TITLE:
Severe Citrus tristeza virus Isolates from Eastern Mexico Are Related to the T36 Genotype Group
AUTHORS:
Patricia Rivas-Valencia, Santiago Domínguez-Monge, Ricardo Santillán-Mendoza, Emiliano Loeza-Kuk, Oscar Pérez-Hernández, Cynthia G. Rodríguez-Quibrera, Claudia Lomas-Barrié
KEYWORDS:
CTV, Epidemiology, Severe Isolates, Stem Pitting, Quick Decline, Coat Protein Gene
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.11 No.10,
September
30,
2020
ABSTRACT:
Citrus tristeza virus (CTV) outbreaks have been reported in the main citrus growing region of
Mexico in the past four years. Recently, in eastern Mexico (the major
citrus-growing region in the country), severe CTV isolates have been detected.
However, the molecular identity of observed isolates remains unestablished. This research was undertaken to elucidate the
molecular characterization of CTV populations spreading in this region and to
compare it with phylogeny of existing
isolates. Genotyping of 32 collected isolates was performed using
reverse-transcription polymerase chain reaction (RT-PCR) with sequence analysis
of the coat protein (CP) gene, putatively associated with pathogenicity. This
protein is a 25 kDa major capsid protein, which forms a long virion body
coating 95% of the particle length. A
comparative sequence analysis was performed using CTV sequences from different geographical origins
already published and deposited in the GenBank databases. Phylogenetic analysis
showed that the degree of sequence divergence among isolates correlated with
their pathogenicity. Based on the sequencing results, the collected isolates
were categorizedn as mild or severe phylogenetic clusters, each being
genetically distinct. The severe group was associated with either a-like or with a T36-like genotype. The latter group
matched with the quick decline and stem pitting drastic symptoms observed in
the field. This study identified the presence of severe CTV isolates related to
the T36-like genotype and to the cause of quick decline and stem pitting in
sweet orange propagated on sour orange rootstock. Knowledge derived from these
analyses could serve to design management strategies for this disease and to
understand the current epidemic outbreak in
scenarios where the most efficient vector is present.