Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: May 1, 2007
Publication Date: June 1, 2007
Citation: Dupont, F.M., Hurkman, W.J., Vensel, W.H., Chan, R., Tanaka, C.K., Altenbach, S.B. 2007. Effects of Mineral Nutrition and Temperature on Accumulation of Gluten Proteins are Related to Their Content of CYs and Met. In: George L. Lookhart, Perry K. W. Ng, editors. Gluten Proteins 2006. Minneapolis, MN: AACCI. p. 38-42. Interpretive Summary: Millions of tons of wheat flour are used every year by the baking and food industries. Variability in wheat flour quality is a common and serious problem for millers and bakers, and much of this variability has been attributed to environmental conditions during grain fill. Controlled environments were used to define the effects of fertilizer and high daytime and nighttime temperature on accumulation of protein by developing wheat grains. Wheat flour proteins were analyzed by various methods. It was discovered that flour protein composition was nearly identical for high protein flour produced by adding ample fertilizer during grain fill or produced by exposing the plants to high temperature during grain fill. No matter how it was produced, the high protein flour had relatively more sulfur-poor proteins than low protein flour. Even though protein composition was very similar for the high protein flours produced by adding fertilizer or growing plants under high temperatures, the flour produced under high temperatures had poor mixing quality. The results indicate that flour composition is influenced by different effects of environment on accumulation of sulfur-poor and sulfur-rich proteins.
Technical Abstract: Excess N and/or high temperature had effects somewhat similar to S-deficiency on flour protein composition. Grain was produced under climate-controlled conditions with average day and nighttime temperatures of 24oC and 17oC (cool), or 37oC and 28oC (hot), from anthesis until maturity. Pots were irrigated with or without NPK (20:20:20) fertilization from anthesis until maturity. Flour proteins were fractionated into NaI-soluble/methanol-insoluble gliadins; NaI-soluble/methanol-soluble albumins, and NaI-insoluble glutenins. Amounts of high and low molecular weight glutenin subunits (HMW-GS, LMW-GS), '-gliadins, and ' + '-gliadins were determined by RP-HPLC. Despite the extremes of temperature and fertilization, flour from three of the four treatments had nearly identical protein compositions. Flour from grain produced under cool conditions with NPK and under hot conditions with or without NPK had greater proportions of S-poor protein types whereas flour from grain produced under cool conditions without NPK was enriched in the S-rich protein types. NPK had little effect under the hot conditions. Although S-poor proteins also increase with S-deficiency, application of S after anthesis did not alter the results, and flour S-content did not indicate S-deficiency. Protein accumulation was followed throughout grain fill by 2DE of KCl-insoluble gluten proteins from endosperm. Under cool conditions, accumulation rates were increased by addition of NPK, with the biggest increases for the S-poor '-gliadins and HMW-GS. Under the hot conditions without NPK, S-poor proteins also accumulated at higher rates and the final flour protein composition was very similar to that from grain produced with NPK under cool conditions. We propose that high temperature or ample N during grain fill favored the production of S-poor gluten proteins. Although flour from three of the four regimens was high in protein, had similar protein composition and had high values for SDS-sedimentation and loaf volume, mixing tolerance was poor for the flours produced under the high temperature regimens.