Theses and Dissertations

Advisor

Dodds, Darrin

Committee Member

Pieralisi, Brian

Committee Member

McCarty, Jack, Jr

Committee Member

Jenkins, Johnie

Committee Member

Reddy, K.; Lu, Shien

Date of Degree

8-7-2025

Original embargo terms

Embargo 2 years

Document Type

Dissertation - Open Access

Major

Agronomy

Degree Name

Doctor of Philosophy (Ph.D.)

College

College of Agriculture and Life Sciences

Department

Department of Plant and Soil Sciences

Abstract

Cotton Gossypium hirsutum L. is a major source of oil, biofuel, and fiber used in an exponentially growing human population. Cotton’s plant growth commonly described indeterminant to intermediate limits plant density in production agriculture. A study was conducted to determine the inheritance of cotton plant height and fruiting branch compactness. Plant breeding models utilized were generation means analysis, half-diallel, and topcross. The Cockerham formula was utilized to estimate the number of genes responsible for the variation observed in the breeding lines. Chi-square analyses and R-Studio® for quantitative genetics analysis were used to achieve the best fit of phenotypic variation. All data were collected at the R.R. Foil Plant Science Research Center, Mississippi State, MS. Data recorded were the number of mainstem nodes, plant height, and number of fruiting branch nodes on fruiting branches originating from mainstem nodes eight and nine, and fruiting branch length to the nearest half centimeter. Parental and the first filial generations were not segregated, so measurements were made on ten representative plants. However, in the F2 and backcross generations, each plant was measured and recorded (ignoring end plants and damaged plants). Discrete phenotypic traits for leaf color and leaf shape were present in two parental lines and segregated as previously reported patterns. Thus, these populations were useful for genetic studies of plant architecture. The Cockerham formula data suggested that one to three genes were responsible for the variation in all plant architecture measurements across all generation mean analysis experiments. Specifically, the data supported two or three gene models with non-allelic gene interaction, which expressed phenotypically in an additive manner, were responsible for plant height and mean fruiting branch node length in each cross. However, epistatic interactions were responsible for branch breadth or branch breadth components of mean internode lengths or number of nodes present in the half diallel experiment.

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