Onion yellow dwarf virus (OYDV(, (genus Potyvirus, family Potyviridae), is one of the significant and damaging pathogens in garlic, onion, and other Allium species, posing a significant limitation to these crops globally. The coat protein (CP) gene of potyviruses serves as a primary molecular marker for their diagnosis and classification. To investigate the genetic diversity of OYDV in northern regions of Iran, three isolates named Sa, K, and Beh were collected from garlic fields in Mazandaran, and their RNA was extracted. A portion of their 3\\\' genome region (1112 bp) was amplified using virus-specific primers (OYDVVKBF/VKBR) through reverse transcription- polymerase chain reaction (RT-PCR) and subsequently sequenced. After trimming the sequences, the complete CP gene of 771 nucleotides was obtained, encoding a protein with a molecular weight of 29.05-29.25 kilodaltons and consisting of 257 amino acids. The three isolates showed 86.05- 89.66% nucleotide (nt) identity and 91.44-96.11% amino acid (aa) identity. The nt and aa sequences of the three isolates were compared with other sequences in GenBank. Results indicated that the Beh isolate (from Behshahr) had the highest nt (98.32%) and aa (99.61%) identity with the G78 isolate (MN059603) from China. The K isolate (from Kelardasht) had the highest nt identity (91.1%) with the G50-2 isolate (MN059587) and the highest aa identity (96.5%) with the G78 isolate from China. The Sa isolate (from Sari) had 89.92% nt identity and 94.55-94.94% aa identity with the sd (AJ409311) and Huimin4 (MT358355) isolates from China. These results indicate high genetic diversity among OYDV isolates in Iran.

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