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Peach trees (Prunus persica L.) with yellowing symptoms on leaves were found in December (summer season) of 2005 in commercial fields in Colonia Caroya, Córdoba, Argentina. This symptom resembled Peach latent mosaic viroid (PLMVd). The viroid-affected trees usually showed vein banding and yellowing symptoms on leaves, fruit suture splitting, delays in budding, flowering and fruit ripening, reduced foliage density, and a spindly appearance. PLMVd is mainly transmitted by the propagation of infected budwood and to a lesser extent by pruning tools and aphids (1). Extraction and partial purification of nucleic acids was made from symptomatic leaves (2) collected during the indicated summer season from seven peach trees from commercial plots. Preliminary identification of the viroid was made by dot-blot hybridization with a PLMVd probe (provided by R. Flores). The positive plants were tested also by reverse transcription (RT)-PCR with PLMVd primers RF-43 (5′-CTGGATCACACCCCCCTCGGAACCAACCGCT-3′) and RF-44 (5′-TGTGATCCAGGTACCGCCGTAGAAACT-3′), which amplify the complete genome. All identified positive samples yielded the correct sized PCR product and four were cloned and sequenced. This local sequence (GenBank Accession No. EU429320) had 97% nucleotide sequence identity with a reported PLMVd sequence (GenBank Accession No. M83545), confirming the identity of the local pathogen as Peach latent mosaic viroid. This result suggests that the source of the pathogen may have been infected budwood introduced from Europe. To our knowledge, this is the first report of this viroid in Argentina. References: (1) R. Flores et al. Mol. Plant Pathol. 7:209, 2006. (2) V. Pallás et al. J. Gen. Virol. 68:3201, 1987. |
