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strawberry chlorotic fleck: identification and characterization of a novel closterovirus associated with the disease.chlorotic fleck, a strawberry disease caused by a graft and aphid transmissible agent, was identified more than 45 years ago in louisiana. since its discovery there has been no additional information on the agent that causes the disease. the mode of transmission implies that a virus is the causal agent of chlorotic fleck. we identified four closteroviruses in the single chlorotic fleck infected strawberry clone known to exist in the united states. sequence analysis indicated that two of the viru ...200717109984
preferential accumulation of severe variants of citrus tristeza virus in plants co-inoculated with mild and severe variants.the viral population in sweet orange plants, either healthy or pre-inoculated with the asymptomatic isolate of citrus tristeza virus (ctv) t32, and then graft- or aphid-inoculated with the stem-pitting isolate t318, was characterized with respect to symptom expression, reaction with monoclonal antibody mca13, single-strand conformation polymorphism (sscp) of genes p18 and p20, bi-directional rt-pcr, and dot-blot hybridisation. all plants inoculated with t318, with or without pre-inoculation, sho ...200717294089
identification and characterization of raspberry mottle virus, a novel member of the closteroviridae.raspberry mosaic is one of the most important viral diseases of raspberry. four virus and virus-like agents, two of which are poorly characterized, have been implicated in the disease complex based on symptom development in rubus indicators. three novel viruses were identified in a red raspberry plant that caused typical raspberry mosaic symptoms when grafted onto indicators. this communication focuses on one of these viruses, raspberry mottle virus (rmov), a new member of the family closterovir ...200717448559
etiology of three recent diseases of citrus in são paulo state: sudden death, variegated chlorosis and huanglongbing.the state of são paulo (ssp) is the first sweet orange growing region in the world. yet, the ssp citrus industry has been, and still is, under constant attack from various diseases. in the 1940s, tristeza-quick decline (t-qd) was responsible for the death of 9 million trees in ssp. the causal agent was a new virus, citrus tristeza virus (ctv). the virus was efficiently spread by aphid vectors, and killed most of the trees grafted on sour orange rootstock. control of the disease resided in replac ...200717505974
completion of the mapping of transcription start sites for the five-gene block subgenomic rnas of beet yellows closterovirus and identification of putative subgenomic promoters.in the positive-sense rna genome of beet yellows closterovirus (byv), the 3'-terminal open reading frames (orfs) 2-8 are expressed as a nested set of subgenomic (sg) rnas. orfs 2-6, coding for the structural and movement proteins, form a 'five-gene block' conserved in closteroviruses. we mapped the 5'-end of the orf 4 sgrna, which encodes the p64 protein, at adenosine-11169 in the byv genome. this completes the mapping of the transcription start sites for the five-gene block sgrnas of byv. compu ...200717521763
a real-time rt-pcr assay for detection and absolute quantitation of citrus tristeza virus in different plant tissues.a real-time rt-pcr assay using sybr green was developed for specific and reliable quantitative detection of citrus tristeza virus (ctv) in infected plants. a general primer set designed from conserved sequences in orfs 1b and 2 enabled amplification of the genomic rna (grna) while excluding most subgenomic and defective rnas. single rt-pcr products of 204 bp (isolate t36) or 186 bp (other isolates) were obtained with no primer-dimer or non-specific amplifications detected. melting curve analysis ...200717573130
transcriptional response of citrus aurantifolia to infection by citrus tristeza virus.changes in gene expression of mexican lime plants in response to infection with a severe (t305) or a mild (t385) isolate of citrus tristeza virus (ctv) were analyzed using a cdna microarray containing 12,672 probes to 6875 different citrus genes. statistically significant (p<0.01) expression changes of 334 genes were detected in response to infection with isolate t305, whereas infection with t385 induced no significant change. induced genes included 145 without significant similarity with known ...200717617431
a stable rna virus-based vector for citrus trees.virus-based vectors are important tools in plant molecular biology and plant genomics. a number of vectors based on viruses that infect herbaceous plants are in use for expression or silencing of genes in plants as well as screening unknown sequences for function. yet there is a need for useful virus-based vectors for woody plants, which demand much greater stability because of the longer time required for systemic infection and analysis. we examined several strategies to develop a citrus triste ...200717651777
persistent infection and promiscuous recombination of multiple genotypes of an rna virus within a single host generate extensive diversity.recombination and reassortment of viral genomes are major processes contributing to the creation of new, emerging viruses. these processes are especially significant in long-term persistent infections where multiple viral genotypes co-replicate in a single host, generating abundant genotypic variants, some of which may possess novel host-colonizing and pathogenicity traits. in some plants, successive vegetative propagation of infected tissues and introduction of new genotypes of a virus by vecto ...200717878952
transgenic resistance to citrus tristeza virus in grapefruit.grapefruit (citrus paradisi) transgenic plants transformed with a variety of constructs derived from the citrus tristeza virus (ctv) genome were tested for their resistance to the virus. most transgenic lines were susceptible (27 lines), a few were partially resistant (6 lines) and only one line, transformed with the 3' end of ctv was resistant. transgene expression levels and sirna accumulation were determined to identify whether the resistance observed was rna-mediated. the responses were vari ...200817882423
quantitative detection of citrus tristeza virus in citrus and aphids by real-time reverse transcription-pcr (taqman).a quantitative and multiplex real-time rt-pcr assay was developed to detect citrus tristeza virus (ctv) along with plant mrna, which serves as an internal control to ascertain rna extraction quality. the real-time technique was validated against 39 ctv strains from around the world as well as with the aphid vector, aphis gossypii, given a 48 h acquisition access period on a ctv source plant. the assay was effective for quantitation of the viral template in infected plants and in single aphids. c ...200817888522
population structure of citrus tristeza virus from field argentinean isolates.we studied the genetic variability of three genomic regions (p23, p25 and p27 genes) from 11 field citrus tristeza virus isolates from the two main citrus growing areas of argentina, a country where the most efficient vector of the virus, toxoptera citricida, is present for decades. the pathogenicity of the isolates was determinated by biological indexing, single-strand conformation polymorphism analysis showed that most isolates contained high intra-isolate variability. divergent sequence varia ...200817999168
occurrence of genetic bottlenecks during citrus tristeza virus acquisition by toxoptera citricida under field conditions.in this study, we address the involvement of t. citricida in strain segregation and genetic bottleneck events by comparing the nucleotide diversity of ctv coat protein (cp) gene variants present in field-grown trees with that of variants retrieved from single apterous aphids. plant material and aphids were collected in orange orchards in the northern part of portugal. shoots from two trees that were found to be positive using elisa and twenty-four apterous aphids from these same trees were selec ...200818049792
stem pitting and seedling yellows symptoms of citrus tristeza virus infection may be determined by minor sequence variants.the isolates of citrus tristeza virus (ctv), the most destructive viral pathogen of citrus, display a high level of variability. as a result of genetic bottleneck induced by the bud-inoculation of ctv-infected material, inoculated seedlings of citrus wilsonii tanaka displayed different symptoms. all successfully grafted plants showed severe symptoms of stem pitting and seedling yellows, while plants in which inoculated buds died displayed mild symptoms. since complex ctv population structure was ...200818074213
in vivo and in vitro expression analysis of the rna-dependent rna polymerase of citrus tristeza virus.expression of the rna-dependent rna polymerase (rdrp) of citrus tristeza virus (ctv) was studied in vivo and in vitro using a polyclonal antiserum raised against the recombinant ctv-rdrp protein. although a 57-kda ctv-rdrp was expected to be expressed by a +1 translational frameshift at the carboxyl terminus of a 400-kda polyprotein, a 50-kda protein was detected in ctv-infected but not in healthy citrus tissue by western blot. this suggests that the rdrp was cleaved from the ctv polyprotein. th ...200818193157
genetic variation and recombination of rdrp and hsp 70h genes of citrus tristeza virus isolates from orange trees showing symptoms of citrus sudden death disease.citrus sudden death (csd), a disease that rapidly kills orange trees, is an emerging threat to the brazilian citrus industry. although the causal agent of csd has not been definitively determined, based on the disease's distribution and symptomatology it is suspected that the agent may be a new strain of citrus tristeza virus (ctv). ctv genetic variation was therefore assessed in two brazilian orange trees displaying csd symptoms and a third with more conventional ctv symptoms.200818199320
citrus tristeza virus: survival at the edge of the movement continuum.systemic invasion of plants by viruses is thought to involve two processes: cell-to-cell movement between adjacent cells and long-distance movement that allows the virus to rapidly move through sieve elements and unload at the growing parts of the plant. there is a continuum of proportions of these processes that determines the degrees of systemic infection of different plants by different viruses. we examined the systemic distribution of citrus tristeza virus (ctv) in citrus species with a rang ...200818434397
three genes of citrus tristeza virus are dispensable for infection and movement throughout some varieties of citrus trees.citrus tristeza virus (ctv), a member of the closteroviridae, possesses a 19.3-kb positive-stranded rna genome that is organized into twelve open reading frames (orfs). the ctv genome contains two sets of conserved genes, which are characteristic of this virus group, the replication gene block (orf 1a and 1b) and the quintuple gene block (p6, hsp70 h, p61, cpm, and cp). with the exception of the p6 gene, they are required for replication and virion assembly. ctv contains five additional genes, p ...200818456299
development and characterization of scar markers linked to the citrus tristeza virus resistance gene from poncirus trifoliata.twelve new dominant randomly amplified polymorphic dna (rapd) fragments associated with a single dominant gene for resistance to citrus tristeza virus (ctv) were identified using bulked segregant analysis of an intergeneric backcross family. these and eight previously reported rapds were mapped in the resistance gene (ctv) region; the resulting localized linkage map spans about 32 cm, with nine close flanking markers within 2.5 cm of ctv. seven of 20 rapd fragments linked with the resistance gen ...199718464859
diversity of citrus tristeza virus strains indicated by hybridization with cloned cdna sequences.cloned cdna sequences 500-2000 base pairs long, derived from a severe citrus tristeza virus (ctv) isolate, were used to study sequence homology with rna of nine other serologically indistinguishable ctv isolates which differed in their biological properties. six of the nine ctv isolates hybridized positively with the tested cdna clones, while three others hybridized differentially with these cdna clones. the potential use of cloned viral sequences for typing of virus strains is discussed.198418506941
molecular cloning of complementary dna sequences of citrus tristeza virus rna.complementary dna (cdna) of citrus tristeza virus (ctv) rna, synthesized using calf thymus dna random primers, was converted to a double-stranded form and inserted into the psti site of the escherichia coli pbr322 plasmid by the g-c tailing method. bacterial clones harbouring virus-specific sequences were detected by colony hybridization with a 32p-labelled viral rna probe. hybridization patterns of denatured virus rna revealed the presence of three types of specific clones: those hybridizing wi ...198318506942
characterization of citrus tristeza virus strains from southern china based on analysis of restriction patterns and sequences of their coat protein genes.citrus tristeza virus (ctv) isolates collected from southern china were characterized by biological indexing on citrus indicators, restriction fragment length polymorphism (rflp), and bi-directional reverse transcription-polymerase chain reaction (bd-pcr) analysis of their coat protein (cp) genes. of the 30 isolates, only two isolates, n3 and n4, did not induce visible symptoms. twenty-eight other isolates induced stem pitting and vein clearing, plant stunting, and leaf yellowing symptoms on mex ...200818626763
citrus tristeza virus: a pathogen that changed the course of the citrus industry.citrus tristeza virus (ctv) (genus closterovirus, family closteroviridae) is the causal agent of devastating epidemics that changed the course of the citrus industry. adapted to replicate in phloem cells of a few species within the family rutaceae and to transmission by a few aphid species, ctv and citrus probably coevolved for centuries at the site of origin of citrus plants. ctv dispersal to other regions and its interaction with new scion varieties and rootstock combinations resulted in three ...200818705856
mapping the chromosomes of poncirus trifoliata raf. by bac-fish.in spite of the importance of citrus in agriculture and recent progress in genetic mapping and cytogenetics of this group, chromosome mapping of citrus species is still limited to rdna probes. in order to obtain a better chromosome characterization of one species from this group, cma/dapi double staining followed by in situ hybridization using 45s rdna and 24 bacs (bac-fish) were used on poncirus trifoliata. the bacs used were obtained from a genomic library of this species and were selected by ...200818758171
fully "recombinant enzyme-linked immunosorbent assays" using genetically engineered single-chain antibody fusion proteins for detection of citrus tristeza virus.abstract recombinant single-chain variable fragment antibodies (scfv) that bind specifically to citrus tristeza virus (ctv), which cause the most detrimental viral disease in the citrus industry worldwide, were obtained from the hybridoma cell lines 3df1 and 3ca5. these scfv were genetically fused with dimerization domains as well as with alkaline phosphatase, respectively, and diagnostic reagents were produced by expressing these fusion proteins in bacterial cultures. the engineered antibodies ...200018943374
chimeric cdna sequences from citrus tristeza virus confer rna silencing-mediated resistance in transgenic nicotiana benthamiana plants.abstract rna silencing has been shown to be an important mechanism for conferring resistance in transgenic, virus-resistant plants. we used this approach to evaluate resistance in nicotiana benthamiana plants transformed with chimeric coding and noncoding sequences from citrus tristeza virus (ctv). several independent transgenic plant lines were generated, using two constructs (pctv1 and pctv2) designed to produce self-complementary transcripts. the pctv1 contained cdna sequences from the ctv ca ...200618943746
spatial and temporal analyses of citrus sudden death as a tool to generate hypotheses concerning its etiology.abstract citrus sudden death (csd), a new disease of unknown etiology that affects sweet orange grafted on rangpur lime, was visually monitored for 14 months in 41 groves in brazil. ordinary runs analysis of csd-symptomatic trees indicated a departure from randomness of symptomatic trees status among immediately adjacent trees mainly within rows. the binomial index of dispersion (d) and the intraclass correlation (k) for various quadrat sizes suggested aggregation of csd-symptomatic trees for al ...200318944366
genetic marker analysis of a global collection of isolates of citrus tristeza virus: characterization and distribution of ctv genotypes and association with symptoms.abstract genetic markers amplified from three noncontiguous regions by sequence specific primers designed from the partial or complete genome sequences of citrus tristeza virus (ctv) isolates t3, t30, t36, and vt were used to assess genetic relatedness of 372 isolates in an international collection. eighty-five isolates were judged similar to the t3 isolate, 81 to t30, 11 to t36, and 89 to vt. fifty-one isolates were mixed infections by two or more identifiable viral genotypes, and 55 isolates c ...200518944413
aphid transmission alters the genomic and defective rna populations of citrus tristeza virus isolates.abstract a total of 14 spanish isolates of citrus tristeza virus (ctv) and 1 isolate from japan were transmitted by aphis gossypii, and the subisolates obtained were compared with the source isolates for symptom expression and double-stranded rna (dsrna) pattern. of the 14 spanish isolates, 9 showed altered dsrna patterns after aphid transmission but only minor variations in the intensity of symptoms induced on mexican lime. northern blot hybridization with complementary dna (cdna) probes corres ...200018944601
examination of the effect of aphid vector population composition on the spatial dynamics of citrus tristeza virus spread by stochastic modeling.abstract aphid vector species population composition is known to affect the spatial patterns of citrus tristeza virus (ctv) and the changes in these patterns over time. however, the biological processes that are associated with virus spread have not been well defined. the spatiotemporal dynamics of ctv were examined using data collected from research plots in the dominican republic and costa rica, where the brown citrus aphid (bca), toxoptera citricida, was the predominant species, and in florid ...199918944697
survey methods for assessment of citrus tristeza virus incidence when toxoptera citricida is the predominant vector.abstract citrus tristeza virus (ctv) incidence may be assessed by sampling groups of citrus trees, recording the groups as ctv positive (one or more infected trees) or ctv negative (no infected trees), and then calculating disease incidence at the scale of the individual tree by means of a formula involving incidence at the group scale and the number of trees per group. this procedure works well when the ctv status of a tree can be regarded as independent of the ctv status of other trees in the ...199918944721
two paths of sequence divergence in the citrus tristeza virus complex.abstract comparison of a sampling of complementary dna (cdna) sequences from the florida citrus tristeza virus (ctv) isolates t3 and t30 to the sequence of the genome of the israeli isolate vt showed a relatively consistent or symmetrical distribution of nucleotide sequence identity in both the 5' and 3' regions of the 19.2-kb genome. in contrast, comparison of these sequences to the sequence of isolate t36 showed a dramatic decrease in sequence identity in the 5' proximal 11 kb of the genome. a ...199918944780
increase and patterns of spread of citrus tristeza virus infections in costa rica and the dominican republic in the presence of the brown citrus aphid, toxoptera citricida.abstract citrus tristeza virus (ctv) was monitored for 4 years by monoclonal antibody probes via enzyme-linked immunosorbent assay in four citrus orchards in northern costa rica and four orchards in the dominican republic following the introduction of the brown citrus aphid, toxoptera citricida. the gompertz nonlinear model was selected as the most appropriate in most cases to describe temporal increase of ctv. ordinary runs analysis for association of ctv-positive trees failed to show a spatial ...199818944934
molecular variability of the 5'- and 3'-terminal regions of citrus tristeza virus rna.abstract isolates of citrus tristeza virus (ctv) differ widely in their biological properties. these properties may depend on the structure of viral rna populations comprising the different isolates. as a first approach to study the molecular basis of the biological variability, we have compared the sequences of multiple cdna clones of the two terminal regions of the rna from different ctv isolates. the polymorphism of the 5' untranslated region (utr) allowed the classification of the sequences ...199818944941
survey methods for assessment of citrus tristeza virus incidence.abstract the assessment of citrus tristeza virus incidence by sampling involves laboratory testing by enzyme-linked immunosorbent assay of leaf material collected in the field. using field data and computer simulation, methods of field data collection were compared. one method was similar to that used by the central california tristeza eradication agency, in which 4 to 6% of the trees in a planting block are sampled and material from each tree sampled is assayed separately. this method was compa ...199818944945
development of an asymmetric pcr-elisa typing method for citrus tristeza virus based on the coat protein gene.the coat protein gene of isolates of citrus tristeza virus (ctv) from 20 citrus-producing regions around the world was amplified by rt-pcr, ta cloned, and characterized by sscp. haplotypes that produced different patterns within each geographic region were sequenced and a database of 153 accessions of ctv was assembled. phylogenetic analysis revealed the existence of seven well-defined clusters (coefficient of differentiation 0.78). an asymmetric pcr-elisa typing (apet) assay was developed in th ...200918992281
nuclear magnetic resonance characterization of metabolite disorder in orange trees caused by citrus sudden death disease.citrus sudden death (csd) is a new disease of sweet orange and mandarin trees grafted on rangpur lime and citrus volkameriana rootstocks. it was first seen in brazil in 1999, and has since been detected in more than four million trees. the csd causal agent is unknown and the current hypothesis involves a virus similar to citrus tristeza virus or a new virus named citrus sudden death-associated virus. csd symptoms include generalized foliar discoloration, defoliation and root death, and, in most ...200919161352
discrimination between mild and severe citrus tristeza virus isolates with a rapid and highly specific real-time reverse transcription-polymerase chain reaction method using taqman lna probes.severe isolates of citrus tristeza virus (ctv) inducing seedling yellows (sy) and/or stem pitting (sp) in grapefruit or sweet orange are a major threat for the citrus industry worldwide. identification of these ctv variants was achieved by quantitative real-time reverse transcription-polymerase chain reaction (rt-pcr) using a general primer set and three taqman locked nucleic acids (lna) probes targeting sequences characteristic of severe, mild (non-sy, non-sp), and t36-like isolates. successful ...200919203284
contribution of recombination and selection to molecular evolution of citrus tristeza virus.the genetic variation of citrus tristeza virus (ctv) was analysed by comparing the predominant sequence variants in seven genomic regions (p33, p65, p61, p18, p13, p20 and p23) of 18 pathogenically distinct isolates from seven different countries. analyses of the selective constraints acting on each codon suggest that most regions were under purifying selection. phylogenetic analysis shows diverse patterns of molecular evolution for different genomic regions. a first clade composed of isolates t ...200919264625
accumulation of a 5' proximal subgenomic rna of citrus tristeza virus is correlated with encapsidation by the minor coat protein.during replication, citrus tristeza virus (ctv) produces large amounts of two unusual subgenomic (sg) rnas that are positive-stranded and 5' coterminal. although these rnas are produced in similar amounts and are similar in size, with lmt1 ( approximately 750 nt) only slightly larger than lmt2 ( approximately 650), we found that the similar sgrnas are produced differently. we previously showed that the lmt1 rna is produced by premature termination during genomic rna synthesis. however, lmt2 prod ...200919446304
differential diagnosis of brazilian strains of citrus tristeza virus by epitope mapping of coat protein using monoclonal antibodies.citrus tristeza virus (ctv) is one of the most important citrus pathogen, and among brazilian ctv strains, the genotype capão bonito (cb) is the most harmful. therefore, the coat protein (cp) gene were cloned and expressed as recombinant protein and used to develop four specific monoclonal antibodies (mabs). our previously data had showed these mabs could recognize different strains of ctv and the present goal is to identify the epitopes of the recombinant cp by elisa screening of overlapping re ...200919540276
complete genome sequences of two distinct and diverse citrus tristeza virus isolates from new zealand.two citrus tristeza virus (ctv) isolates from new zealand that display distinct phenotypes were isolated, examined and sequenced in full. the first isolate, nz-m16, is largely asymptomatic and non-transmissible by the aphid vector toxoptera citricida, while the second, nz-b18, is highly transmissible and induces very severe symptoms on c. sinensis and c. aurantii. phylogenetic analysis of the genome sequences showed that both isolates were approximately 90-93% similar to the vt and t318 isolates ...200919629636
sequence diversity on four orfs of citrus tristeza virus correlates with pathogenicity.the molecular characterization of isolates of citrus tristeza virus (ctv) from eight locations in mexico was undertaken by analyzing five regions located at the opposite ends of the virus genome. two regions have been previously used to study ctv variability (coat protein and p23), while the other three correspond to other genomic segments (p349-b, p349-c and p13). our comparative nucleotide analyses included ctv sequences from different geographical origins already deposited in the genbank data ...200919642988
segregation of distinct variants from citrus tristeza virus isolate sy568 using aphid transmission.a well-studied severe isolate of citrus tristeza virus (ctv) known as sy568 has previously been shown to contain multiple variants of the virus which differ in their genetic and biological characters. aphid transmission was used in an attempt to segregate some of these variants for further characterization. resulting infections gave symptoms which varied from asymptomatic to more severe than the inoculum source. rnase protection assays (rpas) were used to compare nine regions of the ctv genome a ...200919740030
population dynamics of a florida citrus tristeza virus isolate and aphid-transmitted subisolates: identification of three genotypic groups and recombinants after aphid transmission.tristeza is an important citrus disease affecting the viability and productivity of citrus worldwide. the causal agent, citrus tristeza virus (ctv), usually occurs as a mixture of genotypes in nature, with one of the genotypes often dominating the population. ctv has a monopartite, positive-sense rna genome of approximately 19.3 kb and exhibits over 30% diversity in the 5' half and less than 10% in the 3' half among different genotypes. a florida ctv isolate, fs627, was selected for this study. ...200919821734
genetic diversity and evidence for recent modular recombination in hawaiian citrus tristeza virus.the hawaiian islands are home to a widespread and diverse population of citrus tristeza virus (ctv), an economically important pathogen of citrus. in this study, we quantified the genetic diversity of two ctv genes and determined the complete genomic sequence for two strains of hawaiian ctv. the nucleotide diversity was estimated to be 0.0565 + or - 0.0022 for the coat protein (cp) gene (n = 137) and 0.0822 + or - 0.0033 for the p23 gene (n = 30). the genome size and organization of ctv strains ...201019834797
cpm gene diversity in field isolates of citrus tristeza virus from colombia.the nucleotide sequence diversity of the cpm gene from 28 field isolates of citrus tristeza virus (ctv) was assessed by sscp and sequence analyses. these isolates showed two major shared haplotypes, which differed in distribution: a1 was the major haplotype in 23 isolates from different geographic regions, whereas r1 was found in isolates from a discrete region. phylogenetic reconstruction clustered a1 within an independent group, while r1 was grouped with mild isolates t30 from florida and t385 ...200919882104
examination of the responses of different genotypes of citrus to huanglongbing (citrus greening) under different conditions.abstract citrus huanglongbing (hlb) is one of the most devastating diseases of citrus worldwide. the causal agent of hlb in florida is thought to be 'candidatus liberibacter asiaticus'. in this work, we examined the responses of 30 different genotypes of citrus to florida isolates of 'ca. l. asiaticus' under controlled conditions in the greenhouse or growth room. although 'ca. l. asiaticus' was able to multiply in all of the plants, a wide range of responses was observed among different hosts. b ...200919900000
infection with strains of citrus tristeza virus does not exclude superinfection by other strains of the virus.superinfection exclusion or homologous interference, a phenomenon in which a primary viral infection prevents a secondary infection with the same or closely related virus, has been observed commonly for viruses in various systems, including viruses of bacteria, plants, and animals. with plant viruses, homologous interference initially was used as a test of virus relatedness to define whether two virus isolates were "strains" of the same virus or represented different viruses, and subsequently pu ...201019923189
characterization of the mixture of genotypes of a citrus tristeza virus isolate by reverse transcription-quantitative real-time pcr.a multiplex real-time pcr assay was developed to detect and quantify the citrus tristeza virus (ctv) genotypic mixture present in infected plants. ctv isolate fs627, a complex florida isolate containing t36, t30 and vt genotypes and its aphid transmitted subisolates was used. the relative quantitative assay was carried out using specific primers and probes developed from the genotypes of three ctv virus isolates and included the coat protein region of isolate t36 and the 5' end, orf 1a and orf 2 ...201020005260
accumulation of transgene-derived sirnas is not sufficient for rnai-mediated protection against citrus tristeza virus in transgenic mexican lime.mexican lime plants transformed with the 3'-terminal 549 nucleotides of the citrus tristeza virus (ctv) genome in sense, antisense and intron-hairpin formats were analysed for transgene-derived transcript and short interfering rna (sirna) accumulation, and for ctv resistance. propagations from all sense, antisense and empty-vector transgenic lines were susceptible to ctv, except for a single sense-line plant with a complex transgene integration pattern that showed transgene-derived sirnas in ass ...201020078774
the pathogenicity determinant of citrus tristeza virus causing the seedling yellows syndrome maps at the 3'-terminal region of the viral genome.citrus tristeza virus (ctv) (genus closterovirus, family closteroviridae) causes some of the more important viral diseases of citrus worldwide. the ability to map disease-inducing determinants of ctv is needed to develop better diagnostic and disease control procedures. a distinctive phenotype of some isolates of ctv is the ability to induce seedling yellows (sy) in sour orange, lemon and grapefruit seedlings. in florida, the decline isolate of ctv, t36, induces sy, whereas a widely distributed ...201020078776
transgenic expression in citrus of single-chain antibody fragments specific to citrus tristeza virus confers virus resistance.citrus tristeza virus (ctv) causes one of the most destructive viral diseases of citrus worldwide. generation of resistant citrus genotypes through genetic engineering could be a good alternative to control ctv. to study whether production of single-chain variable fragment (scfv) antibodies in citrus could interfere and immunomodulate ctv infection, transgenic mexican lime plants expressing two different scfv constructs, separately and simultaneously, were generated. these constructs derived fro ...201020204695
rapid differentiation and identification of potential severe strains of citrus tristeza virus by real-time reverse transcription-polymerase chain reaction assays.a multiplex taqman-based real-time reverse transcription (rt) polymerase chain reaction (pcr) assay was developed to identify potential severe strains of citrus tristeza virus (ctv) and separate genotypes that react with the monoclonal antibody mca13. three strain-specific probes were developed using intergene sequences between the major and minor coat protein genes (cpi) in a multiplex reaction. probe cpi-vt3 was designed for vt and t3 genotypes; probe cpi-t36 for t36 genotypes; and probe cpi-t ...201020205535
isolates of citrus tristeza virus that overcome poncirus trifoliata resistance comprise a novel strain.the economically important rootstock species poncirus trifoliata is resistant to most isolates of citrus tristeza virus (ctv), but not to members of the ctv resistance-breaking (rb) strain presently found in new zealand. in this study, five known and suspected rb isolates were separated from field mixtures, and their genomes were sequenced in full. it was found that the rb isolates are members of a single phylogenetically distinct clade with an average of 90.3% genomic nucleotide sequence identi ...201020352212
genome analysis of an orange stem pitting citrus tristeza virus isolate reveals a novel recombinant genotype.an orange stem pitting citrus tristeza virus (ctv) isolate ctv-b165 was found to be symptomatically similar to other known ctv-vt isolates however molecular methods failed to classify it as an identifiable ctv genotype. the sequence variation of the indian ctv-b165 isolate was compared to the three well known ctv genotypes, t36, t30, and vt. the genome of the predominant component of ctv-b165 was 19,247 nt in length with 12 open reading frames (orfs) and was structurally identical to the other c ...201020381550
heterologous minor coat proteins of citrus tristeza virus strains affect encapsidation, but the coexpression of hsp70h and p61 restores encapsidation to wild-type levels.the long flexuous bipolar virions of citrus tristeza virus (ctv), a closterovirus, are encapsidated with two capsid proteins at opposite ends: the minor coat protein (cpm) encapsidates the 5' 630 nts of the genomic rna and the major coat protein encapsidates the remainder of the genome. in this study, we found encapsidation of ctv cpm in the absence of other assembly-related proteins is highly specific in contrast to most plant viruses that allow virion assembly by a range of heterologous coat p ...201020399478
molecular characterization of citrus tristeza virus isolates from the northeastern himalayan region of india.citrus tristeza virus (ctv) isolates from the darjeeling hills of the northeastern himalayan region of india were characterized by biological indexing, multiple molecular marker (mmm) analysis, heteroduplex mobility assay (hma) and sequence analysis. variability was studied using the cp gene and a 5' orf1a fragment of the ctv genome. hma and sequence analysis of the 5' orf1a fragment classified darjeeling isolates into two groups, whereas cp gene analysis provided evidence for three different gr ...201020437063
comparison of ftir spectra between huanglongbing (citrus greening) and other citrus maladies.fourier transform infrared (ftir) spectroscopy has the ability to quickly identify the presence of specific carbohydrates in plant materials. the presence of the disease huanglongbing (hlb) in the leaves of infected citrus plants has a distinctive spectrum that can be used to distinguish an infected plant from a healthy plant. however, many citrus diseases display similar visible symptoms and are of concern to citrus growers. in this study several citrus diseases (citrus leaf rugose virus, citru ...201020438136
an atypical 3'-controller element mediates low-level transcription of the p6 subgenomic mrna of citrus tristeza virus.summary citrus tristeza virus (ctv) has within the 3'-half of the genome ten open reading frames (orfs) that are expressed through a series of 3'-coterminal subgenomic (sg) messenger (m)rnas that, in general, function as monocistronic mrnas with only the 5'-most orf translated. yet only nine sg mrnas have been detected, suggesting that orf 3, which is predicted to encode a small hydrophobic protein of approximately 6 kda (p6), might be expressed in some other manner, perhaps from a functionally ...200520565647
transgenic citrus plants expressing the citrus tristeza virus p23 protein exhibit viral-like symptoms.summary the 23 kda protein (p23) coded by the 3'-terminal gene of citrus tristeza virus (ctv), a member of the genus closterovirus with the largest genome among plant rna viruses, is an rna-binding protein that contains a motif rich in cysteine and histidine residues in the core of a putative zinc-finger domain. on this basis, a regulatory role for ctv replication or gene expression has been suggested for p23. to explore whether over-expression of this protein in transgenic plants could affect t ...200120572989
development and application of a multiplex reverse-transcription polymerase chain reaction assay for screening a global collection of citrus tristeza virus isolates.the emerging diversity of citrus tristeza virus (ctv) genotypes has complicated detection and diagnostic measures and prompted the search for new differentiation methods. to simplify the identification and differentiation of ctv genotypes, a multiplex reverse-transcription polymerase chain reaction (rt-pcr) technique for the screening of ctv isolates was developed. variable regions within the open reading frame (orf)-1a of diverse ctv genotypes were identified to develop first a simplex (s) and ...201020839943
somatic hybridization for citrus rootstock breeding: an effective tool to solve some important issues of the mediterranean citrus industry.the prevalence of sour orange rootstock in the southern and eastern part of the mediterranean basin is presently threatened by the spread of citrus tristeza virus (ctv) and its main vector toxoptera citricida, combined with abiotic constraints such as drought, salinity and alkalinity. the search for alternative ctv-resistant rootstocks that also withstand the other constraints is now considered an urgent priority for a sustainable citrus industry in the area. complementary progenitors can be fou ...201121225429
a sensitive and reliable rt-nested pcr assay for detection of citrus tristeza virus from naturally infected citrus plants.a specific and sensitive reverse transcriptase-nested polymerase chain reaction assay (rt-npcr) was developed for the detection of citrus tristeza virus (ctv) from naturally infected citrus samples. two sets of primer pairs were designed by alignment of nucleotide sequences available in genbank database for different genotypes of ctv. rt-npcr reaction components and thermal cycling parameters were optimized and reaction conditions were standardized. sequencing of the pcr products from direct and ...201121298268
citrus tristeza virus infection induces the accumulation of viral small rnas (21-24-nt) mapping preferentially at the 3'-terminal region of the genomic rna and affects the host small rna profile.to get an insight into the host rna silencing defense induced by citrus tristeza virus (ctv) and into the counter defensive reaction mediated by its three silencing suppressors (p25, p20 and p23), we have examined by deep sequencing (solexa-illumina) the small rnas (srnas) in three virus-host combinations. our data show that ctv srnas: (i) represent more than 50% of the total srnas in mexican lime and sweet orange (where ctv reaches relatively high titers), but only 3.5% in sour orange (where th ...201121327514
ectopic expression of the p23 silencing suppressor of citrus tristeza virus differentially modifies viral accumulation and tropism in two transgenic woody hosts.citrus tristeza virus (ctv), a phloem-restricted closterovirus infecting citrus, encodes three different silencing suppressors (p25, p20 and p23), one of which (p23) is a pathogenicity determinant that induces aberrations resembling ctv symptoms when expressed ectopically in transgenic citrus hosts. in this article, the effect of p23 ectopic expression on virus infection was examined in sweet orange (swo), a highly susceptible host, and sour orange (so), which severely restricts ctv cell-to-cell ...201121726389
calculation of diagnostic parameters of advanced serological and molecular tissue-print methods for detection of citrus tristeza virus: a model for other plant pathogens.citrus tristeza virus (ctv) is one of the most important virus diseases that affect citrus. control of ctv is achieved by grafting selected virus-free citrus scions onto ctv-tolerant or -resistant rootstocks. quarantine and certification programs are essential for avoiding the entry and propagation of severe strains of ctv. citrus nurseries in spain and central california (united states) maintain zero-tolerance policies for ctv that require sensitive, specific, and reliable pathogen-detection me ...201221879789
Agroinoculation of Citrus tristeza virus causes systemic infection and symptoms in the presumed nonhost Nicotiana benthamiana.Citrus tristeza virus (CTV) naturally infects only some citrus species and relatives and within these it only invades phloem tissues. Failure to agroinfect citrus plants and the lack of an experimental herbaceous host hindered development of a workable genetic system. A full-genome cDNA of CTV isolate T36 was cloned in binary plasmids and was used to agroinfiltrate Nicotiana benthamiana leaves, with or without coinfiltration with plasmids expressing different silencing-suppressor proteins. A tim ...201121899435
a plant virus evolved by acquiring multiple nonconserved genes to extend its host range.viruses have evolved as combinations of genes whose products interact with cellular components to produce progeny virus throughout the plants. some viral genes, particularly those that are involved in replication and assembly, tend to be relatively conserved, whereas other genes that have evolved for interactions with the specific host for movement and to counter host-defense systems tend to be less conserved. closteroviridae encode 1-5 nonconserved orfs. citrus tristeza virus (ctv), a closterov ...201121987809
top 10 plant viruses in molecular plant pathology.many scientists, if not all, feel that their particular plant virus should appear in any list of the most important plant viruses. however, to our knowledge, no such list exists. the aim of this review was to survey all plant virologists with an association with molecular plant pathology and ask them to nominate which plant viruses they would place in a 'top 10' based on scientific/economic importance. the survey generated more than 250 votes from the international community, and allowed the gen ...201122017770
a personal history of virus-based vector construction.the ability to express foreign genes or to silence endogenous genes in plants has revolutionized both basic and applied plant biology. virus-based expression systems, in which the foreign mrna is greatly amplified by virus replication, can produce very high levels of proteins or peptides in leaves and other tissues. vectors have been available for about 25 years. they are commonplace as laboratory tools, but their initial commercial expectations have not been met for numerous reasons. yet, appli ...201122025032
The evolutionary rate of Citrus tristeza virus ranks among the rates of the slowest RNA viruses.Citrus tristeza virus (CTV) has been intensively studied at the molecular level. However, knowledge regarding the dynamics of its evolution is practically non-existent. In the past diverse authors have referred to CTV as a highly variable virus implying a quick evolution. Others have, in recent times referred to CTV as an exceptionally slow evolving virus. In this work, we used the coat protein (CP) gene to estimate the rate of evolution. This was obtained from a large set of heterochronous CP ...201122071513
Characterizing the citrus cultivar Carrizo genome through 454 shotgun sequencing.The citrus cultivar Carrizo is the single most important rootstock to the US citrus industry and has resistance or tolerance to a number of major citrus diseases, including citrus tristeza virus, foot rot, and Huanglongbing (HLB, citrus greening). A Carrizo genomic sequence database providing approximately 3.5× genome coverage (haploid genome size approximately 367 Mb) was populated through 454 GS FLX shotgun sequencing. Analysis of the repetitive DNA fraction indicated a total interspersed repe ...201122133378
complete genome sequence of mandarin decline citrus tristeza virus of the northeastern himalayan hill region of india: comparative analyses determine recombinant.the complete genome sequence of a mandarin (citrus reticulata) decline ctv isolate, kpg3, of the darjeeling hills of the northeastern himalayan region of india is reported for the first time. the complete kpg3 genome has 19253 nt, and its nucleotide sequence identity ranged from 79% with the florida ctv isolate t36 to 94% with the israel isolate vt, whereas its identity to b165, the other indian isolate, was 89%. phylogenetic analysis indicated that the kpg3 genome is closely related to isolate ...201122160128
characterization of isolates of citrus tristeza virus by sequential analyses of enzyme immunoassays and capillary electrophoresis-single-strand conformation polymorphisms.citrus tristeza virus (ctv) is the causal agent of tristeza disease, which is one of the most devastating diseases of citrus crops worldwide. this paper describes a method for the rapid detection and genotyping of naturally spreading ctv isolates. this method uses elisa or dot-blot immunological tests to detect trees infected with ctv. the reaction wells or membrane spots for which there is a positive reaction are sequentially treated by (i) washing and elution of viral rna from the trapped samp ...201222305960
superinfection exclusion is an active virus-controlled function that requires a specific viral protein.superinfection exclusion, a phenomenon in which a preexisting viral infection prevents a secondary infection with the same or a closely related virus, has been described for various viruses, including important pathogens of humans, animals, and plants. the phenomenon was initially used to test the relatedness of plant viruses. subsequently, purposeful infection with a mild isolate has been implemented as a protective measure against virus isolates that cause severe disease. in the medical and ve ...201222398285
transformation of mexican lime with an intron-hairpin construct expressing untranslatable versions of the genes coding for the three silencing suppressors of citrus tristeza virus confers complete resistance to the virus.citrus tristeza virus (ctv), the causal agent of the most devastating viral disease of citrus, has evolved three silencing suppressor proteins acting at intra- (p23 and p20) and/or intercellular level (p20 and p25) to overcome host antiviral defence. previously, we showed that mexican lime transformed with an intron-hairpin construct including part of the gene p23 and the adjacent 3' untranslated region displays partial resistance to ctv, with a fraction of the propagations from some transgenic ...201222405601
highly-sensitive and label-free indium phosphide biosensor for early phytopathogen diagnosis.the development of highly-sensitive and label-free operating semiconductor-based, biomaterial detecting sensors has important applications in areas such as environmental science, biomedical research and medical diagnostics. in the present study, we developed an indium phosphide (inp) semiconductor-based resistive biosensor using the change of its electronic properties upon biomaterial adsorption as sensing element. to detect biomaterial at low concentrations, the procedure of functionalization a ...201322538056
distribution, genetic diversity and recombination analysis of citrus tristeza virus of india.citrus tristeza virus (ctv) isolates representing all the citrus-growing geographical zones of india were analyzed for nucleotide sequence of the 5'orf1a fragments of the partial lproi domain and for the coat protein (cp) gene. the nucleotide sequences were compared with previously reported indian and ctv genotypes from genbank. the indian isolates had 80-99 % sequence identity for the 5'orf1a and 89-99 % identity for the cp genes. in phylogenetic tree analysis, all the indian and previously rep ...201222562224
enhancement or attenuation of disease by deletion of genes from citrus tristeza virus.stem pitting is a common virus-induced disease of perennial woody plants induced by a range of different viruses. the phenotype results from sporadic areas of the stem in which normal xylem and phloem development is prevented during growth of stems. these alterations interfere with carbohydrate transport, resulting in reduced plant growth and yield. citrus tristeza virus (ctv), a phloem-limited closterovirus, induces economically important stem-pitting diseases of citrus. ctv has three nonconser ...201222593155
strategies for viral cross protection in plants.viral cross protection in plants is known as an acquired immunity phenomenon, where a mild virus isolate/strain can protect plants against economic damage caused by a severe challenge strain/isolate of the same virus. mild strain cross protection (mscp) has been used extensively to control losses caused by a few major virus diseases in some parts of the world. so far, none of the many proposed mechanisms can fully explain the intact process of mscp. in fact, it may be that different mechanisms a ...201222678573
high codon adaptation in citrus tristeza virus to its citrus host.citrus tristeza virus (ctv), a member of the genus closterovirus within the family closteroviridae, is the causal agent of citrus tristeza disease. previous studies revealed that the negative selection, rna recombination and gene flow were the most important forces that drove ctv evolution. however, the ctv codon usage was not studied and thus its role in ctv evolution remains unknown.201222698086
genotype composition of populations of grapefruit-cross-protecting citrus tristeza virus strain gfms12 in different host plants and aphid-transmitted sub-isolates.citrus tristeza virus (ctv) causes severe losses in grapefruit production in south africa and requires mild-strain cross-protection to maintain production. unfortunately, cross-protection breakdown of the pre-immunizing ctv grapefruit mild source gfms12 is prevalent in grapefruit in south africa. the ctv genotype composition of the gfms12 population inoculated onto different hosts was determined by sequencing part of orf1a and the p23 gene of multiple clones from each plant. analysis of the gfms ...201322932923
the genotypes of citrus tristeza virus isolates from china revealed by sequence analysis of multiple molecular markers.the genotypes of ten citrus tristeza virus (ctv) isolates from central china were determined by examining multiple molecular markers (mmms) using 11 primer pairs. the results revealed that one isolate contained a single t30 genotype, two isolates contained a single vt genotype, and the other seven isolates were mixtures of two or more genotypes. sequence analysis of amplified mmms showed a high genetic diversity in chinese ctv populations. the genotypes resembling t36, rb and b165 were identifie ...201322987316
citrus tristeza virus p23: determinants for nucleolar localization and their influence on suppression of rna silencing and pathogenesis.citrus tristeza virus (ctv) encodes a singular protein (p23, 209 amino acids) with multiple functions, including rna silencing suppression (rss). confocal laser-scanning microscopy of green fluorescent protein (gfp)-p23 agroexpressed in nicotiana benthamiana revealed its accumulation in the nucleolus, cajal bodies, and plasmodesmata. to dissect the nucleolar localization signal (nols) typically associated with basic motifs, seven truncated and 10 point-mutated versions of p23 were assayed. delet ...201323387469
citrus leaf blotch virus invades meristematic regions in nicotiana benthamiana and citrus.to invade systemically host plants, viruses need to replicate in the infected cells, spread to neighbouring cells through plasmodesmata and move to distal parts of the plant via sieve tubes to start new infection foci. to monitor the infection of nicotiana benthamiana plants by citrus leaf blotch virus (clbv), leaves were agroinoculated with an infectious cdna clone of the clbv genomic rna expressing green fluorescent protein (gfp) under the transcriptional control of a duplicate promoter of the ...201323560714
citrus biotechnology: achievements, limitations and future directions.citrus is one of the most important commercial and nutritional fruit crops in the world, hence it needs to be improved to cater to the diverse needs of consumers and crop breeders. genetic manipulation through conventional techniques in this genus is invariably a difficult task for plant breeders as it poses various biological limitations comprising long juvenile period, high heterozygosity, sexual incompatibility, nucellar polyembryony and large plant size that greatly hinder cultivar improveme ...200923572908
developing an understanding of cross-protection by citrus tristeza virus.citrus tristeza virus (ctv) causes two citrus diseases that have caused devastating losses in global citrus production. the first disease is quick decline of trees propagated on the sour orange rootstock. the second disease is stem pitting, which severely affects a number of economically important citrus varieties regardless of the rootstock used and results in reduced tree growth and vigor as well as in reduced fruit size and quality. both diseases continue to invade new areas. while quick decl ...201323577008
the closterovirus-derived gene expression and rna interference vectors as tools for research and plant biotechnology.important progress in understanding replication, interactions with host plants, and evolution of closteroviruses enabled engineering of several vectors for gene expression and virus-induced gene silencing. due to the broad host range of closteroviruses, these vectors expanded vector applicability to include important woody plants such as citrus and grapevine. furthermore, large closterovirus genomes offer genetic capacity and stability unrivaled by other plant viral vectors. these features provi ...201323596441
citrus tristeza virus: evolution of complex and varied genotypic groups.amongst the closteroviridae, citrus tristeza virus (ctv) is almost unique in possessing a number of distinct and characterized strains, isolates of which produce a wide range of phenotype combinations among its different hosts. there is little understanding to connect genotypes to phenotypes, and to complicate matters more, these genotypes are found throughout the world as members of mixed populations within a single host plant. there is essentially no understanding of how combinations of genoty ...201323630519
prevalence of citrus tristeza virus in mandarin of sikkim himalayan region.the assessment of citrus tristeza virus incidence in mandarin of sikkim, involving sampling techniques, was estimated by das-elisa. mandarin orchards had high ctv incidence (46.32%), however, differential prevalence with regard to age of plant and location was observed. the ctv prevalence was relatively high in older orchards (51.01%) than that of younger ones (40.80%). under all the plant age groups, south district had the highest ctv incidence (52.50%) and east district had the lowest (37.71%) ...201123637493
citrus tristeza virus p23: a unique protein mediating key virus-host interactions.the large rna genome of citrus tristeza virus (ctv; ca. 20 kb) contains 12 open reading frames, with the 3'-terminal one corresponding to a protein of 209 amino acids (p23) that is expressed from an abundant subgenomic rna. p23, an rna-binding protein with a putative zinc-finger domain and some basic motifs, is unique to ctv because no homologs have been found in other closteroviruses, including the type species of the genus beet yellows virus (despite both viruses having many homologous genes). ...201323653624
citrus tristeza virus-host interactions.citrus tristeza virus (ctv) is a phloem-limited virus whose natural host range is restricted to citrus and related species. although the virus has killed millions of trees, almost destroying whole industries, and continually limits production in many citrus growing areas, most isolates are mild or symptomless in most of their host range. there is little understanding of how the virus causes severe disease in some citrus and none in others. movement and distribution of ctv differs considerably fr ...201323717303
the defective rnas of closteroviridae.the family closteroviridae consists of two genera, closterovirus and ampelovirus with monopartite genomes transmitted respectively by aphids and mealybugs and the crinivirus with bipartite genomes transmitted by whiteflies. the closteroviridae consists of more than 30 virus species, which differ considerably in their phytopathological significance. some, like beet yellows virus and citrus tristeza virus (ctv) were associated for many decades with their respective hosts, sugar beets and citrus. o ...201323734149
emergence and phylodynamics of citrus tristeza virus in sicily, italy.citrus tristeza virus (ctv) outbreaks were detected in sicily island, italy for the first time in 2002. to gain insight into the evolutionary forces driving the emergence and phylogeography of these ctv populations, we determined and analyzed the nucleotide sequences of the p20 gene from 108 ctv isolates collected from 2002 to 2009. bayesian phylogenetic analysis revealed that mild and severe ctv isolates belonging to five different clades (lineages) were introduced in sicily in 2002. phylogeogr ...201323818960
a genetic system for citrus tristeza virus using the non-natural host nicotiana benthamiana: an update.in nature citrus tristeza virus (ctv), genus closterovirus, infects only the phloem cells of species of citrus and related genera. finding that the ctv t36 strain replicated in nicotiana benthamiana (nb) protoplasts and produced normal virions allowed development of the first genetic system based on protoplast transfection with rna transcribed from a full-genome cdna clone, a laborious and uncertain system requiring several months for each experiment. we developed a more efficient system based o ...201323847598
validation of high-throughput real time polymerase chain reaction assays for simultaneous detection of invasive citrus pathogens.a number of important citrus pathogens are spread by graft propagation, arthropod vector transmission and inadvertent import and dissemination of infected plants. for these reasons, citrus disease management and clean stock programs require pathogen detection systems which are economical and sensitive to maintain a healthy industry. to this end, multiplex quantitative real-time pcr (qpcr) assays were developed allowing high-throughput and simultaneous detection of some major invasive citrus path ...201323891873
mild strain cross protection of tristeza: a review of research to protect against decline on sour orange in florida.tristeza, caused by citrus tristeza virus (ctv), has long been present in florida but outbreaks of decline on sour orange rootstock were occasional events until the late 1970s. sour orange rootstock was valued for the high quality of fruit produced and was widely used because of its tolerance of citrus blight, a disease of unknown etiology. research was directed towards the selection and screening of mild strains of ctv which could protect against sour orange decline strains. following the intro ...201324046764
a localized linkage map of the citrus tristeza virus resistance gene region.a localized genetic linkage map was developed of the region surrounding the citrus tristeza virus (ctv) resistance gene (designated ctv) from poncirus trifoliate l., a sexually compatible citrus relative. bulked segregant analysis (bsa) was used to identify potential resistance-associated rapd fragment markers in four intergeneric backcross families that were segregating for ctv resistance. eight rapd fragments were found that were consistently linked to ctv in the four families. map distances a ...199624166392
the rna-dependent rna polymerase of citrus tristeza virus forms oligomers.the rna-dependent rna polymerases (rdrp) from citrus tristeza virus (ctv) were tagged with ha and flag epitopes. differentially tagged proteins were expressed either individually or concomitantly in escherichia coli. immunoprecipitation of the expressed proteins with anti-flag antibody followed by western blot with anti-ha antibody demonstrated that molecules of rdrp from ctv interact to form oligomers. yeast two-hybrid assays showed that molecules of rdrp interact in eukaryotic cells. co-immuno ...201324210106
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