Coupling effects of irrigation and nitrogen fertilizer 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 paste traits of a strong-gluten winter wheat were investigated on a high fertility soil.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 was no significant difference in the above parameters between the irrigation treatments.Nitrogen application could significantly increase grain yield under low irrigation frequency(W0 and W1),while neglected effect on yield was observed with high irrigation frequency(W2 and W3).With the irrigation frequency increase,glutenin content leveled off,but the changes of glutenin composition were not uniformed,in which the soluble glutenin content was increased,while insoluble glutenin content and polymerization index(insoluble glutenin/total glutenin) were reduced.Both dough development time and stability time were becoming shorter.Nitrogen application improved the content of all grain protein compositions and grain quality,in which the increasing magnitude in non-gluten protein(albunin and globulin) was higher than gluten protein(gliadin and glutenin),and soluble glutenin higher than insoluble glutenin.The interactive effects of irrigation and nitrogen on starch composition were significant.Starch content and amylopectin content was increased with adding irrigation frequency in no nitrogen treatment.Irrigation significant increased starch content and amylopectin content in nitrogen treatment compared to non-irrigation one,but there were no significant difference on starch and amylopectin content 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 with adding irrigation frequency.Nitrogen application significantly improved amylopectin content and decreased amylose content in lower frequency irrigation,while amylopectin content was decreased and amylose content was improved by nitrogen application in higher frequency irrigation.