Impact of Heterozygosity and Heterogeneity on Cotton Lint Yield Stability

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Title: Impact of Heterozygosity and Heterogeneity on Cotton Lint Yield Stability
Author: Cole, Clay Brady
Advisors: Thomas G. Isleib, Committee Member
James B. Holland, Committee Member
Christina Cowger, Committee Member
Daryl T. Bowman, Committee Chair
Abstract: Adequate stability of cotton (Gossypium hirsutum L.) lint yield is an integral criterion for cultivar release; however, the magnitude of lint yield variation today is close to six times greater than variation observed in the 1920's. Yield stability has often been associated with genetic diversity. Observing cotton lint yield in diverse population types containing various levels and kinds of genetic diversity over many environments could reveal information about stability and how it relates to diversity. An 18-environment field study was undertaken to observe lint yield stability in four population types of cotton. These populations were pure lines grown in pure stands (homozygous⁄homogeneous), pure lines grown in blended stands (homozygous⁄heterogeneous), hybrids grown in pure stands (heterozygous⁄homogeneous), and hybrids grown in blended stands (heterozygous⁄heterogeneous). Lint yield components were also observed to determine the contribution each had towards lint yield stability. Differences were determined by observing the coefficient of variation (CV) for mean yield and yield components of population types and over environments. We found the heterozygous populations to be more stable than the homozygous populations. This was attributed to the hybrids and blends of hybrids out-yielding the parents and blends of parents in the low-yielding environments. This advantage was not observed in the high-yielding environments and, in effect, reduced the amount of variation observed over all environments. The number of bolls/hectare was the only yield component that showed definitive differences for stability between population types with the heterozygous populations having significantly higher stability than the homozygous populations. The superior stability of the heterozygous populations was attributed to an increased lint production in the lower yielding environments stemming from an increased number of bolls/hectare.
Date: 2007-04-26
Degree: PhD
Discipline: Crop Science

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