engleski

Primary and secondary structures of citrus exocortis viroid found in Croatian citrus cultivars

Samples of various citrus cultivars (lemon, mandarin, orange) showing symptoms of viroid diseases were collected in the summer of 1998 from representative citrus-growing regions in Croatia. A biological test for the presence of viroids was made by transmission to the viroid sensitive citron selection Citrus medica L. 861-S1 with bud graft inoculation. In 5 out of 10 samples, CEVd was detected. Interestingly, all CEVd-positive cultivars were lemons. All 5 CEVd-isolates showed severe symptoms on the experimental citron. Nucleic acids from apex tissues of citron, enriched for viroid RNA by LiCl partitioning and chromatography, were prepared and analyzed by sequencial polyacrylamide gel electrophoresis (sPAGE) for the presence of viroids. The sPAGE analysis confirmed the presence of the viroid RNA in the samples. Viroid-enriched preparations were amplified by RT-PCR employing two pairs of CEVd-specific primers and the viroid cDNA was sequenced by the dideoxy termination technique. Croatian CEVd-variants were 371 nucleotide long and had a unique insertion in the upper strand of V-domain (nucleotide 129). A set of suboptimal secondary structures was determined by computer modelling. This is the first molecular evidence on the presence of CEVd in citrus cultivars grown in Croatia.

exocortis-viroid; citrus; Croatia

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