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Research Project: Genetic Enhancement of Watermelon, Broccoli, and Leafy Brassicas for Economically Important Traits

Location: Vegetable Research

Title: Genome-wide association study in arabidopsis thaliana of natural variation in seed oil melting point, a widespread adaptive trait in plants

item Branham, Sandra
item REBA, A - University Of Texas
item WRIGHT, S - Washington University
item LINDER, C - University Of Texas

Submitted to: Journal of Heredity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2016
Publication Date: 2/11/2016
Citation: Branham, S., Reba, A., Wright, S.J., Linder, C.R. 2016. Genome-wide association study in arabidopsis thaliana of natural variation in seed oil melting point, a widespread adaptive trait in plants. Journal of Heredity. doi: 10.1093/jhered/esw008.

Interpretive Summary: Seed oil melting point, the temperature at which oil becomes liquid, is an important seed quality attribute that determines the lowest temperature at which an oilseed plant can germinate. Evidence supports the idea that natural selection has modified seed oil melting points to co-vary with optimal germination temperatures. Understanding the adaptive genetic basis of variation in seed oil melting point would be beneficial to agricultural scientists working to improve crop tolerance to long-term temperature changes experienced by oilseed species. An ARS scientist at the U.S. Vegetable Laboratory in Charleston, SC, in collaboration with a scientist at the University of Texas at Austin, has identified genes that appear to be responsible for variation in seed oil melting point. These results are a valuable contribution to public and private sector scientists working to modify oilseeds for agricultural and industrial uses.

Technical Abstract: Seed oil melting point is an adaptive, quantitative trait determined by the relative proportions of the fatty acids that compose the oil. Micro- and macro-evolutionary evidence suggests selection has changed the melting point of seed oils to co-vary with germination temperatures because of a trade-off between total energy stores and the rate of energy acquisition during germination under competition. The seed oil compositions of 391 natural accessions of Arabidopsis thaliana, grown under common-garden conditions, were used to assess whether seed oil melting point within a species varied with germination temperature. In support of the adaptive explanation, long-term monthly spring and fall field temperatures of the accession collection sites significantly predicted their seed oil melting points. In addition, a genome-wide association study (GWAS) was performed to determine which genes were most likely responsible for the natural variation in seed oil melting point. The GWAS found a single highly significant association (FDR<0.01) centered on FAD2, which encodes a fatty acid desaturase central to the oil biosynthesis pathway. Four additional regions containing 50 genes of minor association (0.05