Physiological Mechanism And Regulation Approaches For Accumulation Of Grain Protein And Starch In Different Specialty Wheat Varieties

In recent years, wheat grain yield has increased continuously, yet grain quality is not much improved. As a result, the ordinary type of wheat is overstock, while good quality wheat is of shortage and has to import from other countries. So elucidating the physiological mechanism and regulation principles for grain quality formation in wheat is of importance for understanding grain quality physiology and guiding cultural management for quality wheat production. In the present study, different wheat varieties with varied grain protein contents were used to investigate the impact of C and N assimilation, translocation and key regulatory enzyme activities on the formation of grain starch and protein, and the relationships between starch and protein contents and flour quality, to assess the regulating effect of source-sink alteration and varied sucrose and nitrogen supply levels on the formation of grain starch and protein, and further to establish the physiological mechanism and technical approaches for regulation of grain quality in specialty wheats' The main results were summarized as follows:1. Four winter wheat cultivars differing in grain quality, Yumai 34, Xuzhou 26, Yangmai 10 and Yangmai 9 were used to determine the accumulation pattern of grain starch and protein contents and their components, along with flour quality traits. The results showed that grain protein content followed the order of Xuzhou 26>Yumai 34>Yangmai 10>Yangmai 9, while starch content was on the contrary. Albumin content decreased rapidly at the beginning stage and changed a little at later stage of grain filling. Globulin decreased initially and then increased until maturity. Gliadin and glutenin both increased with the progress of grain filling. From the mid stage of grain filling, the contents of albumin, globulin, gliadin, and glutenin also followed the order of Xuzhou 26>Yumai 34>Yangmai 10>Yangmai 9. Consistent with starch content, amylose and amypoctin increased gradually. The protein content was positively correlated to dry gluten and wet gluten significantly, and not correlated to other flour quality traits. Ratio of gliadin/glutenin was positively correlated to gluten index, SDS-sedimentation volume, falling number, while negatively correlated to test weight.2. Three wheat genotypes differing in grain protein content, Xuzhou 26, Yangmai 10 and Yangmai 9 were used to study the differences in grain protein and starch accumulation, and the ability of assimilate synthesis in flag leaves of different varieties. The results showed that Yangmai 9 had higher photosyntheitc rate, activity of sucrose phosphatesynthase (SPS) and sucrose content in flag leaf,than Yangmai 10 and Xuzhou 26. The activities of sucrose synthase (SS) in grain were also higher with Yangmai 9 than Yangmai 10 and Xuzhou 26, while the sucrose content was in a opposite pattern. Soluble starch synthase (SSS), granule bound starch synthase (GBSS) and starch content in wheat grain followed the order of Yangmai 9 >Yangmai 10> Xuzhou 26. Thus, higher starch content was not only linked to the ability of sucrose supply as source, but also to the higher catalytic ability of starch synthase in sink. The activity of glutamine synthase (GS) in flag leaf and grain were higher in Xuzhou 26 than those in yangmai 10 and Yangmai 9, consistent with grain protein content. These results indicated that grain starch and protein synthesis were closely associated with the activities of key regulatory enzymes. The ratio of transferred soluble sugar to nitrogen in vegetative organs was negatively correlated to grain protein content. Therefore, the differential patterns for accumulation and remobilization of carbon and nitrogen in vegetative organs could be one of the most important reasons for different grain protein contents.3. Two wheat varieties differing in grain protein content, Yangmai 9 and Xuzhou 26 were used to investigate the effects of spikelet- and leaf-removal on the accumulation of protein and starch and flour quality in wheat grain. Dry matter weight per stem and grain weight per...