| 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 ... | 2009 | 19629636 |
| citrus tristeza virus transmission by the toxoptera citricida vector: in vitro acquisition and transmission and infectivity immunoneutralization experiments. | citrus tristeza virus (ctv) is transmitted by several aphid species in a semi-persistent manner with toxoptera citricida, the brown citrus aphid (brca), being the most efficient. as yet, the molecular interactions between the virus and its aphid vectors have not been determined. this is the first report of aphids acquiring ctv from preparations through an artificial membrane and then transmitting it to receptor plants. the brca fed across artificial membranes on crude tissue preparations made fr ... | 2006 | 16490262 |
| aphid biology: expressed genes from alate toxoptera citricida, the brown citrus aphid. | the brown citrus aphid, toxoptera citricida (kirkaldy), is considered the primary vector of citrus tristeza virus, a severe pathogen which causes losses to citrus industries worldwide. the alate (winged) form of this aphid can readily fly long distances with the wind, thus spreading citrus tristeza virus in citrus growing regions. to better understand the biology of the brown citrus aphid and the emergence of genes expressed during wing development, we undertook a large-scale 5' end sequencing p ... | 2003 | 15841239 |
| progress on strain differentiation of citrus tristeza virus and its application to the epidemiology of citrus tristeza disease. | citrus tristeza virus (ctv) occurs in most citrus producing regions of the world, and it is the most serious viral pathogen of citrus. with the recent establishment of the brown citrus aphid, toxoptera citricida, its most efficient vector, on madeira island (portugal) and in florida (usa) and the countries of the caribbean basin, the impact of ctv is likely to increase in these regions. since there are many strains of ctv and ctv infections frequently occur as mixtures of several strains, it is ... | 2000 | 11137165 |
| minor coat and heat shock proteins are involved in the binding of citrus tristeza virus to the foregut of its aphid vector, toxoptera citricida. | vector transmission is a critical stage in the viral life cycle, yet for most plant viruses how they interact with their vector is unknown or is explained by analogy with previously described relatives. here we examined the mechanism underlying the transmission of citrus tristeza virus (ctv) by its aphid vector, toxoptera citricida, with the objective of identifying what virus-encoded proteins it uses to interact with the vector. using fluorescently labeled virions, we demonstrated that ctv bind ... | 2016 | 27520823 |
| sequence variation in two genes determines the efficacy of transmission of citrus tristeza virus by the brown citrus aphid. | vector transmission is an important part of the viral infection cycle, yet for many viruses little is known about this process, or how viral sequence variation affects transmission efficacy. here we examined the effect of substituting genes from the highly transmissible fs577 isolate of citrus tristeza virus (ctv) in to the poorly transmissible t36-based infectious clone. we found that introducing p65 or p61 sequences from fs577 significantly increased transmission efficacy. interestingly, repla ... | 2016 | 27644950 |
| 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 ... | 2011 | 21225429 |
| 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 ... | 2009 | 19642988 |
| 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 ... | 1999 | 18944721 |
| 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 ... | 1999 | 18944697 |
| 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 ... | 2003 | 18944366 |
| 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 ... | 2008 | 18049792 |
| 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 ... | 2008 | 17999168 |
| 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 ... | 2013 | 24046764 |
| spatial and temporal spread of citrus tristeza virus and its aphid vectors in the north western area of morocco. | first report of citrus tristeza virus (ctv,closterovirus) in morocco datesback to 1961 in collections of citrus varieties. an exhaustive survey of citrus in the north of the country in 2009 revealed that ctv was spread all over the citrus production area. we attempted to evaluate the relative contribution of different aphid species in the spread of ctv disease in a citrus reticulata orchard at the loukkous region during 2 years (2012 and 2013). the overall ctv incidence estimated in the experime ... | 2016 | 25884375 |
| reference gene validation for quantitative pcr under various biotic and abiotic stress conditions in toxoptera citricida (hemiptera, aphidiae). | the regulation of mrna expression level is critical for gene expression studies. currently, quantitative reverse transcription polymerase chain reaction (qrt-pcr) is commonly used to investigate mrna expression level of genes under various experimental conditions. an important factor that determines the optimal quantification of qrt-pcr data is the choice of the reference gene for normalization. to advance gene expression studies in toxoptera citricida (kirkaldy), an important citrus pest and a ... | 2015 | 26470351 |
| identification, characterization and functional analysis of a chitin synthase gene in the brown citrus aphid, toxoptera citricida (hemiptera, aphididae). | chitin synthase (chs) is a crucial enzyme involved in the final step of the insect chitin biosynthetic pathway. in this study, we cloned the full-length cdna sequence of a chitin synthase gene (tcichs) from the brown citrus aphid, toxoptera citricida, an important citrus pest and the main vector of citrus tristeza virus worldwide. tcichs was expressed during the entire lifecycle and in all insect tissues examined. expression was highest in first-second-instar nymphs, nymph-adult transitions and ... | 2016 | 26991909 |
| 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 ... | 1998 | 18944934 |