Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

G. Kenerick


South Dakota is at the northern limit of winter wheat cultivation in the United States. However, it has been estimated that only 15% of the total winter wheat acreage has been planted to hardy winter wheat cultivars in this state. Records at this station indicate that grain yields of winter hardy cultivars can be 20 to 40% lower than less hardy cultivars in the absence of severe freeze stress. Low grain yields of hardy types is one reason for low preference of these phenotypes by growers. Hardy cultivars usually head late compared to less hardy ones. With late initiation of the inflorescence, it is important that these cultivars exhibit rapid grain development and maturity to avoid the high temperatures and low moisture conditions of mid-summer. Thus, the grain filling period is shortened. Late initiation has an influence on spikelet number, as previously discussed, and could be another detriment to high yield among hardy types. An urgent need exists to understand factors involved in floral initiation of winter wheat and the influence on grain yield. The phenology of the hard red winter wheat class was of interest in this study, as it relates to the range of phenotypes grown in the Northern Great Plains and the climatic adversity which exists. The objectives of this research were: 1) to compare the periods of floral initiation of field-grown hardy and less-hardy phenotypes in South Dakota, 2) to determine the minimum photoperiod requirements for floral initiation of these cultivars, 3) to evaluate the effect of growth temperature on floral primordia, and 4) to examine the changes in protein composition of the developing apex by isoelectric focusing, as a biochemical indicator of the phasic development in winter wheat.

Library of Congress Subject Headings

Winter wheat -- Flowering
Winter wheat -- Flowering time
Winter wheat -- Yield



Number of Pages



South Dakota State University