Development of seed assays for detection of Pseudomonas syringae pv. glycinea in soybean seed
Date
1992
Authors
Alvarez, Elizabeth
Major Professor
Advisor
McGee, Denis
Committee Member
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Abstract
Two new assays, grinding seed and direct plating, were developed for detection of Pseudomonas syringae pv. glycinea (Psg), the causal agent of bacterial blight in soybean seeds. These methods were compared to soaking and soaking-centrifugation assays on 21 soybean seed lots obtained from commercial seed companies and the Seed Science Center at Iowa State University. All four assays ranked the severity of infection similar for the 21 seed lots tested in the study. The sensitivity between tests differed with the grinding assay having a much greater sensitivity for detection of the pathogen in seeds than did the soaking or soaking-centrifugation procedures. The grinding assay is also quicker and less labor-intense than the other tests. The direct plating assay also had a high level of sensitivity, but the test measured incidence of seed infection, whereas the other tests measured colony-forming units. A group of bacterial isolates identified as Psg among the four assays consistently gave the correct response when subjected to the main diagnostic tests used in the assays: pathogenicity, flourescence, oxidase, levan, esculin, protease and antiserum. Similarly, Pseudomonas fluorescens and Erwinia herbicola, also found on seeds, were clearly distinguished from Psg in these tests.
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