Molecular Diagnosis of Iris Yellow Spot Virus (IYSV) on Onion in Iran

Viral symptoms indicative of Iris yellow spot virus (IYSV) were observed on onion in several fields near Chenaran in Khorasan Razavi Province. Mechanical inoculation of herbaceous hosts with onion sap extracts from symptomatic plants showed similar symptoms to those described for IYSV. The mechanically transmitted virus reacted only with antisera specific to IYSV in DAS-ELISA but not with antisera specific to seven other tospoviruses. In RT-PCR, a DNA fragment approximately 822 bp in size was amplified from infected Nicotiana benthamiana by using primers specific to the nucleocapsid (N) gene of IYSV. After cloning and sequencing, the deduced N protein sequence of two isolates (GenBank accession no. HQ148173 and HQ148174) showed 98% amino acid identity with a Sri Lankan isolate, 96% with a Dutch isolate and 92% with a Brazilian isolate. To our knowledge, this is the first molecular characterization of IYSV in Iran.