Location: Grain Quality and Structure Research
2016 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.
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 project is completing the first year of its current 5 year plan. Progress includes completion of analysis of sorghum grain from diverse genetic samples grown at three locations across Kansas. Physical grain traits, protein and starch content and composition and protein digestibility were measured (related to sub-objective 3.A. “Evaluate the variability of grain composition related to protein and starch across multiple growing environments”). A second year of samples from one location was harvested and protein digestibility and grain physical traits measured (also sub-objective 3.A). In addition samples subjected to specific abiotic stresses were analyzed. Detailed compositional analysis has been conducted on diverse sorghum samples grown under irrigated and non-irrigated conditions to examine the effects of drought stress on sorghum grain composition and end-use quality (related to sub-Objective 1.A “determine how timing of drought stress during grain fill impacts protein and starch chemistry and digestibility”). Likewise, the same samples grown under heat tents to induce heat stress were collected and physical grain traits analyzed and the samples are being processed now for their chemical composition (sub-Objective 1.B “determine the degree to which heat stress impacts sorghum grain quality traits”). Research on several other sorghum populations has also begun. An EMS mutant library was harvested and grain physical traits and grain composition studies have begun to discover mutants with unique end-use quality traits (in collaboration with the USDA-ARS Plant Stress Lab in Lubbock, Texas) (sub-Objective 3.A). Also in collaboration with the ARS lab in Lubbock, a stay-green sorghum panel is being analyzed for physical grain traits and composition/end-use quality to determine how stay-green sorghum lines maintain grain quality under drought stress (sub-Objective 1.A). Samples of a carotenoid panel were harvested and carotenoid content and composition is currently being analyzed to identify genetic markers for improving the carotenoid content in sorghum (related to Objective 3 “integrate the stability/variability of grain sorghum compositional quality and bionutrient components across multiple commercial production environments”). Research is also underway related to Objective 2 “Enable new rapid/high-throughput commercial methods to measure grain sorghum composition and quality traits” including comparisons of glucose measurements between an inexpensive handheld glucometer and HPLC for use in grain composition and quality analysis. Preliminary development of NIR calibrations for predicting sorghum grain quality traits and composition has begun. Research on the effectiveness of sorghum anti-oxidants in cell based assays is in progress with extracts from 14 genotypes known to have high total phenolic contents tested for cytotoxicity; no cytotoxicity was observed for any of the lines (related to 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”).
Accomplishments
1. Interactions of environment x management (E x M) on sorghum grain composition and quality. Many factors influence composition and end-use quality of grains. To better understand the interactions between environment and management practices, ARS scientists in Manhattan, Kansas analyzed grain composition and end-use quality of a sorghum hybrid grown in three locations in Kansas under 11 different management conditions. Across the locations and management practices there were a wide range of protein and starch contents found as well as variability in protein digestibility and fermentable sugar levels (an indicator of ethanol production performance). This information will aid in the design of future experiments to include a wider range of genotypes and also provides preliminary evidence on how management practices may improve sorghum grain end-use quality.
