人工合成六倍体小麦的ISSR位点遗传多样性分析

为了解人工合成六倍体小麦品种的遗传多样性,选用了100条ISSR引物对11份人工合成小麦和3个普通小麦材料(TP、HTS-1、CS)进行了遗传多样性分析。筛选出了42条引物可用于遗传多样性分析,其中有24条引物对供试材料具有较强的鉴别能力。42条引物共扩增出了273个条带,每条引物扩增出的条带数是3~12,平均每条为6.5,同时检测到在14份小麦试材中有170(占62.3%)个等位变异位点,引物等位变异数为1~11,平均每个位点出现4.5个等位变异。42条引物扩增产物的多态性信息量(PIC)为0.499~0.879,平均为0.767,多数引物扩增的多态性信息量在0.800左右。14份材料间的遗传相似系数为0.663~0.934,平均为0.790。根据材料间的遗传相似系数聚类,14个材料被聚为3类,其中聚为第2类的试材最多。本研究表明,14份小麦材料遗传相似性较大,亲缘关系较近,但参试材料总体遗传多样性水平较高。聚类分析结果与试材系谱及亲本来源相吻合。结果表明ISSR标记技术可应用于物种的鉴别、遗传多样性研究和遗传图谱构建。     

35份人工合成六倍体小麦的综合评价

为有效利用人工合成六倍体小麦种质资源,拓宽现有种质基础,从国际玉米小麦改良中心引进35份人工合成六倍体小麦,对其株高、穗下节长、穗下茎长、穗长、旗叶面积、分蘖数、穗粒数、生物量、收获系数、产量和千粒重11个主要农艺性状和产量性状,以及籽粒水分含量、蛋白含量、面筋含量、淀粉含量、纤维素含量、硬度、SDS沉降值和Zeleny沉降值8个品质指标进行综合评价。结果表明,这批材料的农艺和产量性状变异系数为7.46%~32.29%,平均为15.36%;多样性指数（H′）为1.85~2.04,平均为1.98。品质性状的变异系数为2.80%~17.55%,平均为10.19%;多样性指数的变化范围为1.87~2.04,平均为1.96。主成分分析表明,前5个主成分构成的信息量为总信息量的82.84%。聚类后方差分析可将材料分为4个类群,类群Ⅲ的产量等相关性状较高,类群Ⅳ的蛋白质含量、纤维含量、面筋含量、硬度和SDS沉降值最高。这批材料的农艺性状、产量和品质性状变异程度大,遗传类型丰富,可作为种质资源加以利用。     

人工合成六倍体小麦后代衍生群体遗传多样性检测

通过四倍体二粒小麦和节节麦杂交而获得的人工合成六倍体小麦,含有丰富的普通小麦品种改良有益基因,作为拓宽普通栽培小麦性状和新品种改良的新的种质资源已广泛应用于普通小麦的遗传改良实践中.利用分布于小麦A、B、D基因组21条染色体、28个不同染色体臂上的37对微卫星引物,对人工合成六倍体小麦与四川成都平原普通栽培小麦主栽品种杂交、回交经多代选择而形成的117份人工合成六倍体小麦衍生后代高代群体系(其中川麦38、川麦42、川麦43和川麦47为审定品种)进行了DNA分子水平上的分析,共检测到256个等位变异,平均每个SSR标记位点检测到6.92个等位变异,变幅在1到14之间.A、B、D基因组中,D基因组表现出的多态性信息含量最低,为0.4276,B基因组次之,为0.5346,A基因组最高,达到0.6145(A＞B＞D).辛普森指数比较的结果也反映出相同的变化趋势,A基因组最高,为1.1874,B基因组次之,为1.0810,D基因组最小,为0.8046(A＞B＞D).综合多态性信息含量和辛普森指数的估值,表明这一批人工合成六倍体小麦衍生后代群体接受的遗传基因既来自人工合成六倍体小麦,又来自普通栽培小麦,显示杂合度类型丰富,具有较高的遗传差异.根据SSR位点获得的等位基因变异片断的分布情况进行UPGMA聚类,发现A、B、D基因组基凶型间的遗传相似系数较低,A、B、D三个基因组所得平均遗传相似系数为0.4721,其中A基因组平均遗传相似系数为0.3797,B基因组平均遗传相似系数为0.4627,D基因组上平均遗传相似系数为0.5815,反映人工合成六倍体小麦后代衍生材料的遗传多样性处于较高水平.研究结果证明利用人工合成六倍体小麦所具有的普通小麦野生近缘种中的基因库改良现代小麦,丰富其遗传基础,减少其生物和非生物胁迫的脆弱性,是一条行之有效的途径.     

人工合成六倍体小麦与普通小麦杂交后代衍生群体的PPO基因分析

四倍体小麦与节节麦杂交培育的人工合成六倍体小麦已广泛应用于国内外小麦品种改良。以引自CIMMYT的Syn768、Syn769、Syn780和Syn786人工合成六倍体小麦分别与中国四川成都平原主栽普通小麦品种杂交、回交的BC2F2：6后代群体中选育的113份优良高代系和川麦38、川麦42、川麦43和川麦47育成品种为材料,采用SSR特异引物Xgwm312标记位点的PAGE凝胶电泳对其PPO基因型进行了研究。结果表明,Xgwm312位点的标记具有多态性,其PCR扩增产物可产生198bp、216bp、232bp和240bp四种等位基因变异片段。在所检测的117份后代衍生群体材料中,65份材料具有198bp片段的等位基因,占全部材料的55．56％;13份含216bp片段的等位基因,其频率为11．11％,35份材料具有232bp片段的等位基因,分布频率为29．91％;只有4份材料含有240bp片段的等位基因,仅占全部材料的3．42％。从每个人工合成六倍体小麦亲本材料所形成的后代衍生群体来看,基因等位变异片段分布频率各不相同。说明PPO基因在小麦杂交后代材料中基因型的表现存在着随机性,与亲本的基因型状况关系极大,并且在后代材料中出现了亲本都没有的240bp等位基因变异片段的材料。通过研究人工合成六倍体小麦与普通小麦杂交后代的PPO基因型,有助于提高分子标记育种效率,也有助于PPO基因型的多态性研究,并为人工合成六倍体小麦在我国小麦品种改良和分子标记育种中的应用提供依据和方法。     

人工合成六倍体小麦在黄淮麦区育种中的利用性评价

为了解人工合成六倍体小麦（synthetic hexaploid wheat,SHW）在黄淮麦区育种改良中的应用价值,利用从国际玉米小麦改良中心引进的5份SHW与普通小麦驻麦305进行杂交、回交,对亲本及BC₂群体的主要农艺性状、产量相关指标和籽粒品质进行调查分析。结果表明,与普通小麦相比,SHW的株高、小穗数、穗粒数、收获系数和千粒重等是其不利性状,但具有较多的分蘖。SHW的纤维含量、面筋含量、蛋白含量和硬度都比驻麦305高（PAAAAA0.05）。BC₂的收获系数较SHW显著提升,其产量虽然比SHW有了较大幅度提升,但仍显著低于普通小麦。BC₂的蛋白质和面筋含量相对于普通小麦亲本显著提升,其中仅2018-2019年的BC₂-SHW1和BC₂-SHW2群体未达显著水平。这表明5份SHW可作为重要的品质改良资源应用于小麦育种中。     

人工六倍体小麦后代衍生群体遗传多样性研究

通过四倍体二粒小麦和节节麦杂交而获得的人工合成六倍体小麦,含有丰富的普通小麦品种改良有益基因,作为拓宽普通栽培小麦性状和新品种改良的新的种质资源已广泛应用于普通小麦的遗传改良实践中.利用分布于小麦A、B、D基因组21条染色体、28个不同染色体臂上的37对微卫星引物,对人工合成六倍体小麦与四川成都平原普通栽培小麦主栽品种杂交、回交经多代选择而形成的117份人工合成六倍体小麦衍生后代高代群体系(其中川麦38、川麦42、川麦43和川麦47为审定品种)进行了DNA分子水平上的分析,共检测到256个等位基因变异,平均每个SSR标记位点检测到6.92个等位变异基因.每个SSR位点等位基因变异数在1～14个,变异幅度较大,表明SSR分子标记在人工合成六倍体小麦中表现出高水平的遗传变异.A,B,D基因组中,D基因组表现出的多态性信息含量最低,为0.427 6,B基因组次之,为0.534 6,A基因组最高,达到 0.614 5(A>B>D).辛普森指数比较的结果也反映出相同的变化趋势,A基因组最高,为1.187 4,B基因组次之,为1.081,D基因组最小,为0.804 6(A>B>D).综合多态性信息含量和辛普森指数的估值,表明这一批人工合成六倍体小麦后代衍生高代群体接受的遗传基因既来自人工合成六倍体小麦,又来自普通栽培小麦,显示杂合度类型丰富,具有较高的遗传差异.根据获得的等位基因变异片断的分布情况进行UPGMA聚类,发现A,B,D基因组基因型间的遗传相似系数较低, A,B,D三基因组37个SSR标记位点所得平均遗传相似系数为0.472 1,A基因组平均遗传相似系数为0.379 7,B基因组平均遗传相似系数为0.462 7,D基因组上平均遗传相似系数为0.581 5,反映出人工合成六倍体小麦后代衍生群体材料的遗传多样性处于较高水平.本研究结果证明利用人工合成六倍体小麦所具有的普通小麦野生近缘种中的基因库改良现代小麦,丰富其遗传基础,减少其生物和非生物胁迫的脆弱性,是一条行之有效的途径.     

人工异源六倍体小麦中甲基化差异的MSAP分析

利用MSAP方法分析了小麦从四倍体到六倍体进化过程中甲基化水平和甲基化遗传模式的变化。结果表明,人工异源六倍体小麦SCA/SQ(AABBDD)及其四倍体母本SCAUP(AABB)、二倍体父本粗山羊草SQ523(DD)的总甲基化水平分别为28.21%,27.53%,24.11%。37对引物检测到1 087条差异的扩增片段,对这些位点的甲基化遗传模式进行分析,结果表明,在人工异源六倍体中发生过甲基化的比例为18.95%,高于去甲基化的比例(2.58%)。这些结果揭示了小麦从四倍体到六倍体的进化过程中,通过对一些功能基因的甲基化来减轻异源多倍化造成的影响。     

Recessive genes controlling resistance to Helminthosporium leaf blight in synthetic hexaploid wheat

A study was conducted under controlled environment conditions in a phytotron to determine the nature of the inheritance of resistance Helminthosporium leaf blight (HLB) in a synthetic hexaploid wheat line, ‘Chirya‐3’, against the isolate KL‐8 of Bipolaris sorokiniana from the major wheat growing region of India. Crosses were made between two susceptible lines ‘WH 147’ and ‘Chinese Spring’. Analyses of F₁ and F₂ populations of these two crosses (‘WH 147’בChirya‐3’ and ‘Chinese Spring’בChirya‐3’) showed that resistance against the isolate in ‘Chirya‐3’ was governed by two recessive genes functioning in a complementary interaction giving an F₂ segregation pattern of 1 : 15 (resistant : susceptible). The segregation pattern of the resistant F₂ progenies in F₃ families from both crosses confirmed that two homozygous recessive genes were responsible for resistance to the isolate of Bipolaris sorokiniana in the synthetic line ‘Chirya‐3’. It is proposed that the genes be designated as hlbr1 and hlbr2.     

Genetic diversity and association mapping of agronomic yield traits in eighty six synthetic hexaploid wheat

Association mapping is a method to identify associations between target traits and genetic markers based on linkage disequilibrium (LD) of a quantitative trait locus. Synthetic hexaploid wheat (SHW) is derived from a cross between Triticum durum Desf. and Aegilops tauschii Coss. that enhances genetic diversity and broadens breeding resources. In this study, phenotypic diversity in 110 wheat accessions (86 SHW germplasm specimens and 24 conventional wheat varieties) was evaluated quantitatively for yield characteristics of grains per spike, thousand kernel weight, and spike length. Phenotypic data were collected over two years at two locations, and 1785 alleles were detected (mean 6.59), ranging from 3 to 11 alleles per locus. The average genetic diversity index was 0.749, with a range from 0.239 to 0.923. The polymorphic information content (PIC) ranged from 0.145 to 0.968, with a mean value of 0.695. The genetic diversity index and PIC indicated that genome B > D > A. Accessions were grouped into three subgroups based on STRUCTURE and unweighted pair-group with arithmetic mean clustering. The mean LD decay across the genome was 11.78 cM. Association mapping between traits and simple sequence repeat markers was performed using the generalized linear model approach. Forty-six SSR loci were significantly associated with the measured agronomic traits in two geographic locations. Together, these results broaden our knowledge of how to harness elite genes and genetic diversity in SHW in genomic and marker-assisted selection.     

Identification of quantitative trait loci for flowering-related traits in the D genome of synthetic hexaploid wheat lines

The gene pool of Aegilops tauschii, the D-genome donor of common wheat (Triticum aestivum L.), can be easily accessed in wheat breeding, but remains largely unexplored. In our previous studies, many synthetic hexaploid wheat lines were produced through interspecific crosses between the tetraploid wheat cultivar Langdon and various A. tauschii accessions. The synthetic hexaploid wheat lines showed wide variation in many characteristics. To elucidate the genetic basis of variation in flowering-related traits, we analyzed quantitative trait loci (QTL) affecting time to heading, flowering and maturity, and the grain-filling period using four different F₂ populations of synthetic hexaploid wheat lines. In total, 10 QTLs located on six D-genome chromosomes (all except 4D) were detected for the analyzed traits. The QTL on 1DL controlling heading time appeared to correspond to a flowering time QTL, previously considered to be an ortholog of Eps-A ^m 1 which is related to the narrow-sense earliness in einkorn wheat. The 5D QTL for heading time might be a novel locus associated with wheat flowering, while the 2DS QTL appears to be an allelic variant of the photoperiod response locus Ppd-D1. Some of the identified QTLs seemed to be novel loci regulating wheat flowering and maturation, including a QTL controlling the grain filling period on chromosome 3D. The exercise demonstrates that synthetic wheat lines can be useful for the identification of new, agriculturally important loci that can be transferred to, and used for the modification of flowering and grain maturation in hexaploid wheat.     

Production of hexaploid triticale by a synthetic hexaploid wheat-rye hybrid method

Grain weight is an important factor contributing to grain yield in wheat. Markers closely linked to grain weight could be used in marker-assisted selection (MAS) to accelerate the wheat breeding process. In this paper, a second backcross recombinant inbred line (BC₂F₄) population, a recombinant inbred line (RIL) population, and one natural population were used to study the relationship between allelic variants of the grain weight gene TaGW2-6A and grain weight, width, and length with the goal of verifying the feasibility using the functional marker Hap-6A-P1/P2 in MAS. The differences in average grain weight, width, and length between haplotypes Hap-6A-G and Hap-6A-A were 8.09 g, 0.22 mm, and 0.38 mm, respectively, in the BC₂F₄ population; 4.01 g, 0.11 mm, and 0.10 mm in the RIL population; and 3.95 g, 0.10 mm, and 0.20 mm in the natural population. All the differences were significant. Sequencing results of the products of second round PCR indicated that a 167 bp TaqI restriction fragment had been generated from small-grain-size materials because of three TaqI restriction sites (TCGA). However, the large-grain-size variant generated a 218 bp fragment due to a single-nucleotide mutation (SNP) (TCGA → TCGG) at the third site. TaGW2-6A expression levels were negative with respect to grain width, length, and weight. For this reason, Hap-6A-G was considered a superior allele. These results contradict those of a previous study, which showed Hap-6A-A to be significantly associated with wider grain and higher grain weight.     

Genome-wide association study reveals favorable alleles associated with common bunt resistance in synthetic hexaploid wheat

Genetic resistance to common bunt is a cost-effective, environmentally friendly, and sustainable approach to controlling the disease. To date, 16 race specific common bunt resistance genes (Bt1-Bt15 and Btp) have been reported in wheat. However, a limited number have been mapped and few markers have been identified, which limits the usage of molecular markers in a marker-assisted breeding program. A total of 125 synthetic hexaploid wheats (SHWs) were evaluated for reactions to a mixture of common bunt races under field conditions in Turkey in 2016 and 2017. The objectives of this study were to identify common bunt resistant genotypes, identify genomic regions conferring resistance to common bunt using 35,798 genotyping-by-sequencing derived single nucleotide polymorphisms (SNPs), and investigate the significant SNPs present within genes using the functional annotations of the underlying genes. We found 29 resistant SHWs that can be used in wheat breeding. The genome-wide association study identified 15 SNPs associated with common bunt resistance and a haplotype block comprising three SNPs in perfect linkage disequilibrium. Five of them were novel and were located on chromosomes 2A, 3D, and 4A. Furthermore, seven of the 15 SNPs were found within genes and had annotations suggesting potential role in disease resistance. This study identified several favorable alleles that decreased common bunt incidence up to 26% in SHWs. These resistant SHWs and candidate genomic regions controlling common bunt resistance will be useful for wheat genetic improvement and could assist in further understanding of the genetic architecture of common bunt resistance.     

Use of a synthetic hexaploid Triticum miguschovae for transfer of leaf rust resistance to common wheat

Summary Triticum miguschovae, a genome addition synthetic, was used as a source for transfer of leaf rust (Puccinia recondita tritici) resistance to common wheat. This synthetic, developed from two wild species Triticum militinae and Aegilops squarrosa, proves a valuable donor of the genes for leaf rust resistance. Leaf rust resistance was transferred from T. miguschovae by both dominant and recessive genes. Stable lines phenotypically similar to their recurrent parents Kavkaz and Bezostaya 1 but differing from them in a high level of leaf rust resistance were obtained. The genes for resistance in 3 selected lines differed from each other and from the known effective genes Lr9, Lr19, and Lr24. The resistance of one of them (line 1229) is controlled by two complementary interacting genes located on chromosome 7B and 1D was revealed by monosomic analysis.     

Inheritance in synthetic hexaploid wheat ‘RSP’ of sprouting tolerance derived from Aegilops tauschii Cosson

An artificial amphiploid ‘RSP’ (2n = 42, AABBDD) between tetraploid landrace Ailanmai (Triticum turgidum L., 2 = 28, AABB) and Aegilops tauschii (DD, 2n = 14) expressed high tolerance to preharvest sprouting which derived from Aegilops tauschii. To determine the inheritance of sprouting tolerance in ‘RSP’, it was crossed with six cultivars which vary in susceptibility to preharvest sprouting. Preharvest sprouting tolerance was assessed on F₂ plants using germination towels. Preharvest sprouting tolerance was inherited as a recessive trait which was controlled by one gene. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular mapping of a dominant non-glaucousness gene from synthetic hexaploid wheat (Triticum aestivum L.)

The leaf and stem surfaces of many land plants are covered with a cuticular wax layer that confers a glaucous appearance or white bloom. Synthetic hexaploid wheat Line 3672 was non-glaucous, and common wheat Line 9753 was glaucous. The cuticular wax was characterized using Scanning Electron Microscopy (SEM). A hybrid using 9753 as female parent and 3672 as male parent was made and 108 F₂ plants and their F₃ progenies were used to map the non-glaucouness gene. Non-glaucousness in Line 3672 was controlled by a single dominant gene, temporarily designated Iw3672. Five SSR markers mapped on chromosome 2DS were linked to Iw3672. Additionally, two EST-derived markers and a SNP marker were developed and were also linked to Iw3672. The order of the eight markers and Iw3672 was Xte6 ₇₃₀ /Xbarc124 ₅₂₀ —Iw3672 —Xwe6 _2100/2150 —Xcau96 ₂₈₇ —Xcfd51 _180/200/230 —Xwe7—Xgdm5 ₁₉₀ —Xgdm35 _246/250 , with the genetic distance for each interval being 0.9 cM, 1.4 cM, 0.9 cM, 0.9 cM, 1.9 cM, 7.2 cM and 2.5 cM, respectively. We concluded that Iw3672 is physically mapped on the distal region of wheat chromosome 2DS.