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Journal of Virology, August 2000, p. 6856-6865, Vol. 74, No. 15
Citrus Research and Education Center, Department of Plant
Pathology, University of Florida, Lake Alfred, Florida
338501; USDA-ARS Horticultural
Research Laboratory, Orlando, Florida 328032;
Interdisciplinary Center for Biotechnology Research,
University of Florida, Gainesville, Florida
326113; and Instituto Valenciano de
Investigaciones Agrarias, 46113 Moncada,4
and Instituto de Biología Molecular y Celular de
Plantas, Universidad Politécnica-Consejo Superior de
Investigaciones Científicas,5 Valencia,
Spain
Received 4 January 2000/Accepted 29 April 2000
The first Citrus tristeza virus (CTV) genomes
completely sequenced (19.3-kb positive-sense RNA), from four
biologically distinct isolates, are unexpectedly divergent in
nucleotide sequence (up to 60% divergence). Understanding of whether
these large sequence differences resulted from recent evolution is
important for the design of disease management strategies, particularly
the use of genetically engineered mild (essentially symptomless)-strain cross protection and RNA-mediated transgenic resistance. The complete sequence of a mild isolate (T30) which has been endemic in Florida for
about a century was found to be nearly identical to the genomic sequence of a mild isolate (T385) from Spain. Moreover, samples of
sequences of other isolates from distinct geographic locations, maintained in different citrus hosts and also separated in time (B252
from Taiwan, B272 from Colombia, and B354 from California), were nearly
identical to the T30 sequence. The sequence differences between these
isolates were within or near the range of variability of the T30
population. A possible explanation for these results is that the
parents of isolates T30, T385, B252, B272, and B354 have a common
origin, probably Asia, and have changed little since they were
dispersed throughout the world by the movement of citrus. Considering
that the nucleotide divergence among the other known CTV genomes is
much greater than those expected for strains of the same virus, the
remarkable similarity of these five isolates indicates a high degree of
evolutionary stasis in some CTV populations.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Sequences of Citrus Tristeza Virus
Separated in Time and Space Are Essentially Identical
*
Corresponding author. Mailing address: University of
Florida, Department of Plant Pathology, Citrus Research and Education Center, 700 Experiment Station Rd., Lake Alfred, FL 33850. Phone: (863)
956-1151. Fax: (863) 956-4631. E-mail: wodtmv{at}lal.ufl.edu.
University of Florida Agricultural Experiment Station journal
series no. R-G7529.
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