Gagarinova Alla G, Babu Mohan, Poysa Vaino, Hill John H, Wang Aiming
Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, Ontario, Canada N5V 4T3.
Virus Res. 2008 Dec;138(1-2):50-6. doi: 10.1016/j.virusres.2008.08.010. Epub 2008 Sep 30.
A naturally occurring Rsv4 resistance-breaking isolate (L-RB) and a closely related non-resistance-breaking isolate (L) of Soybean mosaic virus (SMV) were identified in soybean fields in London, Ontario, Canada. The viral genomes of L and L-RB were completely sequenced. Each isolate has a 9585-nucleotide genome with a single open reading frame encoding a polyprotein of approximately 350 kDa. L-RB and L have a very high sequence similarity (99.6%) at both the nucleotide and amino acid levels. Phylogenetic analysis showed that the two isolates belong to the G2 pathotype. Pathogenicity predictions of all virus/soybean combinations, based on the phylogenetic profile, were confirmed by pathogenicity tests using L and L-RB isolates and soybeans carrying different resistance genes, with an exception that L-RB infected a soybean cultivar carrying Rsv4 resistance. The temporal and spatial proximity of L and L-RB and their high sequence similarity suggest L-RB was likely derived from the SMV-L quasispecies. Recombination analysis did not reveal the evidence of genetic recombination for the emergence of L-RB. Mutations introduced by virus-encoded RNA-dependent RNA polymerase during viral genome replication and selection pressure probably contributed to the occurrence of L-RB.
在加拿大安大略省伦敦市的大豆田中，鉴定出一种天然存在的大豆花叶病毒（SMV）的Rsv4抗性突破分离株（L-RB）和一种密切相关的非抗性突破分离株（L）。对L和L-RB的病毒基因组进行了全序列测定。每个分离株都有一个9585个核苷酸的基因组，带有一个单一开放阅读框，编码一个约350 kDa的多蛋白。L-RB和L在核苷酸和氨基酸水平上都有非常高的序列相似性（99.6%）。系统发育分析表明，这两个分离株属于G2致病型。基于系统发育图谱对所有病毒/大豆组合的致病性预测，通过使用L和L-RB分离株以及携带不同抗性基因的大豆进行致病性试验得到了证实，但有一个例外，即L-RB感染了携带Rsv4抗性的大豆品种。L和L-RB在时间和空间上的接近以及它们的高序列相似性表明，L-RB可能源自SMV-L准种。重组分析未发现L-RB出现的基因重组证据。病毒编码的RNA依赖性RNA聚合酶在病毒基因组复制过程中引入的突变和选择压力可能促成了L-RB的出现。
