Submitted to: Archives of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 2003
Publication Date: October 1, 2003
Citation: Domier, L.L., Latorre, I.J., Steinlage, T.A., McCoppin, N.I., Hartman, G.L., 2003. Variability and transmission by Aphis glycines of North American and Asian soybean mosaic virus isolates. Archives of Virology. 148 (10):1925-1941. Interpretive Summary: Soybean mosaic virus (SMV) causes major diseases of soybean that can reduce soybean yields from 8% to 35%. SMV occurs in virtually all soybean production areas of the USA and is transmitted efficiently through seed and by at least 32 species of aphids. Several SMV strains have been identified that differ greatly in severity depending on the soybean line they infect. Plant breeders have identified at least four soybean genes that confer resistance to SMV. However, this resistance usually is strain-specific, meaning that a single resistance gene often will not protect soybean plants from all SMV isolates. Hence, the diversity of SMV isolates can be an important determinant to the success of a particular resistance-gene deployment strategy. In addition, the introduction of soybean germplasm lines into a region has the potential to carry with them new seed-borne SMV infections for which resistance genes may not have been identified. In this study, we examined the genetic relatedness and molecular variability of SMV isolates from North America and Asia. We found that North American isolates were much less variable than their Asian counterparts. In addition, we found that some portions of the single SMV chromosome were much more variable than others. The less variable regions of the chromosome may be useful in pathogen-derived resistance strategies while the more variable regions of the SMV genome will be more useful in the differentiation of SMV strains and isolates. This work will be of interest to researchers studying the molecular evolution of plant viruses and in developing transgenic resistance to SMV.
Technical Abstract: The variability of North American and Asian strains and isolates of Soybean mosaic virus was investigated in two separate experiments. In the first, polymerase chain reaction (PCR) products representing the coat protein (CP)-coding regions of 38 SMVs were evaluated by restriction fragment length polymorphism (RFLP) analysis. In the second set of experiments, the variability of nucleotide and predicted amino acid sequences of 17 SMVs was assessed in P1, helper component/protease (HC/Pro), and CP-coding regions. The CP predicted amino acid and nucleotide sequences were the most similar and predicted phylogenetic relationships similar to those obtained from RFLP analysis. However, neither RFLP nor sequence analysis of the CP-coding regions grouped the SMVs by geographical origin. In contrast, P1 and HC/Pro sequences separated the North American and Asian SMV isolates into two groups that paralleled previously reported differences in pathogenic diversity of SMV isolates from. While the genetic distances inferred from the nucleotide sequences were similar, the distances inferred by the P1 predicted amino acid sequences were much larger than those from predicted CP amino acid sequences. These likely results from different selection pressures on the two regions and indicates that the P1 region may be the most informative of the three regions analyzed for differentiating SMV isolates.