| Studies on wheat quality have had new advancement, mostly focusing on protein engineering, especially high molecular weight of glutenin subunits (HMW-GS). In recent years many results have showed that HMW-GS plays a very important role in bread-making quality, that is, whether good or poor wheat quality is directly connected with HMW-GS. Meanwhile the importance of 5+10 subunit at Glu-Dl has been verified and applied quality improvement in common wheat. In addition, good varieties in quality, because of negative correlation between quality and characters of output, generally have low grain yield. When the wheats were infected by heavy diseases , the grain yield and kernel size must be lowered, thereby reduced the income of farmers and profits of flour mills.Due to the reasons above, the thesis analyzed the status of wheat quality in Gansu, composition of HMW-GS and also studied the relationships between baking-bread quality and HMW-GS, quality traits of Gansu wheat and resistance to stripe rust. The purposes of the study are to find out new methods in selecting varieties which have resistance and good quality. The main results are as follows:1. Evaluation on Quality of Wheat Varieties in Gansu ProvinceMost varieties in Gansu were high hardness, grain test weight, flour yield, wet gluten content, and water absorption, but the sedimentation value, gross protein content, development time, stability time were low. Most of them, in a word, were only suitable for noodles, steamed bread. Varieties fitting to make bread and biscuit, however, were lack seriously. On the other hand ,according to the above, the status of wheat quality , resource superiority and characteristic of region in Gansu, the breeding of good wheat, properly planting areas and industrial exploitation for special wheat varieties were discussed in the paper.2. The Relationship between HMW-GS and QualityQuality score in Glu-1 loci was positively correlated with sedimentation value andstability time, the coefficient was 0.551,0.673,respectively. Different alleles coding for HMW-GS at 1A IB and 1D chromosome contributed to quality variability, especially 1A and 1D. Stability time of varieties with 5+10 subunit was higher than with 2+12 ,and differences of them were significant; it was the same as that of 1A loci. Sedimentation value and stability time of varieties with 1 subunit were higher than with N and differences of them were significant. Accordingly the effect of HMW-GS on traits of wheat quality was chiefly sedimentation value and stability time.3. Genetic Variation of HMW-GS among Gansu Wheat varietiesVarieties were analyzed by using SDS-PAGE, and the quality score of each variety at Glu-1 had been calculated according to the method described by Payne et al (1987). The average score was 7.6 in 30 spring cultivars and 6.6 in 31 winter ones. The frequency of 5+10 subunit among spring wheats is higher than that among winter wheats. The result showed high molecular weight glutenin subunits were rich, but the frequencies of ones (2 , 17+18, 14+15, 5+10) contacting with good quality were low, mainly due to their parents without expected subunits. This is consistent with relatively poor quality in the area. Therefore it is a direction in quality breeding to raise frequency of 5+10 subunit and enrich good genetic resources.4.Resistant Test of Common Wheat in Gansu to Stripe RustMost varieties have lost resistance to stripe rust, and nowadays it is imperative to select resistant cultivars in Gansu to control the epidemic of stripe rust.5.The Relationships between Wheat Quality Characters and Resistance to Stripe RustDisease incidence was high significant correlation with development and stability time (1% level); it was significantly correlative with sedimentation, evaluation value, and Glu-Dl score (5% level). Stepwise regression of quality parameters as independent variables indicated that stability time was the most important factor in determining disease incidence and the determining coefficient was more than 2...
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