Date of Graduation

12-2013

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor

Richard E. Mason

Committee Member

Pengyin Chen

Second Committee Member

Edward E. Gbur

Third Committee Member

David M. Miller

Keywords

Biological sciences; Abiotic stresses; Quantitive trait loci; Waterlogging; Wheat

Abstract

Waterlogging is caused when water stays superficially in the soil for an extended period of time, creating an anaerobic environment which decreases plant growth and grain yield at maturity. Despite the impact of waterlogging on wheat production both globally and in the southeastern U.S., very little is known about the genetic control of waterlogging tolerance in wheat. The objective of this study was to determine the amount of genetic variation for vegetative stage waterlogging tolerance present within a wheat recombinant inbred line (RIL) population and to identify quantitative trait loci (QTL) associated with tolerance and productivity. Experiments were carried out in both the greenhouse and the field using a RIL population derived from the wheat cultivars `USG3209' and 'Jaypee'. The effect of vegetative stage waterlogging was determined by quantifying fresh shoot biomass, fresh root biomass, dry shoot biomass, dry root biomass, root length, chlorophyll content, tiller number, elongation, and plant height pre and post-treatment under stressed and non-stressed conditions.

In both the greenhouse and the field experiments, biomass traits, chlorophyll content ere significantly reduced by waterlogging stress with percent reduction ranging from 10 to 54%. Significant genetic variation was detected for biomass traits, chlorophyll content, tiller number, elongation, and plant height post-treatment. Root traits showed high sensitivity to waterlogging and significant genotype by treatment interaction. Shoot biomass and root biomass were highly correlated, indicating the possibility of indirect selection for root biomass. The QTL analysis revealed 53 total QTLs, with 34 detected under waterlogging stress. These QTLs clustered into 19 regions distributed throughout the wheat genome. QTL on chromosomes 2A, 2B, 2D, 5A and 5B were found to localize with known genes regulating plant height and flowering time. Other QTL regions located on chromosomes 1B, 2A and 6B appear to be novel for biomass production specific to waterlogging stress and can be used for marker-assisted selection to more efficiently select for waterlogging tolerant lines.

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