Abstract:

Kernel hardness, controlled by a major gene Ha on the short arm of chromosome 5D, has a profound influence on milling performance and end-use quality of common wheat (Triticum aestivum L.). puroindoline protein, expressed by Ha gene and including puroindoline a and b (PINA and PINB), sets up the molecular and genetics basis of wheat kernel hardness. Evaluation of the allelic variation of grain hardness is beneficial to wheat quality improvement. A total of 138 CIMMYT historical cultivars and lines from 23rd Elite Spring Wheat Yield Trial (ESWYT) and 10th Semiarid Wheat Yield Trial (SAWYT) were examined by Single Kernel Characterization System (SKCS) and STS (sequence tagged site) marker to understand the distribution of grain hardness and its puroindoline alleles. Modified SDS-PAGE (sodium dodecyl-sulfate polyacrylamide gel electrophoresis) of Triton X-114 soluble protein, 10% glycerol substituting of water for resolving gels and PDA (piperiazine diacrylamide) substituting of N,N’-methylene bisacrylamide for gels, were used to distinguish PINA and PINB proteins for identifying Pina-D1b/Pinb-D1a allele (a null mutation of puroindoline a). Both serine-codon specific and non-specific primers were used to identify Pina-D1a/Pinb-D1b allele for confirming results of the PCR (polymerase chain reaction) amplification of genome DNA. The results indicated that Pina-D1b/Pinb-D1a was the most popular genotype in the CIMMYT common wheats, and the percentages of Pina-D1b/Pinb-D1a, Pina-D1a/Pinb-D1b and Pina-D1a/Pinb-D1a (wild type) were 85.5%, 6.5% and 8.0% in the surveyed wheats, respectively. SKCS hardness index for Pina-D1b/Pinb-D1a and Pina-D1a/Pinb-D1b genotypes were much higher than that for wild type Pina-D1a/Pinb-D1a. Genotype with Pina-D1b/Pinb-D1a allele showed significantly higher grain hardness than Pina-D1a/Pinb-D1b allele. It was previously reported that Pina-D1a/Pinb-D1b genotype was more desirable for milling and end products quality than Pina-D1b/Pinb-D1a genotype. Therefore, it is recommend that other types of puroindoline allele mutation for reducing the negative influence of the Pina-D1b/Pinb-D1a genotype on processing quality should be introduced in CIMMYT wheat breeding program. Meanwhile, when we introduce cultivars from CIMMYT for the purpose of improving some wheat characters, it is necessary to fully consider the negative effect of the Pina-D1b/Pinb-D1a genotype on milling and baking quality.

Key words: Common wheat, Kernel hardness, Allelic variation, puroindoline protein, STS maker