Doctoral Dissertations

Date of Award

12-1969

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plant, Soil and Environmental Sciences

Major Professor

L.M. Josephson

Committee Members

W.L. Parks, R.A. McLean, Robert Shrode, Edward E.C. Clebsch

Abstract

The inheritance pattern of maize (Zea mays L.) genotypes for response to various potassium levels was investigated for three years at Crossville, Tennessee, using a split plot design in which potassium levels of 0, 60, 120, and 240 pounds of K20 per acre constituted the main plot treatment and genotypes were the split plot treatment. The genotypes consisted of the six F1's, six F2's, 12 first backcrosses and three double crosses of a four parent diallel of the inbreds T101, T105, T111, and T115. The characters studied were grain yield, number of ears per 10 plants, weight per ear, crushing strength and rind thickness of the stalks, frequency of dead stalks, and stalk lodging. The data were subjected to analysis of variance. Comparisons among potassium levels and interactions involving potassium levels were partitioned into components of polynomial regression. Sums of squares associated with genotypes and with interactions involving genotypes were partitioned into among F1's, among F2's, among backcrosses, among double crosses, F1 vs. F2, F1 vs. double cross, and F2 vs. backcross. Regression coefficients for linear and quadratic models were calculated for the individual genotypes. The predicted potassium levels producing the maximum and minimum performance were calculated.

Significant heterogeneity of linear or quadratic response for yield was detected among the backcrosses in all years but among the F1's and F2's in only one year. Double crosses responded similarly in all years. Parental influences were detected among the backcrosses for response in all years although this influence was transmitted to the F1's and F2's in only one year. The F1's responded at a greater rate than the F2's, which Indicates that non additive genetic effects are important in determining response. The predicted potassium level required for maximum yield was lower for the F1's than for the F2’s.

Response to potassium levels for yield was a function of increases in both ear number and ear weight. Generally, an increase in one was accompanied by a decrease in the other.

Rind thickness and crushing strength generally increased with increased potassium additions, but the increase was relatively greater for crushing strength than for rind thickness. Genotype x potassium level interactions involving these characters were generally small and nonsignificant.

The influence of potassium levels on frequency of dead stalks was dependent upon the genotype. Frequencies of dead stalks for some genotypes were reduced considerably with increased potassium additions while others were not greatly influenced.

Stalk lodging was confounded with European corn borer damage and was not very meaningful.

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