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Thesis (M.S.)—University of Nebraska—Lincoln, 1941. Department of Agronomy.


Copyright 1941, the author. Used by permission.


The effects of temperature, soil moisture, humidity, and fertilizers along with other environmental factors can alter the host plant and thereby influence its resistance to disease.

This thesis reports on some relatively easily observed gross changes in nursery-grown sweetclover which have a marked effect on the ability of the plants to withstand invasion of root-rotting organisms.The most striking of these changes is the growth of the roots to enormous size (giantism) as a result of very early seeding and the absence of plant competition in the widely-spaced plant breeding nursery.

The practical significance of this study is that to help control root-rot disease, the plants were grown in a manner so that they will not develop excessively during their first year of growth. In the 1941-42 breeding nursery this was accomplished by starting the spaced plants late in the season.

Due to the ease with which resistance to disease can be increased or decreased, it is suggested that sweetclover might serve as useful plant material in studies on the influence of biochemical and anatomical characters on degeneration and susceptibility to disease.

Advisor:T.A. Kiesselbach