Spontaneous and Divergent Hexaploid Triticales Derived from Common Wheat × Rye by Complete Elimination of D-Genome Chromosomes

Background

Hexaploid triticale could be either synthesized by crossing tetraploid wheat with rye, or developed by crossing hexaploid wheat with a hexaploid triticale or an octoploid triticale.

Methodology/Principal Findings

Here two hexaploid triticales with great morphologic divergence derived from common wheat cultivar M8003 (Triticum aestivum L.) × Austrian rye (Secale cereale L.) were reported, exhibiting high resistance for powdery mildew and stripe rust and potential for wheat improvement. Sequential fluorescence in situ hybridization (FISH) and genomic in situ hybridization (GISH) karyotyping revealed that D-genome chromosomes were completely eliminated and the whole A-genome, B-genome and R-genome chromosomes were retained in both lines. Furthermore, plentiful alterations of wheat chromosomes including 5A and 7B were detected in both triticales and additionally altered 5B, 7A chromosome and restructured chromosome 2A was assayed in N9116H and N9116M, respectively, even after selfing for several decades. Besides, meiotic asynchrony was displayed and a variety of storage protein variations were assayed, especially in the HMW/LMW-GS region and secalins region in both triticales.

Conclusion

This study confirms that whole D-genome chromosomes could be preferentially eliminated in the hybrid of common wheat × rye, “genome shock” was accompanying the allopolyploidization of nascent triticales, and great morphologic divergence might result from the genetic variations. Moreover, new hexaploid triticale lines contributing potential resistance resources for wheat improvement were produced.     

New Variation Identified by SSR in a Wheat Variety Derived from Synthetic Hexaploid Wheat ( Triticum durum× Aegilops tauschii)

Hybridization and polyploidization are important ways for wheat to evolve and to genetically differentiate. Ninety two simple sequence repeat (SSR) molecular markers, which distributed in A, B, and D genomes , were used to perform genetic comparison between Chuan-W5436 (CW5436), a new wheat variety, and its parents, synthetic hexaploid wheat Syn786 (♀ ) and common wheat Mianyang 26 (My26) (♂). The results indicated that alleles were not genetically transmitted from parents (Syn786 (♀) crossed (My26) (♂) ) to the progeny CW5436 as Mendelian proportions . A new variation on a SSR molecular marker loci with novel additive bands was observed in CW5436 but not found in its parents. It suggested that artificial selective stress was an important factor to promote the frequency of significant deviations of the expected allele, resulting in microsatellite sequences of the progeny changed . The affect of the genetic differentiation of SSR molecular marker loci that occurred in wheat crosses and gene transfer on the genetic evolu1tion of wheat was discussed.     

Does Seed Priming Induce Changes in the Levels of Some Endogenous Plant Hormones in Hexaploid Wheat Plants Under Salt Stress？

In order to assess whether salt tolerance could be Improved In spring wheat （Triticum aestivum L.）, the present study was performed by soaking the seeds of two cultlvars, namely MH-97 （salt sensitive） and Inqlab-91 （salt tolerant）, for 12 h In distilled water or 100 mol/m^3 CaCl2, KCI, or NaCI. Primed seeds from each treatment group and non-primed seeds were sown In a field In which NaCI salinity of 15 dS/m was developed. Priming of seeds with CaCl2, followed by priming with KCI and NaCI, was found to be effective In alleviating the adverse effects of salt stress on both wheat cultivars In terms of shoot fresh and dry weights and grain yield. Priming with CaCl2 alleviated the adverse effects of salt stress on hormonal balance In plants of both cultlvars. In MH-97 plants, CaCl2 pretreatment considerably reduced leaf absclslc acid （ABA） concentrations and Increased leaf free salicylic acid （SA） concentrations under both saline and non-saline conditions. In contrast, In the Inqlab-91 plant, CaCl2 Increased free Indoleacetic acid （IAA） and indolebutyrlc acid （IBA） content. However, priming of seeds with CaCl2 did not alter free polyamlne levels in either cultlvar, although spermldlne levels were considerably lower In plants raised from seeds treated with CaCl2 for both cultlvars under saline conditions. Priming with KCI Increased growth In Inqlab-91 plants, but not In MH-97 plants, under saline conditions. The salinity Induced reducUon In auxins （IAA and IBA） was alleviated by NaCI priming In both cultlvars under saline conditions. However, NaCI Increased leaf free ABA content and lowered leaf SA and putresclne levels In Inqlab-91 plants under saline conditions. In conclusion, although all three priming agents （I.e. CaCl2, KCI, and NaCI） were effective In alleviating the adverse effects of salt stress on wheat plants, their effects on altering the levels of different plant hormones were different In the two cuItlvars.     

Short- and Long-eared High-yielding Hexaploid Wheat Cultivars: which has Unexpressed Potential for Higher Yield?

This investigation was designed to assess unexpressed potentialfor high yield and evaluate the sink strength of two high-yieldingwheat cultivars: a tall plant with long ears (LE), and a semi-dwarfwith short ears (SE). This was done by (1) removing one-thirdof the ear's distal end (decapitation), thereby inducing thedevelopment of additional florets, which usually do not form,on the untouched portion of the ear, and (2) by increasing thecompetition between the ears and the vegetative tissue's viathe application of gibberellic acid (GA). The number of grainsincreased on the untouched basal spikelets of the decapitatedears in both cultivars. The LE type fully recovered (100%) thenumber and mass of grains on the untouched portion of the decapitatedear. The decapitated SE type recovered 91% of the grain numberbut only 80% of individual grain mass. Thus, the total yield(number x mass) achieved by the untouched portion of the decapitatedear was 100% in the LE type and 80% in the SE type. Gibberelicacid treatment increased culm length in the tall LE plants butthis did not affect grain number of mass. Conversely, GA hadno significant effect on culm length of the semi-dwarf SE typebut significantly decreased their total grain yield. This effectwas due to a reduction in grain number by 64% of the control,rather than decreasing grain mass. Mean grain mass was not affectedby GA in either cultivar. A gradual increase in insoluble sugarconcentration (starch and fructan) in the ear peduncle duringthe first month after anthesis, followed by a sharp decreaselater, was found in the control and treated plants of both cultivars.In general, the concentrations of both soluble and insolublesugars declined as grain filling progressed, except for a noticeableincrease in total soluble sugars in the peduncles of the decapitatedears of the LE type. The results of this study suggest thatof the two high-yielding wheat cultivars that usually give identicalyields, the one with long multispikelet ears (LE) and lightergrains has significantly greater unexpressed potential for highyield than the cultivar with shorter ears (SE) and heavier grains.Copyright1995, 1999 Academic Press Ear, gibberellic acid, GA, grain number, grain mass, grain yield, sink strength, spikelet, Triticum aestivum, wheat     

Wheat protein inhibitors of α-amylase

The location in the seed, molecular properties and biological role of protein α-amylase inhibitors from wheat are discussed. Inhibition specificity of albumin inhibitors and structural features essential for interaction with inhibited amylases are also examined. The possible significance of these naturally occurring inhibitors in relation to their presence in foods in active form is described. Finally, genetic aspects of the albumin inhibitor production and the possibility of improving nutritional value and insect re     

RFLP Variations of Common Wheat Doubled Haploid Progenies from Wheat×Maize Crosses

Wheat ( Triticum aestivum L. ) and maize ( Zea mays L. ) crosses (the chromosome elimination system) can be used to produce frequently a large number of doubled haploid (DH) wheat lines by embryo rescue and doubling treatment. The resulting DH lines are genetically homogeneous. Significant RFLP variations were detected in common wheat DH progenies from wheat and maize crosses by using wheat rDNA clone pta71 and two maize DNA clones (MR13 and MRSO) homologous to wheat genome as probes. The results revealed that the copy number and restriction fragment length of rDNA in some wheat DH progenies was changed, and also that deletion was detected in several DH plants when probed with MR13 and MR5O. In particular, the RFLP pattern of DH line No. 18 was greatly changed using MR13 as a probe. In this line, three new bands, 40.0 kb, 2.5 kb and 2.0 kb emerged while a 4.3 kb intense band from the parental common wheat genome disappeared. This change may be related to a quite large DNA rearrangement within the wheat genomic DNA or an insertion by alien maize DNA fragment.     

Intestinal Absorbability of Wheat Allergens,Subunits of a Wheat α-Amylase Inhibitor,Expressed by Bacteria

Wheat CM2, CM3 and CM16 proteins are known as subunits of the tetrameric α-amylase inhibitor as well as major allergens to baker’s asthma. The purpose of this study is to produce these CM proteins by bacteria in a quantity adequate for studying thepenetration characteristics of the CM proteins through intestinal mcosa in rats and Caco-2 cells. cDNAs encoding the mature proteins were expressed in Escherichia coli and purified by an Ni²⁺-chelating column. The recombinant proteins were radioiodinated and admministrered orally to rats or applied to the apical site of the Caco-2 cell monolayer. The radioactivity in the trichloroacetic acid-insoluble fraction, which was mainly composed of peptides with molecular mass less than that of the intact CM proteins, in the serum and the basolateral medium was highest in recombinant CM3. Accordingly, the intestinal absorption of these three proteins in the form present in wheat should be evaluated.     

Chromosomal Behavior during Meiosis in the Progeny of Triticum timopheevii × Hexaploid Wild Oat

The meiotic behavior of pollen mother cells (PMCs) of the F₂ and F₃ progeny from Triticum timopheevii × hexaploid wild oat was investigated by cytological analysis and sequential C-banding-genomic in situ hybridization (GISH) in the present study. A cytological analysis showed that the chromosome numbers of the F₂ and F₃ progeny ranged from 28 to 41. A large number of univalents, lagging chromosomes, chromosome bridges and micronuclei were found at the metaphase I, anaphase I, anaphase II and tetrad stages in the F₂ and F₃ progeny. The averages of univalents were 3.50 and 2.73 per cell, and those of lagging chromosomes were 3.37 and 1.87 in the F₂ and F₃ progeny, respectively. The PMC meiotic indices of the F₂ and F₃ progeny were 12.22 and 20.34, respectively, indicating considerable genetic instability. A sequential C-banding-GISH analysis revealed that some chromosomes and fragments from the hexaploid wild oat were detected at metaphase I and anaphase I in the progeny, showing that the progeny were of true intergeneric hybrid origin. The alien chromosomes 6A, 7A, 3C and 2D were lost during transmission from F₂ to F₃. In addition, partial T. timopheevii chromosomes appeared in the form of univalents or lagging chromosomes, which might result from large genome differences between the parents, and the wild oat chromosome introgression interfered with the wheat homologues’ normally pairing.     

Inhibition of α-Amylase Acting in Hexaploid Triticale Lines by Exogenous Abscisic Acid

Hexaploid triticale introgressive lines developed after recombination of A-genome with A^m-genome of diploid wheat (Triticum monococcum) were analysed in respect of grains responsiveness to exogenous ABA treatment. This was assessed by in vivo bioassay as grain germination indices, and by α-amylase assay as quantity of synthesised α-amylase measured with the technique of radial diffusion in agarose gel. The results showed an important diminishing of seedling length caused by ABA (variable in different lines) as well as genotype dependant variability of α-amylase synthesis inhibition. The differences of ABA responsiveness were seen both in whole grains and in embryoless half-grains as a direct reaction of the aleurone layer. Variation of grain sensitivity to ABA treatment compared with two sprouting resistance indices showed a significant correlation with Falling Number values in grains, but not with a dormant grains germination in spikes. This is an evidence that in triticale precocious starch decompose in unripened and ungerminated grains is dependent on genotype ABA-responsiveness of the aleurone layer. This revised version was published online in July 2006 with corrections to the Cover Date.     

Morphological Variability of Wheat Powdery Mildew in the Context of Its Parasitic Adaptation to Wheat–Aegilops Lines with Different Resistance

The interaction between the pathogen and wheat–Aegilops lines with different resistance as well as their parental forms in the course of powdery mildew infection was studied using scanning electron microscopy. The course of infection in the line 51/99i and its parental form, the Rodina variety, proved to be similar. The plants of both genotypes featured pronounced adhesion of the primary infection structures to the surface of plant epidermal cells and the formation of large, well-developed colonies of the fungus, which was evidence for parasite–host compatibility. The development of powdery mildew on the line 135/99i was similar to that on the parental form Aegilops speltoides K-389. The pathogen–host interaction was characterized by a longer incubation period. Sparse fungal colonies were formed from mycelial hyphae with multiple hyphal lobes, and their adhesion to the surface of the epidermal cells was disturbed in most cases. Such a pattern of pathogen development indicated that the host plants had some resistance factors operating mainly at the level of pathogen penetration. The types of resistance in lines 95/99i and 56/99i were not characteristic of the parental form Ae. speltoides K-389, but they were described for Ae. speltoides samples from other natural ranges (Ryabchenko et al., 2002). This fact suggests that the immune potential of Ae. speltoides as a species is polygenic, and its elements can be transmitted to hybrids irrespective of concrete plants used as the donors of resistance.     

The Effects of Water Stress on Photosystem Ⅱ in Wheat

The fluorescence yield at room temperature, the capacity of excitation energy distribution between photosystem Ⅰ and Ⅱ by Mg2+, variable fluorescence yield, variable fluorescence quenching rate and fluorescence complementary area were decreased under water stress. These indicated that photosystem Il was impaired. The inhibited variable fluorescence yield could be partly recovered by the addition of artificial electron donor DPC. Therefore, water stress inhibited not only the oxidizing site of photosystem Ⅱ but also impaired partly the reaction center of photosystem Ⅱ.     

Extracellular Production of l-Lysine α-Oxidase in Wheat Bran Culture of a Strain of Trichoderma viride

A mold strain Y244-2 capable of producing l-lysine α-oxidase, a new enzyme catalyzing the α-oxidative deamination of l-lysine, was identified as Trichoderma viride. Among strains belonging to the genus Trichoderma tested, only Trichoderma viride Y244-2 produced the enzyme in wheat bran culture. The maximum enzyme production by the mold grown on wheat bran was observed after 10 and 14 days incubation with and without NaN0₃, respectively. Addition of NaN0₃, NH₄N0₃, adenine, purine nucleosides, l-histidine, glycine or l-glutamine to wheat bran stimulated the production of the enzyme. In the liquid culture, the enzyme was produced extracellulary under the aerobic conditions, although the production was much lower than that in the wheat bran culture.     

Effect of “External” Superoxide Anion on Apoptosis in Coleoptiles of Wheat Seedlings

A derivative of phthalic acid, dibutylphthalate (DBP), which has gametocidal effect at the concentration of approximately 10(-4) M, increased apoptosis in coleoptiles of wheat seedlings. This was associated with activation of chromatin margination and generation of mitochondria-containing vesicles. At the same concentration, DBP activated the release by the coleoptiles of superoxide anion into the environment. Lower (10(-5) M) and higher (10(-3) M) concentrations of DBP virtually had no effect on either process. A probable mechanism of effect of the "external" superoxide anion on apoptosis within the plant cell is discussed.     

Light-Induced Biogenesis of Chlorophyll–Protein Complexes in Developing Wheat Thylakoids

It is shown that the apoproteins of core complexes (CC) I and II, the - and -subunits of CF₁ ATP-synthase complexes, are present in seedlings grown under intermittent light (IML). The levels of light-harvesting complex (LHC) apoproteins in the 30- to 18-kD region increase rapidly upon exposure to continuous light (CL). The newly synthesized LHC apoproteins appear to be present predominantly in monomeric forms that later assemble into higher-order oligomeric forms. During the early stages of greening of wheat seedlings, polypeptides in the 20.5-19 and 17.5-15.5 kD regions (so-called early light-induced proteins (ELIP)) are observed, but they disappear fully after 6 h. As greening proceeds, the 727-nm band in low-temperature fluorescence spectra (77 K) gradually shifts to longer wavelength (740-742 nm), which clearly demonstrates the light-driven biogenesis of LHC I and its assembly with CC I.     

Inheritance and Sequence Homology Analysis of the Maize DNA Introgressed into the Wheat Doubled Haploid Plant Through Wheat×Maize Cross

A maize (Zea mays L.) genome-specific repeated DNA sequence (clone MR64) has been transferred into one DH line of wheat through wheat (Triticum persicum Vav. ex Zhuk.) and maize cross. In the present study by RFLP analysis the authors proved that this DNA sequence could stably transmit into DH3 plants, the next generation derived from DH2 self-crossing. A similarity search in all DNA databases using BLASTN program showed that the DNA sequence of MR64 had as high as 93% identity to PREM-2 and 79% to Opie-2 in nucleotides. Both PREM-2 and Opie-2 are known as retrotransposons in maize genome, suggesting that MR64 likely is the partial sequence of a maize retrotransposon. Therefore, the results indicate that some retrotransposon might involve the DNA introgression from maize to wheat genome through wide fertilization. Stable inheritance of this maize genome-specific retrotransposon-like DNA in the wheat genome opens up the possibility of using retrotransposon as a new tool for gene tagging, function analysis, and insertional mutagenesis in wheat genome.     

In Vitro Culture of Wheat and Genetic Transformation — Retrospect and Prospect

This review focuses on the improvement of wheat (Triticum aestivum L.) via tissue and cell culture and its use in gene transfer techniques. Success of the latter critically depends on the ability to regenerate plants from cells or tissues cultured in vitro. Hence, we have devoted attention to the attempts made so far in obtaining regenerants from diverse explants. Although it is known that immature embryos are the best source for initiating morphogenic cultures, basic information related to the process of differentiation can also be gained by studying less responding tissues. The opportunity provided by anther and microspore culture in wheat improvement and the progress made is also presented.

To enhance tissue culture responses, identification of chromosomes, gene loci, and genes is of cardinal importance. We have also surveyed the progress made in this regard by conventional but incisive plant-breeding techniques. Gene rearrangements in tissue culture leading to the appearance of somaclonal or gametoclonal variation are of interest in selection of useful cell lines. The last part of the review is devoted to work done on transient gene expression and transformation with emphasis on recent developments.