Cross Protection Incompleteness: A Possible Cause for Natural Spread of Citrus Tristeza Virus After a Prolonged Lag Period in Israel

In Pakistan citrus groves in general are facing a serious problem of decline that is attributed to different causes. The major cause, however, is the prevalence of citrus virus and virus-like diseases; Citrus tristeza virus (CTV) is of utmost concern. Although CTV has been identified and characterized on the basis of serological and physical properties, no information is available on the strains of CTV in Pakistan. The identification of CTV strains will be helpful in developing strategies to control the decline of citrus trees to a great extent. Many citrus growing countries have successfully used the technique of cross protection to minimize the drastic effect of severe CTV strains. By pre-immunization of the citrus tree with mild strains, the decline can be controlled to increase the life span of the citrus tree. In this study we focus on the possibility of establishing a cross protection technique in Pakistan against the CTV strains.  

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Breakdown of Cross-Protection of Grapefruit from Decline-Inducing Isolates of Citrus tristeza virus Following Introduction of the Brown Citrus Aphid

Plant Disease ◽

10.1094/pdis.2003.87.9.1116 ◽

2003 ◽

Vol 87 (9) ◽

pp. 1116-1118 ◽

Cited By ~ 8

Author(s):

C. A. Powell ◽

R. R. Pelosi ◽

P. A. Rundell ◽

M. Cohen

Keyword(s):

Immunosorbent Assay ◽

Citrus Tristeza Virus ◽

Cross Protection ◽

Enzyme Linked Immunosorbent Assay ◽

Experimental Area ◽

Toxoptera Citricida ◽

The Cross ◽

Tristeza Virus ◽

Citrus Tristeza

A 21-year-old replicated field planting of 84 ‘Ruby Red’ grapefruit trees cross-protected with three mild isolates of Citrus tristeza virus (CTV) was assessed for decline-inducing and non-decline-inducing isolates of the virus 5 years after the brown citrus aphid (BrCA) (Toxoptera citricida Kirkaldy) first was established in the experimental area. Prior to the introduction of the BrCA, the cross-protecting mild isolates had significantly reduced detectable infection with decline-inducing isolates of CTV for 16 years (average infection of 13% in cross-protected trees compared with 67% in unprotected trees). After the introduction of the BrCA, infections with decline-inducing CTV (measured by enzyme-linked immunosorbent assay) were 57, 81, and 71% for trees protected with three mild isolates, respectively, compared with 95% in unprotected trees. These results suggest that the introduction of BrCA accelerated the breakdown of cross-protection against decline-inducing isolates of CTV in grapefruit.

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Walking Together: Cross-Protection, Genome Conservation, and the Replication Machinery of Citrus tristeza virus

Viruses ◽

10.3390/v12121353 ◽

2020 ◽

Vol 12 (12) ◽

pp. 1353

Author(s):

Svetlana Y. Folimonova ◽

Diann Achor ◽

Moshe Bar-Joseph

Keyword(s):

Citrus Tristeza Virus ◽

Fluorescent Protein ◽

Field Tests ◽

Fruit Trees ◽

Plant Viruses ◽

Cross Protection ◽

Virus Variant ◽

Tristeza Virus ◽

Direct Confirmation ◽

Citrus Tristeza

“Cross-protection”, a nearly 100 years-old virological term, is suggested to be changed to “close protection”. Evidence for the need of such change has accumulated over the past six decades from the laboratory experiments and field tests conducted by plant pathologists and plant virologists working with different plant viruses, and, in particular, from research on Citrus tristeza virus (CTV). A direct confirmation of such close protection came with the finding that “pre-immunization” of citrus plants with the variants of the T36 strain of CTV but not with variants of other virus strains was providing protection against a fluorescent protein-tagged T36-based recombinant virus variant. Under natural conditions close protection is functional and is closely associated both with the conservation of the CTV genome sequence and prevention of superinfection by closely similar isolates. It is suggested that the mechanism is primarily directed to prevent the danger of virus population collapse that could be expected to result through quasispecies divergence of large RNA genomes of the CTV variants continuously replicating within long-living and highly voluminous fruit trees. This review article provides an overview of the CTV cross-protection research, along with a discussion of the phenomenon in the context of the CTV biology and genetics.

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