Pre-harvest glyphosate application and effects on wheat starch chemistry: Analysis from application to harvest

Authors: SIMSEK, SENAY - North Dakota State University; MALALGODA, MANEKA - North Dakota State University; HOWATT, KIRK - North Dakota State University; Ohm, Jae-Bom

Submitted to: Journal of Food Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/2020
Publication Date: 6/18/2020
Citation: Simsek, S., Malalgoda, M., Howatt, K., Ohm, J. 2020. Pre-harvest glyphosate application and effects on wheat starch chemistry: Analysis from application to harvest. Journal of Food Biochemistry. 44:e13330. https://doi.org/10.1111/jfbc.13330.
DOI: https://doi.org/10.1111/jfbc.13330

Interpretive Summary: Glyphosate herbicide is used as a drying agent to facilitate harvest in crop cultivation. Starch is a very important biochemical component that influences processing and end-use quality in cereal crops. However, there is limited information on the influence of the application of glyphosate herbicide on chemical properties of starch in cereal crops. This research aimed to determine the influence of pre-harvest glyphosate application on chemical properties of starch in a hard red spring wheat. A glyphosate-based herbicide was sprayed at the ripe stage (recommended) and the soft dough stage (early application). Grain samples were collected before the herbicide application and every three days after application until harvest and analyzed for starch chemical properties. Glyphosate application timing did not impact the shape and distribution of starch granules in grain. Glyphosate application also did not influence size and composition of starch molecules. However, the application at the soft dough stage was shown to change thermal responses of starch granules when heating. The glyphosate application was also observed to influence fine chemical structure of starch molecules. Overall, this study shows that pre-harvest glyphosate application can affect wheat starch chemistry, especially when applied earlier than the recommended time. This result is valuable basic information clarifying the effect of glyphosate application on starch chemical properties.

Technical Abstract: The objective of this study was to determine influence of pre-harvest glyphosate application on chemical properties of starch in a hard red spring wheat. A glyphosate-based herbicide was sprayed at the ripe stage (recommended) and the soft dough stage (early application). Grain samples were collected before the herbicide application and every three days after application until harvest and analyzed for starch chemical properties. Glyphosate application timing did not impact the spatial distribution and morphology of starch granules, as well as the percentage or molecular weight of amylose and amylopectin. The application at soft dough stage increased thermal parameters measured by differential scanning calorimetry such as peak height, peak area and enthalpy. The glyphosate application also affected amylopectin chain length. The application decreased the average amylopectin chain length, affecting the proportion of short and medium length amylopectin. Overall, this study shows that pre-harvest glyphosate application can affect wheat starch chemistry, especially when applied earlier than recommended.