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Host Effect on the Molecular and Biological Properties of a Citrus exocortis viroid Isolate from Vicia faba

August 2007 , Volume 97 , Number  8
Pages  1,004 - 1,010

Mónica Gandía , Lucía Bernad , Luis Rubio , and Núria Duran-Vila

Departamento de Protección Vegetal y Biotecnología. Instituto Valenciano de Investigaciones Agrarias (IVIA), Apartado oficial, 46113 Moncada (Valencia) Spain.

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Accepted for publication 29 March 2007.

Citrus exocortis viroid (CEVd) is the casual agent of citrus exocortis disease, and has been found in naturally infected citrus and noncitrus hosts. Field isolates of CEVd may infect susceptible hosts as a complex of genetically related sequence variants (haplotypes). In the present work, a CEVd isolate recovered from a symptomless broad bean plant was characterized as a heterogeneous population with a nucleotide diversity of 0.026, which did not contain a predominant haplotype. When nucleic acid extracts of this infected broad bean were used to inoculate tomato, the plants displayed symptoms and the CEVd population was more homogeneous, with a nucleotide diversity of 0.007. However, when nucleic acid extracts from this tomato isolate were back inoculated to new broad bean plants, this isolate did not revert to the original population, because it showed low nucleotide diversity (0.001) and induced symptoms in the broad bean plants. Symptomless broad bean plants may act as reservoirs of highly heterogeneous populations of CEVd variants, providing an excellent inoculum source in terms of its potential to infect a broad range of putative hosts. The epidemiological implications are discussed.

© 2007 The American Phytopathological Society