| Rice is one of the major crops in China. For the latest decades, rice production has been dramatically improved; however, rice quality has not been improved yet. With the improvement of people's living and the opening of grain markets, the requirement of rice with good quality has become higher and higher. As breeding of new rice variety or hybrid with good quality should be based on the correct understanding of genetic mechanism for quality traits of rice, researches on quality traits of rice appears to be particularly important.Rice quality was considered mainly of been affected by its dominant components--starch. Rice starch consists of amylose and amylopectin. Amylose is synthesized by granule-bound starch synthase (GBSS) encoded by Wx gene, while amylopectin is synthesized by a series of enzymes, including soluble-bound starch synthase, starch branching enzyme and starch debranching enzyme, each of which has different isoforms, so the process of amylopectin synthesis is very complex. A great deal of research on synthesis of starch and the impact of starch property on rice quality has been carried out in the past, and it is generally believed that the quality of rice is determined by amylose content(AC). Apart from amylose content, it is fairly different for rice varieties with similar AC in quality , which indicated that degree of polymerization and chain length distribution of amylopectin may also be an important factor to affect quality of rice. In our research, Guichao 2 with high yield and inferior quality, was used as recurrent receptor parent to backcross with the Suyunuo, the donor parents, a good quality rice variety. Genes related to amylopectin structure in Suyunuo, including Sbe1,Sbe3,Isa,Pull and SSSI were transferred into the Guichao2 through backcross method with six generations with molecular marker-assisted selection, and therefore five near-isogenic lines were obtained. The effects of above five genes were analyzed in functional differentiation and contribution of alleles to rice quality. The results are as follows:1,By molecular marker-assisted selection, the alleles in Suyunuo, such as Sbe1,Sbe3,Isa,Pull and SSSI was backcrossed into the Guichao2,which is recurrent receptor parent, to construct five NIL. There are 30 separate lines in each of the target gene.2,The genetic background of the five NIL were detected by using 83 SSR markers randomly distributed on the rice genome and 11 markers for genes related to starch synthesis. The results showed that genetic backgrounds of five NIL are the same as the one of recurrent parent, in which the similarities is 97.20%-99.66%, as are in agronomic traits and appearance quality. The results showed that the above five NIL can be used to analyze the genetic effects of genes on starch traits.3,Variations in starch physiochemical properties were investigated among five NILs and their recurrent parent,which showed that NIL of SSSI gene decreased up to 3.51% in AAC, and the other NIL of gene AAC have changed. Five NILs showed no difference in Gel consistency(GC) and Gelatinization temperature(GT). In RVA profile, five genes of NIL behaved difference on different characteristic values. For example, the RVA profile of NIL-SSSI showed differences in PKV, HPV, CPV, PaT, while the other NIL exhibited difference of one or two characteristic values. The results showed the alleles on amylopection synthesis from Guichao 2 and Suyunuo have been differentiated in function, resulting in different genetic effects.
|
PDF Full Text Request