Separation and quantitation of plant and insect carbohydrate isomers found on the surface of cotton

Authors: Peralta, Donna; Fortier, Chanel; Delhom, Christopher - Chris; Rodgers Iii, James; THIBODEAUX, DEVRON - Retired ARS Employee

Submitted to: American Association of Textile Chemists and Colorists Journal of Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2016
Publication Date: 7/28/2016
Citation: Peralta, D.V., Fortier, C.A., Delhom, C.D., Rodgers III, J.E., Thibodeaux, D.P. 2016. Separation and quantitation of plant and insect carbohydrate isomers found on the surface of cotton. American Association of Textile Chemists and Colorists Journal of Research. 3(4):13-23. https://doi.org/10.14504/ajr.3.4.2.
DOI: https://doi.org/10.14504/ajr.3.4.2

Interpretive Summary: Cotton stickiness researchers have worked to create ion chromatography (IC) carbohydrate separation methods of cotton surface sugars which allow for minimal analysis time and reduced operational costs. These sugars have been studied in an effort to pinpoint the causes of cotton stickiness phenomena and because analytical chemistry methods are largely considered more consistent than mechanical physical testing methods. According to previous studies, certain levels of the insect honeydew carbohydrates melezitose and trehalulose deposited on the cotton surface are indicative of either whitefly or aphid contamination, which may cause problems during cotton processing. Obtaining reliable IC values for those surface sugars is paramount in diagnosing a contamination. Since raffinose and sucrose are isomers of melezitose and trehalulose, respectively, it can be difficult to fully separate them from the entomological sugars via IC, especially when the analysis time is shortened. We have tried a previously published IC instrumental method, which cut down the analysis time, but the retention peaks of the entomological sugars and their isomers overlapped. This overlap cause the amounts of melezitose and trehalulose to be incorrect; thereby causing the identification of the pest responsible for the contamination to be incorrect. By testing cotton sample water extracts (ranging from LOW to HEAVY Minicard stickiness ratings) via an IMPROVED IC method, we have shown decreases of ~ 78 to 99% in melezitose amounts present, when compared to the previous method. Therefore, where there was once reason to believe that there was an aphid contamination in these particular cotton samples, because of the level of melezitose previously determined; these findings serve as a proof-of-concept that improving the separation method may suggest that the contamination was likely due to whiteflies.

Technical Abstract: Cotton stickiness researchers have worked to create ion chromatography (IC) carbohydrate separation methods which allow for minimal analysis time and reduced operational costs. Researchers have also tried to correlate scientifically backed IC data with the available physical stickiness tests, such as Minicard. According to previous studies, certain levels of the carbohydrates melezitose and trehalulose deposited on the cotton surface are indicative of either whitefly or aphid contamination, which may cause problems during cotton processing. Obtaining reliable IC values for those surface sugars is paramount in diagnosing a contamination. Since raffinose and sucrose are isomers of melezitose and trehalulose, respectively, it can be difficult to fully separate them from the entomological sugars via IC, especially when the analysis time is shortened. We have deduced that utilizing a previously published IC instrumental method may cut down the analysis time, but the retention peaks of the entomological sugars and their isomers may overlap, which causes discrepancies in the IC detection. By testing the water extracts of five raw cotton samples (ranging from LOW to HEAVY Minicard stickiness ratings) via an IMPROVED IC method, we have shown decreases of ~ 78 to 99% in melezitose amounts present, when compared to the previous method. Therefore, where there was once reason to believe that there was an aphid contamination in these particular cotton samples, because of the level of melezitose previously determined; these findings serve as a proof-of-concept that improving the separation method may suggest that the contamination was likely due to whiteflies.