Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2000
Publication Date: 6/1/2000
Citation: Hall, J.S., French, R.C., Morris, T.J., Stenger, D.C. 2000. Accumulation of fixed nucleotide substitutions during passages of wheat streak mosaic virus. American Phytopathological Society Abstracts. Phytopathology 90: Supplement 533
Technical Abstract: The temporal pattern of genetic variation was followed for a WSMV isolate. A limiting dilution sub-isolate of WSMV Sidney 81 was subjected to nine serial passages in three host species in a constant environment. Changes in the consensus genotype were assayed by SSCP and sequence analyses. Fixed substitutions accumulated at an essentially linear rate (c.a. 0.3 nt/passage) in wheat, barley, and maize. Most of the observed changes were single nucleotide changes and occurred within the NIa and CP genes, although some multiple substitutions and changes in other regions of the genome also were observed. The number of transversions and nonsynonymous substitutions were significantly higher (P< 0.025) in the CP gene compared to the rest of the WSMV genome. No evidence for host-directed selection was observed. Accumulation of fixed mutations in the WSMV genome over time is more consistent with a stochastic model of genetic mutation and drift than with a deterministic model. With sufficient time and opportunities for genetic isolation (e.g. transmission bottlenecks and cross-protection), drift may account for much of the genotypic variation within WSMV field populations.