Dryland Wheat Domestication Changed the Development of Aboveground Architecture for a Well-Structured Canopy

We examined three different-ploidy wheat species to elucidate the development of aboveground architecture and its domesticated mechanism under environment-controlled field conditions. Architecture parameters including leaf, stem, spike and canopy morphology were measured together with biomass allocation, leaf net photosynthetic rate and instantaneous water use efficiency (WUE_i). Canopy biomass density was decreased from diploid to tetraploid wheat, but increased to maximum in hexaploid wheat. Population yield in hexaploid wheat was higher than in diploid wheat, but the population fitness and individual competition ability was higher in diploid wheats. Plant architecture was modified from a compact type in diploid wheats to an incompact type in tetraploid wheats, and then to a more compact type of hexaploid wheats. Biomass accumulation, population yield, harvest index and the seed to leaf ratio increased from diploid to tetraploid and hexaploid, associated with heavier specific internode weight and greater canopy biomass density in hexaploid and tetraploid than in diploid wheat. Leaf photosynthetic rate and WUE_i were decreased from diploid to tetraploid and increased from tetraploid to hexaploid due to more compact leaf type in hexaploid and diploid than in tetraploid. Grain yield formation and WUE_i were closely associated with spatial stance of leaves and stems. We conclude that the ideotype of dryland wheats could be based on spatial reconstruction of leaf type and further exertion of leaf photosynthetic rate.     

Evidence for autoploid evolution in the artemisia ludoviciana complex of the Pacific Northwest

TheArtemisia ludoviciana complex of the Northwest is considered to be an intervarietal autoploid complex on the basis of evidence obtained from cytogenetic analysis. The evidence includes the occurrence of chromosomal races within all but two of the inclusive taxa, the degree and constancy of multivalent formation in the polyploid races, and the high degree of homology among the genomes of the various taxa as demonstrated by the pairing relationships in the F₁ progeny. Both triploid and tetraploid progeny were produced in diploid-tetraploid crosses, and the tetraploid offspring were fully as fertile as the natural tetraploids. The triploids, on the other hand, produced very few viable pollen grains. The production of tetraploid offspring in interracial crosses could provide a mechanism for gene flow from the diploid to the tetraploid population. With the observation of both diploid and tetraploid populations ofA. douglasiana, in addition to the well-known hexaploid, a reasonable doubt is cast upon the putative amphidiploid origin of the hexaploid via hybridization betweenA. suksdorfii andA. ludoviciana.     

Hybridization in the genera Vulpia and Festuca (Poaceae): meiotic behaviour of artificial hybrids

The course of meiosis, including an analysis of chromosome configurations, is described for five diploid × diploid Vulpia crosses, five tetraploid × diploid Vulpia crosses, one hexaploid × diploid Festuca × Vulpia cross, one tetraploid × hexaploid Vulpia × Festuca cross, and one hexaploid × hexaploid Vulpia × Festuca cross. In most cases there was 97.5% or more pollen sterility, but two heptaploid plants obtained (presumably by non-reduction) from a hexaploid × diploid cross had about 60% stainable pollen. In the diploid hybrids pairing was quite extensive, and in V. ligustica × V. geniculata it was more or less as in the parent species (mode 7 bivalents, with regular separation). In the triploid hybrids the modal situation was 7 bivalents + 7 univalents, but evidence concerning the genomes which were pairing was equivocal. Evidence from the crosses at higher ploidy levels shows that both homogenetic and heterogenetic pairing does occur, although the relative amounts are uncertain. The results in general support the current classsification of Vulpia , except that they suggest the removal of V. alopecuros from section Loretia.     

Sterols in different cytological races of Urginea indica

The identification of phytosterols in roots, bulbs and leaves of diploid, triploid, tetraploid and hexaploid cytotypes of Urginea indica was carrie     

Differences in Zinc Efficiency among and within Diploid, Tetraploid and Hexaploid Wheats

Greenhouse experiments were carried out with six diploid, ninetetraploid and seven hexaploid wheats, including wild and primitivegenotypes, to study the influence of varied zinc (Zn) supplyon the severity of Zn deficiency symptoms, shoot dry matterproduction and shoot Zn concentrations. In addition to wildand primitive genotypes, one modern tetraploid cultivar withhigh sensitivity to Zn deficiency and two modern hexaploid cultivars,one highly sensitive to and one resistant to Zn deficiency,were included for comparison. Plants were grown for 44 d ina severely Zn-deficient calcareous soil, with (+Zn; 5 mg Znkg^-1soil) and without (-Zn) Zn fertilization. Visible Zn deficiencysymptoms, including whitish-brown necrotic patches on leaf blades,appeared very rapidly and severely in all tetraploid wheat genotypes.Compared with tetraploid wheats, diploid and hexaploid wheatswere less sensitive to Zn deficiency. With additional Zn, shootdry matter production was higher in tetraploid than diploidand hexaploid wheats. However, under Zn-deficient conditionstetraploid wheats had the lowest shoot dry matter production,indicating the very high sensitivity of tetraploid wheats toZn deficiency. Consequently, Zn efficiency expressed as theratio of shoot dry matter produced under Zn deficiency to Znfertilization, was much lower in tetraploid wheats than in diploidand hexaploid wheats. On average, Zn efficiency ratios were36% for tetraploid, 60% for diploid and 64% for hexaploid wheats.Differences in Zn efficiency among and within diploid, tetraploidand hexaploid wheats were positively related to the amount ofZn per shoot of the genotypes, but not to the amount of Zn perunit dry weight of shoots or seeds used in the experiments.The seeds of the accessions of tetraploid wild wheats containedup to 120 mg Zn kg^-1, but the resulting plants showed very highsensitivity to Zn deficiency. By contrast, hexaploid wheatsand primitive diploid wheats with much lower Zn concentrationsin seeds had higher Zn efficiencies. It is suggested that notonly enhanced Zn uptake capacity but also enhanced internalZn utilization capacity of genotypes play important roles indifferential expression of Zn efficiency. The results of thisstudy also suggest the importance of the A and D genomes asthe possible source of genes determining Zn efficiency in wheat.Copyright 1999 Annals of Botany Company Seeds, Triticum aestivum, Triticum monococcum, Triticum turgidum, zinc concentrations, zinc deficiency, zinc efficiency.     

Effect of ploidy levels on the activities of Δ1-pyrroline-5-carboxylate synthetase,superoxide dismutase and peroxidase in Cenchrus species grown under water stress

The effects of ploidy levels on the activities of Δ¹-pyrroline-5-carboxylate synthetase (P5CS; EC not assigned), superoxide dismutase (SOD; EC 1.15.1.1) and guaiacol peroxidase (POX; EC 1.11.1.7), as well as malondialdehyde (MDA) and proline contents were studied in two months old plants of Cenchrus species. The Cenchrus species represent three ploidy levels: diploid, tetraploid, hexaploid and two life spans: annual and perennial. Plants were subjected to water stress for 2, 4, 6 and 8 d by withholding water under glasshouse conditions. Although the levels of proline increased with the magnitude of water stress, the P5CS activity did not show a corresponding increase in all species. Peroxidase and superoxide dismutase activities showed an increase or steady state in the early phase of drought and then declined with the further increase in the magnitude of water stress, indicating differing behaviors of species towards drought tolerance. Under drought, diploid Cenchrus species had a higher POX activity, MDA accumulation and lower proline content than tetraploid species. Lower POX and higher P5CS activities and proline contents, however, were observed in hexaploid and tetraploid species. Taken together, our findings suggest that diploid species have a less efficient antioxidant system to scavenge reactive oxygen species than tetra and hexaploid Cenchrus. This may result in a corresponding variability in growth and persistence under natural grasslands. The study also paves the way for investigations on the molecular events associated with drought in Cenchrus species differing in ploidy and life span.     

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     

Endopolyploidy in the roots of rye,Secale cereale L.

2,4-D was applied to the roots of diploid and tetraploid corn. After the application the mitotic division in the meristem of root tips was blocked; the mitotic division in differentiated cells of cortex and central cylinder, on the other hand, was provoked. In the cortex of diploid corn (variety ?eské) predominantly tetraploid were found cells with 28 chromosomes and, to a lesser extent, octoploid and diploid ones with 56 and 14 chromosomes respectively. In the cortex of tetraploid corn (variety Bernburger Tetraroggen), most cells were octoploid with 56 chromosomes; the metaphase levels with 112 and 28 chromosomes, e.g. 16-ploid and tetraploid cells, were found less frequently. The relations between the numbers of cells with different polyploidy were similar in both the varieties. The first endoreduplication cycle was different polyploidy were similar in both the varieties. The first endoreduplication cycle was found to occur in the region where the cortex cells finish their elongation. In the central cylinder of the roots of diploid corn most cells were found to be diploid, in tetraploid corn most cells were tetraploid.     

Phylogenetic analysis reveals the origins of tetraploid and hexaploid species in the Japanese <Emphasis Type="Italic">Lepisorus thunbergianus</Emphasis> (Polypodiaceae) complex

The Japanese Lepisorus thunbergianus complex contains diploid and tetraploid races of L. thunbergianus and a hexaploid species, L. mikawanus. Here, we performed molecular phylogenetic analysis on this complex to delimit species and to elucidate the evolutionary origins of tetraploid and hexaploid species. Chloroplast DNA (cpDNA) phylogeny supported the monophyly of the complex. Based on a single-copy nuclear gene (PgiC) tree, the tetraploid L. thunbergianus samples could be classified into two variants: an allotetraploid of hybrid origin between diploid L. thunbergianus and Japanese L. angustus and another allotetraploid of hybrid origin between diploid L. thunbergianus and an unknown diploid race of L. tosaensis. These variants can be recognized morphologically and distinguished from their parent species. Hence, here we described these allopolyploids as new species, L. nigripes and L. kuratae, respectively. The hexaploid species L. mikawanus has three types of PgiC alleles, each of which was derived from diploid L. thunbergianus, L. tosaensis, and Japanese L. angustus, while cpDNA shows that it is included in Japanese L. thunbergianus clade. Based on the cpDNA phylogeny and PgiC nucleotide sequences, we therefore concluded that L. mikawanus is an allohexaploid that originated through hybridization between tetraploid species, L. nigripes and an unknown ancestral diploid race of L. tosaensis.     

A case of genome partition in polyploid oats

Summary At the second generation of the interspecific cross between the cultivated hexaploid (2n = 42) oat A. Sativa and the wild tetraploid (2n = 28) A. Murphyi, a plant having hexaploid and diploid (2n = 14) sectors was selected. Meiosis was highly regular in the diploid sector but the tillers failed to proceed beyond the boot stage and no seeds were produced. It is suggested that this diploid sector represents an entire genome of one of the diploid progenitors of the hexaploid oat.     

不同倍性小麦对盐胁迫的适应性差异

植物染料在工业化应用过程中存在着资源限制,目标色相不丰富、色牢度不理想、植物染料本身的鉴别和成品的鉴别等问题。为了丰富染料植物资源的来源和提高染料植物资源的利用效率,该研究对西双版纳傣族利用的染料植物及其染色工艺涉及的相关植物进行了系统调查。2014年10月到2016年1月,采用半结构式访谈法对西双版纳14个村寨的56个关键信息人进行访谈,收集信息包括使用着色植物、媒染植物和助染植物的种类、傣名、利用部位和资源来历,以及预处理和染色过程工艺条件与技术步骤;采用参与式观察法对4种色相的10个染色工艺过程进行了记录,采集了凭证标本和图像资料;对调查信息进行了整理编目。结果表明：西双版纳地区的傣族使用11种着色植物和17种助染植物;目标色相有红、黄、蓝和绿。分析了傣族染料植物资源的发掘潜力、傣族利用植物染色对于染料植物利用的应用启发。该研究详细深入地记录了西双版纳傣族使用的染料植物的种类及其相关的组合和染色的过程。该研究结果对民族民间染料植物与染色工艺的产业化应用具有重要借鉴意义,为染料植物资源筛选及其染色工艺条件优化提供了参考。     

Revisiting meiotic pairing in wheat synthetics in relation to the evolution of the meiotic system in wheat

A large panel of hexaploid wheat synthetics was developed. Their tetraploid parents consisted of either four extracted wheat tetraploids (ETWs) or four natural present-day tetraploids, and their diploid parents consisted of twenty accessions of Aegilops tauschii. Analysis of meiotic behaviour of the synthetics showed that chromosome pairing is highly variable and depends on the progenitor. The meiotic behaviour in the four ETWs was compared to that of the natural tetraploid wheats. It appears there was no evolution at the hexaploid level of the meiotic genes carried by the A and B genomes. We also reach the conclusion that the neo-allohexaploids at the origin of present-day wheat had a meiotic behaviour close to that of the present-day hexaploid wheat. It is likely that other neo-hexaploids with an impaired meiosis were formed, but they had no future due to their more or less rapid disappearance due to increasing aneuploidy level and structural changes, mainly Robertsonian translocations.     

Haploid Wheat Induction by Crosses Between Different Ploidy Wheat and Different Populations of Maize

Haploid embryo and plant producing frequencies were studied by crossesing diploid, tetraploid and hexaploid wheat with landraces,hybrids and inbred lines of maize. It showed significant differences among the wheat and maize populations. The tetraploid and hexaploid wheat were better than the diploid. High frequencies were obtained by using tetraploid wheat of Triticum turgidum cv. TG14 and maize landraces cv. Xiaoyumi and Xiao Huangmaya. The highest haploid plant producing frequency (6.95 %) was obtained in the TG14 × Xiaoyumi.     

Cytological studies on mixoploidy and embryonic development in mosaic silkworms induced by low temperature treatment

Mosaicism in silkworms is easily inducible by applying a cold shock to the hybrid eggs between two strains with different markers at the early developmental stage. When BF₁ eggs from the cross between a tetraploid female (which had been induced from the cross between a red egg and a white egg strain) and a male of the red egg strain were exposed to a cold shock, hexaploid eggs and two types of mosaic eggs were obtained: black-black (BB-) mosaic eggs, which possessed two kinds of black serosa cells with different-sized nuclei, and black-red (BR-) mosaic eggs. Cytological studies on the embryos from these mosaic eggs revealed that the BB-mosaic type was a 3n/6n mixoploid, while the BR-mosaic type was mixoploid with n/2n/3n, n/3n, or 2n/6n constitution. The hatchability of BB- and BR-mosaic eggs was considerably lower than that of either n/2n or 2n/4n mixoploid eggs obtained by a cold treatment of diploid eggs. Since abnormal development was observed at a high frequency in the embryos from BB- and BR-mosaic eggs at the blastokinesis stage, it is speculated that the coexistence of hexaploid or triploid cells may be a factor in the induction of such abnormality in early embryogenesis.     

Parasexuality and Ploidy Change in Candida tropicalis

Candida species exhibit a variety of ploidy states and modes of sexual reproduction. Most species possess the requisite genes for sexual reproduction, recombination, and meiosis, yet only a few have been reported to undergo a complete sexual cycle including mating and sporulation. Candida albicans, the most studied Candida species and a prevalent human fungal pathogen, completes its sexual cycle via a parasexual process of concerted chromosome loss rather than a conventional meiosis. In this study, we examine ploidy changes in Candida tropicalis, a closely related species to C. albicans that was recently revealed to undergo sexual mating. C. tropicalis diploid cells mate to form tetraploid cells, and we show that these can be induced to undergo chromosome loss to regenerate diploid forms by growth on sorbose medium. The diploid products are themselves mating competent, thereby establishing a parasexual cycle in this species for the first time. Extended incubation (>120 generations) of C. tropicalis tetraploid cells under rich culture conditions also resulted in instability of the tetraploid form and a gradual reduction in ploidy back to the diploid state. The fitness levels of C. tropicalis diploid and tetraploid cells were compared, and diploid cells exhibited increased fitness relative to tetraploid cells in vitro, despite diploid and tetraploid cells having similar doubling times. Collectively, these experiments demonstrate distinct pathways by which a parasexual cycle can occur in C. tropicalis and indicate that nonmeiotic mechanisms drive ploidy changes in this prevalent human pathogen.     

Study on the response of diploid,tetraploid and hexaploid species of wheat to the elevated CO2

Study was done to compare the response of Triticum aestivum (hexaploid), Triticum durum (tetraploid) and Triticum monococcum (diploid) wheat species to the elevated CO₂ using Free Air CO₂ Enrichment (FACE) facility. It was demonstrated that the modern cultivar of wheat Triticum aestivum (hexaploid) was largely sink limited. It appeared to have less photosynthesis per unit leaf area than Triticum monococcum (diploid wheat). While leaf size, grain weight and amylase activity increased with the ploidy level from diploid to hexaploid wheat forms, the photosynthetic rate was reduced significantly. These wheat species responded differentially to the elevated CO₂. The larger leaf area and greater seed weight and presence of 38 KDa protein band caused by elevated CO₂ had additive effect in improving the productivity of hexaploid wheat by changing the source sink ratio. Whereas, such a source sink balance was not induced by elevated CO₂ in diploid wheat. The increasing CO₂ may present opportunities to breeders and possibly allow them to select for cultivars responsive to the elevated CO₂ with better sink potential.Key words: Elevated CO₂, FACE technology, Photosynthesis, Seed weight, Source sink ratio, Triticum     

Rapid Elimination of Low-Copy DNA Sequences in Polyploid Wheat: A Possible Mechanism for Differentiation of Homoeologous Chromosomes

To study genome evolution in allopolyploid plants, we analyzed polyploid wheats and their diploid progenitors for the occurrence of 16 low-copy chromosome- or genome-specific sequences isolated from hexaploid wheat. Based on their occurrence in the diploid species, we classified the sequences into two groups: group I, found in only one of the three diploid progenitors of hexaploid wheat, and group II, found in all three diploid progenitors. The absence of group II sequences from one genome of tetraploid wheat and from two genomes of hexaploid wheat indicates their specific elimination from these genomes at the polyploid level. Analysis of a newly synthesized amphiploid, having a genomic constitution analogous to that of hexaploid wheat, revealed a pattern of sequence elimination similar to the one found in hexaploid wheat. Apparently, speciation through allopolyploidy is accompanied by a rapid, nonrandom elimination of specific, low-copy, probably noncoding DNA sequences at the early stages of allopolyploidization, resulting in further divergence of homoeologous chromosomes (partially homologous chromosomes of different genomes carrying the same order of gene loci). We suggest that such genomic changes may provide the physical basis for the diploid-like meiotic behavior of polyploid wheat.     

INDUCTION OF CELL PROLIFERATION IN THE MOUSE BLADDER BY 4-ETHYLSULPHONYL-NAPHTHALENE-1 -SULPHONAMIDE

The reaction of the bladder epithelium of mice, following stimulation with a carcinogen, 4-ethylsulphonylnaphthalene-1-sulphonamide (ENS), was studied. A wave of cell division was induced in the resting epithelium, diploid and tetraploid cells being the main dividing elements; some of the high ploidy surface cells also underwent division. The cell cycle time for the diploid and tetraploid cells appeared to be identical. There was considerable variation in the intensity and timing of the onset of cell division in the bladder epithelium of individual animals. ENS caused severe damage to the surface cells of the bladder epithelium as indicated by increased lysosomes and the formation of large vacuoles.     

Nucleoli and ploidy in Potorous cells (PTK2) in vitro

Most cells of the male PTK₂ cell line contain one nucleolus, and they are diploid. However, a proportion of cells have more than one nucleolus. Cells with two and three nucleoli were isolated and cloned into viable populations. Greater than 90% of the cells in these clonal populations maintained the abnormal nucleolar number of the originally isolated cell. Karyotype analysis of cells with two and three nucleoli demonstrated that the cells were respectively tetraploid and hexaploid. It was concluded that in PTK₂ cells, nucleolarity is a good index of ploidy even if the ploidy level is abnormal. Furthermore, long term monitoring of the tetraploid cells demonstrated virtually no tendency towards reversion to the diploid condition as suggested by other studies in Potorous.