Document Type

Thesis - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Plant Science


Studies were conducted on the persistence in of Corynebacterium insidiosum, the alfalfa wilt bacterium, and on an antagonistic variant of that species. The persistence was followed by plate counting colonies from soils heavily inoculated with cells of this bacterium. The antagonistic variant of the species was studied directly and from cells or culture filtrates spot-planted on agar media containing seeding of other bacteria. Most cells of the wilt bacterium remained viable on glass surfaces for over 7 months at different temperatures, and in moist sterilized soil for over 72 days at room temperature. The calls persisted for only a few days in moist non-sterilized soil at room temperature, for 66 days in moist sterilized and non-sterilized soils at freezing or slightly –above freezing temperatures, and for over 5.5 months in very dry or moist soil at below-freezing temperatures. The bacterium persisted for a longer period in some soils that in others, regardless of the texture or pH of those soils. It persisted longer in moist sterilized soil than in a similar soil contaminated with a small amount of non-sterilized soil or streptomycete. Soil microorgannisms thus were considered responsible for the rapid decline of C. insidiosum in soil, with streptomycetes probably contributing to the decline.

Library of Congress Subject Headings

Alfalfa -- Diseases and pests


Includes bibliographical references




South Dakota State University