Minor Variants of Orf1a, p33, and p23 Genes of VT Strain Citrus Tristeza Virus Isolates Show Symptomless Reactions on Sour Orange and Prevent Superinfection of Severe VT Isolates

Grazia Licciardello; Giuseppe Scuderi; Marcella Russo; Marina Bazzano; Moshe Bar-Joseph; Antonino F Catara

doi:10.3390/v15102037

Minor Variants of Orf1a, p33, and p23 Genes of VT Strain Citrus Tristeza Virus Isolates Show Symptomless Reactions on Sour Orange and Prevent Superinfection of Severe VT Isolates

Viruses. 2023 Sep 30;15(10):2037. doi: 10.3390/v15102037.

Authors

Grazia Licciardello¹, Giuseppe Scuderi², Marcella Russo², Marina Bazzano², Moshe Bar-Joseph³, Antonino F Catara⁴

Affiliations

¹ CREA-Council for Agricultural Research and Economics, Research Centre for Olive, Citrus and Tree Fruit, 95024 Acireale, Italy.
² Agrobiotech Soc. Coop. z.i. Blocco Palma I, Stradale Lancia 57, 95121 Catania, Italy.
³ The S. Tolkowsky Laboratory, Department of Plant Pathology, The Volcani Center, Agricultural Research Organization, Bet Dagan 50250, Israel.
⁴ Formerly, Department of Phytosanitary Science and Technologies, University of Catania, 95123 Catania, Italy.

Abstract

The control of tristeza quick decline (QD) of citrus is based on the use of rootstocks that are tolerant or resistant to the Citrus tristeza virus (CTV), but some of them show bio-agronomic limits. The application of cross-protection (CP) has been insufficiently explored. The present study examined the possibility of QD control by cross-protection (CP) following reports showing the dependence of the CP strategy on the close genetic relationships between the protective and challenging CTV isolates. Taking advantage of deep sequencing technologies, we located six naturally infected trees harboring no-seedling yellow (no-SY) and no QD decline (mild) VT isolates and used these for challenge inoculation with three QD VT isolates. Symptom monitoring showed that all six Sicilian mild no-SY isolates, based on their genomic relatedness and mild symptoms reactions, provide effective protection against the three severe local VT isolates. The differences between the six mild and three severe isolates were confined to just a few nucleotide variations conserved in eight positions of three CTV genes (p23, p33, and Orf1a). These results confirm that the superinfection exclusion (SIE mechanism) depends on close genetic relatedness between the protective and challenging severe VT strain isolates. Ten years of investigation suggest that CP could turn into an efficient strategy to contain CTV QD infections of sweet orange trees on SO rootstock.

Keywords: cross-protection; genome sequencing; quick decline; superinfection exclusion.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Citrus*
Closterovirus* / genetics
Genome, Viral
Plant Diseases
Superinfection* / genetics

Supplementary concepts

Citrus tristeza virus

Grants and funding

This study was initially supported by projects funded by Science and Technology Park of Sicily, by MIUR and MISE, and by Assessorato delle Risorse Agricole ed Agroalimentari, Regione Siciliana. The work was finalized and developed thanks to resources provided by the project S.I.R.P.A. n. 08CT7211000254, funded by PO FESR Sicilia 2014–2020, action 1.1.5.