Structural development of the shoot and root systems of two winter wheat cultivars, Triticum aestivum L.

The structural development of the stems and basal anchorageroots of Galahad and Hereward winter wheat cultivars (Triticumaestivum L.) were investigated and related to their mechanicalfunction. Stem and root morphology, anatomy and mechanical propertieswere examined from tillering (March) up to maturity (August),together with plant weight distribution. This allowed us tocalculate a ‘factor of safety’ against root andstem failure throughout development. As the plants grew taller the stem and the anchorage ‘coronalroots’ increased in bending strength countering the increasingmechanical demands. The bending strength, in turn, was correlatedwith the amount of lignified material around the stem and rootperimeter. Structural development ceased by ear emergence, whenthe plant was at its tallest, but because the ear weight continuedto rise the ‘self-weight’ moment pushing the plantover continued to increase. This meant that the ‘safetyfactors’ of both cultivars against both root and stemmechanical failure decreased throughout development. In bothcultivars the safety factors against root failure were lowerthan for stem failure, and Galahad had lower factors of safetythan Hereward. All these findings were consistent with resultsof field trials; failure tends to occur late in development,during grain filling, and is localized to the root system, whilstGalahad is more prone to lodging than Hereward. The pattern of mechanical development of winter wheat seemsto be one which would maximize its reproductive success, maintainingits structural integrity especially early in development whileinvesting in a minimum of structural material. Key words: Safety factor, anchorage, lodging, biomechan-ics, structural development     

Microsatellites confirm the authenticity of inter-varietal chromosome substitution lines of wheat (Triticum aestivum L.)

Ninety-five wheat microsatellite markers (WMS) were used to verify the authenticity of the set of Saratovskaya 29/Yanetzkis Probat inter-varietal wheat chromosome substitution lines developed using Saratovskaya 29 as the recipient variety. Polymorphic markers were available for all chromosome arms except 4DS, 6DS and 7DS. Each chromosome substitution line was tested by 2–8 microsatellite markers. The results demonstrate that most of the lines are correct. Out of 21 lines tested 17 showed the expected microsatellite pattern of the donor variety. Two entire chromosomes, 1B and 7A, and two chromosome arms, 3AL and 6DS, were not substituted with Yanetzkis Probat in their respective lines. Three microsatellite markers located in the distal regions of chromosome arms 4AL, 3BS and 5BL in the corresponding substitution lines did not reveal the expected microsatellite pattern of the recipient variety. The possible causes of the incorrect substitution line development and the appearance of incorrect distal microsatellite markers are discussed. The data confirm the idea that microsatellite markers provide ideal tools for testing the authenticity of genetic stocks of wheat. Received: 27 August 1999 / Accepted: 8 October 1999     

Relationship between grain yield, osmotic adjustment and benzoxazinone content in Triticum aestivum L. cultivars

Fifteen wheat genotypes were grown under water deficit to ascertain the role of osmotic adjustment (OA) and the concentration of benzoxazinones in sustaining grain yield. A positive correlation between osmotic adjustment capacity and yield was observed in wheat genotypes cultivated under field conditions. The weight gain of plants exposed to drought was in agreement with the OA values (R(2) = 0.93). However, when wheat plants were infested by cereal aphids, this correlation was not found. The benzoxazinones 2,4-dihydroxy-1,4-benzoxa-zin-3-one (DIBOA) and 2,4-dihydroxy-7-methoxy-1,4 benzoxazin-3-one (DIMBOA) are defensive secondary metabolites present in wheat and others cereals. The content of these compounds varied in wheat genotypes and increased with drought and aphid infestation. A positive correlation between weight gain of irrigated-infested plants and drought-infested plants and the contents of benzoxazinones was observed. These results suggest that plants with better OA capacity and high benzoxazinone content should have better field yields.     

Plant growth and cation composition of two cultivars of spring wheat (Triticum aestivum L.) differing in P uptake efficiency.

Phosphorus (P)-zinc (Zn) interactions were investigated in two wheat cultivars (Brookton versus Krichauff) differing in P uptake efficiency. The experiment was done in a growth chamber. Rock phosphate (RP) or CaHPO4 (CaP) were used as P sources, and ammonium nitrate (AN) or nitrate only (NO) were used as nitrogen sources. Two Zn levels were used, 0.22 mg x kg(-1) (LZ) and 2.2 mg ZnSO4.7H2O x kg(-1) (HZ), respectively. P availability significantly affected plant biomass production, but Zn supply had little effect. Plants fed ammonium nitrate had significantly lower concentrations of cations than those fed nitrate only. Cultivar Brookton (with higher P uptake efficiency) consistently had lower concentrations of cations than cv. Krichauff (with low P uptake efficiency) under limited P supply. The differences in concentrations of cations increased with the decrease in P availability, but were not affected by Zn supply. The ratio of potassium in roots to shoots of cultivar Brookton was always higher than in cultivar Krichauff. Based on these findings, it is postulated that the lower concentrations of cations in cultivar Brookton are related to root exudation of organic anions, and a conceptual model is established to describe the regulation of root exudation of organic anions and concentrations of cations.     

The antioxidant enzymes activity in leaves of inter-varietal substitution lines of wheat (Triticum aestivum L.) with different tolerance to soil water deficit

Understanding of the genetic basis of physiological properties, which are most relevant to water-deficit tolerance would be helpful for genomic-assisted improvement of bread wheat. A set of bread wheat inter-varietal single chromosome substitution lines (ISCSLs) of variety ‘Janetzkis Probat’ (JP) in the genetic background of ‘Saratovskaya’ 29 (S29) were used to reveal the critical chromosomes in wheat genome controlling tolerance to water deficit. The same lines were involved in the identification of chromosomes associated with the activity of antioxidant enzymes that are closely related to the detoxification of H₂O₂ [catalase (CAT), ascorbate peroxidase, dehydroascorbate reductase and glutathione reductase (GR)]. The recipient cultivar S29 was highly drought tolerant while the donor JP was sensitive. Using non-metric multidimensional scaling of yield components and indices of drought tolerance/susceptibility chromosomes 2A and 4D, substitution in the genetic background of S29 was found to lead to a critical decrease of water-deficit tolerance. The drop of tolerance correlated with a sharp decline of cumulative activity of the catalase and the enzymes of ascorbate–glutathione cycle in wheat leaves. Clear evidence was obtained for the involvement of genes present on the homoeologous group 2 chromosomes in the control of GR and CAT activity. Substitution of the chromosome 4D had a significant reducing impact on the CAT activity level.     

Effect of abscisic acid and cold acclimation on the cytoskeletal and phosphorylated proteins in different cultivars of Triticum aestivum L

In winter wheat, the tubulin and 60 kDa-phosphorylated proteins/actin ratio is considerably higher in the roots than in the leaves. Differences in the content of the main cytoskeletal proteins were also found in the leaves of the different cultivars. It is suggested that the lower amount of the tubulin and 60 kDa-phosphorylated proteins and higher content of actin determine the greater tubulin cytoskeletal stability in the leaves and their higher frost resistance, as compared with the roots. Also, it is possible that the higher content of the tubulin and 60 kDa-phosphorylated proteins defines the lower microtubule (MT) stability in the leaves of the low frost resistant cultivar than in the leaves of the more frost resistant ones. In the roots and leaves of the low frost resistant cultivar, the low stability of the numerous tubulin structures is apparently one reason for the abscisic acid (ABA)-induced reduction of the cytoskeletal and 60 kDa-phosphorylated proteins in the cells. The cold acclimation compensated the ABA effect in the roots of the very frost resistant cultivar in the most extent. This suggests the existence of the different pathways in the increased plant cell frost resistance through the action of ABA and low temperature.     

Formation of phenol compounds in various cultivars of wheat (Triticum aestivum L.)

The formation of soluble phenol compounds, including flavonols, was studied in winter (Erythrospermum, Lutescens 230, and R 47-28) and spring cultivars (Lada) of wheat (Triticum aestivum L.). The contents of soluble phenol compounds and flavonols were 1.8-2.6 and 0.5-1.3 mg/kg fresh weight, respectively. These results illustrate the similarity of phenol metabolism in leaves of winter and spring wheat cultivars. The exception was the cultivar R 47-28 that accumulated the maximum amount of phenol compounds (e.g., flavonols). In this cultivar the ratio of flavonols reached 50% of total soluble phenol content. In other cultivars, this parameter did not exceed 25-35%. The data indicate that the cultivar R 47-28 differs from other wheat cultivars in the metabolism of phenol compounds. The observed differences are probably related to genetic modifications of the cultivar R 47-28 during selection.     

Association mapping of kernel size and milling quality in wheat (Triticum aestivum L.) cultivars

Association mapping is a method for detection of gene effects based on linkage disequilibrium (LD) that complements QTL analysis in the development of tools for molecular plant breeding. In this study, association mapping was performed on a selected sample of 95 cultivars of soft winter wheat. Population structure was estimated on the basis of 36 unlinked simple-sequence repeat (SSR) markers. The extent of LD was estimated on chromosomes 2D and part of 5A, relative to the LD observed among unlinked markers. Consistent LD on chromosome 2D was <1 cM, whereas in the centromeric region of 5A, LD extended for approximately 5 cM. Association of 62 SSR loci on chromosomes 2D, 5A, and 5B with kernel morphology and milling quality was analyzed through a mixed-effects model, where subpopulation was considered as a random factor and the marker tested was considered as a fixed factor. Permutations were used to adjust the threshold of significance for multiple testing within chromosomes. In agreement with previous QTL analysis, significant markers for kernel size were detected on the three chromosomes tested, and alleles potentially useful for selection were identified. Our results demonstrated that association mapping could complement and enhance previous QTL information for marker-assisted selection.     

Analysis of gene-derived SNP marker polymorphism in US wheat (Triticum aestivum L.) cultivars

In this study, we developed 359 detection primers for single nucleotide polymorphisms (SNPs) previously discovered within intron sequences of wheat genes and used them to evaluate SNP polymorphism in common wheat (Triticum aestivum L.). These SNPs showed an average polymorphism information content (PIC) of 0.18 among 20 US elite wheat cultivars, representing seven market classes. This value increased to 0.23 when SNPs were pre-selected for polymorphisms among a diverse set of 13 hexaploid wheat accessions (excluding synthetic wheats) used in the wheat SNP discovery project (). PIC values for SNP markers in the D genome were approximately half of those for the A and B genomes. D genome SNPs also showed a larger PIC reduction relative to the other genomes (P < 0.05) when US cultivars were compared with the more diverse set of 13 wheat accessions. Within those accessions, D genome SNPs show a higher proportion of alleles with low minor allele frequencies (<0.125) than found in the other two genomes. These data suggest that the reduction of PIC values in the D genome was caused by differential loss of low frequency alleles during the population size bottleneck that accompanied the development of modern commercial cultivars. Additional SNP discovery efforts targeted to the D genome in elite wheat germplasm will likely be required to offset the lower diversity of this genome. With increasing SNP discovery projects and the development of high-throughput SNP assay technologies, it is anticipated that SNP markers will play an increasingly important role in wheat genetics and breeding applications. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

cis-Jasmone induces accumulation of defence compounds in wheat, Triticum aestivum

Liquid phase extraction (LPE) and vapor phase extraction (VPE) methodologies were used to evaluate the impact of the plant activator, cis-jasmone, on the secondary metabolism of wheat, Triticum aestivum, var. Solstice. LPE allowed the measurement of benzoxazinoids, i.e. 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA), 2-hydroxy-7-methoxy-1,4-benzoxazin-3-one (HMBOA) and 6-methoxy-benzoxazolin-2-one (MBOA), and phenolic acids such as trans-p-coumaric acid, syringic acid, p-hydroxybenzoic acid, vanillic acid and cis- and trans-ferulic acid. Using LPE, a significantly higher level of DIMBOA was found in aerial parts and roots of T. aestivum following treatment with cis-jasmone, when compared with untreated plants. Similar results were obtained for phenolic acids, such as trans-ferulic acid and vanillic acid in roots. Using VPE, it was possible to measure levels of 2-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (HBOA), benzoxazolin-2(3H)-one (BOA), ferulic acid, syringic acid and coumaric acid. The levels of HBOA in aerial parts and roots were significantly greater in cis-jasmone treated plants compared to untreated plants. cis-Jasmone is known to be a plant activator in terms of production of defence-related volatile semiochemicals that repel aphids and increase the foraging activity of aphid parasitoids. These results show, for the first time, that cis-jasmone also induces selective production of secondary metabolites that are capable of directly reducing development of pests, diseases and weeds.     

Agrobacterium-Mediated Transformation and Plant Regeneration of Triticum aestivum L.

The use of two Agrobacterium tumefaciens strains for transformation of Triticum aestivum L. cv. Vesna was studied. Immature embryos, isolated 15 d after pollination, were co-cultivated with the super-binary LBA4404/pTOK233 and the binary AGL1/pDM805 vectors. While the transient GUS-intron expression was high (69.9 and 80.0 %), the number of plants regenerated on selective media containing hygromycin or phosphinotricin did not exceed 0.4 and 0.13 %, respectively. Nevertheless, the regenerated plants were fertile and produced seeds. The T₀ plants, as well as the T₁ seedlings, displayed the activity in the β-glucuronidase histochemical assay and a positive signal in PCR analysis for the presence of uidA gene sequences in their genomes. The data suggest that the transformation of wheat cv. Vesna with both Agrobacterium strains is feasible. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hybridization between Triticum aestivum L. and Agropyron michnoi Roshev.

Summary Intergeneric hybrids between Triticum aestivum cv Chinese Spring (2n=6x=42, AABBDD) and Agropyron michnoi Roshev. (2n=4x=28, PPPP) were obtained by embryo culture. Their spike characteristics were similar to those of common wheat but, unlike their parents, they were long-awned. The average meiotic chromosome pairing at MI of F₁ hybrids was: 6.39 I +3.75 rodII+8.64 ringII+0.81 III+0.30 IV+0.04 V, the bivalent and multivalent formation of which was much higher than expected from the genomic formulae. It is especially worthwhile to note that the F₁ hybrids were self-fertile, self set being 0.15%, and seeds were easily obtained from the backcross of f₁ plants with hexaploid and tetraploid wheats; here the seed set was more than 20.0%. The polyploid taxa and the position of A. Michnoi in Agropyron are discussed.     

Genealogical analysis of resistance to fusarium head blight in Russian and Ukrainian cultivars of common wheat Triticum aestivum L.

The GRIS3.5 information analytical system of wheat genetic resources was used to trace the possible ways of the transmission of fusarium head blight resistance from ancestors to progenies in extended pedigrees of 149 Russian and Ukrainian cultivaris of winter common wheat. Analysis of variance was performed for the coefficient of parentage computed between the cultivars under study and the putative sources of resistance and revealed that groups of resistant and susceptible cultivars differed in the distribution of contributions of the sources. In the resistant group, significant results were obtained for the contributions of Odesskaya 16, Hostianum 237, and Frontana. Pedigree analysis showed that fusarium head blight resistance was most commonly transmitted from Hostianum 237 through Odesskaya 16 and its derivatives. The landrace Khar’kovskaya probably served as a source of resistance in the case of Hostianum 237. In addition, the set of resistance sources included Kooperatorka, Hope, SanPastore, Triticum timopheevii Zhuk., and Secale cereale. Some well-known sources of fusarium head blight resistance varying in genetic determinants—Sumai 3, Wangshuibai, Wuhan 1, Nyubay (China), Nobeokabozukomugi, Shinchunaga (Japan), Arina (Switzerland), Fundulea-201R (Romania), and Renan (France)—have so far not being employed in breeding in Russia and provide an important reserve for breeding for resistance.     

Aqueous silicate complexes in wheat, Triticum aestivum L.

The chemical speciation of silicon in xylem exudate from wheat (Triticum aestivum L.) was examined by ²⁹Si NMR spectroscopy. Wheat plants were grown to maturity in silicon‐free nutrient medium, and then transferred to a solution containing 0.02 mm ²⁹Si‐enriched silicic acid. After 30 min the shoots were excised and xylem exudate was collected. Within 10 min the Si concentration of the xylem exudate reached values greatly in excess of that of the starting nutrient solution, eventually reaching levels as high as 8 mm . Silicon‐29 nuclear magnetic resonance spectra indicated the existence of only two Si‐containing species in the xylem exudate, mono and disilicic acid (H₄SiO₄^o and (HO)₃Si(µ‐O)Si(OH)₃^o) in a ratio of approximately 7 : 1. Significantly, there was no evidence of organosilicate complexes. Nevertheless, the efficiency by which the plant concentrates aqueous silicon indicates active mechanisms of silicon transport across root cell membranes.     

A simplified AFLP method for fingerprinting of common wheat (Triticum aestivum L.) cultivars

The simplified AFLP method was developed and evaluated for identification and genetic diversity studies of wheat cultivars. Selective primers exploited in AFLP assay based on a single cutting enzyme PstI ((PstI)AFLP) generated total of 111 robust fragments, including 67 (60%) monomorphic and 12 (11%) cultivar-specific markers. Average similarity between 15 cultivars was 0.650, and varied from 0.293 ('Hope' vs. 'Aurora') to 0.865 ('Norman' vs. 'Hornet'). Mean similarities within groups of winter wheat cultivars with and without 1BL/1RS chromosome were 0.713 and 0.685, respectively. A higher variation was found in the group of spring wheats: 0.677. The obtained results confirm the usefulness of the proposed modification of the AFLP technique for diversity studies and identification of common wheat cultivars.     

Nickel toxicity and peroxidase activity in seedlings of Triticum aestivum L.

Ni²⁺ toxicity was evaluated in Triticum aestivum L. by its effects on root and shoot length, dry matter production and water content. Over a threshold value of 20 mmol m^?3 Ni²⁺ the degree of toxicity increases as a function of the Ni²⁺ concentration in the medium. Ni²⁺-treated roots show enhanced lipid peroxidation; the higher Ni²⁺ treatment (40mmol m^?3) also increases leakage of K⁺. In roots and shoots, Ni²⁺ enhances both guaiacol and syringaldazine extracellular peroxidase activity. The increase in extracellular peroxidase activity is also associated with an increase in the phenolic contents of roots and shoots. The observed growth inhibition might be partly the result of the effect of Ni²⁺ on cell turgor and cell-wall extensibility. Intracellular soluble peroxidases are also stimulated by Ni²⁺; such effects, independently of the substrate, were detected in extracts of Ni²⁺-treated shoots at a lower Ni²⁺ concentration than in the roots. Intracellular peroxidases might act as scavengers of peroxide radicals produced as a result of nickel toxicity.     

Sulfur stress-induced antioxidative responses in leaves of Triticum aestivum L.

Antioxidative responses were investigated in leaves of wheat (Triticum aestivum L.) grown at varying S levels ranging from deficiency to excess (1, 2, 4, 6 and 8 mM S). Optimum yield was observed in plants supplied with 4 mM S. Wheat responded to S deficiency and excess supply by decreasing growth of root and shoot. Chlorosis in young leaves was observed after 15 days of deficient S supply. The biomass and concentration of photoassimilatory pigments decreased in plants grown at 1, 2, 6 and 8 mM S supply. The concentration of thiobarbituric acid reactive substances (TBARS), cysteine, nonprotein thiol and hydrogen peroxide (H₂O₂) increased in plants grown under S stress. Accumulation of TBARS and H₂O₂ in leaves indicated oxidative damage in S-deficient and S-excess plants. Deficient and excess levels of S showed an increase in the activities of antioxidative enzymes superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6), peroxidase (EC 1.11.1.7), ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2).     

Dynamics of genetic diversity in winter common wheat Triticum aestivum L. cultivars released in Russia from 1929 to 2005

Genealogical analysis was used to study the dynamics of genetic diversity in Russian cultivars of winter common wheat from 1929 to 2005. The Shannon diversity index of the total set of released cultivars remained almost unchanged, although the number of original ancestors (landraces and genetic lines) increased almost tenfold in the period under study. This was explained in terms of the dependence of the modified Shannon diversity index on two parameters, the number of original ancestors and the mean coefficient of parentage. Significant direct effects were revealed: a positive effect of the former parameter and a negative of the latter. As a result, the increase in the number of original ancestors was compensated by the increase in relatedness of cultivars. Genetic erosion of realized diversity was observed, as a half of Russian landraces were lost. Although the mean coefficient of parentage did not reach its critical value (R = 0.25), cultivars of some regions (Central and Volga-Vyatka) proved to be closely related. A favorable gradual decrease in the mean coefficient of parentage was observed in the past 15 years. A set of modem winter wheat cultivars, which were introduced in the Russian State Catalog from 2002 to 2005, displayed a cluster structure. The overwhelming majority of cultivars formed two clusters originating from Bezostaya 1 (67% of cultivars) and Mironovskaya 808 (31%).     

Genetic diversity of reaction of common wheat (Triticum aestivum L.) cultivars to light intensity

The effect of low light intensity (LI) on the period from sprouting to earing was studied in 12 cultivars of the spring common wheat under controlled conditions. Differences between cultivars with respect to their responses to LI (RLIs) were found both for those that were photoperiod-sensitive and those that were almost photoperiod-neutral. Specifically, a prolonged photoperiod and a low LI differently increased the period from sprouting to earling in different cultivars. Genetic analysis of the RLI demonstrated, for the first time, that the weak response was incompletely dominant in F1. The results of genetic analysis agree with the hypothesis that the cultivars Pitic 62 and Novosibirskaya 22 differ in alleles of two loci controlling the RLI in wheat.