[Molecular identification and sequence analysis of broad bean wilt virus 2 isolates from atractylodes macrocephala...

To identity the pathogen that causes the mosaic and yellowing symptoms on Atractylodes macrocephala Koidz in Jiangxian, Shanxi province, biological inoculation, sequence-independent amplification (SIA),RT-PCR and other identification methods were used. The results showed that the chlorotic and necrosis symptoms occurred in the indicator plant Chenopodium quinoa after it was infected with the pathogen,and the same symptoms appeared after the reinoculation of healthy Atractylodes macrocephala Koidz; this reflected that the disease was likely to be caused by a virus. The results of SIA and sequencing showed that Broad bean wilt virus 2 (BBWV2) was present in severely mosaic Atractylodes macrocephala Koidz leaves. To further characterize the BBWV2 isolate from Atractylodes macrocephala (BBWV2-Am), the polyprotein partial gene encoded by BBWV2-Am RNA2 was cloned and sequenced. Sequence alignments showed that the nucleotide sequence identity of BBWV2-Am SCP and LCP genes ranged from 79.3% to 87.2% and from 80.1% to 89.2% compared to other BBWV2 strains,respectively; the deduced amino acid sequence similarities of the two gene products ranged from 91.2% to 95.7% and from 89.44 to 95.5%, respectively,compared to those of other BBWV2 strains. Phylogenetic comparisons showed that BBWV2-Am was most likely to be related to BBWV2-Rg,but formed an independent branch. This is the first report of BBWV2 in Atractylodes macrocephala Koidz.