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Thesis (M.S.)—University of Nebraska—Lincoln, 1938. Department of Agronomy.


Copyright 1938, the author. Used by permission.


The present experiment was designed to study the varietal reaction to controlled low temperature. The primary object was to secure additional data concerning the correlation between the reaction to controlled low temperature and low temperature in the field, when measuring the cold resistance of winter wheats. It was desired to know the extent to which several freezing periods, each with adequate replications, would agree with previously obtained correlations when compared with field results.

Survivals of winter wheat from artificially produced low temperatures were compared with field data as a measure of their cold resistance.

The 30 varieties of winter wheat grown in the Uniform Winterhardiness Nursery in 1937 and 1938 were studied in these tests.

Four freezing periods, approximately November 15, December 5, December 15, and January 15, were used. Material frozen directly from the field was replicated 12 times and that dehardened 4 times each year.

Correlation coefficients between the average survivals from the freezing periods for that material frozen directly from the field range from +0.6719 to +0.8815 for the two years, all of which are highly significant.

A correlation coefficient of +0.8095 was obtained when the average survivals of two years controlled data was compared with field results, indicating that controlled low temperature, when adequately replicated, offer as good a measure of cold resistance of winter wheat as do the many winterhardiness nurseries.

Hardiness tends to increase from November to January as shown by increased survivals with a progressive lowering of the exposure temperature.

All varieties do not build up their hardiness in the same manner, some make decidedly steady increases, some more slowly, and others inconsistent.

Plants lost some hardiness in 24 hours when placed in favorable growing conditions.

Advisor: K. S. Quisenberry