Doctor of Philosophy (PhD)


Plant, Enviromental and Soil Sciences

Document Type



Cotton is sold by weight, but a bale’s lint price per pound is determined by its fiber quality profile. Cotton quality is defined by a set of standardized properties (length, strength, elongation, uniformity, color, trash, and micronaire) collected on every United States bale. Each cotton fiber is the remnant of a single cell which upon harvest exists as a dry, hollow tube of crystalline cellulose. The length, perimeter, and thickness are a fiber’s physical dimensions. These dimensions influence both the mechanics involved in yarn spinning and the quality of the yarn produced. Genetic and environmental factors affect the development and consequently, the final properties of cotton crops. However, information is lacking about the degree of influence they impart, especially on fiber perimeter (fineness) and cell wall thickness (maturity), both components of micronaire. The goals of this dissertation were to: 1) Summarize and review the techniques available to industry to measure fiber perimeter and maturity in order to discuss their advantages and limitations, 2) Validate the use Cottonscope to measure fiber quality variation, 3) Determine the significance of within-plant yield variation, and 4) Determine the significance of within-plant quality variation. Small differences in micronaire are often indistinguishable, making breeding efforts difficult. With new instruments, selecting for the components of micronaire may increase selection efficiency and genetic gain compared to breeding for micronaire directly. In addition, these results show that yield and quality within genotypes are highly variable, and a significant amount of the variation is attributable to a boll’s fruiting site. Substantial bias can be introduced if boll sampling does not consider fruiting position. The results show that plot sampling techniques can greatly influence fiber quality testing results and as a result the effectiveness of genetic selection. The Cottonscope is a very accurate and precise tool for measuring fiber fineness and maturity ratio and improving the interpretation of micronaire. Micronaire had strong correlation with fiber fineness data. Breeding for lower micronaire would be a useful strategy to improve fiber fineness in environments where low fiber maturity is not a problem.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Myers, Gerald