Date of Graduation

7-2015

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

Edward Gbur

Second Committee Member

Trenton Roberts

Third Committee Member

Ainong Shi

Keywords

Biological sciences; Association mapping; Elemental toxicity; Qtl; Waterlogging; Wheat

Abstract

Soil waterlogging (WL) affects wheat production worldwide, including the southern of the U.S. Little is known about the genetics of tolerance mechanisms to WL, particularly of potentially toxic elements such as aluminum, iron and sodium. The objectives of this study were to use association mapping (AM) to identify SNP associated with the EC in the vegetative tissue of a set of 240 diverse soft winter wheat genotypes (AM panel) grown under field WL and to determine the impact of WL on wheat yield (GY) and yield components in a set 28 adapted cultivars (YT)

YT study showed reductions in GY of 42%, resulting of the combined effect of decreases in total biomass, kernel-weight per spike and spikes m-2. Strong negative correlations were observed between GY and accumulation of aluminum, iron and sodium, indicating likely elemental toxicity. Cultivars ‘Jamestown’ and ‘USG3555’ were found to be the most tolerant to WL, as these prevented large reductions in spikes m-2, kernel weight per spike, kernel number per spike, thousand kernel weight and thus total grain yield.

The AM panel was evaluated over two growing seasons in both Stuttgart Arkansas (AR 13 and AR14) and St. Joseph Louisiana (LA13 and LA14) under WL. Elemental accumulation (EC) measured using ICP-AES found significant genotypic variation for Al in both AR13 and LA14, for Fe in AR13 and for Na in AR13 and AR14, with the percent of phenotypic variation explained by genotype ranging from 0 to 60%. Overall, EC were higher in the 2012-2013 than in 2013-2014 growing season. AM for aluminum, sodium and iron identified nine chromosomes that had marker-trait associations that were consistently detected at the same SNP or SNPs in LD (<30 cM) across multiple data-sets. Overall, detected individual SNPs explained a small percent of the phenotypic variance, ranging from R2 = 0.03 to 0.07, indicating variation in EC to be quantitatively inherited within this AM panel. Chromosomes 2B and 5A were found to contain the majority of SNP with Fe, Na and Al concentration. This is the first study evaluating genetic diversity for the EC in wheat under WL.

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