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Document Type

Dissertation - University Access Only

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Plant Science

First Advisor

Zeno Wicks III


Five corn populations synthesized on the basis of number of mesocotyl roots and degree of root branching were evaluated under controlled conditions of 3 moisture regimes and six temperature treatments. These genotypes were also tested for cold tolerance and yield performance over a diverse set of environments in South Dakota at 9 and 5 different locations during 1987 and 1988, respectively. The moisture treatments (well watered, moderately stressed, and severely stressed) significantly affected the expression of secondary roots, dry weight of the root, shoot and plant. Other seedling root traits were not significantly affected by the moisture treatments. Population 2, selected for high degree of root branching maintained that trait in all moisture regimes. A significant population x moisture interaction was observed for number of secondary roots and primary seminal root length. Populations varied considerably in their relative sensitivity to the temperature treatments (10 - 35 0C with 5 degree increments). Populations having a high degree of root branching responsed with less variations to temperatures compared to other populations. In yield ii evaluations, populations selected for a high number of mesocotyl roots and high degree of root branching outyielded other populations in all 3 environments during 1987. The 300 kernel weight did not vary significantly among populations. During the 1988 yield trials populations were similar in performance at two locations. At other locations populations differed significantly and populations with high number of mesocotyl roots and high degree of root branching were comparatively superior in performance. No significant differences were observed among populations for various morphological components e.g. leaf area, plant height and root pulling resistance. Populations with a high degree of root branching had the most negative solute potentials at full turgor during the anthesis stage. In cold tolerance studies no significant differences were observed among populations in 1987 (a warm spring) but in 1988 populations with a high number of mesocotyl roots and high degree of root branching had a higher percent emergence and accumulated greater amounts of dry matter than the other populations. Correlation coefficients determined among yield and other agronomic traits were either of lower magnitude or non significant. Correlations among seedling root characteristics were strong and highly significant.

Library of Congress Subject Headings

Corn -- Roots -- Morphology
Corn -- Climatic factors
Corn -- Drought tolerance
Genotype -- environment interaction




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