determining the distribution of beet necrotic yellow vein virus and its vector in marvdasht area by serological and pcr methods

during the summer of 2004, a survey was conducted to determine the incidence and distribution of beet necrotic yellow vein virus (bnyvv) and its vector (polymyxa betae keskin) in marvdasht, fars province of iran.  a total of 353 root samples were collected randomly as well as 124 samples from plants showing rhizomania- associated symptoms.  the presence of bnyvv in the samples were tested by triple-antibody sandwich enzyme-linked immunosorbent assay (tas-elisa) using the specific antisera against bnyvv (adgen diagnostic, uk). bnyvv was serologically detected in 48.2% and 81.0% of randomly and symptomatically collected samples, respectively.  root beard extracts that were positive for bnyvv in elisa tests were mechanically inoculated on indicator host plants, which resulted in chlorotic followed by necrotic lesions in chenopodium quinoa and local necrotic lesion in c. amaranticolor. reverse transcription polymerase chain reaction (rt-pcr) using specific primers for bnyvv rna 1 to 4 confirmed the presence of bnyvv in the samples. as bnyvv is transmitted by p. betae and preserved a long time in resting spores of this fungus, distribution of this fungus was also determined.  the samples were tested by pcr for evaluation of the presence of p. betae using the specific primers and the vector was found in 94% of the fields surveyed.  finally rna 4 of bnyvv was partially sequenced and compared with other submitted sequences in genebank and showed 99.3% and 99.6% similarity with japanese and italian isolates, respectively.