Submitted to: Journal of Cereal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/21/2010
Publication Date: 6/1/2010
Citation: Chen, F., Zhang, F., Morris, C.F., Xu, H., He, Z., Xia, X., Cui, D. 2010. Molecular characterization of the Puroindolin a-D1b allele and develpment of an STS marker in wheat (Triticum aestivum L.). Journal of Cereal Science. 52:80-82. Interpretive Summary: In this detailed study, four Chinese wheat varieties (Chinese Spring, Yunong 202, Gaocheng 8901 and Shaan 253) and eight CIMMYT cultivars and advanced breeding lines (M0299, M0293, M0215, M0191, M0181, Mo 0272, RDWG/MILAN, CMH82A.1294/2*KAUZ//MUNIA/CHT O/3/MILAN) were used for the characterization of Pina-D1b genotype and development of molecular markers. Before this study, the PINA null phenotype was generally identified by SDS-PAGE, and varieties lacking PINA were simply assigned Pina-D1b. Although this result could be supported with lack of amplification using PCR primers for Pina-D1a, the results were still equivocal. Further, Pina-D1b is only one of a few possible PINA null genotypes. Failure to generate a Pina amplicon may be a result of poor DNA quality or mistakes by operators, even if Pinb-D1a primers are used as a control for DNA quality. Therefore, the STS marker Pina-N developed in this study will be very useful to positively identify Pina-D1b alleles in bread wheat.
Technical Abstract: Kernel texture (grain hardness) is a leading quality characteristic of bread wheat (Triticum aestivum L.) as it dramatically influences its milling and processing properties, and consequently is utilized in the classification and marketing of grain. According to many previous reports (reviewed in Bhave and Morris, 2008 a, b), the molecular basis of kernel texture results from the puroindoline genes at the Hardness (Ha) locus on the distal end of the short arm of chromosome 5D, and includes Puroindoline a (Pina-D1) and Puroindoline b (Pinb-D1). Soft endosperm varieties possesses the ‘wild type’ puroindoline alleles (Pina-D1a and Pinb-D1a), whereas to date, all wheat varieties with hard endosperm have been found to possess one or more mutations (rarely more than one) in Pina or Pinb. Different mutations in Pina and Pinb can result in different levels of kernel texture (reviewed in Morris, 2002; Morris and Bhave, 2008; Bhave and Morris, 2008 a, b). Since the mechanism by which the puroindolines soften endosperm is unknown, only simple genetic phenotype associations can be made. Nevertheless, a conjectural model describes several possible genotypes: 1) PINA is absent but PINB is wild type, 2) PINA is wild type but PINB is absent, 3) PINA is wild type but PINB has an altered primary structure, and 4) PINA has an altered primary structure but PINB is wild type. Two of the most prevalent hardness haplotypes among commercial wheat cultivars involve types 1 and 3 (Pina-D1b/Pinb-D1a and Pina-D1a/Pinb-D1b, respectively). Based on kernel texture analysis, several studies indicate that the ‘Pina-null’ (Pina-D1b) allele is harder than the Gly-to-Ser (Pinb-D1b) allele (Morris et al., 1998, 2001; Cane et al., 2004; Chen et al., 2005, 2006; Chang et al., 2006; Dubreil et al., 1998; Giroux et al., 2000; Martin et al., 2001; Morris and Massa, 2003; Xia et al., 2005), and may be generally less desirable from a milling standpoint. The Pina-D1b genotype may also have a relatively inferior processing quality of steamed bread, pan bread, and Chinese noodle than the Pinb-D1b genotype (Chen et al., 2007). Consequently, it is of great practical value to identify the hard allele of each of these two prevalent haplotypes.