The difference of soluble sugar contents and starch synthetic key enzyme activities between high and low starch cultivar of cassava

The difference of soluble sugar contents and starch synthetic key enzyme activities between high starch cultivar and low starch cultivar were studied in this experiment, of which FuXuan01, GR891, SC124, and SC201 were used as materials. The results showed that the contents of reducing sugar in root tube of low starch cultivars were higher than those of high starch cultivars in all growth periods, the contents of sucrose in root tube of high starch cultivar were higher than those of low starch cultivars in the early growth period, but, lower in the late growth period, and there were almost no difference in the contents of soluble sugar in root tube between high starch cultivar and low starch cultivar in the early growth period, but notable difference in the late growth period and the soluble sugar contents of low starch cultivars were higher than those of high starch cultivars. It also-showed that the activities of ADPGPpase, SSS, and SBE （starch branching enzyme） of high starch cultivars were higher than those of low starch cultivars. It was evident that there were close correlations between the content of sucrose, reducing sugar and soluble sugar in root tube, and the activities of ADPGPpase, SSS, SBE, and the starch accumulation in the root tubers of cassava. It was quite evident in this experiment that the soluble sugar and starch synthetic key enzyme were main factors controlling starch accumulation in root tubers. These results provided important indication for physiological controlling in high starch cultivation and gene engineering breeding of high starch cultivar of cassava.

Characteristics of Starch synthesis,Yield and Quality Provide Insights into Rice-Tartary Buckwheat Utilization and Improvement

[Objectives] Rice-Tartary buckwheat is a special type of Tartary buckwheat with easy hulling thin shell.This study was conducted to characterize the carbohydrate metabolism,quality and yield and provide a basis for food processing and breeding of rice-Tartary buckwheat.[Methods]The local rice-Tartary buckwheat‘cv.Xiaomiqiao’(XMQ) was used to explore the characteristics of photosynthesis,starch synthesis enzyme activities,traits of yield and quality,as compared to Tartary buckwheat‘cv.Jinqiao 2’(JQ2).[Results]XMQ showed significantly lower values of net photosynthetic rate,ADPGase activity and starch synthase activity at one or more periods during grain filling than JQ2.The effective branch number and grain number per plant of XMQ were similar to that of JQ2 regardless of different years,but the 1 000-grain weight was significantly lighter that resulted in the significantly lower yield.XMQ accumulated similar contents of starch(amylose,amylopectin) and protein(glutelin,albumin,prolamin,globulin) to those of JQ2,but exhibited significantly lower flavonoid content.The values of peak viscosity and hot paste viscosity in XMQ were similar to those of JQ2,but the values of cool paste viscosity,breakdown and setback were significantly lower.In conclusion,XMQ showed low yield due to the insufficient of photosynthesis and starch synthesis.XMQ exhibited high nutritional quality as well as normal Tartary buckwheat and stored 18.88 mg/g of flavonoid,that might be consumed as daily diet.[Conclusions]The present results will provide a basis for utilization and improvement of rice-Tartary buckwheat.