Date of Award
Master of Science
L. N. Skold
Smith Worley, Vernon H. Reich
Studies were carried out to develop yield models for selected Upland cotton genotypes to determine the interrelations of yield components and their relative contributions to cotton yield. Data used in these investigations were collected in 1968 and 1969 by the cotton breeding and quality investigations program, Pee Dee Experiment Station, Florence, South Carolina. This yield model study utilized four selected genotypes both individually and collectively, in equating yield to the volume of a rectangular parallelepiped. Axes (X), (Y), and (Z) of the geo-metric model represented the equivalent number of bolls per square meter, the equivalent number of seeds per boll, and the weight of seed cotton per seed, respectively. The results indicated that the primary gain in yield improvement would be made by exerting selection pressure on the number of bolls per unit area. Concurrent selection pressure should also be placed on the number of seeds per boll and weight of seed cotton per seed in order to maintain these components at acceptable levels. Data collected for the yield components in each test entry across 13 locations in 1968, 12 locations in 1969, and 25 locations in 1968-1969 combined, were used to calculate simple correlation coefficients between components. These analyses permitted comparisons of the within years results with those obtained when additional component variations were introduced. These analyses indicated that cause and effect relationships were involved between many of the component pairs. These studies indicated that a large population includ-ing several environments would be necessary for drawing conclusions about component relationships. Multiple regression analyses were used to determine the relative contributions of the components to lint yield, and to rank them in order of importance. The number of bolls per unit area accounted for 81 to 91% of the total lint yield variation. Boll size contri-buted 6 to 14% and seed weight in grams per 100 bolls 2 to 4% to the total lint yield variation. The remaining components increased the araltiple correlation only .0002 to .0004 in those analyses. The total multiple correlation coefficient was .99 in all cases.
Maner, Buford A., "Yield models, components, and interrelationships in upland cotton, Gossypium hirsutum L. " Master's Thesis, University of Tennessee, 1970.