CIMMYT新型人工合成小麦Pina和Pinb基因等位变异

六倍体人工合成小麦由硬粒小麦（Triticum turgidum subsp. durum）与粗山羊草（Aegilops tauschii Coss.）杂交产生,是研究小麦进化过程中基因变异的重要材料。以国际玉米小麦改良中心（CIMMYT）提供的57份由野生二粒小麦（T. turgidum subsp. dicoccoides）与粗山羊草杂交产生的新型人工合成六倍体小麦为材料，用单籽粒特性测定仪和Pina、Pinb特异性PCR引物对其籽粒硬度变异以及控制籽粒硬度的主效基因Pina和Pinb的分布情况进行了研究。结果表明，这些材料的SKCS硬度值变异较大，从10.5到42.6，其中15~30的占78%。共有Pina-D1a、Pina-D1c、Pinb-D1h和Pinb-D1j 4种等位变异型，基因型为Pina-D1a/Pinb-D1j的8个，占14%；基因型为Pina-D1c/Pinb-D1h的49个，占86%。方差分析表明，基因型Pina-D1a/Pinb-D1j与Pina-D1c/Pinb-D1h对籽粒硬度的影响差异不显著，但父本粗山羊草和母本野生二粒小麦以及二者间的互作对籽粒硬度有显著影响，说明除Pina和Pinb外，还有其他微效基因影响籽粒硬度的形成。

Allelic Variations of Puroindoline a and Puroindoline b Genes in New Type of Synthetic Hexaploid Wheats from CIMMYT

Triticum dicoccoides and Aegilops tauschii are important germplasm resources of rich genetic variability for improvement of hexaploid wheat (T. aestivum). This variability can be accessed by utilizing synthetic hexaploid wheat lines with genomes from Ae. tauschii and T. dicoccoides. Two methods can be employed to incorporate Triticum dicoccoides and Aegilops tauschii genes into a hexaploid wheat. One is the direct cross method of hybridization between Ae. tauschii and hexaploid wheat, another is an indirect method of synthetic hexaploids by crossing tetraploid wheat with Ae. tauschii. Genes from tetraploid wheat and Aegilops tauschii are then available via direct crossing of synthetic hexaploids to T. aestivum. The CIMMYT (International Maize and Wheat Improvement Center) has produced two types of synthetic hexaploids. One is the progeny of T. turgidum ssp. durum crossing with Ae. tauschii, another is the new type synthetic wheat which produced by crossing Triticum dicoccoides with Aegilops tauschii. Grain hardness is a major factor influencing the end-use quality. Genes for grain hardness in common wheat reside on Ha locus of chromosome 5DS. The wild-type alleles (Pina-D1a, Pinb-D1a) determine soft endosperm, while the hard phenotypes result from mutations in either Pina or Pinb. In order to understand the evolution of genes for grain hardness, studies have focused on the wild relatives of common wheat, particularly on Ae. tauschii, the supposed donor of the D genome in common wheat. Puroindoline a in Ae. tauschii contained 99.3% amino acid sequence homology to the wheat cultivar ‘Penawawa’ and 90.5% amino acid sequence homology in puroindoline b. Among 50 Ae. tauschii accessions, four alleles of puroindoline a and four alleles of puroindoline b were identified, encoding two and three different proteins, respectively. However, the effect that these sequence polymorphisms may have on kernel texture is unknown, as no test method of texture has been developed for Ae. tauschii. The incorporation of Ae. tauschii into synthetic hexaploid facilitates the analysis of puroindoline sequence polymorphism and other genetic effects on kernel texture, using testing methods designed for hexaploid wheat, such as the Perten single kernel characterization system (SKCS). Analysis of synthetic hexaploid can also facilitate the analysis of the effect of the A and B genomes, contributed by the tetraploid wheat parent on kernel texture. Studies on Ae. tauschii and synthetic hexaploid wheat derived from hybridization of T. turgidum ssp. durum with Ae. tauschii demonstrated a number of novel Pina and Pinb sequences. However, none of these Pina and Pinb mutations produced a hard endosperm texture in synthetic wheat. To further understand the mechanism of grain hardness formation in Ae. tauschii and synthetic wheat, a total of 57 new type synthetic hexaploid lines derived from the crosses T. dicoccoides×Ae.tauschii were employed to evaluate the SKCS hardness and detect puroindoline alleles using gene specific PCR primers. Four allelic variations of Pina and Pinb were identified, i.e., Pina-D1a, Pina-D1c, Pinb-D1h, and Pinb-D1j. Eight lines were Pina-D1a/Pinb-D1j types, accounting for 14%, and 49 were Pina-D1c/Pinb-D1h types, accounting for 86%. Kernel texture differed significantly among the synthetic hexaploid lines, ranging from 10.5 to 42.6, with significant difference among the parental types, T. dicoccoides or Ae. tauschii. The interactions between parental genotypes had also a significant influence on kernel texture. These results indicated that there might be some genes besides Ha locus associated with the kernel texture.