Identification Of Genotypes For Waxy Protein And Puroindoline Protein In Shaanxi Wheats

Quality properties of starch are strongly affected by the compositions of waxy proteins (Wx genes) in wheat (Triticum aestivum L.). Kernel hardness is highly correlated with the marketing classification, milling and processing quality of wheat (Triticum aestivum L.). It is very important to analyze the composition of waxy proteins (Wx genes), distribution of grain hardness and composition of their puroindoline genotypes in Shaanxi wheat cultivars and advanced lines, and establish stable and efficient methods and systems detecting Wx genes for rapid evaluation of germplasm resources, hereditary improvement of quality, cultivar popularization and food processing in wheat breeding programs. In this study, (1) SDS-PAGE method was employed to survey the composition of Wx proteins in 173 Shaanxi wheat cultivars and lines. Based on the evaluation of the validity of STS markers for Wx genes, two types of multiplex PCR systems were built up. (2) Based on the kernel hardness of 171 Shaanxi wheat cultivars and advanced lines using a Single Kernel Characterization System (SKCS) in this study, molecular markers and gene sequencing were used to understand puroindoline genotypes of hard wheats identified by SKCS. The main results of this study were as follows.The results using SDS-PAGE method showed that twenty of these cultivars and lines from Shaanxi were the null Wx-B1 type (11.6%), and one of them was waxy wheat lacked all three Wx proteins (Wx-A1, Wx-B1 and Wx-D1) (0.6%). There were distinct differences in the mutation frequency of Wx proteins among diverse wheat regions of Shaanxi. The results identified by four co-dominant and two dominant STS markers for Wx genes were all identical to those detected by SDS-PAGE method. Using six effective molecular markers above, two multiplex PCR systems were established. The multiplex PCRâ… could identify four alleles at Wx-B1 and Wx-D1 loci, and multiplex PCRâ…¡were also used to detect four alleles at Wx-B1 and Wx-D1 loci. The genetypes of all wheat cultivars and lines using the two multiplex PCRs were coincided with those detected by SDS-PAGE method and the corresponding single PCR, respectively.The results using the SKCS method showed that, among the examined cultivars, 37 were classified as soft (21.6%), while 11 were mixed in hardness (6.4%), and 123 were uniformly hard (72.0%). There were distinct differences in the frequencies of soft, mixed and hard types among three diverse regions of Shaanxi. The results using molecular markers and gene sequencing in 123 hard wheats indicated that, four mutation types were observed. Genotypes Pina-D1b, Pinb-D1b, Pinb-D1d and Pinb-D1p were fund in 15, 98, 2 and 8, respectively. The percentages of genotypes Pina-D1b, Pinb-D1b, Pinb-D1d and Pinb-D1p were 12.2%, 79.7%, 1.6% and 6.5% in hard wheats, respectively.This study characterized the composition of waxy proteins (Wx genes), distribution of grain hardness and composition of their puroindoline genotypes in Shaanxi wheats. It is helpful to improving quality and cultivars popularization in wheat breeding programs. The six STS markers and two multiplex PCRs can be used in molecular marker-assisted selection for Wx genes, which will increase the efficiency of evaluation of wheat starch properties and speed up selection procedure in wheat molecular breeding programs.