Location: Grain Quality and Structure Research
2018 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 third year of its current 5 year plan. Progress this year includes additional analysis 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. Work on analyzing sorghum grain composition grown under heat tents to evaluate the effect of heat stress has been completed and a manuscript detailing the findings is being written. Likewise, a manuscript was completed and has been accepted for publication detailing previous work analyzing a stay-green sorghum panel that was grown under different drought stress treatments. This panel was grown by collaborators at the USDA-ARS Plant Stress Lab in Lubbock, Texas. In addition, grain composition and end-use quality analysis was completed that support three germplasm releases with collaborators at Kansas State University and USDA-ARS Plant Stress Lab in Lubbock, Texas. Approximately 400 samples were screened for grain composition and end-use quality traits for collaborators with the USDA-ARS Plant Stress Lab in Lubbock to support development of sorghum germplasm with improved end-use quality, especially with regards to waxy starch. Related to Objective 2: Enable new rapid/high-throughput commercial methods to measure grain sorghum composition and quality traits, an additional ~50 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 (NIR) spectroscopy calibration curve to predict carotenoid content in sorghum has been completed and the additional samples analyzed are part of research to validate the NIR calibration curve. Work on developing NIR curves for predicting basic sorghum grain composition was continued by evaluating how moisture levels in grain impact the accuracy of NIR calibration curves for measuring protein content. Additional samples are currently being analyzed for starch content to improve the existing calibration curves for predicting starch content. Collaborative research was also started with USDA-ARS scientists in the Sustainable Biofuels and Co-products Research Unit in Wyndmoor, Pennsylvania to determine if NIR could predict surface wax content in sorghum grain. Research to develop a high-throughput assay for measuring anti-oxidant levels in food compatible extracts of high polyphenol sorghum samples has been started and the method is currently being validated. Work on developing an NIR method to determine the composition of corn-sorghum flour mixtures has been started with preliminary results showing that NIR can be used successfully for this application. A real-time polymerase chain reaction (PCR) method is also being developed for this research to help validate the NIR calibration curves. This research is being conducted following discussions with stakeholders and ethanol industrial partners and supports expanded use of sorghum for new markets. Related to Objective 3: Integrate the stability/variability of grain sorghum compositional quality and bionutrient components across multiple production environments, sorghum germplasm identified as high polyphenol lines was grown in winter nurseries in Mexico and Puerto Rico and was analyzed for polyphenol and antioxidant content. Samples identified as containing high levels of polyphenols were prepared for an animal feeding trial to test their effectiveness in inhibiting colorectal cancer. Experiments were also conducted to determine the location in the grain where the most effective polyphenols were located and how particle size of isolated sorghum bran impacts anti-cancer properties. A second set of high polyphenol sorghum samples were obtained from collaborators at the USDA-ARS Tropical Crops and Germplasm lab in Mayaquez, Puerto Rico. Research is in progress to analyze polyphenolic compounds in these samples and identify specific compounds responsible for bioactivity. Research was also completed analyzing samples grown in Ethiopia and processed into traditional food products. These samples were analyzed for nutritional composition and quality (protein content and protein digestibility, as well as iron and zinc content) and for anti-nutritional components such as trypsin inhibitor levels and phytic acid content.
Accomplishments
1. Grain composition analysis of sorghum to support genetic improvement of sorghum. Sorghum breeders at the state and federal level continue to develop new sorghum parental lines for hybrid production and the sorghum industry. To provide information on the grain composition and quality of new sorghum germplasm, ARS scientists in Manhattan, Kansas analyzed new varieties of sorghum for grain composition and end-use quality traits such as total protein, total starch, protein digestibility and ethanol fermentation efficiency that were being released by collaborators at Kansas State University (Manhattan, Kansas) and USDA-ARS (Lubbock, Texas) which included herbicide resistant sorghum and sugar cane aphid resistant sorghum lines. This research will provide information on grain composition and end-use quality of these lines to the sorghum seed industry interested in utilizing these materials in hybrid sorghum production.
2. Optimization of polyphenol extraction from sorghum using food grade solvents. Sorghum grain contains a number of unique phenolic compounds and certain lines have high levels of polyphenols. These types of compounds have many potential human health benefits including anti-cancer properties. In order to study the anti-cancer properties of high polyphenol sorghum varieties, ARS scientists in Manhattan, Kansas optimized the extraction of sorghum polyphenols using solvents that are compatible for use in the food industry. This research will enable the testing of sorghum varieties for anti-cancer properties using a system that could be directly used by the food industry and open new markets for sorghum utilization.
3. Analysis of nutritional composition and quality sorghum flour and food products. Sorghum flour can be used to produce a number of different types of food products and in parts of the world sorghum is a major human food staple. It is well known that when wet-cooked, sorghum nutritional quality decreases due to a reduction in protein digestibility. While some reasons for the reduced protein digestibility are known, there has been very little research that has compared interaction of sorghum variety by food production method. ARS scientists in Manhattan, Kansas analyzed nutrient content (protein, iron, and zinc), protein digestibility and the presence of anti-nutritional compounds (protease inhibitors and phytic acid) in genetically diverse sorghum samples made into different types of traditional food products. Food processing decreased nutritional quality, but not the same degree for a given variety and food type. Thus, it may be possible to select specific sorghum varieties for the production of a specific food type with improved nutritional quality. This research will help sorghum breeders identify specific types of sorghum for specific end-uses and improve the nutritional quality of sorghum based foods.
Review Publications
Bean, S.R., Ioerger, B.P., Wilson, J.D., Tilley, M., Rhodes, D.H., Herald, T.J. 2018. Structure and chemistry of the sorghum grain. Book Chapter. p. 1-260.
Bandara, Y., Tesso, T.T., Bean, S.R., Dowell, F.E., Little, C.R. 2017. Impacts of fungal stalk rot pathogens on physicochemical properties of sorghum grain. Plant Disease. 101(12):2059-2068. https://doi.org/10.1094/PDIS-02-17-0238-RE.
Vu, T.T., Bean, S.R., Hsieh, C.F., Shi, Y. 2017. Preparation and characterization of sorghum flour with increased resistant starch content. Journal of the Science of Food and Agriculture. https://doi.org/10.1002/jsfa.8346.
Girard, A.L., Castell-Perez, M., Bean, S.R., Adrianos, S.L., Awika, J.M. 2016. Effect of condensed tannin profile on wheat flour dough rheology. Journal of Agricultural and Food Chemistry. 64(39):7348-7356.
Kaufman, R.C., Wilson, J.D., Bean, S.R., Xu, F., Shi, Y.C. 2017. Sorghum starch properties as affected by growing season, hybrid, and kernel maturity. Journal of Cereal Science. 74:127-135. https://doi.org/10.1016/j.jcs.2017.01.014.
Bize, M., Smith, B., Aramouni, F., Bean, S.R. 2016. The effects of egg and diacetyl tartaric acid esters of monoglycerides addition on gluten-free sorghum bread quality. Journal of Food Science. 82(1):194-201.
Cobb, A.B., Wilson, G.T., Goad, C.L., Bean, S.R., Tesso, T.T., Wilson, J.D. 2017. Assessing the influence of farm fertility amendments, field management, and sorghum genotypes on soil microbial communities and grain quality. Applied Soil Ecology. 119:367-374. https://doi.org/10.1016/j.apsoil.2017.06.010.
Pang, B., Zhang, K., Bean, S.R., Kisekka, I., Zhang, M., Wang, D. 2018. Evaluating effects of deficit irrigation strategies on grain sorghum attributes and biofuel production. Journal of Cereal Science. 79:13-20. https://doi.org/10.1016/j.jcs.2017.09.002.
Smolensky, D., Rhodes, D.H., Mcvey, D.S., Fawver, Z.T., Perumal, R., Herald, T.J., Noronha, L.E. 2018. High-polyphenol sorghum bran extract inhibits cancer cell growth through DNA damage, cell cycle arrest, and apoptosis. Journal of Medicinal Food. DOI:10.1089/jmf.2018.0008.
