二倍体、四倍体和六倍体小麦产量及水分利用效率

试验选用了6个不同染色体倍性的小麦进化材料（3个二倍体、2个四倍体和1个六倍体）,分别在不同水肥条件下研究其根系、地上生物量、产量、蒸腾耗水量和水分利用效率等指标,旨在阐明小麦进化材料产量及水分利用效率的差异及水肥条件对这些特性的影响。试验表明：不同倍性小麦进化材料的生物量、产量和水分利用存在显著的差异,而且水肥条件对其有显著影响。在染色体倍性由2n→4n→6n的进化过程中,小麦根系及地上生物量均先增加后降低,而产量却显著增加,这与收获指数的增加有关。小麦产量的大小顺序为：T.aestivum〉T.dicoccum〉T.dicoccoides〉Ae.squarrosa〉Ae.speltoides〉T.boeoticum。水分亏缺显著降低小麦的生物量、产量和收获指数;在不同水分条件下,增加施肥量有利于这些指标的增加。但是水分亏缺下,增加施肥却降低各小麦材料的根系生物量。随小麦的进化,蒸腾耗水量显著降低,这与其生育期缩短有关;而生物量水分利用效率和产量水分利用效率却显著升高,且后者的差异要大于前者。各小麦产量水分利用效率的大小排序与产量的完全一致。水分亏缺处理显著减少各小麦进化材料的蒸腾耗水量47％～52％,而显著增加生物量水分利用效率3％～40％;但水分亏缺对产量水分利用效率的促进作用却随染色体倍性的增加而降低,甚至降低六倍体小麦T.aestivum的产量水分利用效率19％。不同水分条件下,高肥处理均有利于蒸腾耗水量、生物量水分利用效率和产量水分利用效率的增加。     

The nucleolar organisers of tetraploid and hexaploid wheats revealed by in situ hybridisation

Summary The technique of in situ hybridisation of cloned ribosomal DNA has been used to establish the numbers of nucleolar organising sites in a range of tetraploid and hexaploid wheats.     

Uptake and retranslocation of leaf-applied cadmium (109Cd) in diploid, tetraploid and hexaploid wheats

Uptake and retranslocation of leaf-applied radiolabeled cadmium (109Cd) was studied in three diploid (Triticum monococcum, AA), four tetraploid (Triticum turgidum, BBAA) and two hexaploid (Triticum aestivum, BBAADD) wheat genotypes grown for 9 d under controlled environmental conditions in nutrient solution. Among the tetraploid wheats, two genotypes were primitive (ssp. dicoccum) and two genotypes modern wheats (ssp. durum). Radiolabelled Cd was applied by immersing the tips (3 cm) of mature leaf into a 109Cd radiolabelled solution. There was a substantial variation in the uptake and export of 109Cd among and within wheat species. On average, diploid wheats (AA) absorbed and translocated more 109Cd than other wheats. The largest variation in 109Cd uptake was found within tetraploid wheats (BBAA). Primitive tetraploid wheats (ssp. dicoccum) had a greater uptake capacity for 109Cd than modern tetraploid wheats (ssp. durum). In all wheats studied, the amount of the 109Cd exported from the treated leaf into the roots and the remainder of the shoots was poorly related to the total absorption. For example, bread wheat cultivars were more or less similar in total absorption, but differed greatly in the amount of 109Cd retranslocated. The diploid wheat genotype 'FAL-43' absorbed the lowest amount of 109Cd, but retranslocated the greatest amount of 109Cd in roots and remainder of shoots. The results indicate the existence of substantial genotypic variation in the uptake and retranslocation of leaf-applied 109Cd. This variation is discussed in terms of potential genotypic differences in binding of Cd to cell walls and the composition of phloem sap ligands possibly affecting Cd transport into sink organs.     

Heterochronic development of the floret meristem determines grain number per spikelet in diploid, tetraploid and hexaploid wheats

Background and Aims

The inflorescence of grass species such as wheat, rice and maize consists of a unique reproductive structure called the spikelet, which is comprised of one, a few, or several florets (individual flowers). When reproductive growth is initiated, the inflorescence meristem differentiates a spikelet meristem as a lateral branch; the spikelet meristem then produces a floret meristem as a lateral branch. Interestingly, in wheat, the number of fertile florets per spikelet is associated with ploidy level: one or two florets in diploid, two or three in tetraploid, and more than three in hexaploid wheats. The objective of this study was to identify the mechanisms that regulate the architecture of the inflorescence in wheat and its relationship to ploidy level.

Methods

The floral anatomy of diploid (Triticum monococcum), tetraploid (T. turgidum ssp. durum) and hexaploid (T. aestivum) wheat species were investigated by light and scanning electron microscopy to describe floret development and to clarify the timing of the initiation of the floret primordia. In situ hybridization analysis using Wknox1, a wheat knotted1 orthologue, was performed to determine the patterning of meristem formation in the inflorescence.

Key Results

The recessive natural mutation of tetraploid (T. turgidum ssp. turgidum) wheat, branching head (bh), which produces branched inflorescences, was used to demonstrate the utility of Wknox1 as a molecular marker for meristematic tissue. Then an analysis of Wknox1 expression was performed in diploid, tetraploid and hexaploid wheats and heterochronic development of the floret meristems was found among these wheat species.

Conclusions

It is shown that the difference in the number of floret primordia in diploid, tetraploid and hexaploid wheats is caused by the heterochronic initiation of floret meristem development from the spikelet meristem.Key words: Triticum, wheat, inflorescence, spikelet, floret, meristem, heterochrony, heterochronic development, knotted1, polyploidy     

Microsatellite mapping of the genes for brittle rachis on homoeologous group 3 chromosomes in tetraploid and hexaploid wheats

The brittle rachis character, which causes spontaneous shattering of spikelets, has an adaptive value in wild grass species. The loci Br1 and Br2 in durum wheat (Triticum durum Desf.) and Br3 in hexaploid wheat (T. aestivum L.) determine disarticulation of rachides above the junction of the rachilla with the rachis such that a fragment of rachis is attached below each spikelet. Using microsatellite markers, the loci Br1, Br2 and Br3 were mapped on the homoeologous group 3 chromosomes. The Br2 locus was located on the short arm of chromosome 3A and linked with the centromeric marker, Xgwm32, at a distance of 13.3 cM. The Br3 locus was located on the short arm of chromosome 3B and linked with the centromeric marker, Xgwm72 (at a distance of 14.2 cM). The Br1 locus was located on the short arm of chromosome 3D. The distance of Br1 from the centromeric marker Xgdm72 was 25.3 cM. Mapping the Br1, Br2 and Br3 loci of the brittle rachis suggests the homoeologous origin of these 3 loci for brittle rachides. Since the genes for brittle rachis have been retained in the gene pool of durum wheat, the more closely linked markers with the brittle rachis locus are required to select against brittle rachis genotypes and then to avoid yield loss in improved cultivars.     

Evidence for maternal effect in the inheritance of grain protein in crosses between cultivated and wild tetraploid wheats

Summary Reciprocal crosses were made between cultivated wheat (Triticum turgidum var. durum) and a high-protein line of wild tetraploid wheat (T. turgidum var. dicoccoides). F₁ grains (on maternal spikes) were very similar to the selfed grains on the maternal parent in protein percentage, weight and protein content. These traits were also analyzed in F₃ grains developed on F₂ spikes of segregating populations derived from reciprocal crosses between the same cultivated parent and another high-protein line of var. dicoccoides. No significant differences in the mean values of these traits were found between the reciprocal crosses, indicating no cytoplasmic effect. It has been concluded that these grain characteristics are largely determined by the maternal plant.Recipient of Sir Charles Clore Postdoctoral FellowshipThe Marshall and Edith Korshak Professor of Plant Cytogenetics     

灌浆期水分亏缺条件下二、四、六倍体小麦收获指数和水分利用效率的演化

为揭示不同倍性小麦生长发育、产量性状及水分利用对灌浆期水分亏缺响应的差异,选用二倍体野生一粒小麦(Triticum boeoticum)、栽培一粒小麦(T.monococcum),四倍体野生二粒小麦(T.dicoccoides)、栽培二粒小麦(T.dicoccon),和两个普通六倍体小麦(T.aestivum)品种‘长武134’和‘陕253’6个小麦品种作为供试材料。采用盆栽控水的方法,测定和分析了不同灌浆期土壤水分条件下小麦株高、旗叶叶面积、穗长、根干重、地上生物量、根冠比、千粒重、粒数、产量、收获指数、蒸腾耗水量和水分利用效率等性状的变化。在小麦染色体倍体由二倍体向六倍体进化的过程中,小麦地上生物量、千粒重、穗粒数、产量、收获指数和水分利用效率都显著增加。随着土壤水分从正常→中度亏缺→重度亏缺的减少,收获指数先增大后减小,分别为41.26%、42.48%和38.19%;生物量水分利用效率逐渐增大,分别为2.39、2.43和2.53g·kg–1;产量水分利用效率分别为1.05、1.10和1.04g·kg–1。在灌浆期水分条件是影响收获指数和水分利用效率的关键因素之一。灌浆期的水分亏缺有利于六倍体小麦的收获指数和四倍体的生物量水分利用效率的提高。中度的水分亏缺有利于四倍体和六倍体产量水分利用效率的提高。     

Proteome analysis of diploid,tetraploid and hexaploid wheat: towards understanding genome interaction in protein expression

Hexaploid wheat (Triticum aestivum L.) is derived from a complex hybridization procedure involving three diploid species carrying the A, B and D genomes. The proteome patterns of diploid, tetraploid and hexaploid wheat were analyzed to explore the genome interaction in protein expression. At least two species from each of the diploid and tetraploid were used to compare their proteome maps with a hexaploid wheat cv. Chinese Spring. The ancestral cultivars were selected based on their history of closeness with the cultivated wheat. Proteins were extracted from seed flour and separated by two-dimensional electrophoresis (2-DE) with isoelectric focusing of pH range from 4-10. 2-DE maps of cultivated and ancestral species were analyzed by computer assisted image analyzer. The region of high molecular weight glutenin subunits of hexaploid wheat showed similarity with those of the diploid donors, BB and DD genomes. The omega gliadin, which is controlled by B genome in common wheat, was assumed to have evolved as a result of interaction between AA and BB genomes. The low molecular weight glutenins and alpha and beta gliadin regions were contributed by the three genomes. This result suggests that the function of donor genomes particularly in the expression of proteins in hexaploid wheat is not totally independent; rather it is the product of interactions among the diploid genomes in the hexaploid nuclear constitutions. The expression of nonstorage proteins was affected substantially due to the removal of the D genome from hexaploid constitution. Location of the structural gene controlling one of the alpha amylase inhibitor proteins in the nonstorage protein region was identified in the short arm of chromosome 3D.     

Seed-storage-protein loci in RFLP maps of diploid, tetraploid, and hexaploid wheat

 Linkages between high- and low-molecular-weight (M_r) glutenin, gliadin and triticin loci in diploid, tetraploid and hexaploid wheats were studied by hybridization of restriction fragments with DNA clones and by SDS-PAGE. In tetraploid and hexaploid wheat, DNA fragments hybridizing with a low-M_r glutenin clone were mapped at the XGlu-3 locus in the distal region of the maps of chromosome arms 1AS, 1BS, and 1DS. A second locus, designated XGlu-B2, was detected in the middle of the map of chromosome arm 1BS completely linked to the XGli-B3 gliadin locus. The restriction fragments mapped at this locus were shown to co-segregate with B subunits of low-M_r glutenins in SDS-PAGE in tetraploid wheat, indicating that XGlu-B2 is an active low-M_r glutenin locus. A new locus hybridizing with the low-M_r clone was mapped on the long arm of chromosome 7A^m in diploid wheat. No glutenin protein was found to co-segregate with this new locus. Triticin loci were mapped on chromosome arms 1AS, 1BS, and 1DS. A failure to detect triticin proteins co-segregating with DNA fragments mapped at XTri-B1 locus suggests that this locus is not active. No evidence was found for the existence of Gli-A4, and it is concluded that this locus is probably synonymous with Gli-A3. Recombination was observed within the multigene gliadin family mapped at XGli-A11 (1.2 cM).1 Although these closely linked loci may correspond to the previously named Gli-A1 and Gli-A5 loci, they were temporarily designated XGli-A1.1 and XGli-A1.2 until orthology with Gli-A1 and Gli-A5 is established. Received: 25 March 1997 / Accepted: 23 June 1997     

Development and validation of a new Ppo-A1 marker useful for marker-assisted selection in tetraploid wheats

Polyphenol oxidase (PPO) activity is a major cause of undesirable brown color of semolina. In tetraploid wheat, the Ppo-A1 gene is significantly involved in the phenotypic expression of PPO activity. The main goal of this study was to develop and validate a more efficient marker for Ppo-A1 to facilitate marker-assisted selection for low PPO activity in tetraploid wheat breeding programs. A large tetraploid wheat collection, including durum cultivars, domesticated and wild accessions, was used to evaluate the PPO activity. The heritability values indicated that the phenotypic expression of PPO activity was mainly due to genotypic effect. PPO18, and a new marker named MG18, were used to study the Ppo-A1 allelic variation in a tetraploid wheat collection. PPO18 analysis detected four alleles (Ppo-A1b, Ppo-A1e, Ppo-A1f and Ppo-A1g). The high frequency of Ppo-A1g (no PCR product) detected in the tetraploid wheat collection, led to the development of a new genome-specific Ppo-A1 marker (MG18). MG18 analysis identified the same alleles as PPO18 which were associated with low or high PPO activity. The new MG18 marker was more efficient than PPO18 in detecting the four different alleles of Ppo-A1 in the tetraploid wheat collection. Indeed, the accessions assigned to the Ppo-A1g group, according to PPO18, when tested with MG18, were better classified in the four alleles of the Ppo-A1 gene. The MG18 analysis proved that the PPO18 marker overestimated the number of accessions with Ppo-A1g. Therefore, MG18 can be applied to large-scale marker-assisted selection for PPO activity in durum breeding programs.     

Embryo rescue response and genetic analyses in interspecific crosses of oilseed Brassica species

Embryo rescue technique is widely utilized to save developing embryo from abortion in interspecific hybridization of plants. In Brassica species, success of an embryo rescue depends on the age of embryo, developmental stage of embryo, and media composition. In this study, ten crosses were conducted between diploid oilseed species B. rapa × tetraploid B. napus and B. rapa × tetraploid B. juncea along with their reciprocal crosses. The immature embryos from parents and crosses were cultured at 14 d after pollination in MS and ½ MS medium without any growth regulators for direct embryogenesis. Embryos were found at different stages of development during isolation, from globular to cotyledonary, indicating that rate of embryo development depends on genotype. Embryos isolated at the cotyledonary stage showed the highest regeneration percentage (av. 83.29%) and required the lowest time to regenerate (5.8 d) compared with another type of embryo, torpedo stage, cultured. Embryo rescued in ½ MS media accounted for 10–51%, 4.0–61%, 6.0–21%, and 5.0–43% greater shoot length, root length, number of leaves, and days to flowering, respectively, in different cross combinations compared with full-strength MS media. The results indicated that the rate of regeneration from embryo is higher in ½ MS media compared with full-strength MS media. Percent regeneration from the cultured embryos differed significantly in different cross combinations. Days required for regeneration from embryos, length of siliqua, and the number of ovules per siliqua accounted for high heterosis and broad sense heritability. The findings of this experiment would be useful in developing cost-effective embryo rescue protocol and desired interspecific hybrids through embryo rescue in Brassica species.

     

Comparative mapping of genes for glume colouration and pubescence in hexaploid wheat (Triticum aestivum L.)

Microsatellite markers were used to map the major genes Bg (determining black glume colour), Rg1 and Rg3 (red glume), and a locus determining smokey-grey coloured glume to the distal ends of the short arms of the homoeologous group 1 chromosomes, proximally (or closely linked) to Xgwm1223 and distal to Xgwm0033. On this basis, we propose that these genes represent a set of homoeoloci, designated Rg-A1, Rg-B1, and Rg-D1. Rg3 and Bg appear to be variant alleles of Rg-A1. Both Rg3 and Bg are closely linked with the major glume pubescence gene Hg. Similarly, the hexaploid wheat smokey-grey glume gene and Rg2 represent alleles at Rg-D1. The microsatellite markers linked to the Rg genes were used to analyse a phenotypically and genotypically characterized set of Siberian spring wheats. A coincidence between the presence of the 264-bp allele of Xgwm0136 and Rg-A1b (Rg3) was observed; so Xgwm0136 can probably be used as a diagnostic marker for this gene.     

Expression and suppression of resistance to greenbug (Homoptera: Aphididae) in synthetic hexaploid wheats derived from Triticum dicoccum x Aegilops tauschii crosses

Fifty-eight synthetic hexaploid wheats, developed by crossing Triticum dicoccum Schrank. and Aegilops tauschii (Coss.) Schmal., were evaluated at the seedling stage, together with their parents, for resistance to greenbug (Schizaphis graminum Rondani) under greenhouse conditions. Seedlings of different synthetic hexaploids showed large phenotypic differences for resistance. All the T. dicoccum parents were susceptible, while high levels of resistance were observed in some of the Ae. tauschii parents. Of the synthetic hexaploids derived from resistant Ae. tauschii parents, a high proportion (76%) showed levels of resistance to the greenbug biotype used that were comparable to those of the resistant parent. While there were clear indications of the presence of suppressor genes for greenbug resistance in the A and/or B genomes of T. dicoccum in some synthetics, positive epistatic interaction was also found in synthetic hexaploids with higher levels of resistance than that of either parent. Resistance from different Ae. tauschii accessions was expressed differently when crossed with the same T. dicoccum, indicating diversity among the resistance genes present in the test synthetic hexaploid wheats. Based on resistance reactions, the genes conferring greenbug resistance in these synthetic hexaploids are probably different from resistance genes previously transferred to wheat from Ae. tauschii.     

Cytological characterization,powdery mildew resistance and storage protein composition of tetraploid and hexaploid 1BL/1RS wheat-rye translocation lines

Summary Progenies of a tetraploid 1BL/1RS wheat-rye translocation line, CV 256, selected from the cross Cando x Veery, were analyzed by means of Giemsa C-banding. CV 256 is cytologically stable for the presence of the 1BL/1RS translocation but still segregating for A- and B-genome chromosomes of Cando and Veery. In CV 256, nucleolar activity of the 1RS NOR locus is suppressed, as judged by the absence of a secondary constriction in that rye segment and the capability of organizing nucleoli. PAGE analysis of prolamins confirmed the presence of two 1RS secalins in all single seeds analyzed. SDS-PAGE analysis of reduced glutenins of single seeds indicated that some seeds contained the Cando Glu-B1 locus (subunits 6+8), some contained the Veery Glu-B1 locus (subunits 7+9) while others contained all four subunits, indicating that the material was heterozygous. Pm8 resistance is expressed in the tetraploid 1BL/1RS translocation line based on the reactions of six well-defined powdery mildew isolates. However, Pm8 resistance is not expressed in the hexaploid wheat cultivars Olymp, Heinrich and Florida, which also contain the 1BL/1RS translocation. Obviously, the existence of the 1BL/1RS translocation is not a proof for the expression of the associated genes. PAGE results did not show a clear linkage between powdery mildew resistance and the presence of 1RS secalins.     

Chloroplast inheritance in the sea daffodil (Pancratium maritimum,Amaryllidaceae) through controlled crosses,seed germination and molecular analyses

Chloroplast inheritance is a very important information to obtain when cpDNA is used to study phylogeography or reconstruct phylogenies. A procedure used for the analyses of chloroplast inheritance in the sea daffodil (Pancratium maritimum) is described using multi-facet approach (artificial cross, germination and end-point PCR amplification).     

GluDy allele variations in Aegilops tauschii and Triticum aestivum: implications for the origins of hexaploid wheats

To investigate the evolution and geographical origins of hexaploid wheat, we examined a 284 bp sequence from the promoter region of the GluDy locus, coding for the y subunit of high-molecular-weight glutenin. Fourteen different alleles were found in 100 accessions of Aegilops tauschii and 169 of Triticum aestivum. Two alleles were present in both species; the other 7 alleles from Ae. tauschii and 5 from T. aestivum were unique to their respective species. The two shared alleles differed at only one nucleotide position within the region sequenced, but their apparent association with the common haplotypes GluD1a and GluD1d, which have substantial differences within their GluDy coding regions, makes it unlikely that the alleles evolved independently in Ae. tauschii and T. aestivum. The results therefore support previous studies which suggest that there were at least two Ae. tauschii sources that contributed germplasm to the D genome of T. aestivum. The number of alleles present in T. aestivum, and the nucleotide diversity of these alleles, indicates that this region of the D genome has undergone relatively rapid change since polyploidisation. Ae. tauschii from Syria and Turkey had relatively high nucleotide diversity and possessed all the major GluDy alleles, indicating that these populations are probably ancient and not the result of adventive spread. The presence in the Turkish population of both of the shared alleles suggests that hexaploid wheat is likely to have originated in southeast Turkey or northern Syria, within the Fertile Crescent and near to the farming villages at which archaeological remains of hexaploid wheats are first found. A second, more recent, hexaploidisation probably occurred in Iran.