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Updated: Aug 11, 2026

Combining Analysis of DNA in a Crude Virion Extraction with the Analysis of RNA from Infected Leaves to Discover New Virus Genomes
Published on: July 27, 2018
Viroid Diseases in Pome and Stone Fruit Trees and Koch's Postulates: A Critical Assessment
Francesco Di Serio1, Silvia Ambrós2, Teruo Sano3
1Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, 70126 Bari, Italy. francesco.diserio@ipsp.cnr.it.
Abstract:
Composed of a naked circular non-protein-coding genomic RNA, counting only a few hundred nucleotides, viroids-the smallest infectious agents known so far-are able to replicate and move systemically in herbaceous and woody host plants, which concomitantly may develop specific diseases or remain symptomless. Several viroids have been reported to naturally infect pome and stone fruit trees, showing symptoms on leaves, fruits and/or bark. However, Koch's postulates required for establishing on firm grounds the viroid etiology of these diseases, have not been met in all instances. Here, pome and stone fruit tree diseases, conclusively proven to be caused by viroids, are reviewed, and the need to pay closer attention to fulfilling Koch's postulates is emphasized.
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