Variability and transmission by Aphis glycines of North American and Asian Soybean mosaic virus isolates

Abstract

The variability of North American and Asian strains and isolates of Soybean mosaic virus was investigated. First, polymerase chain reaction (PCR) products representing the coat protein (CP)-coding regions of 38 SMVs were analyzed for restriction fragment length polymorphisms (RFLP). Second, the nucleotide and predicted amino acid sequence variability of the P1-coding region of 18 SMVs and the helper component/protease (HC/Pro) and CP-coding regions of 25 SMVs were assessed. The CP nucleotide and predicted amino acid sequences were the most similar and predicted phylogenetic relationships similar to those obtained from RFLP analysis. Neither RFLP nor sequence analyses of the CP-coding regions grouped the SMVs by geographical origin. The P1 and HC/Pro sequences were more variable and separated the North American and Asian SMV isolates into two groups similar to previously reported differences in pathogenic diversity of the two sets of SMV isolates. The P1 region was the most informative of the three regions analyzed. To assess the biological relevance of the sequence differences in the HC/Pro and CP coding regions, the transmissibility of 14 SMV isolates by Aphis glycines was tested. All field isolates of SMV were transmitted efficiently by A. glycines, but the laboratory isolates analyzed were transmitted poorly. The amino acid sequences from most, but not all, of the poorly transmitted isolates contained mutations in the aphid transmission-associated DAG and/or KLSC amino acid sequence motifs of CP and HC/Pro, respectively.

Similarities in Seed and Aphid Transmission Among Soybean mosaic virus Isolates

“…SMV strains G2 and G7 were provided by J. Hill (Iowa State University, Ames); SMV G5 was obtained from American Type Culture Collection (Manassas, VA); and G7F was recovered from an original culture of Cho and Goodman (9). SMV isolates 413, 746, and 1083 were collected from field plots on the Crop Sciences Research and Education Center in Urbana, IL (13). SMV isolate 88799 was obtained from infected seeds of PI 88799.…”

“…Since SMV rarely infects alternative host species, seedborne infections are the primary sources of inoculum for SMV infections (18). Controlling seed-borne SMV infections has become more important with the discovery of Aphis glycines Matsumara in North America, which can efficiently transmit SMV among soybean plants (10,13,19). SMV isolates can be divided into strains (G1 through G7) based on the symptoms they produce on a differential set of soybean lines (9,36).…”

Plant Pathogen Forensics: Capabilities, Needs, and Recommendations

“…Also relevant is the rate at which the pathogens change. For example, the genome of SMV appears to be more stable than that of PPV, although new strains of SMV are reported relatively frequently (49,55,92). Furthermore, some isolates described as new may actually be strains or recombinants of existing viruses (65).…”

“…In some cases, information may be gleaned from comparisons between populations in different countries or within regions of the same country. North American isolates of SMV were less diverse than those obtained from Asian countries, possibly because Asia is likely the center of viral origin and the opportunity for pathogen evolution has existed longer there (49). Deployment of host resistance genes in a crop species may select for variants that overcome the resistance; for TSWV and many other pathogens, this phenomenon can occur within only a few growing seasons.…”

“…For SMV, the reactions produced on differential host cultivars still provide the most definitive means of strain identification (4,55). Molecular analyses (sequence analysis, RT-PCR, and restrictotyping) show promise but have not yet been applied to a sufficient number of virus isolates to be able to relate the results to those produced from reactions on host differentials or to provide a sense of the virus' variability in nature (49,81,92,156).…”