Juglans regia: A Novel Natural Host for Hostuviroid impedihumuli and Its Molecular Profiling

Hostuviroid impedihumuli is a circular, positive-sense, single-stranded RNA viroid, 295–303 nucleotides in length, belonging to the family Pospiviroidae and the genus Hostuviroid. The most stable secondary structure of viroid RNA has been shown to adopt a rod-like or semi-rod-like conformation. A comprehensive study was conducted to detect viroids in walnut (Juglans regia) trees. A total of 230 walnut samples were collected from various provinces across Türkiye and subjected to molecular analysis. Both one-step real-time RT-PCR and conventional RT-PCR methods were employed, using primers specifically designed for the detection of H. impedihumuli. Molecular analyses revealed that 11.3% of the samples were infected with H. impedihumuli. The viroid sequences obtained were compared with homologous sequences in the GenBank database, showing nucleotide similarity rates ranging from 89.5% to 99.3%. To the best of our knowledge, this study presents the first documented occurrence of H. impedihumuli in walnut, representing a novel host record for both Türkiye and the global plant health community.