Location: Cereal Crops Research
2018 Annual Report
Objectives
Objective 1. Identify, develop, validate, and implement new measurements of malting quality, especially those relating to protein mobilization during germination, in barley germplasm in order to identify those genotypes showing enhanced malting quality attributes. Objective 2. Apply standard malting quality assessments to germplasm submitted by collaborating public sector barley breeding programs, researchers, and other stakeholder organizations in order to identify new (barley) varieties with suitable malting quality attributes.
Approach
Surveying populations that have been extensively genotyped and mapped for malting
quality will allow us to generate datasets that include process (proteinase
activity), phenotype (malting quality), and genotype (>3000 SNP loci) information. Examining a range of barley genetic resources will enable us to use that genetic diversity to identify fundamental processes underlying malting quality. We will use this information to identify new targets and develop additional mechanisms to screen for improved malting barley genotypes. The new screening mechanisms may involve biochemical measurements that we could implement in our malting quality analysis program. Alternatively, the new tests could utilize genetic tools that breeders could incorporate into their own germplasm characterization, simplifying and streamlining their malting quality selection process.
Progress Report
Malting quality analyses support. The ARS in Madison, Wisconsin responded to over 6,700 requests for malting quality analytical data from public-sector barley germplasm enhancement programs and collaborating barley researchers. Barley testing was performed on over 140 samples to assist stakeholders in their selection of material for pilot scale malting and brewing trials to determine suitability of germplasm for release as an approved malting quality variety with the potential for value added payment. The reduced-scale ethodologies developed for generating malts and for conducting many standard tests have been adopted by additional barley research programs.
Phenotypic and Genotypic evaluation of Preharvest Sprouting (PHS) in 2 and 6 row barley. Over 120 two and six row malting barleys have been evaluated for propensity to preharvest sprout. Defined as precocious germination of seed prior to harvest, preharvest sprouting results in significant losses to growers of malting barley and therefore presents a tangible risk of reduced returns. Preharvest sprouting is most common in regions with excessive rain or humidity during seed ripening. Each of the 120 lines were grown in replicated field trials at Montana State Ag Station. The barley “heads” were harvested and challenged to preharvest sprout in artificial rain chambers. ARS scientists in Madison Wisconsin, in collaboration with scientists at Montana State University demonstrated variability in resistance levels within the germplasm interrogated, and therefore promise of developing genetic resources for combating the issue. Simultaneous to the PHS screening, ARS scientists in Madison Wisconsin, characterized three genes associated with controlling germination capacity in cereal crops. Each of the three genes were fully sequenced (DNA sequencing) in each of the 120 lines to hunt for mutations that control the level of PHS resistance in the barley lines. The DNA sequence evaluation (genotyping) revealed mutation in barley lines that also show resistance to PHS.
Beta glucan content in wild barley. Beta glucans are naturally occurring polysaccharides that are constituents of cell walls in cereals. Beta glucans have both positive and negative impacts in post harvest products made from cereals. In food consumption, beta glucans have been associated with decreased cholesterol levels and as a prebiotic by boosting beneficial gut bacteria in the host. In the brewing industry, malts that have been made from high beta glucan barley have a negative industrial impact causing filtration issues by gumming and thus slowing the lautering process. ARS scientists in Madison, Wisconsin, in collaboration with scientists at University of Minnesota, evaluated the beta glucan content within a population of over 230 Wild Barley lines. This evaluation was conducted on 2 reps of the 230 lines; one rep from 2005 field season and another from 2015, thus representing 2 samplings. Populations of wild barley offer a slightly different and also wider genetic makeup than contemporary malting barley populations and therefore represent a resource for new gene discovery. The study thus far has revealed a wide range in beta glucan content in our wild barley lines, 2-12% which is far greater than the contemporary malting barleys which typically range from 4-6%. Genome wide associations are currently being interrogated to unravel novel gene and regulators of beta glucan content.
Evaluation of reference primers from stably expressed genes for normalization of qPCR on samples obtained from Micromalted Barley: Progress was made in the identification of stably expressed genes in a micromating (controlled) germination experiment. Two barley varieties relevant to the U.S. malting and brewing industries were chosen: two-row malting variety (Conrad) and a six-row malting variety (Legacy). Stable reference genes are paramount when comparing gene expression results across varieties and developmental time points. Thirteen putative reference genes were analyzed and nearly all demonstrated a level of stability appropriate for expression studies. Furthermore, we are able to reduce the number of reference genes used in typical experiment thereby saving costs and time.
Accomplishments
Review Publications
Walling, J.G., Zalapa, L.A., Vinje, M.A. 2018. Evaluation and selection of internal reference genes from two- and six-row U.S. malting barley varieties throughout micromalting for use in RT-qPCR. PLoS One. 13(5)/e0196966. https://doi.org/10.1371/journal.pone.0196966.
Liao, Y., Zhang, X., Li, B., Liu, T., Chen, J., Bai, Z., Wang, M., Shi, J., Walling, J.G., Wing, R., Jiang, J., Chen, M. 2018. Comparison of Oryza sativa and Oryza brachyantha genomes reveals selection-driven gene escape from the centromeric regions. The Plant Cell. https://doi.org/10.1105/tpc.18.00163.
