Identification and relative incidence of luteoviruses infecting sugar beet in Iran.

Yellowing symptom in sugar beet (Beta vulgaris L.) were make by different viruses including those belong to poleroviruses (Luteoviridae) e.g. Beet mild yellowing virus-BMYV, Beet western yellows virus-BWYV-USA and Beet chlorosis virus-BChV. A survey was conducted in 10 commercial sugar beet growing provinces, for determine the occurrence of poleroviruses infecting sugar beet. A total of 1796 random and 511 symptomatic samples were collected. Mosaic, chlorosis, yellowing, vein clearing, vein necrosis and stunting were the most prevalence symptoms in the visited fields. Poleroviruses were detected by BWYV-USA polyclonal antibody using Tissue blot immunoassay- TBIA technique. According to the serological assay 240 (13.4%) of random samples was infected with BWYV-USA. The highest virus incidence among the surveyed provinces was recorded in Qazvin, (30.6%) fallowed by Khorasan-Razavi (17.3%), Kermanshah (16.16%), Esfahan (13.6%), Semnan (11.8%), Fars (5.9%), Zanjan (3.2%), Khuzestan (3.1%), West Azarbye-jan (3/0%) and Hamedan (2.1%) respectively. A total of 111 random samples that have positive reaction in TBIA test were selected for determination of the presence of each poleroviruses using RT-PCR and restriction analysis. In this respect by a universal primer that could detect the three poleroviruses, we amplified 560 bp coat protein PCR products. Restriction analysis using SmaI and RsaI reveled that 54.1%, 13.5% and 8.1% of samples just were infected with one of the BMYV, BWYV-USA and BChV respectively. Also, 17.1%, 3.6%, 0.9% and 0/9 % of these samples have mixed infection with BMYV/BWYV/USA, BMYV/BChV, BWYV-USA/BChV and BMYV/BWYV-USA/BChV respectively. The result of this study showed that the BMYV have the most distribution from the other poleroviruses. BMYV and BWYV-USA have been reported from Iran, although this is first report of BChV in Iran.