Degree Type

Dissertation

Date of Award

1990

Degree Name

Doctor of Philosophy

Department

Microbiology

First Advisor

John H. Hill

Second Advisor

Donald P. Durand

Abstract

Soybean mosaic virus (SMV) and Glycine max (L.) Merr. (soybean) were used as a model system to study virus disease resistance in plants. Soybean lines exist that contain a single allelic gene conferring resistance to SMV. Aspects of the model investigated were: (1) characterization of factors influencing disease resistance; (2) identification of virus-encoded functions altered in resistant plants; (3) effects of leaf tissue extracts from resistant soybean on the cell-free translation of SMV RNA;Observations of the interaction of the known strains of SMV with soybean lines of varying susceptibility to infection, led to the following hypotheses: (1) Environmental conditions (e.g., temperature) may influence disease resistance in lines of soybean resistant to infection by SMV; (2) Co-inoculation of soybean plants with virulent and avirulent strains of SMV may allow complementation that could lead to systemic movement of the avirulent virus strain in the resistant lines of soybean; and (3) Leaf extracts from resistant soybean may affect the cell-free translation of SMV RNA. To test the first hypothesis, several soybean lines, containing a gene that conditions resistance to SMV (i.e., Pl 96983, L78-379, and Davis), were grown to the primary leaf stage of growth, inoculated with an avirulent strain of SMV (G2), and placed at either 10, 15, 20, 25, 30, or 35°C for 10 days. Trifoliolate leaves from plants were assayed for presence of SMV by using a method developed in this study (press blot). Evidence is presented that low temperatures (i.e., 10°C) allowed systemic spread of the G2 strain of SMV in these soybean lines. To test the second hypothesis, resistant lines were inoculated with SMV-G2 along with either SMV-G7 or G7a. Evidence is presented that suggests complementation occurred between SMV-G2 and SMV G7 or G7a leading to systemic spread of SMV-G2. To test the third hypothesis, leaf extracts from the soybean cultivar Davis were fractionated and added to cell-free translation reactions directed by either SMV-G2 or -G7 RNAs. Inhibitors of translation from David and Williams '82 were largely responsible for no accumulation of translation products by either G2 or G7 RNAs with leaf extracts at protein concentrations of 500 ug/ml or 1000 ug/ml. Effects did not correlate with disease resistance;A comparative analysis of cell-free translation profiles of the isolates representing strains of SMV formed discrete groupings. Translation products from rabbit reticulocyte lysates formed groups that correlated with pathogenicity; however, analysis of products from wheat germ extracts formed groups that appeared to have no biological significance.

DOI

https://doi.org/10.31274/rtd-180813-13116

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Louis Michael Mansky

Language

en

Proquest ID

AAI9101366

File Format

application/pdf

File Size

215 pages

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