scholarly journals Survey Methods for Assessment of Citrus tristeza virus Incidence in Urban Citrus Populations

Plant Disease ◽  
2002 ◽  
Vol 86 (4) ◽  
pp. 367-372 ◽  
Author(s):  
G. Hughes ◽  
T. R. Gottwald ◽  
K. Yamamura
Keyword(s):  
Survey Methodology ◽  
Citrus Tristeza Virus ◽  
Survey Methods ◽  
Acceptance Sampling ◽  
Large Area ◽  
Two Stage ◽  
Commercial Cultivation ◽  
Virus Incidence ◽  
Tristeza Virus ◽  
Citrus Tristeza

This article concerns survey methodology for pathogens in urban citrus populations, motivated in particular by the need for assessments of Citrus tristeza virus (CTV) incidence. We envisage a large area R not devoted primarily to the commercial cultivation of citrus, that nevertheless has a substantial population of citrus trees. It is desired to sample the citrus population of area R in order to be able to make a statement about the level of infection of the population with CTV, or with particular isolates thereof. We describe a two-stage acceptance sampling scheme in which area R is divided into N sampling units, of which n are inspected. The size of the sampling units, while much smaller than R, is still large, so subsampling is carried out, introducing the possibility of misclassification of sampling units. To account for misclassification of sampling units, a larger number must be inspected than if it were assumed that there were no misclassifications. We describe the calculation of sample sizes required for subsampling within sampling units and for the total number of sampling units to be inspected, using parameters that can be adjusted to meet different specified regulatory scenarios.

scholarly journals Survey Methods for Assessment of Citrus Tristeza Virus Incidence

1998 ◽  
Vol 88 (7) ◽  
pp. 715-723 ◽  
Author(s):  
G. Hughes ◽  
T. R. Gottwald
Keyword(s):  
Field Data ◽  
Citrus Tristeza Virus ◽  
Survey Methods ◽  
Enzyme Linked Immunosorbent Assay ◽  
Central California ◽  
Accuracy And Precision ◽  
Virus Incidence ◽  
Field Data Collection ◽  
Tristeza Virus ◽  
Citrus Tristeza

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 compared with an alternative method in which about 25% of the trees in a block are sampled, and material from groups of four trees is bulked and assayed together. Our comparative study indicated that the latter method results in increased accuracy and precision of estimates of citrus tristeza virus incidence without increasing unduly the number of laboratory assays required.

scholarly journals Survey Methods for Assessment of Citrus tristeza virus Incidence in Citrus Nurseries

Plant Disease ◽  
2001 ◽  
Vol 85 (8) ◽  
pp. 910-918 ◽  
Author(s):  
G. Hughes ◽  
T. R. Gottwald
Keyword(s):  
Characteristic Function ◽  
Population Size ◽  
Operating Characteristic ◽  
Citrus Tristeza Virus ◽  
Survey Methods ◽  
Sample Sizes ◽  
Operating Characteristics ◽  
Operating Characteristic Function ◽  
Tristeza Virus ◽  
Citrus Tristeza

Monitoring of plant health takes place in citrus nurseries to prevent the distribution of infected plants to commercial groves. In this article, both analytical and simulation methods are used to characterize schemes by which such monitoring may be carried out, in the particular context of Citrus tristeza virus infection. Two aspects of such schemes are discussed in detail. The inclusiveness of a sample is an assessment of the degree of redundancy that occurs because, in some samples, the progeny of identically infected propagation material may appear more than once. The operating characteristic function shows the probability of reaching a decision, based on sampling, that a population of daughter plants has an incidence of infection less than or equal to some adopted threshold level for any actual level of incidence in the population. If the same proportion of the population is assessed at different population sizes, both the inclusiveness and the operating characteristic function vary with population size. However, sample sizes may be calculated so that a specified operating characteristic function is maintained as population size varies. The sample sizes required to meet the conditions specified on the operating characteristics do not increase proportionally with population size. Under such a scheme, fewer samples might need to be taken from large populations of daughter plants than would be the case if a constant percentage sampling scheme were adopted.

scholarly journals Incidence, Transmissibility, and Genotype Analysis of Citrus tristeza virus (CTV) Isolates from CTV Eradicative and Noneradicative Districts in Central California

Plant Disease ◽  
2005 ◽  
Vol 89 (8) ◽  
pp. 859-866 ◽  
Author(s):  
R. K. Yokomi ◽  
R. L. DeBorde
Keyword(s):  
Citrus Tristeza Virus ◽  
Transmission Rate ◽  
Aphis Gossypii ◽  
Cotton Aphid ◽  
Central California ◽  
Virus Incidence ◽  
The Impact ◽  
Tristeza Virus ◽  
Tulare County ◽  
Citrus Tristeza

Growers in 45% (44,100 ha) of the citrus acreage in California stopped eradicating Citrus tristeza virus (CTV)-infected trees from their fields in 1995-96. The impact of leaving infected trees on the rate of CTV spread was determined by comparing temporal incidence of CTV in plots in Strathmore, Tulare County without eradication with incidence in a plot in McFarland, Kern County with eradication. From 1997 to 2003, CTV incidence in the Strathmore plots ranged from 6 to 42%, with annual spread rates from 1.6 to 3.6%. CTV incidence in the McFarland plot increased from 0 to 5% between 2001 and 2003 before infected trees were removed. Using a subplot hierarchical bulk sampling method, virus incidence over a 3-year period in a 6.5 km2 area near McFarland was estimated to range from 0.09 to 0.69%, which indicated that CTV suppression was still being achieved in this area. Vector tests using the cotton aphid, Aphis gossypii, identified highly transmissible isolates (30 to 61% transmission rate) and a larger proportion of highly transmissible isolates were found in the McFarland plots. Thirty-six CTV isolates from recently infected plot trees were obtained and analyzed. None of these isolates reacted with monoclonal antibody MCA13 that detects presumptive CTV severe strains. Molecular analysis using polymerase chain reaction and sequence-specific primers showed that all isolates had a genotype identical to the T30 mild isolate from Florida.

scholarly journals Stability of Citrus tristeza virus protective isolate 'Pêra IAC' according to SSCP analysis of old and new lines of three sweet orange varieties

2015 ◽  
Vol 41 (1) ◽  
pp. 8-12 ◽  
Author(s):  
Waldecy Matos da Silva Leonel ◽  
Maria Júlia Corazza ◽  
Carlos Alexandre Zanutto ◽  
Gerd Walter Müller ◽  
Sergio Alves Carvalho ◽  
...  
Keyword(s):  
Citrus Tristeza Virus ◽  
Sweet Orange ◽  
Shoot Tip ◽  
Polymorphism Analysis ◽  
Protective Capacity ◽  
Single Strand Conformational Polymorphism ◽  
Commercial Cultivation ◽  
Low Genetic Diversity ◽  
Tristeza Virus ◽  
Citrus Tristeza

Clonal cleaning, followed by pre-immunization with protective complexes of Citrus tristeza virus(CTV), allowed the commercial cultivation of Pêra sweet orange, a variety that has great importance for Brazilian citriculture but is sensitive to the virus. The use of mild protective isolates in other citrus varieties, even those more tolerant to CTV, can also be of interest to prevent the spread of severe isolates. The aim of this study was to characterize, by means of SSCP (Single Strand Conformational Polymorphism) analysis of the coat protein gene, CTV isolates present in plants of the sweet orange cultivars Pêra, Hamlin and Valencia propagated from four budwood sources: 1) old lines, 2) nucellar lines, 3) shoot-tip-grafted lines, and 4) shoot-tip-grafted lines pre-immunized with the mild CTV protective isolate 'PIAC'. We also evaluated the correlation of the obtained SSCP patterns to stem pitting intensity, tree vigor and fruit yield. SSCP results showed low genetic diversity among the isolates present in different trees of the same variety and same budwood source and, in some cases, in different budwood sources and varieties. Considering tristeza symptoms, lower intensity was noted for plants of new, shoot-tip-grafted and pre-immunized shoot-tip-grafted lines, compared to old lines of the three varieties. The observed SSCP patterns and symptomatology suggested that more severe CTV complexes infect the plants of old lines of all three varieties. The protective complex stability was observed in the SSCP patterns of CTV isolates of some shoot-tip-grafted and pre-immunized clones. It was concluded that the changes detected in other electrophoretic profiles of this treatment did not cause loss of the protective capacity of CTV isolate 'PIAC' inoculated in the pre-immunization.

First report of citrus tristeza virus in commercial citrus orchards in Tunisia

2021 ◽  
Author(s):  
Asma Najar ◽  
Imen Hamdi ◽  
Souad Mahmoud ◽  
Lassaad Medhioub ◽  
Imed Jaouadi ◽  
...  
Keyword(s):  
Citrus Tristeza Virus ◽  
First Report ◽  
Citrus Orchards ◽  
Tristeza Virus ◽  
Citrus Tristeza

A model for the spread and control of citrus tristeza virus disease

1989 ◽  
Vol 16 (3) ◽  
pp. 315-320
Author(s):  
Ruth Marcus ◽  
Hovav Talpaz ◽  
Moshe Bar-Joseph
Keyword(s):  
Citrus Tristeza Virus ◽  
Virus Disease ◽  
And Control ◽  
Tristeza Virus ◽  
Citrus Tristeza

Sscp analysis of variations in haplotypes of citrus tristeza virus isolated from yuzu (Citrus junos) in geographically separate regions of Korea

2006 ◽  
Vol 49 (1) ◽  
pp. 88-96 ◽  
Author(s):  
Dae Hyun Kim ◽  
Hye Kyung Shim ◽  
Jae Wook Hyeon ◽  
Hyeog Mo Kwon ◽  
Kwang Sik Kim ◽  
...  
Keyword(s):  
Citrus Tristeza Virus ◽  
Sscp Analysis ◽  
Citrus Junos ◽  
Tristeza Virus ◽  
Citrus Tristeza
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