peach rootstock and, after two months, the sprouted apricot was inoculated by chip‐grafting. In the second assay, apricot cultivars were grafted on to a previously chip‐inoculated GF305 showing strong PPV symptoms. Localisation of virus was studied in apricot stem by immuno‐tissue printing and sharka symptoms in GF305 and apricot leaves were also observed. Virus was mainly localised in the xylem, and sometimes in the cortex and pith. Results revealed that, while all the cultivars allowed limited virus movement from the inoculation point, only the susceptible cultivars (Screara, Bebeco and Colomer) allowed long distance movement and even showed symptoms in leaves.

Occurrence of plum pox virus in plums, myrobalans, blackthorns, apricots and peaches in South Moravia along the Austrian border

A survey on the occurrence of plum pox virus (PPV) in plums, myrobalans, blackthorns, apricots and peaches was carried out in the South Moravian region along the Austrian border. Results of tests by ELISA and evaluation of PPV symptoms showed only scattered or isolated occurrence of PPV. This situation can be used for gradual elimination of PPV in the South Moravian region.

Transfer of Plum Pox Virus Coat Protein Genes from a Plum Pox-resistant Transgenic Clone of Prunus domestica Plum to Its Progeny through Hybridization

Sharka or plum pox virus (PPV) is a major disease of stone fruit and causes severe economic losses in Europe. There is little resistance to PPV in most Prunus species, thus genetic engineering represents a potentially useful approach to obtain resistant germplasm. Transgenic plums containing the PPV coat protein (CP) or the related papaya ringspot virus (PRV)-CP gene were produced through Agrobacterium tumefaciens-mediated transformation. These transgenic plum clones were then evaluated for resistance to PPV infection in the greenhouse by graft or aphid inoculation with PPV. While symptoms of PPV appeared in most transgenic clones, all plants of PPV-CP transgenic clone C5 were symptomless and ELISA and immunocapture-reverse transcriptase PCR negative for over three years following inoculation with two strains of PPV (Ravelonandro et al., Plant Dis. 81:1231-1235, 1997). Clone C5, which contains multiple copies of the PPV-CP gene, was hybridized with PRV-CP transgenic plants or untransformed plum cultivars. Progeny were obtained containing no transgenes, only the PPV-CP, only the PRV-CP, or both the PRV-CP and PPV-CP transgenes. Seedlings were inoculated with PPV. At 5 and 11 months post-inoculation, seedlings containing the PPV-CP genes from C5 were symptomless and ELISA negative. Seedlings containing only PRV-CP transgenes or non-transformed controls showed symptoms of PPV infection and were ELISA positive. These results indicate that the PPV-CP transgenes can be transferred to progeny through hybridization and that these genes can impart resistance to PPV in transgenic seedlings. The inheritance of the multicopy inserts of the PPV-CP and PRV-CP transgenes is being analyzed. The combined effects of both transgenes on resistance to PPV and the stability of PPV resistance in the progeny of the resistant C5 transgenic line are currently under evaluation.

Prunus tomentosa as a Diagnostic Host for Detection of Plum Pox Virus and Other Prunus Viruses.

The efficacy of seedlings of Prunus persica cv. GF 305, P. persica cv. Siberian C, and P. tomentosa (Nanking Cherry) as diagnostic indicators of plum pox infection, and of P. tomentosa for other Prunus viruses was evaluated by graft-inoculation with eight different strains or isolates of plum pox virus (PPV) representative of the Marcus (M) and Dideron (D) serogroups; and one isolate each of Prunus necrotic ringspot virus (PNRSV), prune dwarf virus (PDV), and sour cherry green ring mottle virus (GRMV). The initial PPV symptoms that developed in P. tomentosa within 30 days after inoculation were chlorotic banding along the midrib spreading to lateral veins from the leaf base upward, giving the appearance of a chlorotic oak-leaf pattern. Symptoms caused by PPV-M could be distinguished from those caused by PPV-D. Virus titers in infected P. tomentosa and GF 305 were higher than those in Siberian C when measured by triple antibody sandwich enzyme-linked immunosorbent assay. Infections by PNRSV, PDV, and GRMV were evident with the first flush of vegetative growth.

Transformation of Plum with the Papaya Ringspot Virus Coat Protein Gene and Reaction of Transgenic Plants to Plum Pox Virus

Transgenic plum plants expressing the papaya ringspot virus (PRV) coat protein (CP) were produced by Agrobacterium-mediated transformation of hypocotyl slices. Hypocotyl slices were cocultivated with Agrobacterium tumefaciens strain C58/Z707 containing the plasmid pGA482GG/CPPRV-4. This plasmid carries the PRVCP gene construct and chimeric NPTII and GUS genes. Shoots were regenerated on Murashige and Skoog salts, vitamins, 2% sucrose, 2.5 μm indolebutyric acid, 7.5 μm thidiazuron, and appropriate antibiotics for selection. Integration of the foreign genes was verified through kanamycin resistance, GUS assays, polymerase chain reaction (PCR), and Southern blot analyses. Four transgenic clones were identified. Three were vegetatively propagated and graft-inoculated with plum pox virus (PPV)-infected budwood in a quarantine, containment greenhouse. PPV infection was evaluated over a 2- to 4-year period through visual symptoms, enzyme-linked immunosorbent assay, and reverse transcriptase PCR assays. While most plants showed signs of infection and systemic spread of PPV within l-6 months, one plant appeared to delay the spread of virus and the appearance of disease symptoms. Virus spread was limited to basal portions of this plant up to 19 months postinoculation, but, after 32 months symptoms were evident and virus was detected throughout the plant. Our results suggest that heterologous protection with PRVCP, while having the potential to delay PPV symptoms and spread throughout plum plants, may not provide an adequate level of long-term resistance.