| The experiment was carried out in field conditions in the farm of Henan Agricultural University in growing seasons of 2006-2008.Experiment was a factorial combination of four sowing dates and four cultivars.The objective of this study was to gain a better understanding of how sowing dates and grain positions affect grain protein and amylose content. Pasting properties and flour farinograms and extensograms parameters of different gluten wheat cultivars were also measured. Moreover, under sowing dates, A- and B-type isolated from starch were analysed to evaluate grain size distribution and their pasting properties.1. For all three spikelet positions, in AS produced the lowest protein contents, while CS and BS spikelet positions had difference with different wheat cultivars : protein content was greater in CS than in BS in Lankaoaizao8,but it was lower in CS than in BS in another cultivars.Grain position was the most important source of variation for protein content of grain. For four genotypes,G1 or G2 in CS or BS produced the heavier grain protein contents than G3 in CS or BS and grains in AS. With grain positions increasing, protein contents of grains were decreased.Comparison among the same spikelet groups , grain protein contents in CS had greatest varition.Sowing dates had significant effect on protein contents of grain.For three spikelet positions in Yumai34,Yumai49 and Yumai50(except for AS in Yumai50 was the highest in S2),S1 showed the highest protein content in grains.Althrough this trend was similar in AS of Lankaoaizao8, S4 showed the highest in CS and BS.2. Protein components were affected significantly by sowing date and genotype . Results showed that glutentin was protein components with the highest grain concentration,and globulin showed the lowest concentration. There were significant different among genotypes for grain protein components. Lankaoaizao8 showed the highest albumin and globulin concentration .Yumai34 showed the highest gliadin and glutentin concentration and Yumai50 showed the lowest. Among four sowing dates , gliadin concentrations of grain in Lankaoaizao8 and Yumai50 were the highest in S3 , in Yumai34 was S1 and in Yumai49 was S2 .Glutenin concentrations of grain in Yumai34 and Yumai50 were the highest in S3 and S2 , respectively ,while in Yumai49 and Lankaoaizao8 were in S1 .Albumin and gliadin concentrations of grain in Yumai49 and Yumai50 were the highest in S4 , while in Yumai34 were in S1 and S4 , respectively .3. In general , grains in CS produced the lowest amylose concentration and G1 or G2 in BS showed the lowest amylose concentration , while G3 in BS had the highest amylose concentration .The greatest varition in CS on amylose concentration was found among different spikelet positions in Lankaoaizao8, Yumai34 and Yumai49 with sowing dates, while in BS of Yumai50 was found . With the delay of sowing date , there was more variation among grain positions of the same spikelet and there was more obvious different among spikelet groups .4. Four paste parameters (such as peak viscosity , trough viscosity , final viscosity and set back)were significantly influenced by sowing dates and genotypes . In general ,the effect of genotype on pasting properties was greater than the effect of sowing date . With difference of sowing dates , pasting parameters behaved showed the highest value in S1 for Lankaoaizao8 , Yumai34 and Yumai50 , but peak viscosity and trough viscosity showed in S3 , and final viscosity showed in S2 .5. Wheat starch A- and B-type starch granules differed significantly in terms of their pasting properties , A-type starch granules showed higher value of major pasting parameters (such as peak viscosity , trough viscosity , final viscosity and set back) and lower peak temperature than B-type starch granules . Peak viscosity , trough viscosity and final viscosity of A- and B- in Yumai49 were higher than in Yumai34 , but peak temperature and break down in Yumai49 was lower than in Yumai34 . With delay of sowing dates , the propotion of B-type granules in starch increased , the major pasting parameters of A- and B-type starch granules increased significantly in Yumai34, while the major pasting parameters of A-type starch granules in Yumai49 showed the highest value in S3, peak viscosity and final viscosity of B-type starch granules showed in S3 ,but trough viscosity showed in S1 .6. Farinograms and extensograms parameters were significantly influenced by sowing dates and genotypes .With regard to different gluten-content wheat cultivars, Farinograms and tensions parameters of Yumai34 showed the highest value ,one exception was softness ,which showed the highest value in Yumai50 . With the delay of sowing dates , although th value of resistance in Yumai34 increased , the value of extension decreased. The stable period of Lankaoaizao8 prolonged and resistance increased in S4 . The value of softness in Yumai50 increased in S4, but there was no significant sowing date effect on another farinograms and tensions parameters . 7. Generally, grains in CS or BS produced greater 1000-grain weight than in AS. Grain position affected 1000-grain weight. G1 in AS showed higher 1000-grain weight than G2, while G2 in CS and BS showed the highest 1000-grain weight The greatest effect of position on 1000-grain weight was found among grain position in CS.Yield and its components were significantly influenced by sowing dates and genotypes . For four wheat cultivars, S2 produced the highest spikelet number , early sowing and late sowing decreased the spike number . S3 produced the highest kernels per-spike, and the kernels per-spike of Yumai50 had the greatest variation among four sowing dates. S1 showed the highest 1000-grain weight for Yumai50 and Yumai49 , while S2 had the highest 1000-grain weight for Yumai34 and S3 had the highest 1000-grain weight for Lankaoaizao8 . For four sowing dates , S2 produced the highest yield for Lankaoaizao8 and Yumai34, S3 showed the highest yield for Yumai50 . For Yumai49 , the yield of S1 S2 and S3 were above signifcantly S4 .Above results showed that there was significant differenence of quality traits among diefferent spikelet positions and grain positions in wheat spike, and sowing date affected significantly quality traits of spikelet positions and grain positions. In wheat production, the optimum sowing dates should be chosed according to not only the quality changes in different culitivars but also the grain yield. And cultivating measures should be taken to increase the balance of nutrient concentrations within the spike and improve grain quality of the whole spike .
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