Segregation of Sweet Orange Stem Pitting Types and Stunting Factors in Subcultures from the Severe SY568 Strain of Citrus tristeza virus

Williams, A. P.; Mathews, D. M.; Heick, J. A.; Dodds, J. A.

doi:10.5070/c52g54n8sd

Cited by 2 publications

(1 citation statement)

References 7 publications

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“…For example, in a study examining CTV stem pitting and stunting in Madam Vinous sweet orange, two of the infected trees received the same rating of moderately stunted. However, while one of them was found to have “many deep” stem pits, the other only developed “few shallow” ones ( Williams et al, 2002 ). The severity of the stunting observed in the T68-1-infected trees can be regarded as an almost complete cessation of the radial stem growth, with the stem thickness after 2 years being only marginally larger than that at the time of grafting.…”

Section: Resultsmentioning

confidence: 99%

Transcriptomic alterations in the sweet orange vasculature correlate with growth repression induced by a variant of citrus tristeza virus

et al. 2023

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Citrus tristeza virus (CTV, family Closteroviridae) is an economically important pathogen of citrus. CTV resides in the phloem of the infected plants and induces a range of disease phenotypes, including stem pitting and quick decline as well as a number of other deleterious syndromes. To uncover the biological processes underlying the poorly understood damaging symptoms of CTV, we profiled the transcriptome of sweet orange (Citrus sinensis) phloem-rich bark tissues of non-infected, mock-inoculated trees and trees singly infected with two distinct variants of CTV, T36 or T68-1. The T36 and T68-1 variants accumulated in the infected plants at similar titers. With that, young trees infected with T68-1 were markedly repressed in growth, while the growth rate of the trees infected with T36 was comparable to the mock-inoculated trees. Only a small number of differentially expressed genes (DEGs) were identified in the nearly asymptomatic T36-infected trees, whereas almost fourfold the number of DEGs were identified with the growth-restricting T68-1 infection. DEGs were validated using quantitative reverse transcription-PCR. While T36 did not induce many noteworthy changes, T68-1 altered the expression of numerous host mRNAs encoding proteins within significant biological pathways, including immunity and stress response proteins, papain-like cysteine proteases (PLCPs), cell-wall modifying enzymes, vascular development proteins and others. The transcriptomic alterations in the T68-1-infected trees, in particular, the strong and persistent increase in the expression levels of PLCPs, appear to contribute to the observed stem growth repression. On the other hand, analysis of the viral small interfering RNAs revealed that the host RNA silencing-based response to the infection by T36 and that by T68-1 was comparable, and thus, the induction of this antiviral mechanism may not contribute to the difference in the observed symptoms. The DEGs identified in this study promote our understanding of the underlying mechanisms of the yet unexplained growth repression induced by severe CTV isolates in sweet orange trees.

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Section: Resultsmentioning

confidence: 99%

Transcriptomic alterations in the sweet orange vasculature correlate with growth repression induced by a variant of citrus tristeza virus

et al. 2023

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

Velázquez-Monreal¹,

Mathews²,

Dodds³

2009

Phytopathology®

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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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Segregation of Sweet Orange Stem Pitting Types and Stunting Factors in Subcultures from the Severe SY568 Strain of Citrus tristeza virus

Cited by 2 publications

References 7 publications

Transcriptomic alterations in the sweet orange vasculature correlate with growth repression induced by a variant of citrus tristeza virus

Transcriptomic alterations in the sweet orange vasculature correlate with growth repression induced by a variant of citrus tristeza virus

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

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