First Detection and Molecular Characterization of Peach latent mosaic viroid in a New Natural Host: Walnut (Juglans regia L.)

Abstract

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 for the first time PLMVd infections in walnut (Juglans regia L.) in the world. Twelve walnut leaves, all from symptomless plants, were obtained from a nearby 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 infected by PLMVd detected in mid-summer of 2018 and in autumn of 2019. Analysis of nucleotide sequence of two walnut isolates (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 features of these two distinct PLMVd-walnut isolates detected in Malatya (Turkey).