Effect Of Dietary Fiber On Cooking Quality And Digestion Properties And Fine Mapping Of The High Dietary Fiber Mutant Cw

Dietary fiber(DF) is a kind of edible plant components or synthetic carbohydrates including high molecular weight, low molecular weight dietary fibers, analogs of polysaccharides and resistant starch, which cannot be digested and absorbed in the small intestine, but fermented in the large intestine. Dietary fiber plays an important role in the balance of diet, and insufficient intake of DF can lead to several chronic diseases. Cereal endosperm cell wall is the main source of dietary fiber for human, and non-starch polysaccharides (NSP) of endosperm cell walls were the main components of cereals dietary fiber. In addition, resistant starch is another important component of cereal dietary fiber, which can effectively control the postprandial blood glucose levels, prevent and control of obesity, type ? diabetes and cardiovascular disease in metabolic syndrome.As a staple food for more than half the world's population, rice is designated as the high glycemic index (GI) foods, develop new varieties with low GI is becoming a potential subject. In this paper, the effect of NSP on eating quality and starch digestion characteristics were studied. Meanwhile, a high dietary fiber mutant cw was identified based on morphological characters and measurement of carbohydrates after in vitro digestion, and the genetic characteristics of cw were also analyzed. The main results are as follows:1. Amylopectin plays an important role in formation of resistant starch, its' possible interaction between starch and endosperm cell wall may retard the hydrolysis of starch. Both mutant line RS4 (RS, ca.10%) and the wild-type R7954 had normal seed vigor, resistant starch can be hydrolyzed and utilized by seed itself, showed no disadvantageous for seed vigor. During germination, amylose and amylopectin of R7954were synchronically hydrolyzed, while in RS4, the amylopectin was preferred to be used. After 10 days germination, there was still some starch left in the seed of RS4, showed special X-ray diffraction pattern with only two peaks appeared at 16.90° and 21.62°. The starch residue contained high percentages of resistant starch and amylopectin and adhered tightly to the endosperm cell wall.2. NSP affects the cooking quality and digestion properties of rice, which is depend on the components of NSP and the rice cultivers. After degradation or partly degradation, the gelatinization temperature (GT), gel consistency (GS) and swellingpower (SP) of rice were increased; the hot paste viscosity (HPV), setback (SB), cold gel hardness (HD) and chewiness (CH) of rice were decreased. The content of rapid digestible starch (RDS) was decreased, while the content of slowly digestible starch (SDS) was increased. In this study, the digestion characteristics of Indica waxy rice showed more changes than others, the cooking qualities of Indica rice had more changes than others.3. Based on the physiochemical and morphological characters of cw after in vitro hydrolysis, a high-throughput method for screening of high dietary fiber rice lines was developed. Compared with R7954 and Nipponbare, cw owned higher NSP and RScontent content. The digestion residue of cw showed intact grain shape with blue-purple color after stained by iodine buffer, while the digestion residue of R7954 and Nipponbar could not maintain the integrity shape of grain, showing irregular shape as cotton. With this method, high and low dietary fiber content lines can be distinguished accurately.4. The mutant line cw was controlled by a recessive nuclear gene and a dominant nuclear gene together under Indica/Japonica genetic background, and was controlled by a recessive nuclear gene nuclear gene under Indica/Indica genetic background. Mutant genecw(t)was finely mapped between markers RM22540 and cwll on the chromosome 8 with the physical distance of 175 kb. Based on recombinant inbred lines, the association analysis of candidate genes showed that GBSSI, AGPS2 and SSIIIa came from cw had positively correlationwith high resistant starch. Meanwhile, During seed development, at the early stage of seed filling (5 days after flowering), the activities of SShad positive correlation with RS accumulation; after 5 DAF, the activities of AGPase and BE had negative correlation with RS accumulation while the activities of DBE had positive correlation with RS accumulation.