اولین گزارش از وقوع ویروئید Apple hammerhead viroid از ارقام تجاری درختان سیب در استان های البرز، سمنان و مازندران

Plant viroids are among the factors causing damage to orchard and crop products. In this study, in order to investigate plant viroids in apple crops, sampling was conducted in the main apple cultivation areas in the provinces of Alborz, Semnan, and Mazandaran during the years 2020 to 2021. A total of 20 orchards were visited, and 170 leaf samples from apple trees showing symptoms, including deformation, chlorotic or necrotic leaf spots, and yellow veins, were collected. Most of the samples were from commercial varieties such as Gala, Golden Delicious, Red Delicious, and Shafi Abadi. The leaf samples were subjected to next-generation sequencing (NGS) using the Illumina HiSeq 2500. NGS revealed the presence of viroid agents, Apple hammerhead viroid (AHVd) and Hop stunt viroid (HSVd), in Iran and determined their complete genome sequences. The presence of these viroids, revealed by NGS, was confirmed by RT-PCR and showed that HSVd was the most prevalent viroid in the studied areas. In this research, the AHVd isolates, identified as a new and highly prevalent viroid in Iranian apple orchards, were analyzed phylogenetically.It was proven that the high molecular diversity of AHVd in the isolates is due to single nucleotide differences and deletion events. The structural and genetic molecular characteristics of this viroid were also analyzed and examined. As a result, NGS provided new data on the presence of viroids in apple trees in Iran. AHVd was reported for the first time in apples from Iran. The highest prevalence of AHVd was found in Mazandaran province in the Gala and Shafi Abadi varieties and HSVd was most prevalent in the Golden Delicious and Shafi Abadi varieties in Mazandaran province. The current HTS analysis expands our genomic information on apple-infecting viroids and enables a rapid response to emerging viroid diseases in this fruit tree.