Identification of Beet necrotic yellow vein virus type(s) in Iran.

Single-strand conformation polymorphism analysis was found to be a powerful tool for rapidly assigning large number of beet necrotic yellow vein virus (BNYVV) isolates to known strain groups as well as for detecting mixed infection, minor variants or new strain groups. For typing of BNYVV in Iran, 20 isolates from Azarbbayejan-gharbi, Esfahan, Fars, Hamedan, Kermanshah, Khorasan, Khuzestan, Qazvin, Semnan and Zanjan provinces (two isolates from each province) were tested by SSCP of RT-PCR products of RNA1 to 4. Also, the main areas for field grown sugar beet (Beta vulgaris L.) production were surveyed for the occurrence and relative incidence of (BNYVV) during the growing seasons of 2001 and 2003. Random root samples from 3972 plants were collected in 103 commercial sugar beet fields of 10 provinces and analyzed using tissue-blot immunoassay (TBIA). Serological diagnosis were confirmed by immunoelectron microscopy and reverse transcription followed by the polymerase chain reaction (RT-PCR) using the specific oligonucleotide primers designed to amplify various regions on BNYVV RNA 1 to 4. The uniformity of the pattern obtained by SSCP analyses showed the existence of a unique strain of BNYVV in the surveyed provinces. The isolates studied were similar to type A, which has been previously described. A 515 bp amplified fragment related to RNA5 were not observed among the studied isolates. TBIA results showed that the highest incidence of BNYVV infection was occurred in Khorasan (72.1%), followed by Fars (71.6%), Esfahan (70.2%), Zanjan (61.7%), Qazvin (51.4%), Semnan (51.1%), Kermanshah (28.7%), Azarbayejan-e-gharbi (22.5%) and Hamedan (4.3%), with the overall incidence of 49.1%. The presence of BNYVV also was recorded in symptomatic root samples from Ardabil and Chaharmahal-va-Bakhtiary. Occurrence of this virus was detected in all provinces except Khuzestan. To our knowledge, this is the first record of A type BNYVV on sugar beet in Iran. Until 1996, rhizomania had been detected only in Fars province, nevertheless this study showed the occurrence of BNYVV in many parts of Iran. The possible origin of this virus in Iran is discussed.