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Tristeza Virus (tristeza + virus)

Distribution by Scientific Domains
Life Sciences100%

Kinds of Tristeza Virus

  • citrus tristeza virus
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    Selected Abstracts

    Sensitive and Specific Digoxigenin-labelled RNA Probes for Routine Detection of Citrus tristeza virus by Dot-blot Hybridization

    JOURNAL OF PHYTOPATHOLOGY, Issue 6 2006
    L. Barbarossa
    Abstract A non-radioactive dot-blot hybridization assay for the successful detection of Citrus tristeza virus (CTV) RNA in total nucleic acid extracts of infected citrus was developed. Two digoxigenin (DIG)-labelled minus-sense riboprobes, complementary to the coat protein gene sequence of a Chinese and an Apulian CTV isolate were synthesized. Several citrus tissues were evaluated as optimal virus source and leaf petioles were found appropriate material for reliable detection. The hybridization assay showed a detection limit corresponding to 0.2 mg of fresh infected tissue. The riboprobes allowed CTV detection in isolates from different geographical areas, grown in the screenhouse or in the field, resulting in similar hybridization patterns. The infected trees were tested during different seasons with positive results, although from July to August most of the samples gave a weaker hybridization signal, compared to other seasons. The high sensitivity and reliability of the molecular hybridization assay described make it a good alternative to serological methods for CTV detection. [source]

    Comparative Sequence Analysis of Coat Protein Gene of Iranian Citrus tristeza virus Isolates

    JOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2005
    A. Barzegar
    Abstract Twenty-two isolates of Citrus tristeza virus (CTV) collected from two different geographical regions of Iran were characterized based on coat protein (CP) gene sequences. Thirteen virus isolates were collected from northern parts of Iran with high distribution of CTV infection and nine isolates were obtained from southern regions where the presence and aphid transmission of CTV was previously reported. All isolates were recovered from field trees showing varied CTV symptoms such as decline in most citrus varieties on sour orange rootstock, inverse pitting on some sour orange rootstocks below bud union, mild-to-moderate stem pitting on the trunk of some sweet orange. Isolates F, G, MB1, MB7, MB2, MB8, MB9, MB11 and MB17 were recovered from healthy looking Miyagawa Satsuma on trifoliate rootstock originally infected with CTV imported from Japan in late-1960s. The presence of virus in citrus samples was confirmed using polyclonal as well as monoclonal antibody. The CTV CP gene of all isolates was amplified by reverse transcriptase polymerase chain reaction (RT,PCR) using CP gene-specific primers yielding 672 bp amplicon. The restriction fragment length polymorphism (RFLP) profile, nucleotide and deduced amino acid sequences were analysed and compared with each other and also with some other exotic CP gene sequences of CTV isolates available in GenBank. Analysis of our data revealed that Iranian isolates have high similarity to California SY568 severe stem pitting and Japanese NUagA seedling yellows strains (up to 97%). The dendrogram generated from the deduced amino acid sequence could separate MB1, MB2, MB8, MB9, MB11 and MB17 isolates from others. However, no major dissociation between the isolates from northern and southern region could be obtained. [source]

    Variation of haplotype distributions of two genomic regions of Citrus tristeza virus populations from eastern Spain

    MOLECULAR ECOLOGY, Issue 2 2003
    F. D'Urso
    Abstract Genetic variation in natural populations of Citrus tristeza virus (CTV) was studied using haplotypes detected by single-strand conformation polymorphism (SSCP) analysis of two genomic regions (p20 gene and segment A, located in ORF1a). Analysis of 254 samples from 125 trees, collected at 12 different sites, yielded 8 different haplotypes for p20 and 5 for segment A. The most frequent haplotype of p20 was predominant at all sites, but several sites differed in the predominance of segment A haplotypes. At most sites, the homozygosity observed for the p20 gene tended to be higher than expected in a neutral evolution, whereas the opposite was true for segment A. Comparison of the populations at different sites showed that 44 of the 66 possible population pairs were genetically distinct for segment A, but only six pairs differed for the p20 gene. Analysis of molecular variance grouping trees by site, scion variety, rootstock or age, showed that variation in segment A was significantly affected by site, tree age and rootstock, and that variation between trees in each group and within trees was even more important. In contrast, variation in p20 was affected only by site and rootstock, each factor contributing to < 2% of the variation. The data suggest that sequence variations in segment A must be functionally less important and that it has less evolutionary constraints than p20. Detection of different haplotypes in neighbour trees or in samples from the same tree may help explain part of the variability observed in CTV symptom expression. [source]

    Citrus tristeza virus resistance in a core collection of sour orange based on a diversity study of three germplasm collections using QTL-linked markers

    PLANT BREEDING, Issue 4 2008
    G. P. Bernet
    Abstract Seven markers linked to QTL involved in CTV accumulation, leafminer resistance and apomictic reproduction were used to characterize 64 sour orange (Citrus aurantium L.) accessions from three national collections in order to identify a representative core in which the resistance behaviour against two Citrus tristeza virus (CTV) isolates was studied. Different degrees of apomixis were found between the foreign collections. Most of the C. aurantium accessions fall into three main groups based on three multilocus genotypes. The haplotype diversity at three CTV accumulation QTL-linked markers was further studied by sequence analysis of alleles. Genotypic and allelic diversity at one of them, tightly linked to Ctv-R2 in Poncirus trifoliata (L.) Raf., match the plant,CTV interaction types reported among Poncirus and Citrus species. Only those selected accessions from the major group presented CTV resistance during 30 months of continuous growth, but later the resistance broke down in some plants. CTV tolerance appears related to slow growing genotypes. Certain micronutrients: Mn, and B depending on the accession, might play a relevant role in this host,pathogen interaction particularly in alkaline soils. [source]

    Comparison of viral RNA populations of pathogenically distinct isolates of Citrus tristeza virus : application to monitoring cross-protection

    PLANT PATHOLOGY, Issue 3 2002
    A. Sambade
    The population of sequence variants of Citrus tristeza virus (CTV) isolates of different geographic origins and pathogenicity properties was characterized by single-strand conformation polymorphism (SSCP) analysis of cDNA of the genes p18, p13, p20 and p23. The mild isolates analysed here usually yielded a SSCP profile with two DNA bands, suggestive of a predominant sequence variant, whereas the SSCP profile of the most virulent isolates contained more than two DNA bands, indicating that their viral populations are likely to be more complex. The set of SSCP profiles of the four genes allowed identification of individual isolates, but no profile characteristic of a geographic area or a biogroup was found. Sweet orange plants singly inoculated with a mild or with a severe isolate yielded the SSCP profile characteristic of each isolate, whereas the SSCP profile of plants successively inoculated with both isolates was a composite of the two individual profiles. The SSCP profile of plants singly inoculated remained constant, but the profile of doubly inoculated plants varied with time. Plants in which the SSCP profile of the severe isolate became predominant showed stem pitting, and those in which the predominant profile corresponded to the mild isolate remained symptomless. The results indicate that SSCP analysis can be used to study changes in RNA populations of doubly inoculated plants and to monitor cross-protection between mild and severe isolates. [source]