Coupling effects of irrigation and nitrogen fertilization on grain protein and starch quality of strong-gluten winter wheat

Effects of irrigation and nitrogen fertilization on the grain yield, protein composition, protein quality, starch composition and starch pasting properties of a strong-gluten winter wheat were investigated in a high fertility field. Compared with non-irrigation treatment, grain yields under irrigation treatments were significantly increased, but the content of grain protein, monomeric protein and flour wet gluten was reduced. There were no significant differences in the above parameters between the irrigation treatments. Nitrogen application could significantly increase grain yield under low irrigation frequency (W₀ and W₁), while the neglected effect on yield was observed with high irrigation frequency (W₂ and W₃). With the increase of irrigation frequency, the glutenin content leveled off, but the changes of glutenin composition were not uniform, in which the soluble glutenin content was increased, while the insoluble glutenin content and polymerization index (the ratio of insoluble glutenin to total glutenin) were reduced. Both dough development time and stability time became shorter with the increased irrigation frequency. Nitrogen application improved the content of all grain protein fractions and grain quality, in which the increased degree in non-gluten protein (albumin and globulin) was higher than gluten protein (gliadin and glutenin), and the increased degree in soluble glutenin was found higher than that of insoluble glutenin. The interactive effects of irrigation and nitrogen on starch composition were significant. Starch content and amylopectin content was increased as irrigation frequency added in non-nitrogen treatment. Compared to non-irrigation treatment, irrigation significantly increased the starch content and the amylopectin content in nitrogen application treatment, but the starch and amylopectin content had no significant difference between irrigation treatments. Amylose content and the ratio of amylose to amylopectin were reduced while RVA indexes (peak viscosity, breakdown, final viscosity and setback) were increased as irrigation frequency was increased. Nitrogen application significantly improved the amylopectin content and decreased the amylose content in lower frequency irrigation, while the amylopectin content was decreased and the amylose content was enhanced by nitrogen application in higher frequency irrigations. __________ Translated from Plant Nutrition and Fertilizer Science, 2007, 13(3): 361–367 [译自: 植物营养与肥料学报]