矮秆基因对小麦部分农艺性状的效应

以中国主要麦区的124份小麦品种为材料,利用分子标记和系谱分析相结合,对其按照所含的矮秆基因Rht-B1b、Rht-D1b和Rht8进行分类,结合田间株高、旗叶长、小穗数和穗粒数以及室内苗期根系长度等农艺形状的调查,分析不同矮秆基因对小麦农艺性状的效应.结果显示:(1)参试的124份小麦品种(系)中23份含有Rht-B1b,7份含有Rht-D1b,22份含有Rht8基因,34份同时含有Rht-B1b和Rht8,16份同时含有Rht-D1b和Rht8,可分为6组.(2)Rht-B1b和Rht-D1b在降低株高的同时也缩短了旗叶的长度和苗期叶长,Rht8对株高的影响较弱,对旗叶和苗期叶长的影响也较小;3个矮秆基因对苗期根系长度、小穗数没有显著影响;Rht-D1b和Rht8显著增加穗粒数.研究表明,矮秆基因Rht8对小麦株高以及其他农艺性状的影响均较小,但能够显著增加穗粒数,是小麦矮化育种中比较理想的矮秆基因.     

Haplotype variation of Green Revolution gene Rht-D1 during wheat domestication and improvement

Green Revolution made a substantial contribution to wheat yields worldwide in the 1960 s and 1970 s. It is of great importance to analyze the haplotype variation of Rht-D1, the Green Revolution gene, during wheat(Triticum aestivum L.)domestication and breeding to understand its evolution and function in wheat breeding history. In this study, the Rht-D1 and its flanking regions were sequenced and single nucleotide polymorphisms were detected based on a panel of 45 accessions of Aegilops tauschii, 51 accessions of landraces and 80 accessions of commercial varieties. Genetic diversity in the wild accessions was much higher than that in the varieties and higher than that reported previously. Seven haplotypes(Hapl I to Hapl VII) of Rht-D1 were identified and their evolutionary relationships were proposed. In addition to the well-known Green Revolution allele Rht-D1b, Hapl VII(an allele Rht-D1k) was identified in early breeding varieties, which reduced plant height by 16%. The results suggested that Rht-D1k had been used in breeding before the Green Revolution and made a great contribution to wheat production worldwide.Based on the breeding history and molecular evidence, we proposed that the wheat Green Revolution in China and International Maize and Wheat Improvement Center(CIMMYT)occurred independently.     

青海育成小麦5个主效矮秆基因的分子检测

为系统了解青海小麦矮秆基因的分布特点,并进一步为青海高原小麦的株高育种提供优异种质资源。本研究利用5个矮秆基因的特异性分子标记对82份青海小麦品种资源中的矮秆基因进行了检测,并对不同矮秆基因的降秆效应进行了分析。结果表明:82份青海育成小麦品种中有49份材料至少含有一个矮秆基因,其中Rht-B1b的分布频率最高,约占参试材料的28.0%,其次是分布频率为23.2%的Rht8基因,而矮秆基因Rht-D1b、Rht5以及Rht12的分布频率分别为9.8%、13.4%、9.8%。在49份含有不同种类矮秆基因的材料中,其中16份材料同时含有2种及以上的矮秆基因,即RhtB1b和Rht8、Rht-D1b和Rht8、Rht-B1b和Rht5、Rht-D1b和Rht5、Rht8和Rht5、Rht-B1b和Rht12、Rht5和Rht12,并未发现同时含有矮秆基因Rht-B1b和Rht-D1b的品种;2份材料分别含有3种矮秆基因,即Rht-B1b、Rht8、Rht12和Rht-B1b、Rht5、Rht8;其余31份材料仅含有1种矮秆基因。82份青海育成小麦材料中仅含有Rht-B1b的材料11份,平均株高为86.2 cm,其降秆效应为5.7%;只含有Rht-D1b的材料有5份,平均株高为84.9 cm,其降秆效应为7.1%;仅含有Rht8的材料有9份,平均株高为88.6 cm,其降秆效应为3.1%。因此,在青海育成小麦品种中,矮秆基因的降秆效应为Rht-D1bRht-B1bRht8。     

Effects of dwarfing genes on the genetic background of wheat varieties in southern Ukraine

The effects of the Rht8c, Rht-B1b, Rht-B1e, and Rht-D1b genes on wheat height have been investigated. Variations in these effects are significantly modified by the genetic background and year conditions. A combination of the Rht8c, Rht-B1a, Rht-D1b, and Ppd-D1a alleles is the most advantageous for the conditions of southern Ukraine, since it is associated with optimal plant height under contrasting conditions within different years. The genotypes of some varieties were shown to include gene(s) that were unidentifiable by the molecular markers and significantly decreased plant height.     

Novel Natural Allelic Variations at the Rht-1 Loci in Wheat

Plant height is an important agronomic trait. Dramatic increase in wheat yield during the“green revolution”is mainly due to the widespread utilization of the Reduced height (Rht)-1 gene. We analyzed th...     

Inheritance of resistance to Fusarium head blight in three European winter wheat populations

Fusarium head blight (FHB) resistance is of particular importance in wheat breeding programmes due to the detrimental effects of this fungal disease on human and animal health, yield and grain quality. Segregation for FHB resistance in three European winter wheat populations enabled the identification of resistance loci in well-adapted germplasm. Populations obtained from crosses of resistant cultivars Apache, History and Romanus with susceptible semi-dwarfs Biscay, Rubens and Pirat, respectively, were mapped and analysed to identify quantitative trait loci (QTL) for FHB severity, ear emergence time and plant height. The results of the present study together with previous studies in UK winter wheat indicated that the semi-dwarfing allele Rht-D1b seems to be the major source for FHB susceptibility in European winter wheat. The high resistance level of the cultivars Romanus and History was conditioned by several minor resistance QTL interacting with the environment and the absence of Rht-D1b. In contrast, the semi-dwarf parents contributed resistance alleles of major effects apparently compensating the negative effects of Rht-D1b on FHB reaction. The moderately resistant cultivar Apache contributed a major QTL on chromosome 6A in a genome region previously shown to carry resistance loci to FHB. A total of 18 genomic regions were repeatedly associated with FHB resistance. The results indicate that common resistance-associated genes or genomic regions are present in European winter wheats.     

"Perfect" markers for the Rht-B1b and Rht-D1b dwarfing genes in wheat

PCR-based markers were developed to detect the point mutations responsible for the two major semi-dwarfing genes Rht-B1b ( Rht1) and Rht-D1b ( Rht2) in wheat. These markers were validated by testing 19 wheat varieties of known Rht genotype. They included Rht-B1b and Rht-D1b dwarfs, double-mutant varieties and tall wheats. These were correctly genotyped with the Rht-B1b and Rht-D1b-specific primers, as well as markers specific for the tall alleles Rht-B1a and Rht-D1a. Using a family of doubled-haploid lines segregating for Rht-B1b and Rht-D1b, the markers were mapped to the expected homoeologous regions of chromosomes 4B and 4D, respectively. Both markers were strongly correlated with a reduction in height, accounting for 23% ( Rht-B1b) and 44% ( Rht-D1b) of the phenotypic variance in the population. These markers will have utility in marker-assisted selection of the Rht-B1b and Rht-D1b genes in wheat breeding programs.     

Whole Genome Association Mapping of Plant Height in Winter Wheat (Triticum aestivum L.)

The genetic architecture of plant height was investigated in a set of 358 recent European winter wheat varieties plus 14 spring wheat varieties based on field data in eight environments. Genotyping of diagnostic markers revealed the Rht-D1b mutant allele in 58% of the investigated varieties, while the Rht-B1b mutant was only present in 7% of the varieties. Rht-D1 was significantly associated with plant height by using a mixed linear model and employing a kinship matrix to correct for population stratification. Further genotyping data included 732 microsatellite markers, resulting in 770 loci, of which 635 markers were placed on the ITMI map plus a set of 7769 mapped SNP markers genotyped with the 90 k iSELECT chip. When Bonferroni correction was applied, a total of 153 significant marker-trait associations (MTAs) were observed for plant height and the SSR markers (−log₁₀ (P-value) ≥4.82) and 280 (−log₁₀ (P-value) ≥5.89) for the SNPs. Linear regression between the most effective markers and the BLUEs for plant height indicated additive effects for the MTAs of different chromosomal regions. Analysis of syntenic regions in the rice genome revealed closely linked rice genes related to gibberellin acid (GA) metabolism and perception, i.e. GA20 and GA2 oxidases orthologous to wheat chromosomes 1A, 2A, 3A, 3B, 5B, 5D and 7B, ent-kaurenoic acid oxidase orthologous to wheat chromosome 7A, ent-kaurene synthase on wheat chromosome 2B, as well as GA-receptors like DELLA genes orthologous to wheat chromosomes 4B, 4D and 7A and genes of the GID family orthologous to chromosomes 2B and 5B. The data indicated that besides the widely used GA-insensitive dwarfing genes Rht-B1 and Rht-D1 there is a wide spectrum of loci available that could be used for modulating plant height in variety development.     

Susceptibility to <Emphasis Type="Italic">Fusarium </Emphasis>head blight is associated with the <Emphasis Type="Italic">Rht-D1b</Emphasis> semi-dwarfing allele in wheat

Fusarium head blight (FHB) is an important disease of wheat worldwide. The cultivar Spark is more resistant than most other UK winter wheat varieties but the genetic basis for this is not known. A mapping population from a cross between Spark and the FHB susceptible variety Rialto was used to identify quantitative trait loci (QTL) associated with resistance. QTL analysis across environments revealed nine QTL for FHB resistance and four QTL for plant height (PH). One FHB QTL was coincident with the Rht-1D locus and accounted for up to 51% of the phenotypic variance. The enhanced FHB susceptibility associated with Rht-D1b is not an effect of PH per se as other QTL for height segregating in this population have no influence on susceptibility. Experiments with near-isogenic lines supported the association between susceptibility and the Rht-D1b allele conferring the semi-dwarf habit. Our results demonstrate that lines carrying the Rht-1Db semi-dwarfing allele are compromised in resistance to initial infection (type I resistance) while being unaffected in resistance to spread within the spike (type II resistance).     

Influence of the gibberellin-sensitive Rht8 dwarfing gene on leaf epidermal cell dimensions and early vigour in wheat (Triticum aestivum L.)

BACKGROUND AND AIMS: The gibberellin-insensitive Rht-B1b and Rht-D1b dwarfing genes are known to reduce the size of cells in culms, leaves and coleoptiles of wheat. Resulting leaf area development of gibberellin-insensitive wheats is poor compared to standard height (Rht-B1a and Rht-D1a) genotypes. Alternative dwarfing genes to Rht-B1b and Rht-D1b are available that reduce plant height, such as the gibberellin-responsive Rht8 gene. This study aims to investigate if Rht8 has a similar dwarfing effect on the size of leaf cells to reduce leaf area. METHODS: The effect of Rht8 on cell size and leaf area was assessed in four types of epidermal cells (interstomatal, long, sister and bulliform) measured on leaf 2 of standard height (rht8) and semi-dwarf (Rht8) doubled-haploid lines (DHLs). The DHLs were derived from a cross between very vigorous, standard height (rht8) ('Vigour18') and less vigorous, semi-dwarf (Rht8) ('Chuan-Mai 18') parents. KEY RESULTS: Large differences were observed in seedling vigour between the parents, where 'Vigour18' had a much greater plant leaf area than 'Chuan-Mai 18'. Accordingly, 'Vigour18' had on average longer, wider and more epidermal cells and cell files than 'Chuan-Mai 18'. Although there was correspondingly large genotypic variation among DHLs for these traits, the contrast between semi-dwarf Rht8 and tall rht8 DHLs revealed no difference in the size of leaf 2 or average cell characteristics. Hence, these traits were independent of plant height and therefore Rht8 in the DHLs. Correlations for leaf and average cell size across DHLs revealed a strong and positive relationship between leaf width and cell files, while the relationships between leaf and cell width, and leaf and cell length were not statistically different. The relative contribution of the four cell types (long, sister, interstomatal and bulliform) to leaf size in the parents, comparative controls and DHLs is discussed. CONCLUSIONS: Despite a large range in early vigour among the DHLs, none of the DHLs attained the leaf area or epidermal cell size and numbers of the vigorous rht8 parent. Nonetheless, the potential exists to increase the early vigour of semi-dwarf wheats by using GA-sensitive dwarfing genes such as Rht8.     

Semi-dwarfing Rht-B1 and Rht-D1 loci of wheat differ significantly in their influence on resistance to Fusarium head blight

Fusarium head blight (FHB) is an important disease of wheat worldwide. Soissons is one of the most resistant varieties grown in UK. The current study was undertaken to identify QTL for FHB resistance in Soissons and to determine whether the semi-dwarfing alleles Rht-B1b and Rht-D1b have a similar influence on susceptibility to FHB. A Soissons (Rht-B1b; Rht-D1a) × Orvantis (Rht-B1a; Rht-D1b) doubled haploid (DH) population was assessed for FHB resistance in three trials. Soissons contributed a single, stable major FHB QTL linked to the Rht-D1 locus. In contrast, the Rht-B1b allele (contributed by Soissons) conferred no negative effect on FHB resistance, even conferring a very minor positive effect in one trial. The influence of the Rht-B1b and Rht-D1b alleles on FHB resistance was further investigated using both Mercia and Maris Huntsman near-isogenic lines. Under high disease pressure both Rht-B1b and Rht-D1b significantly decreased Type 1 resistance (resistance to initial infection). However, whilst Rht-D1b has no effect on Type 2 resistance (resistance to spread of the fungus within the spike), Rht-B1b significantly increased Type 2 resistance. Our study demonstrates that the choice of semi-dwarfing gene used in plant breeding programmes may be a significant consideration where resistance to FHB is an important breeding target.     

New cis-regulatory elements in the Rht-D1b locus region of wheat

Fifteen gene-containing BACs with accumulated length of 1.82-Mb from the Rht-D1b locus region were sequenced and compared in detail with the orthologous regions of rice, sorghum, and maize. Our results show that Rht-D1b represents a conserved genomic region as implied by high gene sequence identity, good maintenance of gene colinearity, and the presence of multiple conserved noncoding sequences (CNSs) that are shared by other grass species. Eight cis-regulatory elements in these CNSs around grass DELLA genes were detected.     

The 'Green Revolution' dwarfing genes play a role in disease resistance in Triticum aestivum and Hordeum vulgare

The Green Revolution dwarfing genes, Rht-B1b and Rht-D1b, encode mutant forms of DELLA proteins and are present in most modern wheat varieties. DELLA proteins have been implicated in the response to biotic stress in the model plant, Arabidopsis thaliana. Using defined wheat Rht near-isogenic lines and barley Sln1 gain of function (GoF) and loss of function (LoF) lines, the role of DELLA in response to biotic stress was investigated in pathosystems representing contrasting trophic styles (biotrophic, hemibiotrophic, and necrotrophic). GoF mutant alleles in wheat and barley confer a resistance trade-off with increased susceptibility to biotrophic pathogens and increased resistance to necrotrophic pathogens whilst the converse was conferred by a LoF mutant allele. The polyploid nature of the wheat genome buffered the effect of single Rht GoF mutations relative to barley (diploid), particularly in respect of increased susceptibility to biotrophic pathogens. A role for DELLA in controlling cell death responses is proposed. Similar to Arabidopsis, a resistance trade-off to pathogens with contrasting pathogenic lifestyles has been identified in monocotyledonous cereal species. Appreciation of the pleiotropic role of DELLA in biotic stress responses in cereals has implications for plant breeding.     

Genetisches Modell der autosomal-rezessiv erblichen proximalen spinalen Muskelatrophie

Proximal spinal muscular atrophy (SMA) is one of the most common autosomal recessive diseases. According to the achieved milestones, SMA is divided into 3 groups: SMA types I–III. SMA is caused by mutations in the survival motor neuron 1 (SMN1) gene, which is located on chromosome 5. Wild type alleles usually have one or two SMN1 gene copies, disease alleles may show deletions, large scale deletions, or point mutations. The proposed genetic model is based on published data on SMA types I–III. The complex genetic model of SMA allows all parameters—even those which have not been assessed so far—to be calculated. The SMN1 allele frequencies included the following: normal allele b (1 copy of SMN1): ≈?0.9527; normal allele c (2 copies of SMN1): ≈?0.0362; deletion a (0 copies of SMN1): ≈?0.0104; point mutation d (1 copy of SMN1): ≈?0.0003; large scale deletion g (0 copies of SMN1): ≈?0.0004. The result is a gene frequency of approximately 1:90 and a carrier frequency of about 1:46.     

REAL-TIME PCR方法测定转基因小麦中外源基因拷贝数

采用SYBR GreenⅠ real-time PCR方法检测7株转基因小麦中外源半夏凝集素基因的拷贝数。以小麦蜡质基因（wx012）作为内参基因,以未转基因小麦基因组DNA为内参基因标准品进行5倍梯度稀释得到内参基因CT值与起始模板量的相关性标准曲线：y=-0.2667x+6.98;以含半夏凝集素基因（pta）的质粒DNA为目的基的因标准品同样进行5倍梯度稀释,建立目的基因CT值与起始模板量的相关性标准曲线：y=-0.2118x+4.53。通过SYBR GreenⅠ real-time PCR分别获得每一样本中目的基因和内参基因的CT值,将CT值分别代入标准曲线计算该样本中内参基因和目的基因起始模板量,目的基因与内参基因起始模板量比值即是目的基因在该转基因植株中的拷贝数。计算结果为：单拷贝的有1株,2个拷贝1株,3拷贝和4拷贝的各有2株,其中有1株为假阳性植株。     

Dominant and pleiotropic effects of a GAI gene in wheat results from a lack of interaction between DELLA and GID1

Dominance, semidominance, and recessiveness are important modes of Mendelian inheritance. The phytohormone gibberellin (GA) regulates many plant growth and developmental processes. The previously cloned semidominant GA-insensitive (GAI) genes Reduced height1 (Rht1) and Rht2 in wheat (Triticum aestivum) were the basis of the Green Revolution. However, no completely dominant GAI gene has been cloned. Here, we report the molecular characterization of Rht-B1c, a dominant GAI allele in wheat that confers more extreme characteristics than its incompletely dominant alleles. Rht-B1c is caused by a terminal repeat retrotransposons in miniature insertion in the DELLA domain. Yeast two-hybrid assays showed that Rht-B1c protein fails to interact with GA-INSENSITIVE DWARF1 (GID1), thereby blocking GA responses and resulting in extreme dwarfism and pleiotropic effects. By contrast, Rht-B1b protein only reduces interaction with GID1. Furthermore, we analyzed its functions using near-isogenic lines and examined its molecular mechanisms in transgenic rice. These results indicated that the affinity between GID1 and DELLA proteins is key to regulation of the stability of DELLA proteins, and differential interactions determine dominant and semidominant gene responses to GA.     

More than one mutant allele causes infantile Tay-Sachs disease in French-Canadians

Two Tay-Sachs disease (TSD) patients of French-Canadian origin were shown by Myerowitz and Hogikyan to be homozygous for a 7.6-kb deletion mutation at the 5' end of the hexosaminidase A α-subunit gene. In order to determine whether all French-Canadian TSD patients were homozygotes for the deletion allele and to assess the geographic origins of TSD in this population, we ascertained 12 TSD families of French-Canadian origin and screened for occurrence of mutations associated with infantile TSD. DNA samples were obtained from 12 French-Canadian TSD families. Samples were analyzed using polymerase-chain-reaction (PCR) amplification followed by hybridization to allele-specific oligonucleotides (ASO) or by restriction analysis of PCR products. In some cases Southern analysis of genomic DNA was performed. Eighteen of the 22 independently segregating mutant chromosomes in this sample carried the 7.6-kb deletion mutation at the 5' end of the gene. One chromosome carried the 4-nucleotide insertion in exon 11 (a “Jewish” mutation). In this population no individuals were detected who had the substitution at the splice junction of exon 12 previously identified in Ashkenazi Jews. One chromosome carried an undescribed B¹ mutation; this allele came from a parent of non-French-Canadian origin. Patients in three families carried TSD alleles different from any of the above mutations. The 5' deletion mutation clusters in persons originating in southeastern Quebec (Gaspé) and adjacent counties of northern New Brunswick.