Date of this Version
Thesis (M.S.)—University of Nebraska—Lincoln, 1958. Department of Agronomy.
Several morphological characteristics were studied in four tall and eighteen semi-dwarf varieties of winter wheat grown at replicated nurseries at two locations in Nebraska and one in Colorado. The number of tillers, number of kernels per head and weight of kernels, the three principal components of yield, were among the characteristics studied.
When the semi-dwarf selections were grouped together according to pedigree and compared with the tall varieties, an inverse relationship between yield and plant height existed. Contrary to expectation, the semi-dwarf selections which were higher yielding than Pawnee, Cheyenne and the other tall varieties studied usually produced a lower number of head-bearing tillers per one foot of row than did the tall varieties. A close association between general yield level at a station and number of tillers produced was apparent.
At Scottsbluff, where yields were approximately twice those recorded at Lincoln, the number of head-bearing tillers also was approximately twice the number counted at Lincoln.
Head length, number of spikelets per head and number of kernels per head usually bore a close relationship to one another. A consistent association of number of kernels per head with grain yield could not be established on an individual variety basis, whereas is group comparisons a positive relationship was evident. The relationship of kernel weight and yield of grain could not be demonstrated.
Grain-straw determinations indicated that the high yielding semi-dwarf selections were more efficient grain producers than the tall growing varieties.
Yield was not correlated with any one morphologic characteristic at all locations. However, the combined data from all locations produced a highly significant positive correlation between yield and number of kernels per head, and significant negative correlations between yield and (1) plant height and (2) number of tillers.
Flag leaf measurements at Lincoln revealed a much wider, but shorter lead for the semi-dwarf selections than for the tall varieties.
Advisor: V. A. Johnson.