Occurrence of Prunus necrotic ringspot virus and Prune dwarf virus in wild cherries in the locality velehrad (South Moravia, Czech Republic)

The occurrence and spatial distribution of PDV and PNRSV in a seed wild cherry (Prunus avium) orchard were studied during the period 1996 - 1999. Each year any newly infected trees were immediately removed. The cumulative infection rate of PDV-positive trees reached 4.7% and number of new infections per year was 1.2 %, on average. Although the number of centers was found to be decreasing (from 22 in 1996 to 10 in 1999), eradication of PDV was not achieved. Only one case of PNRSV infection was found in 1997

Occurrence of Prunus necrotic ringspot virus and Prune dwarf virus in wild cherries in the locality velehrad (South Moravia, Czech Republic)

The occurrence and spatial distribution of PDV and PNRSV in a seed wild cherry (Prunus avium) orchard were studied during the period 1996 - 1999. Each year any newly infected trees were immediately removed. The cumulative infection rate of PDV-positive trees reached 4.7% and number of new infections per year was 1.2 %, on average. Although the number of centers was found to be decreasing (from 22 in 1996 to 10 in 1999), eradication of PDV was not achieved. Only one case of PNRSV infection was found in 1997.Keywords: PDV, PNRSV, ELISA, epidemiolog

Geographical gradient of the <em>eIF4E</em> alleles conferring resistance to potyviruses in pea (<em>Pisum</em>) germplasm

<div><p>Background</p><p>The eukaryotic translation initiation factor 4E was shown to be involved in resistance against several potyviruses in plants, including pea. We combined our knowledge of pea germplasm diversity with that of the <i>eIF4E</i> gene to identify novel genetic diversity.</p><p>Methodology/Principal findings</p><p>Germplasm of 2803 pea accessions was screened for <i>eIF4E</i> intron 3 length polymorphism, resulting in the detection of four <i>eIF4E^A-B-C-S</i> variants, whose distribution was geographically structured. The <i>eIF4E^A</i> variant conferring resistance to the P1 PSbMV pathotype was found in 53 accessions (1.9%), of which 15 were landraces from India, Afghanistan, Nepal, and 7 were from Ethiopia. A newly discovered variant, <i>eIF4E^B</i>, was present in 328 accessions (11.7%) from Ethiopia (29%), Afghanistan (23%), India (20%), Israel (25%) and China (39%). The <i>eIF4E^C</i> variant was detected in 91 accessions (3.2% of total) from India (20%), Afghanistan (33%), the Iberian Peninsula (22%) and the Balkans (9.3%). The <i>eIF4E^S</i> variant for susceptibility predominated as the wild type. Sequencing of 73 samples, identified 34 alleles at the whole gene, 26 at cDNA and 19 protein variants, respectively. Fifteen alleles were virologically tested and 9 alleles (<i>eIF4E^{A-1-2-3-4-5-6-7}</i>, <i>eIF4E^B-1</i>, <i>eIF4E^C-2</i>) conferred resistance to the P1 PSbMV pathotype.</p><p>Conclusions/Significance</p><p>This work identified novel <i>eIF4E</i> alleles within geographically structured pea germplasm and indicated their independent evolution from the susceptible <i>eIF4E^S1</i> allele. Despite high variation present in wild <i>Pisum</i> accessions, none of them possessed resistance alleles, supporting a hypothesis of distinct mode of evolution of resistance in wild as opposed to crop species. The Highlands of Central Asia, the northern regions of the Indian subcontinent, Eastern Africa and China were identified as important centers of pea diversity that correspond with the diversity of the pathogen. The series of alleles identified in this study provides the basis to study the co-evolution of potyviruses and the pea host.</p></div

Identification and ecology of alternative insect vectors of &#8216;Candidatus Phytoplasma solani&#8217; to grapevine

Bois noir, a disease of the grapevine yellows complex, is associated with 'Candidatus Phytoplasma solani' and transmitted to grapevines in open fields by the cixiids Hyalesthes obsoletus and Reptalus panzeri. In vine-growing areas where the population density of these vectors is low within the vineyard, the occurrence of bois noir implies the existence of alternative vectors. The aim of this study was to identify alternative vectors through screening of the Auchenorrhyncha community, phytoplasma typing by stamp gene sequence analyses, and transmission trials. During field activities, conducted in Northern Italy in a vineyard where the bois noir incidence was extremely high, nine potential alternative insect vectors were identified according to high abundance in the vineyard agro-ecosystem, high infection rate, and harbouring phytoplasma strains characterized by stamp gene sequence variants found also in symptomatic grapevines. Transmission trials coupled with molecular analyses showed that at least eight species (Aphrodes makarovi, Dicranotropis hamata, Dictyophara europaea, Euscelis incisus, Euscelidius variegatus, Laodelphax striatella, Philaenus spumarius, and Psammotettix alienus/confinis) are alternative vectors of 'Candidatus Phytoplasma solani' to grapevines. These novel findings highlight that bois noir epidemiology in vineyard agro-ecosystems is more complex than previously known, opening up new perspectives in the disease management

First Report of Apricot pseudo-chlorotic leaf spot virus Infecting Plum (Prunus domestica) in the Czech Republic

Apricot pseudo-chlorotic leaf spot virus (APCLSV) is a novel, still poorly known Trichovirus in the family Betaflexiviridae. It is most closely related to Apple chlorotic leaf spot virus (ACLSV) (2,4) and infects stone fruit trees of the Prunus genus. Its presence has so far been detected in apricot, plum, Japanese plum, and peach trees in Italy, Spain, France, Hungary, Turkey, Jordan, and Australia (1,2,4). During the summers of 2008 and 2010, leaf samples of old Czech local plum cultivars were obtained from the Holovousy collection and assessed for the presence of viruses belonging to the Capillovirus, Trichovirus, and Foveavirus genera using the polyvalent degenerate oligonucleotides (PDO) nested reverse transcription (RT)-PCR test (3). Following amplification from total RNAs extracts, the amplicons were cloned and several clones were sequenced for each plant sample. In plum (Prunus domestica) cv. Babce, a mixture of amplicons was observed and BlastN and BlastX analyses of the obtained sequences revealed the presence of ACLSV and APCLSV. The 310-bp APCLSV amplicon (GenBank Accession No. JN790294) showed highest identity (82.9% in nucleotide sequence and 97.1% in amino acid sequence) with the Sus2 isolate of APCLSV (4) and clustered with APCLSV isolates in a phylogenetic analysis. APCLSV infection was further confirmed with an APCLSV-specific RT-PCR assay (4), which yielded a product of the expected 205-bp size (GenBank Accession No. JN653070) with closest homology again to the Sus2 APCLSV isolate (83.4 and 94.3% nucleotide and amino acid identity, respectively). To our knowledge, this finding represents the first detection of APCLSV in domestic plums in the Czech Republic, extending our vision of APCLSV diversity and its geographic distribution. For unknown reasons, APCLSV has almost always been reported in mixed infection with ACLSV (1,2,4) and the situation in cv. Babce does not deviate from this trend. This has greatly hindered the analysis of the pathogenicity of APCLSV, a situation further complicated in the current case because the Babce cultivar was also infected by Plum pox virus. References: (1) M. Barone et al. Acta Hortic. 781:53, 2008. (2) T. Candresse et al. Virus and Virus-Like Diseases of Pome and Stone Fruit Trees. A. Hadidi et al., eds. The American Phytopathological Society, St. Paul, MN, 2011. (3) X. Foissac et al. Phytopathology 95:617, 2005. (4) D. Liberti et al. Phytopathology 95:420, 2005. </jats:p