Location: Grain Quality and Structure Research
2017 Annual Report
Objectives
Objective 1: Integrate commercial grain sorghum quality traits with the timing and duration of heat and/or drought stress during grain fill.
• Sub-Objective 1.A. Determine how timing of drought stress during grain fill impacts protein and starch chemistry and digestibility.
• Sub-Objective 1.B. Determine the degree to which heat stress impacts sorghum grain quality traits.
Objective 2: Enable new rapid/high-throughput commercial methods to measure grain sorghum composition and quality traits.
• Sub-Objective 2.A. Develop an in-vitro cellular antioxidant activity assay for measuring the efficacy of sorghum bioactive compounds in response to radical oxidative species.
• Sub-Objective 2.B. Determine the effectiveness of a blood glucometer in determining fermentation efficiency using sorghum grain.
Objective 3: Integrate the stability/variability of grain sorghum compositional quality and bionutrient components across multiple commercial production environments.
• Sub-Objective 3.A. Evaluate the variability in sorghum grain composition related to protein and starch across multiple growing environments.
• Sub-Objective 3.B. Characterize phytonutrient composition in tannin and black sorghum germplasm grown at multiple locations.
Objective 4: Molecular biological technologies will employ gene flow analysis to identify sorghum compositional and quality traits variants migrating through field/commercial sorghum breeding programs.
Approach
Sorghum [Sorghum bicolor (L.) Moench] is an important drought tolerant crop in regions of the Great Plains where water is limited and rainfall unpredictable. Sorghum has been primarily used for animal feed in the U.S. but recently has seen increasing use in the food and biofuel industries which has provided a new growth area for sorghum utilization. That said, there has not been extensive research conducted on grain quality factors related to sorghum. Recent advances have been made regarding improving sorghum protein and starch digestibility at the genetic level, yet little is known about how environmental factors impact sorghum grain quality attributes and nutritional bioavailability. Sorghum is typically grown under non-irrigated conditions and can face serious drought and heat stress during grain fill. Drought and heat stress may become more prevalent in sorghum growing regions due to climate change and have the potential to severely impact sorghum grain composition and end-use quality traits. Consistency is an important quality attribute of cereal crops and further research is required to quantify the degree to which sorghum grain quality is impacted by the environment. Our research will support on-going efforts to improve sorghum grain quality at the genetic level by providing grain quality information to breeding programs about the stability of various traits. We will provide knowledge of how drought and heat stress impacts sorghum grain quality, ultimately providing information necessary for the sorghum breeding community to improve the end-use quality of sorghum.
Progress Report
The overall goal of this project is to evaluate the impact of environment on sorghum grain quality and composition, particularly the effect of heat and drought stress. The project is completing the second year of its current 5 year plan. Progress this year includes completion of grain composition analysis on two sample sets related to Objective 1: Integrate commercial grain sorghum quality traits with the timing and duration of heat and/or drought stress during grain fill. The first project completed was related to samples grown under heat tents to evaluate how heat stress impacts grain quality. Data analysis on the compositional data is in progress. The second set of samples finished was a stay-green sorghum panel that was grown under different drought stress treatments was completed. This panel was grown by collaborators at the USDA-ARS Plant Stress Lab in Lubbock, Texas. This experiment will provide information on how the timing of drought stress impacts sorghum grain quality as well as potentially identify sources of germplasm that are resistant to changes in grain composition when exposed to drought stress. Related to objective 2: enable new rapid/high-throughput commercial methods to measure grain sorghum composition and quality traits, an additional ~200 samples were analyzed for carotenoid content as part of a project to screen diverse germplasm for carotenoid content and composition. Initial work on developing a Near-infrared region (NIR) calibration curve to predict carotenoid content in sorghum has been completed. Work on developing NIR curves for predicting basic sorghum grain composition was also completed for the following traits: protein content, fat content, tannin content and total phenolic levels. Additional samples to expand the calibration population are being analyzed. Research on the effectiveness of sorghum anti-oxidants in cell based assays is in progress with extracts from thirteen sorghum lines with high total phenols evaluated in a cellular based assay. Preliminary results suggest that sorghum phenolic compounds may play a role in cancer cell death. Related to objective 3: integrate the stability/variability of grain sorghum compositional quality and bionutrient components across multiple production environments, work to characterize grain quality traits in a diverse sorghum association mapping panel has been completed, with efforts focused on physical grain traits which are important for disease resistance as well as milling and processing of grains. Two years of data have now been collected on this population with a third year to be completed in the following growing season. Research on the effect of soil-plant interactions on grain quality and composition was also completed and a manuscript submitted. This research evaluated how soil microbes such as arbuscular mycorrhizal fungi influence grain composition, resulting in increased grain yield and protein content for some treatments. Finally, to support increased utilization of sorghum and take advantage of novel grain quality traits in sorghum, research was conducted to develop and optimized a zein-sorghum flour bread formula to take advantage of the ability of zein to form a visco-elastic dough and unique health attributes of sorghum flour.
Accomplishments
1. Grain quality analysis of samples exposed to different drought stress treatments. Drought stress can have major impact on sorghum grain composition and reduce the quality and value of the crop. To better understand how drought stress impacts sorghum grain quality, ARS scientists in Manhattan, Kansas analyzed grain composition of sorghum that was subjected to drought stress both pre-flowering and post-flower (samples were grown by ARS scientists in Lubbock, Texas). This research will provide information on how the timing of drought stress impacts sorghum grain quality, as well as potentially identify sorghum lines that resist changes to quality when exposed to drought stress.
2. Impact of soil microbes on sorghum grain composition and end-use quality. Soil microbes such as arbuscular mycorrhizal fungi can associate with plant roots and extend the reach of root systems and increase plant access to growth-limiting resources. To better understand how sorghum-plant microbe interactions may impact sorghum grain composition and end-use quality, ARS scientists in Manhattan, Kansas analyzed grain composition of sorghum landraces and commercial hybrids grown with little fertilization but with arbuscular mycorrhizal fungi present in the soil. The sorghum landraces had increased grain production and increased grain protein content compared to the commercial sorghum hybrids. Soil microbe-sorghum interactions have the potential to reduce fertilization usage and cost while maintaining sorghum end-use quality. This research was conducted in collaboration with scientists at Oklahoma State University.
3. Development of zein-sorghum flour bread. ARS scientists in Manhattan, Kansas optimized a bread formula containing isolated corn proteins (zein) and sorghum flour. This formula took advantage of the ability of zein to form visco-elastic dough and sorghum flour’s unique health attributes. Breads were successfully made from a dough based system using white sorghum flour, black sorghum flour, and tannin containing sorghum flour. The optimized formula had substantially improved dough properties and loaf volume compared to initial conditions.
Review Publications
Cobb, A.B., Wilson, G.T., Goad, C.L., Bean, S.R., Kaufman, R.C., Herald, T.J., Wilson, J.D. 2016. The role of arbuscular mycorrhizal fungi in grain production and nutrition of sorghum genotypes: Enhancing sustainability through plant-microbial partnership. Agriculture, Ecosystems and Environment. 233:432-440. doi:10.1016/j.agee.2016.09.024.
Rhodes, D.H., Hoffman, L., Rooney, W.L., Herald, T.J., Bean, S.R., Boyles, R., Brenton, Z.W., Kresovich, S. 2017. Genetic architecture of kernel composition in global sorghum germplasm. BMC Genomics. doi:10.1186/s12864-016-3403-x.
Rhodes, D.H., Gadgil, P., Perumal, R., Tesso, T., Herald, T.J. 2017. Genome-wide association study dissects the genetic architecture of polyphenols and antioxidant capacity in a sorghum diversified collection. Journal of Cereal Science. 94(2):190-198.
Shen, Y., Su, X., Rhodes, D.H., Herald, T.J., Xu, J., Chen, X., Smith, S., Wang, W. 2017. The pigments of sorghum pericarp are associated with the contents of cartenoids and pro-vitamin A. International Journal of Food And Nutritional Sciences. 6(3)48-56.
Huggins, T., Mohammed, S., Sengodon, P., Ibrahim, A., Tilley, M., Hays, D. 2017. Changes in leaf epicuticular wax load and its effect on leaf temperature and physiological traits in wheat cultivars (Triticum aestivum L.) exposed to high temperatures during anthesis. Journal of Agronomy and Crop Science. 204:49-61. https://doi.org/10.1111/jac.12227.
Su, X., Rhodes, D.H., Xu, J., Chen, X., Davis, H., Wang, D., Herald, T.J., Wang, W. 2017. Phenotypic diversity of anthocyanins in sorghum accessions with various pericarp pigments. Journal of Nutrition and Food Sciences. doi: 10.4172/2155-9600.1000610.
