Genetic Diversity Of Wx Genes Of Wheat

Wheat endosperm amylose content plays an important role in wheat flourquality and uses. In the past, the studies on wheat starch quality were mainlyconcentrated on chemistry analysis and biochemisty level, yet the correlationbetween amylose content and corresponding gene for synthesis and geneticdiversity were studied little. The waxy gene(abbreviated as Wx) encodes the granule bound starchsynthase(GBSS, EC. 3. 4. 1.11), which is also called the Wx protein,responsible for the synthesis of amylose in wheat. The common wheat hasthree different Wx proteins, and the sites of three Wx genes are named Wx-A1,Wx-B1, and Wx-D1, which has been locate on chromosomes 7A, 4A and 7D,respectively. It has been reported that amylose content and amylopectincontent are related to the expression of these three Wx genes. Lack of one ofthe three Wx genes will result in the decrease of synthase activity, which madethe amylose content decrease and the amylopectin content increase, and thestarch compontent, flour quality and food processing quality change. 32 wheat cultivars of Shangdong were used in this experiment. First, apolymorphic SSR of Wx in 3'end was studied, and the correlation betweenpolymorphic SSR and amylose content was also studied. Second, thepolymorphism of Wx-B1 genes near 4th intron in 5'end in 20 wheat cultivarswas studied, and their relationship to amylose content was discussed. Theresults are as follows:1. The result indicated that both Wx-A1a and Wx-D1a were present in all 32 cultivars. Two fragments were found in all cultivars by polymerase chain 3小麦 Wx 基因的遗传多样性研究 reaction amplification using primers. One fragment of PCR was 204bp, the expected size fragment, which had been located on chromosome 7DS, and the other fragment was 225-346bp, which had been located on chromosome 7AS, and showed length polymorphism.2. The analysis showed that the amylose level was highly correlated to the length of the fragment of polymorphic SSR. The length of fragment amplified was longer in cultivars of high amylose content, while the length of fragment amplified was shorter in cultivars of low amylose content. Amylose content among the various SSR genotypes was statistically significantly different as analyzed using genotypes of the SSR motifs.3. The fragment amplified near 4th intron region appeared polymorphic characteristic with BamHI digestion in 20 wheat cultivars,and the polymorphism of fragment is highly related to amylose content.4. The fragment in cultivars of amylose content about 22.5%-26.5% cann't been digested by BamHI, while the others of amylose content beyond 30% can be digested. PCR-BamHI molecular marker can be used to select wheat cultivars of intermediate amylose content, and improve wheat quality.5. A molecular marker-assisted selection (MAS) system based on PCR was established.