| Corn-soybean relay-cropping developped quickly in recent years. it made full use of light, heat, water, fertilizer and other resources, improved the soybean planting area, increased soybean production, played an important role in easing regional food security.However, relay-cropping soybean was grown in the later stage of corn growth, the shading of corn leading to soybean vegetative growth affected, so that the quality of soybean was affected. Former research on relay-cropping soybean quality was limitted to the change of protein, fat content, the study on the characteristics of relay-cropping soybean storage protein, amino acid, fatty acid accumulation charateristics and systematic evaluation of nutritional quality was less, and its mechanism was unknown. Therefore,3soybean cultivars of different quality characteristics was used in the expriment, in2011-2012.Evaluated systematically nutritional value of soybean, disclosed the nutrients accumulation regular pattern, and made use of proteomics means to explore the mechanism of quality formation of relay-cropping soybean, aimed at provide the basis for further improve the quality of soybean.The main results showed as follows:1.Three different soybean cultivars were used to study soluble sugar, nitrogen content and the quality formation regular pattern and yield during soybean seed growth process under solo-cropping and relay-cropping. Results showed that relay-cropping soybean soluble sugar, nitrogen and the nutrient accumulation regular pattern were consistent with the solo-cropping soybean,but the soluble sugar content of relay-cropping soybean grain was higher than solo-cropping soybean, nitrogen content of relay-cropping soybean grain was lower than the solo-cropping soybean,indecated stem and leaf source organs transported to grain of relative more carbohydrates after seed-filling period.As a whole relay-cropping soybean grain protein,11S and7S content was lower than solo-cropping soybean,but the ratio of11S/7S was higher than solo-cropping soybean, total amino acid,essential amino acid and the first limiting amino acid (methionine and cysteine) content were higher than solo-cropping soybean, fat content increased,saturated fatty acid content reduced and unsaturated fatty acid increased,Yield per plant decreased. But different soybean cultivar quality formation and yield responsed differently to relay-cropping, middle type soybean D2pod number per plant, grain number per plant and grain weight per plant closed to even higher than solo-cropping.High oil type soybean Dl rangeability of saturated fatty acids, unsaturated fatty acids was greater than D2and D3. High protein type soybean D3rangeability of protein, fat, and the subunit content and ratio, amino acid variation was greater than Dl and D2, it showed that middle type soybean D2had better adaptability to shade under relay-cropping environment. In conclusion, relay-cropping effected differently on growth and nutrient accumulation of different quality characteristics soybean, so it determined protein, fat nutritional quality good and bad of soybean seeds.2.Evaluated systematacially the nutritional value of three soybean cultivars of different quality type under corn-soybean relay-cropping,and compared compare to solo-cropping. The results showed that relay-cropping soybean protein content was reduced by0.99percent point (P=0.018), fat contentincreased by0.54percent point(P=0.024),storage protein11S/7S ratio as high as2.84, significantly increased0.09(P=0.029) than solo-cropping. High protein type soybean D3storage protein11S/7S ratio is as high as3.05, significantly higher than solo-cropping5.53%(P=0.001), high oil type soybean D1and middle type soybean D2higher than solo-cropping2.40%(P=0.081) and2.88%(P=0.031) respectively, indicated relay-cropping soybean (D3) could be provide high quality protein materials to soybean protein products completely. relay-cropping soybean five kinds of chemical analysis indicators:Amino acid score(AAS), Chemical score(CS), Essential amino acid index(EAAI), Score of RCAA(SRCAA) and Essential Amino Acid Relative Ratio(EAARR) respectively is:64.34,76.82,82.10,83.08,78.06, and the variation compared to Solo-cropping respectively is2.38(P=0.002),3.01(P=0.012),0.03(P=0.209),0.45(P=0.202),-0.19(P=0.754) under FAO/WHO mode, high oil soybean D1amino acid general score was higher than D2and D3, but High protein soybean D3amino acid score(AAS) improved6.79%(P=0.001), significantly higher than that of D1and D2.Relay-cropping soybean essential fatty acids relative contents increased by2.02%(P=0.045) compare with solo-cropping,the ratio of polyunsaturated fatty acids and saturated fatty acid (P/S) increased by2.56%(P=0.015) compared with solo-cropping. High oil soybean D1essential fatty acid relative content(66.7%) and P/S ratio (4.3) was significantly higher than D2and D3,and increased the most.Therefore, relay-cropping soybean not only didn’t reduce the nutritional value of amino acids and improved nutritional quality of soybean protein and oil. High protein type soybean with high quality protein, high oil soybean amino acids, fatty acids composition of high nutrition value, and middle type soybean nutritional quality was affected by solo-cropping less.3.Applied differential proteomics means study the mechanism of quality differences of relay-cropping soybean and solo-cropping soybean. Results showed that relay-cropping soybean grain had38differentially expressed protein sopts at20days after poding,28spots were identified,8proteins of unknown functions. These proteins were mainly associated with resistance, resistance to nutrition, associated with energy metabolism, protein and amino acid metabolism, fatty acid synthesis. Acetyl-CoA carboxylase and pyruvate dehydrogenase expression quantity of relay-cropping soybean grain increased relative to solo-cropping soybean, it promoted glycolysis products pyruvate acid oxidative decarboxylation into acetyl coenzyme A irreversibly,increased the precursor of fat synthesis and reduced the precursor of protein synthesis,so it explained fat content increased and protein content decreased of relay-cropping soybean. At the same time, protein beta hemisphere beta subunits of relay-cropping soybean decreased,beta hemisphere protein was the main component of soybean storage protein,thus the ratio of11S/7S increased relatively,improved the pracessing characteristics of soybean storage protein.Phosphoglycerate kinase and Malate dehydrogenase of relay-cropping soybean expression quantity increased, thus to generate more carbon skeleton source for Cys and Met carbon, and the S-adenosylmethionine synthase expression quantity decreased, reduced the consumption of methionine, thus improved amino acid composition and raised the amino acid nutritional value of relay-cropping soybean. Acetyl-CoA was precursor substance of the fatty acid synthesis, the study found that acetyl-coA carboxylase and biotin carboxylase expression quantity increased of relay-cropping soybean, which benefits the accumulation of precursor substance of fatty acid synthesis, the key enzyme Enoyl-ACP reductase of fatty acid synthesis pathway in the last stage expression quantity increased, this also was helpful for the synthesis of fatty acids.In conclusion, as a result of relay-cropping soybean vegetative growth was affected by the corn shading, it resulted in the protein expression quantity increased or reduced that related to amino acid, fatty acid metabolic process during seed filling period. So that changed quality formation regular pattern and determined the composition of nutritional ingredients and nutritional value of soybean seed.Different soybean cultivars responsed differently to relay-cropping.so through this research could lay the foundation for the improvement of relay-cropping soybean quality,also for the optimization and promotion of cultivation pattern. |
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