Examination of the Effect of Aphid Vector Population Composition on the Spatial Dynamics of Citrus Tristeza Virus Spread by Stochastic Modeling

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 Florida, where the BCA was absent and the melon aphid, Aphis gossypii, was the predominant vector. Data were analyzed using a spatiotemporal stochastic model for disease spread, and parameter values were evaluated using Markov chain Monte Carlo stochastic integration methods. Where the melon aphid was the dominant species, the model parameter likelihood values supported the hypothesis that the disease was spread through a combination of random background transmission (transmission originating from inoculum sources outside the plot) and a local interaction (transmission from inoculum sources within the plot) operating over short distances. Conversely, when BCA was present, results often suggested a local short-range transmission interaction that was not restricted to nearest-neighbor interactions and that the presence of background infection was not necessary to explain the observations.

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The Effect of Aphid Vector Population Composition on Local and Background Components of Citrus Tristeza Virus Spread

International Organization of Citrus Virologists Conference Proceedings (1957-2010) ◽

10.5070/c50zs6g731 ◽

2000 ◽

Vol 14 (14) ◽

Author(s):

T. R. Gottwald ◽

G. Gibson ◽

S. M. Garnsey ◽

M. Irey

Keyword(s):

Citrus Tristeza Virus ◽

Virus Spread ◽

Population Composition ◽

Aphid Vector ◽

Vector Population ◽

Tristeza Virus ◽

Citrus Tristeza

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Separation of Citrus Tristeza Virus Isolates in Mixed Infections through Transfer by Single Brown Citrus Aphids

HortScience ◽

10.21273/hortsci.40.3.694 ◽

2005 ◽

Vol 40 (3) ◽

pp. 694-696 ◽

Cited By ~ 3

Author(s):

Charles A. Powell ◽

Youjian Lin

Keyword(s):

Citrus Tristeza Virus ◽

Sweet Orange ◽

Mixed Infections ◽

Citrus Paradisi ◽

Inoculum Sources ◽

Toxoptera Citricida ◽

Orange Trees ◽

Tristeza Virus ◽

Virus Isolates ◽

Citrus Tristeza

One hundred single brown citrus aphid (BCA) (Toxoptera citricida Kirkaldy) transmission attempts were made from each of 16 different citrus trees [8 grapefruit (Citrus paradisi Macf.) and 8 sweet orange (C. sinensis (L.) Osbeck)] previously inoculated with decline-inducing (T36-CTV), non-decline-inducing (T30-CTV), a mixture of the two Citrus tristeza virus isolate types, or no CTV. Successful CTV transmission occurred in 1.5% of attempts from grapefruit trees that had been bark-chip-inoculated with T36-CTV, 3% of attempts from orange trees inoculated with T36-CTV, 3% of attempts from grapefruit trees inoculated with both T36- and T30-CTV, 4% of attempts from orange trees inoculated with both T36- and T30-CTV, 1.5% of attempts from grapefruit trees inoculated with T30-CTV, and 3.5% of attempts from orange trees inoculated with T30-CTV. Single BCA were able to recover T30-like-CTV from trees believed to be inoculated only with T36-CTV, and T36-like-CTV from trees believed to be inoculated only with T30-CTV, suggesting that these inoculum sources were also mixtures of T36-CTV and T30-CTV. The T36-CTV was not immunologically detectable in some of the trees from which it was transmitted indicating that single BrCA can recover T36-CTV from a T36-CTV/T30-CTV mixture in which the T36-CTV is an undetectable, minority component.

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Spread of Citrus Tristeza Virus in Citrus Orchards in Central California

Plant Disease ◽

10.1094/pdis-08-19-1791-re ◽

2020 ◽

Vol 104 (7) ◽

pp. 1925-1931

Author(s):

Raymond K. Yokomi ◽

Mark S. Sisterson ◽

Subhas Hajeri

Keyword(s):

Citrus Tristeza Virus ◽

Virus Spread ◽

Central California ◽

Aphid Control ◽

Citrus Orchards ◽

Individual Trees ◽

Extension Center ◽

Tristeza Virus ◽

Tulare County ◽

Citrus Tristeza

In California, citrus tristeza virus (CTV) is regulated by a State Interior Quarantine. In CTV abatement districts in central California, trees with CTV that react to MCA13 (MCA13-positive [MCA13+]), a strain-discriminating monoclonal antibody, are rogued to prevent virus spread. The Tulare County Pest Control District, however, does not participate in this abatement program except for a 1.6-km2 zone around the Lindcove Research and Extension Center, Exeter, CA. To quantify CTV spread under these two disparate management programs, CTV surveys were conducted in abatement plots with mandatory aphid control and nonabatement plots. Abatement plot surveys used hierarchical sampling of 25% of trees with samples pooled from four adjacent trees. Detection of MCA13+ CTV in a sample prompted resampling and testing of individual trees. From 2008 to 2018, incidence of CTV increased by an average of 3.9%, with only two MCA13+ samples detected. In contrast, in nonabatement plots, incidence of CTV increased by an average of 4.6% between 2015 and 2018. Increase in MCA13-negative (MCA−) isolates was 11 times greater than that of MCA13+ isolates, with the number of MCA13+ trees increasing by 19 trees between 2015 and 2018. MCA13− isolates were more randomly distributed, suggesting primary spread, whereas MCA13+ CTV isolates were more aggregated, suggesting some secondary spread. These results suggest that spread of MCA13+ isolates was limited by a combination of tree removal and aphid vector suppression. MCA13+ samples were VT isolates with some mixtures with T30 isolates. Despite the presence of VT isolates, all CTV-infected trees were asymptomatic.

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Segregation of Distinct Variants from Citrus tristeza virus Isolate SY568 Using Aphid Transmission

Phytopathology ◽

10.1094/phyto-99-10-1168 ◽

2009 ◽

Vol 99 (10) ◽

pp. 1168-1176 ◽

Cited By ~ 7

Author(s):

J. J. Velazquez-Monreal ◽

D. M. Mathews ◽

J. A. Dodds

Keyword(s):

Citrus Tristeza Virus ◽

Aphid Transmission ◽

Single Infection ◽

Mild Strain ◽

Rnase Protection ◽

Genetic Characteristics ◽

Inoculum Sources ◽

Tristeza Virus ◽

Severe Isolate ◽

Citrus Tristeza

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 and determine whether unique strains could be identified. Five aphid-transmitted subcultures, with fingerprints that were different from those of the inoculum sources in at least one genomic area, were then cloned, sequenced, and compared with known isolates. An asymptomatic strain was shown to be different in every area of the CTV genome when examined by RPA and sequencing of selected regions. Mixed-infection studies using graft transmission of the asymptomatic subculture and two of the more severe aphid-transmitted subcultures showed that the mild strain was not able to compete well when in the presence of any of the severe variants tested, and its titer was significantly reduced from that seen in single infection. The mild strain and a selected severe strain were singly graft inoculated into five different citrus hosts (sweet orange, grapefruit, sour orange, lemon, and lime), where they maintained their distinct biological and genetic characteristics.

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Effects of Strain, Source Plant, and Temperature on the Transmissibility of Citrus Tristeza Virus by the Melon Aphid

Phytopathology ◽

10.1094/phyto-63-716 ◽

1973 ◽

Vol 63 (6) ◽

pp. 716 ◽

Cited By ~ 37

Author(s):

M. Bar- Joseph

Keyword(s):

Citrus Tristeza Virus ◽

Source Plant ◽

Melon Aphid ◽

Tristeza Virus ◽

Citrus Tristeza

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Minor Coat and Heat Shock Proteins Are Involved in the Binding of Citrus Tristeza Virus to the Foregut of Its Aphid Vector, Toxoptera citricida

Applied and Environmental Microbiology ◽

10.1128/aem.01914-16 ◽

2016 ◽

Vol 82 (21) ◽

pp. 6294-6302 ◽

Cited By ~ 22

Author(s):

N. Killiny ◽

S. J. Harper ◽

S. Alfaress ◽

C. El Mohtar ◽

W. O. Dawson

Keyword(s):

Heat Shock ◽

Citrus Tristeza Virus ◽

Viral Proteins ◽

Aphid Vector ◽

Toxoptera Citricida ◽

Shock Proteins ◽

Tristeza Virus ◽

Minor Coat Protein ◽

Citrus Tristeza

ABSTRACTVector 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 binds specifically to the lining of the cibarium of the aphid. Throughin vitrocompetitive binding assays between fluorescent virions and free viral proteins, we determined that the minor coat protein is involved in vector interaction. We also found that the presence of two heat shock-like proteins, p61 and p65, reduces virion bindingin vitro. Additionally, treating the dissected mouthparts with proteases did not affect the binding of CTV virions. In contrast, chitinase treatment reduced CTV binding to the foregut. Finally, competition with glucose,N-acetyl-β-d-glucosamine, chitobiose, and chitotriose reduced the binding. These findings together suggest that CTV binds to the sugar moieties of the cuticular surface of the aphid cibarium, and the binding involves the concerted activity of three virus-encoded proteins.IMPORTANCELimited information is known about the specific interactions between citrus tristeza virus and its aphid vectors. These interactions are important for the process of successful transmission. In this study, we localized the CTV retention site as the cibarium of the aphid foregut. Moreover, we demonstrated that the nature of these interactions is protein-carbohydrate binding. The viral proteins, including the minor coat protein and two heat shock proteins, bind to sugar moieties on the surface of the foregut. These findings will help in understanding the transmission mechanism of CTV by the aphid vector and may help in developing control strategies which interfere with the CTV binding to its insect vector to block the transmission.

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