Adult plant and seedling resistance to powdery mildew in a Triticum aestivum × Triticum militinae hybrid line

In the progeny of a cross between the common wheat cultivar Tähti and Triticum militinae, a member of the timopheevii group of tetraploid wheats, several hybrid lines were selected that are characterized by improved seedling and adult plant resistance (APR) to powdery mildew. An F₂ single-seed descendant mapping population segregating for seedling resistance and APR to powdery mildew was analysed for the identification of quantitative trait loci (QTL). The main QTL responsible for APR was detected on the long arm of chromosome 4A tightly linked to the Xgwm160 locus on a T. militinae translocation explaining up to 54% of phenotypic variance. The same translocation influenced seedling resistance to powdery mildew upon inoculation of plants with a synthetic population of Blumeria graminis DC. f. sp. tritici, and explained 28–33% of the phenotypic variance.     

Synthesis and evaluation of Triticum durum — T. monococcum amphiploids

Summary Nine Triticum durum — T. monococcum amphiploids (AABBA^mA^m) were synthesized by chromosome doubling of sterile triploid F₁ hybrids involving nine T. durum (AABB) cultivars and a T. monococcum (A^mA^m) line. The triploid F₁ hybrids had a range of 4–7 bivalents and 7–13 univalents per PMC. The synthetic amphiploids, however, showed a high degree of preferential pairing of chromosomes of the A genomes of diploid and tetraploid wheats. The amphiploids were meiotically stable and fully fertile. Superiority of four amphiploids for tiller number per plant, 100-grain weight, protein content and resistance to Karnal bunt demonstrated that these could either be commercially exploited as such after overcoming certain inherent defects or used to introgress desirable genes into durum and bread wheat cultivars. Methods for improvement of these amphiploids are discussed.     

α-amylase inhibitors in Triticum aestivum: Purification and physical-chemical properties

Two α-amylase inhibitors in aqueous extracts of wheat flour have been resolved by DEAE-Sephadex chromatography. α-Amylase inhibitor I, the major inhibitor, was homogeneous by disc gel electrophoresis. It had a MW of 20 000 daltons and an isoelectric point of 6·7. α-Amylase inhibitor II had two minor contaminants when analysed by electrophoresis. These inhibitors were classified as typical wheat albumin proteins. A third α-amylase inhibitor was discovered when it was observed that an albumin protein which is found only in Triticum aestivum varieties of wheat could also inhibit pancreatic α-amylase. All three of these inhibitors could be distinguished by their characteristic electrophoretic mobilities.     

Development and QTL assessment of Triticum aestivum–Aegilops tauschii introgression lines

A set of 84 bread wheat lines, each containing a single homozygous introgression of the Aegilops tauschii genome was produced in the ‘Chinese Spring’ background via backcrossing of the D-genome chromosome substitution lines ‘Chinese Spring’/Sears’s ‘Synthetic 6x’ with the recurrent parent and subsequent selfing. The development of the lines was accompanied by microsatellite marker assisted selection. With the exception of three telomeric regions at chromosomes 1DL, 4DL and 7DS, and a region of less than 24 cM on the chromosome arm 3DL, the genome of Ae. tauschii is fully represented in these lines. The newly developed lines were used for the discovery of morphological and agronomical quantitative trait loci (QTLs) from the wild species. Fifty-two introgression lines were grown in the field and evaluated for six traits including flowering time, plant height, ear length, spikelet number, fertility and grain weight per ear. Seventeen significant QTLs were detected, Ae. tauschii contributed favourable alleles at nine loci influencing five traits. The whole set of 84 homozygous lines provides a tool for further testing the effects and stability of the detected QTLs and for the evaluation of new traits.     

Agronomic Characteristics and Cytogenetic Observation of the Hybrid F1 from Triticum aestivum and Aegilops triuncialis

In order to efficiently introduce the genes of Aegilops triuncialisL. for resistance to powdery mildew into Triticum aestivum L., it is of importance to understand the genetic mechanism of their F 1 hybrid. It was shown that the bivalent frequency was higher than that of the theoretical value. It resulted from the combination of the wheat inhibitors of 5B Ph gene which located respectively on C and U genome of Aegilops triuncialis L. The results of chromosome in situ hybridization with the C genome-specific repetitive sequence, pAeca212, as the probe further indicated that some chromosomes of the C genome of Ae. caudata L. paired with the chromosomes of the other genomes.     

Effect of 2,4-D on Seedling Physiology and Cytogenetical Studies in Triticum aestivum and Phalaris minor (Gramineae)

Effects of 2, 4 -D on seedling growth and chromosomal abnormalities were studied in Triticum aestivum and Phalaris minor. Seeds were soaked at different concentrations of 2,4 -D （0.01%, 0.1%, 1.0% ） for 4, 8, 12 and 16 hours. 2,4-D suppressed the germination more severely in P. minor than in T. aestivum. Shoot and root length was retarded with the increase of concentration and time of treatment in both species. Generally radical was more negatively affected than coleoptile and emergence of radical was not observed at 1.0% concentration at 8, 12, and 16 hours of treatment in T. aestivum while in P. minor there was a total lack of radical emergence at 1.0% concentration for all durations of treatment. Stiff and curled roots and undifferentiated callus like scutellar tissues were observed in T. aestivum, while in P. minor the coleoptile obtained was lean, pale green in colour and was lying flat on filter paper. Mitotic index decreased, while chromosomal abnormalities, bridges and laggards were increased with the increase of concentration and soaking time however, laggards were not observed in T. aestivum. Clumping and chain formation of chromosomes at metaphase was also noticed in P. minor.     

Effect of 2,4-D on Seedling Physiology and Cytogenetical Studies in Triticum aextivum and Phalaris minor(Gramineae)

Effects of 2, 4 -D on seedling growth and chromosomal abnormalities were studied in Triticum aestivum and Phalaris minor. Seeds were soaked at different concentrations of 2, 4 -D (0.01%, 0.1%, 1.0%) for 4, 8, 12 and 16 hours. 2, 4 -D suppressed the germination more severely in P. minor than in T. aestivum. Shoot and root length was retarded with the increase of concentration and time of treatment in both species. Generally radical was more negatively affected than coleoptile and emergence of radical was not observed at 1.0% concentration at 8, 12, and 16 hours of treatment in T. aestivum while in P. minor there was a total lack of radical emergence at 1.0% concentration for all durations of treatment. Stiff and curled roots and undifferentiated callus like scutellar tissues were observed in T. aestivum, while in P. minor the coleoptile obtained was lean, pale green in colour and was lying flat on filter paper. Mitotic index decreased, while chromosomal abnormalities, bridges and laggards were increased with the increase of concentration and soaking time however, laggards were not observed in T. aestivum. Clumping and chain formation of chromosomes at metaphase was also noticed in P. minor.     

Identification of SNPs and development of allele-specific PCR markers for γ-gliadin alleles in Triticum aestivum

The coding regions of 28 entries of hexaploid wheat gamma-gliadin genes, gene fragments or pseudogenes in GenBank were used for nucleotide alignment. These sequences could be divided into nine subgroups based on nucleotide variation. The chromosomal locations of five of the seven unassigned subgroups were identified through subgroup-specific polymerase chain reactions (PCR) using Chinese Spring group-1 nulli-tetrasomic lines. Multiple single nucleotide polymorphisms (SNPs) and small insertions/deletions were identified in each subgroup. With further mining from wheat expressed sequence tag databases and targeted DNA sequencing, two SNPs were confirmed and one SNP was discovered for genes at the Gli-A1, Gli-B1 and Gli-D1 loci. A modified allele-specific PCR procedure for assaying SNPs was used to generate dominant DNA markers based on these three SNPs. For each of these three SNPs, two allele-specific primer sets were used to test Chinese Spring and 52 commercial Australian wheat varieties representing a range of low-molecular-weight (LMW) alleles. PCR results indicated that all were positive with one of the primer sets and negative with the other, with the exception of three varieties containing the 1BL/1RS chromosomal translocation that were negative for both. Furthermore, markers GliA1.1, GliB1.1 and GliD1.1 were found to be correlated with Glu-A3 a, b or c, Glu-B3 b, c, d or e and Glu-D3 a, b or e LMW glutenin alleles, respectively. Markers GliA1.2, GliB1.2 and GliD1.2 were found to be correlated with the Glu-A3 d or e, Glu-B3 a, g or h and Glu-D3 c alleles, respectively. These results indicated that the gamma-gliadin SNP markers could be used for detecting linked LMW glutenin subunit alleles that are important in determining the quality attributes of wheat products.     

Effects of Interaction Between Cadmium and Plumbum on Phytochelatins and Glutathione Production in Wheat （Triticum aestivum L.）

Phytochelatins (PCs) may function as a potential biomarker for metal toxicity. However, less attention has been paid to the effects of metal interactions on the production of PCs and glutathione (GSH), the most prominent cellular thiol. In the present study, the effects of interactions between cadmium (Cd) and plumbum (Pb) on the production of PCs and GSH were monitored over a period of 14 d in wheat (Triticum aestivum L.) tissues. The results showed that combination of Cd and Pb led to synergistic growth inhibition in wheat. Exposure to Cd or Pb increased levels of PCs in a concentration-, tissue-, and time-dependent manner. Cadmium was more effective that Pb in increasing PCs production. Compared with the effects of Cd or Pb alone on the production of PCs, the combination of Cd and Pb acted synergistically, resulting in an enhanced production of PCs. Cadmium also stimulated GSH production in a concentration-, tissue-, and time-dependent manner. However, Pb had no obvious effects on GSH levels. The combination of Pb and Cd antagonized GSH production over the course of the growth period. The results of the present study suggest that metal interactions should be considered in the application of PCs and GSH as potential biomarkers for the evaluation of metal toxicity.     

Induzione Sperimentale Della Maschio-Sterilità in Triticum

Abstract

Experimental induction of male sterility in Triticum. — Prolonged artificial illumination (12-24 h. every 24 hours) and high temperature (20-25[ddot]C.) induce in « Denti de cani » plants (Meletti, 1955) the transformation of the stamens, which tend to take morphological characteristics of female organs (Meletti, 1960). The prolonged illumination induces, also at temperatures inferior to 20[ddot]C., a remarkable increase of the percentage of « Denti de cani » flowers which have reduced anthers without pollen grains.     

Development of Triticum aestivume——Leymus mollis Translocation Lines and Identification of Resistance to Stripe Rust

<正>Wheat stripe rust,caused by Puccinia striiformis f.sp.tritici,is one of the most widely distributed and destructive fungal diseases worldwide.Since 1995,most Chinese wheat cultivars have lost their stripe rust resistance due to the subsequent emergence of the new races CYR30,CYR31,CYR32,and CYR33(Han et al.,2010).Therefore,it is necessary to seek effective resistance genes and develop new resistance germplasm for wheat resistance breeding.     

Zinc and iron concentration QTL mapped in a Triticum spelta × T. aestivum cross

Key message

Ten QTL underlying the accumulation of Zn and Fe in the grain were mapped in a set of RILs bred from the cross Triticum spelta × T. aestivum . Five of these loci (two for Zn and three for Fe) were consistently detected across seven environments.

Abstract

The genetic basis of accumulation in the grain of Zn and Fe was investigated via QTL mapping in a recombinant inbred line (RIL) population bred from a cross between Triticum spelta and T. aestivum. The concentration of the two elements was measured from grain produced in three locations over two consecutive cropping seasons and from a greenhouse trial. The range in Zn and Fe concentration across the RILs was, respectively, 18.8–73.5 and 25.3–59.5 ppm, and the concentrations of the two elements were positively correlated with one another (rp =+0.79). Ten QTL (five each for Zn and Fe accumulation) were detected, mapping to seven different chromosomes. The chromosome 2B and 6A grain Zn QTL were consistently expressed across environments. The proportion of the phenotype explained (PVE) by QZn.bhu-2B was >16 %, and the locus was closely linked to the SNP marker 1101425|F|0, while QZn.bhu-6A (7.0 % PVE) was closely linked to DArT marker 3026160|F|0. Of the five Fe QTL detected, three, all mapping to chromosome 1A were detected in all seven environments. The PVE for QFe.bhu-3B was 26.0 %.     

Quantitative Trait Loci Mapping for ChlorophyⅡ Fluorescence and Associated Traits in Wheat （ Triticum aestivum）

Parameters of chlorophyll fluorescence kinetics （PCFKs） under drought stress condition are generally used to characterize instincts for dehydration tolerance in wheat （Triticum aestivum L.）. Therefore, it is important to map quantitative trait loci （QTLs） for PCFKs in wheat genetic improvement for drought tolerance. A doubled haploid （DH） population with 150 lines, derived from a cross between two common wheat varieties, Hanxuan 10 and Lumai 14, was used to analyze the correlation between PCFKs and chlorophyll content （CHIC） and to map QTLs at the grainfilling stage under conditions of both rainfed （drought stress, DS） and well-watered （WW）, respectively. QTLs for these traits were detected by QTLMapper version 1.0 based on the composite Interval mapping method of the mixed-linear model. The results showed a very significant positive correlation between Fv, Fm, Fv/Fm and Fv/Fo. The correlation coefficients were generally higher under WW than under DS. Also, there was a significant or a highly significant positive correlation between Fv, Fm, Fv/Fm, Fv/Fo and CHIC. The correlation coefficients were higher in the DS group than the WW group. A total of 14 additive QTLs （nine QTLs detected under DS and five QTLs under WW） and 25 pairs of eplstatlc QTLs （15 pairs detected under DS and 10 pairs under WW） for PCFKs were mapped on chromosomes 6A, 7A, 1B, 3B, 4D and 7D. The contributions of additive QTLs for PCFKs to phenotype variation were from 8.40% to 72.72%. Four additive QTLs （two QTLs detected under DS and WW apiece） controlling Chic were mapped on chromosomes 1A, 5A and 7A. The contributions of these QTLs for ChIC to phenotype variation were from 7.27% to 11.68%. Several QTL clusters were detected on chromosomes 1B, 7A and 7D, but no shared chromosomal regions for them were identified under different water regimes, indicating that these QTLs performed different expression patterns under rainfed and well-watered conditions.     

Agronomic Trait and Protein Component of F2 Hybrid Originated from Intergeneric Somatic Hybridization Between Triticum aestivumand Agropyron elongatum

Protoplasts derived from common wheat ( Triticum aestivum L． cv. Jinan 177) were fused with UV-treated protoplasts of Agropyron elongatum (Host) Nevski by PEG method, and fertile asymmetric somatic hybrid plants resembling wheat morphology were obtained. The F2 hybrid plants could be divided into 3 types according to their morphology. Type Ⅰ hybrids had high and loosely standing stalks with big spikes and grains. TypeⅡ hybrids were dwarf and compact in shape with high tillering ability and smaller spikes. Type Ⅲ hybrids were similar to typeⅠas a whole but had more compact and erect spikes. All the F2 hybrid lines were superior to wheat in seed protein content, although some difference existed between themselves. Protein analysis of immature embryos and flag leaves from hybrids by two-dimensional electrophoresis showed that they possessed characteristic proteins of both parents and some new proteins. There existed also some different kinds of proteins in different lines.     

Isolation and Properties of an α-Amylase Inhibitor (0.53) from Wheat (Triticum aestivum)

A droplet gel-entrapping method used for enzyme immobilization was improved to simplify the procedure and to increase the enzyme stability. This immobilization technique is suitable for coupled enzyme reactions requiring cofactors. Leucine dehydrogenase (LeuDH) and formate dehydrogenase (FDH) were freeze-dried with bovine serum albumin, dextrin and stabilizers. The freeze-dried enzyme powder was suspended in a methylcellosolve solution containing polyethyleneglycol(#4000)diacrylate, N,N′-methylenebisacrylamide and 2-hydroxyethylacrylate, and the suspension was gelled with initiators. The gel was cut up and the pieces were washed in a buffer to remove the methylcellosolve and the dextrin inside. The maximum conversion ratio for a LeuDH-FDH gel column was determined to be 99.8% by means of the recycling reaction. On longterm operation at 30 °C for leucine production, the initial conversion ratio (7.2%) gradually decreased to 6.6% over the first 10 days. However, the conversion ratio remained almost constant after the 10th day. The effects of flow rate, temperature, pH, and the concentrations of formate, α- ketoisocaproate, ammonium and NAD on the leucine productivity with the gel column were also investigated.     

Experimental and modelling studies of drought‐adaptive root architectural traits in wheat (Triticum aestivum L.)

Abstract

This paper presents an interdisciplinary approach to crop improvement that links physiology with plant breeding and simulation modelling to enhance the selection of high‐yielding, drought‐tolerant varieties. In a series of field experiments in Queensland, Australia, we found that the yield of CIMMYT wheat line SeriM82 ranged from 6% to 28% greater than the current cultivar Hartog. Physiological studies on the adaptive traits revealed that SeriM82 had a narrower root architecture and extracted more soil moisture, particularly deep in the profile. Results of a simulation analysis of these adaptive root traits with the cropping system model APSIM for a range of rain‐fed environments in southern Queensland indicated a mean relative yield benefit of 14.5% in water‐deficit seasons. Furthermore, each additional millimetre of water extracted during grain filling generated an extra 55 kg ha^?1 of grain yield. Further root studies of a large number of wheat genotypes revealed that wheat root architecture is closely linked to the angle of seminal roots at the seedling stage – a trait which is suitable for large‐scale and cost‐effective screening programmes. Overall, our results suggest that an interdisciplinary approach to crop improvement is likely to enhance the rate of yield improvement in rain‐fed crops.     

Breeding for the future: what are the potential impacts of future frost and heat events on sowing and flowering time requirements for Australian bread wheat (Triticum aestivium) varieties?

Extreme climate, especially temperature, can severely reduce wheat yield. As global warming has already begun to increase mean temperature and the occurrence of extreme temperatures, it has become urgent to accelerate the 5–20 year process of breeding for new wheat varieties, to adapt to future climate. We analyzed the patterns of frost and heat events across the Australian wheatbelt based on 50 years of historical records (1960–2009) for 2864 weather stations. Flowering dates of three contrasting‐maturity wheat varieties were simulated for a wide range of sowing dates in 22 locations for ‘current’ climate (1960–2009) and eight future scenarios (high and low CO₂ emission, dry and wet precipitation scenarios, in 2030 and 2050). The results highlighted the substantial spatial variability of frost and heat events across the Australian wheatbelt in current and future climates. As both ‘last frost’ and ‘first heat’ events would occur earlier in the season, the ‘target’ sowing and flowering windows (defined as risk less than 10% for frost (<0 °C) and less than 30% for heat (>35 °C) around flowering) would be shifted earlier by up to 2 and 1 month(s), respectively, in 2050. A short‐season variety would require a shift in target sowing window 2‐fold greater than long‐ and medium‐season varieties by 2050 (8 vs. 4 days on average across locations and scenarios, respectively), but would suffer a lesser decrease in the length of the vegetative period (4 vs. 7 days). Overall, warmer winters would shorten the wheat season by up to 6 weeks, especially during preflowering. This faster crop cycle is associated with a reduced time for resource acquisition, and potential yield loss. As far as favourable rain and modern equipment would allow, early sowing and longer season varieties (i.e. in current climate) would be the best strategies to adapt to future climates.     

Purification and characterization of a hydroxamic acid glucoside β-glucosidase from wheat (Triticum aestivum L.) seedlings

A beta-glucosidase (EC 3.2.1.21) with a high affinity for cyclic hydroxamic acid beta-D-glucosides was purified from 48-h-old wheat (Triticum aestivum L.) seedlings. The activity occurred transiently at a high level during the non-autotrophic stage of growth, and the nature of the transient occurrence was correlated with that of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside (DIMBOA-Glc). The glucosidase had maximum activity at an acidic pH (pH 5.5) and the purified enzyme showed a high affinity for DIMBOA-Glc, Vmax and Km being 4100 nkat/mg protein and 0.27 mM, respectively. It also hydrolyzed p-nitrophenol beta-glycosides, as well as flavone and isoflavone glucosides, but to a lesser extent. The results indicated that the primary natural substrate for the glucosidase is DIMBOA-Glc and that the enzyme is involved in defense against pathogens and herbivores in non-autotrophic wheat. The glucosidase was found to be present as oligomeric forms with a molecular mass of 260-300 kDa comprising 60- and 58-kDa monomers. The N-terminal 12-amino-acid sequences of the two monomers were identical (Gly-Thr-Pro-(Ser?)-Lys-Pro-Ala-Glu-Pro-Ile-Gly-Pro), and showed no similarity to those of other plant glucosidases. Polyacrylamide gel electrophoresis under nondenaturing condition indicated the existence of at least eight isozymes. Three cultivars of Triticum aestivum had the same zone of glucosidase activity on zymograms, but the activity zones of the Triticum species, T. aestivum L., T. spelta L. and T. turgidum L., had different mobilities.