Investigation of hop stunt and peach latent mosaic viroids in fruit trees in Malatya province and the molecular characterization of the identified isolates

Peach latent mosaic viroid (PLMVd) occurs naturally in peach and nectarines worldwide including North and South America, Europe, Asia and Australia with high infection frequencies. Here, our experimental findings revealed PLMVd infectionsin in walnut (Juglans regia L.) for the first time in the world. Twelve walnut leaves, all from symptomless plants, were obtained from a walnut germplasm collection in Malatya (Turkey). Genomic RNAs were extracted using a commercial RNA isolation kit and the complete viroid genome was amplified by reverse transcriptase polymerase chain reaction (RT-PCR) assay using end to end primer pair. The PCR amplicons of expected size (approx. 0.34-kb DNA fragments) were cloned into pGEM-T Easy vector and transformed into competent Escherichia coli strain JM109. Purified plasmids were sequenced bidirectionally. Of the 12 walnut specimens tested by RT-PCR, 4 were found to be infected by PLMVd detected in mid-summer of 2018 and in autumn of 2019. Analysis of nucleotide sequence of two walnut isolates Malatya 1- Malatya 2 (Acces. no: MN857143-MN857144) confirmed the presence of PLMVd and shared 96.6-98.8% similarity (Acces. no: MN857143) and 97-98.8% similarity (Acces. no: MN857144) with peach, nectarine and cherry isolates of the world. By identifying walnut as an alternate host, we confirm that PLMVd potentially may infect other fruit trees cultivated worldwide. Here, we also report molecular characteristics of these two distinct PLMVd-walnut isolates detected in Malatya (Turkey). KEY WORDS: Viroid, walnut disease, RT-PCR, new host