Quantitative trait loci impacting grain beta-glucan content in wild barley (Hordeum vulgare ssp. spontaneum) reveal genes associated with cell wall modification and carbohydrate metabolism

Authors: Walling, Jason; SALLAM, AHMAD - University Of Minnesota; STEFFENSON, BRIAN - University Of Minnesota; Henson, Cynthia; Vinje, Marcus; Mahalingam, Ramamurthy

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2022
Publication Date: 5/10/2022
Citation: Walling, J.G., Sallam, A.H., Steffenson, B.J., Henson, C.A., Vinje, M.A., Mahalingam, R. 2022. Quantitative trait loci impacting grain beta-glucan content in wild barley (Hordeum vulgare ssp. spontaneum) reveal genes associated with cell wall modification and carbohydrate metabolism. Crop Science. 62(3):1213-1227. https://doi.org/10.1002/csc2.20734.
DOI: https://doi.org/10.1002/csc2.20734

Interpretive Summary: Developing genetic tools for improvement of quality traits in crops can be challenging. Often the varieties of crops of economic importance to humans lack the necessary genetic diversity to identify the genes that drive traits in potentially novel and useful way. One method to overcome this limitation is to look at genetically related species, or subspecies of conventional crops that retain a broader diversity of genes (alleles). Here we use such an approach to identify regions of the barley genome that affect the beta glucan content in barley seeds. Beta glucan content is important to 2 distinct end products: 1) the nutritional benefits of diets consuming grain high in beta glucan and 2) the malted barley used in brewing and distilling which works best if grain beta glucan is low. Using a subspecies of varietal barley, a wild barley called Hordeum spontaneum, we were able to identify chromosomal locations that modulate the amount of beta glucan in barley seeds. These genomic locations can be used as selectable markers in breeding programs to rapidly identify those varieties that are genetically predisposed to have low or high in beta glucan in the seeds thereby offering the industries improved varieties for their distinct end products.

Technical Abstract: Barley seeds are a rich source of Beta-glucans that can help reduce the cholesterol content in human diets. However, high levels of this polysaccharide in the seeds causes inefficiencies such as slow lautering during the brewing process due to the higher wort viscosity. Thus, depending on the end use, barley breeding programs have opposing goals with respect to beta-glucan. Discovery of new alleles for beta-glucan content in exotic barley germplasm could have significant commercial importance. We leveraged the Wild barley (Hordeum vulgare spp. spontaneum) Diversity Collection (WBDC) (N=314) to characterize both the variation in beta-glucan content found in this subspecies and to reveal chromosomal regions associated with this trait. Grain beta-glucan content ranged from 2.56% to 11.73% in the WBDC. Within structured subpopulations, geographical coordinates as well as annual precipitation data of original collection sites associated with differing levels of beta-glucan content and thus may have played a role in establishing grain beta-glucan levels in the subpopulations. Genome-Wide Association Study (GWAS) identified a total of 13 QTLs spread across the seven barley chromosomes that explained most of the variation in beta-glucan content in the WBDC. Previously reported genes associated such as beta-glucan synthases and hydrolases (e.g., callose synthase) were found within these QTL regions. Genes such Patatin and Nudix hydrolase provide novel targets for manipulating grain beta-glucan in barley. RNA-seq data from both developing and germinating barley seeds for the annotated gene stable IDs in the QTL regions provided further functional support for the genes of interest found within each QTL.