Potential for nitrate reduction in wheat (triticum aestivum L.)

Following the prevalent agronomic practice of applying N fertilizer in two splits at optimum levels recommended for maximum yield viz. 120 kg N ha, to two wheat (Triticum aestlvum L.) cultivars, which differ in in vivo nitrate reductase (NR) activity, it was observed that the activity is high in the first formed leaf blades and declines in the successively formed ones. Enhancement in the activity subsequent to incubation of excised leaf blades in NO₃ ^‐ suggests that the substrate (NO^‐ ₃) is limiting and that the leaf blades, particularly the upper ones, have the potential to reduce additional amounts of NO₃ ^‐. High NR cultivar has greater potential than the low NR cultivar. The studies suggest that it may be possible to increase the NO₃ ^‐ moles reduced and thus enhance the reduced N content in case the nitrogen is available at later stages of growth.     

Changes in bacterial populations along roots of wheat (Triticum aestivum L.) seedlings

Summary In this study the bacterial populations on root tips (1–2 days old) of wheat (Triticum aestivum L.) were compared with the populations on root segments about 1 week older (root base). The isolates were characterized with a set of physiological tests and the test results were used to group the bacteria by means of cluster analysis. Some clusters contained bacteria that occurred mainly on the root tips and were characterized by the ability to produce acid from different sugars and by the presence of the enzymes nitrate reductase, lipase, and oxidase; they were sensitive to high salt concentrations in the media. Another cluster included significantly more isolates from the root-base segments; these bacteria were characterized by a negative reaction to most of the physiological tests; the colonies formed by these bacteria had yellow pigmentation. Possiblemechanisms for the changes in the bacterial populations are discussed.     

Drought stress-induced oxidative stress and antioxidative responses in four wheat (Triticum aestivum L.) varieties

Drought stress was imposed on four varieties of wheat (Triticum aestivum L.), Mohan Wonder (MW), Kedar (K), Gayetri (GY) and Gandhari (GN), for 3, 6 and 9 days. The activities of all five tested antioxidative enzymes, peroxidase, ascorbate peroxidase, catalase, glutathione reductase and superoxide dismutase, were enhanced initially in varieties K and GN, whereas in MW and GY, catalase and superoxide dismutase showed a decrease in activity at all periods of drought stress. Peroxidase and glutathione reductase activities increased even on the ninth day of stress in K and GN, but all other activities showed a decrease after 3 days of stress. H₂O₂ accumulation increased with drought stress, but in K and GN there was decrease during prolonged drought stress. Lipid peroxidation increased significantly due to drought stress, which was higher in the case of MW and GY. Proline, phenol and ascorbate content increased with period of drought stress. Carotenoid accumulation also increased initially. Total chlorophylls showed a general decrease during drought stress. The results of this study indicate that two of the varieties, MW and GY, are susceptible to drought stress, whereas the other two, K and GN, are tolerant, with peroxidase and glutathione reductase being most important in conferring tolerance.     

Effects of genotype and weed control on the nutrient composition of winter spelt (Triticum aestivum ssp. spelta L.) and common wheat (Triticum aestivum ssp. vulgare)

The renaissance of spelt is associated with the development of alternative farming and a trend to maintain biodiversity. The present study carried out a comparison between two methods of weeding (mechanical and chemical) as well as a cereal cultivar influence on chemical composition of spelt and wheat. The research material was taken from field experiments carried out during three years. In order to assess the chemical composition, the following cereal cultivars were used: lines of winter spelt – STH 8 and STH 11 and a winter common wheat cv. Tonacja. In all cases, the overall protein content in spelt was significantly higher than in common wheat. Spelt grain is also richer in fats than common wheat. A visible tendency to higher concentration of raw fibre was observed when mechanical weeding was applied. Also, mechanical weeding as well as the variety significantly influenced β-glucan content. The study of the impact of a weeding method and a variety does not clearly show the direction of the amino acid content changes. The research indicates that there are ample opportunities to shape the level of nutrients, which decide about spelt grain application in the food industry through agronomic factors (methods of weeding and cultivar).     

Investigating environmental factors that cause extreme gluten quality deficiency in winter wheat (Triticum aestivum L.)

Unstable breadmaking quality of wheat due to environmental influence has been a problem for Norwegian milling industries. Large variation in gluten quality was observed from field trials with Norwegian winter wheat conducted in several locations between 2005 and 2013. Moreover, extremely poor gluten quality was observed in several locations in the 2007 and 2011 season, and indicated almost complete loss of breadmaking quality. To investigate the environmental factors which cause extremely weak gluten, gluten proteins were characterized in samples selected within the 2011 season. The results revealed that the proportion of large glutenin polymers decreased in wheat samples with extremely weak gluten. Moreover, re-polymerization of large glutenin polymers, which normally occur during the resting period of a dough, did not take place in gluten prepared from these samples. Incubation of total proteins extracted from these samples in an in vitro system showed a drastic degradation of gluten proteins indicating protease activities. The origin of the proteases remains unclear; however, exogenous proteases derived from Fusarium spp. seem to play a key role for protein degradation, and thus causing severe quality deficiency. A genotypic difference was found between the two cultivars and one of them had higher resistance against the factors influencing gluten quality in negative way.     

Macronutrient accumulation in wheat crop (Triticum aestivum L.) with Azospirillum brasilense associated with nitrogen doses and sources

Abstract

New studies are needed to optimize the nitrogen (N) amount that can be applied to utilize the Azospirillum brasilense benefits. In addition, information regarding the interaction between the urease inhibitor and biological nitrogen fixation (BNF) and how they affect the macronutrients accumulation are also needed. We evaluate the effect of N sources and doses associated with A. brasilense regarding the macronutrients accumulation in straw and grains and wheat grain yield in tropical conditions. A randomized block experimental design was used with four replications in a 2?×?5?×?2 factorial arrangement as follows: two N sources (urea and urea with urease enzyme inhibitor NBPT; five N doses (0, 50, 100, 150, and 200?kg ha^?1) applied in topdressing; with and without A. brasilense inoculation. We found that an increase in N doses positively influenced the accumulation of macronutrients in straw and grains and the wheat grain yield. N sources have similar effects. Inoculation with A. brasilense increased accumulation of Mg and S in straw and P, Ca, and Mg in grains, regardless of the N dose. The inoculation with A. brasilense associated with 140?kg ha^?1 of N increased wheat grain yield. The inoculation can contribute in a more sustainable way to wheat nutrition and optimizing N fertilization.     

镉胁迫下小麦根系的生理生态变化

本文通过水培和砂培两种方法 ,研究了镉胁迫下小麦 (TriticumaestivmL .)根系的生理生态变化。通过研究镉对小麦根系生长发育状况 ,根系活力 ,根系对矿质元素的吸收 ,探讨镉胁迫下植物根系的生理生态效应。研究结果表明 :镉影响根系的长度、生物量、体积和根系活力。Cd2 + 在低浓度 (处理浓度低于 5mg/L)作用下 ,随处理浓度的升高 ,刺激小麦根系的长度、生物量、体积相应地升高 ;当处理浓度高于相应浓度时 ,根长度、生物量、体积相应随浓度升高而降低。镉胁迫下根系活力受到抑制。水培和砂培中 ,镉对根系的影响趋势一致 ,但是影响幅度有差异。砂培好于水培。镉影响小麦根对矿质元素的吸收 ,Ca、Cu、Fe、K、Mg、Mn、Na、Zn吸收情况不太一致。Ca、Cu、Fe、Mg、Mn、Na的吸收量随Cd2 + 浓度升高而增加 ,K、Zn的吸收量随Cd2 + 浓度升高而减少     

Evaluation of Genetic Diversity Among Bulgarian Winter Wheat (Triticum aestivum L.) Varieties During the Period 1925–2003 Using Microsatellites

Simple sequence repeats (SSRs) were used to study the genetic diversity within old and modern Bulgarian winter wheat (Triticum aestivum L.) varieties released in 20th century. A set of 91 varieties were screened by 19 wheat microsatellite markers (WMS), covering 17 wheat chromosomes, and one secalin-specific marker for rye chromosome arm 1RS. A total of 136 allelic variants were detected at 22 loci, ranging from 2 to 11, with an average of 6.8 alleles per marker. For 7 markers, null alleles were detected. The occurrence of rare alleles (frequency <2%) was observed for 13 markers. The polymorphism information content (PIC) values of the markers ranged from 0.10 (WMS0165 on 4AS) to 0.81 (WMS0437 on 7DL) with an average of 0.51. Approximately 74% of the varieties, mostly non-commercial, showed heterogeneity, with an average level of 10.1%. For the majority of markers, the relative frequencies of alleles varied considerably among different groups of varieties, revealing the effects of different selection between breeding centres. Some alleles, present in old genotypes, were lost, and new alleles have been introduced into modern varieties. Genetic diversity values over different periods of release were high, starting at 0.64 for varieties developed before 1960 to reach 0.71 in 1990s, revealing no declining trends in the diversity due to breeding activity. The cluster analysis discriminated all varieties (except for two) and revealed distinct groups of old and modern varieties, released from the main breeding centres in Northern, Southern and Western Bulgaria.     

Availability of soil and fertilizer nitrogen to wheat (Triticum aestivum L.) following rice-straw amendment

Summary A pot experiment was conducted to study the N availability to wheat and the loss of ¹⁵N-labelled fertilizer N as affected by the rate of rice-straw applied. The availability of soil N was also studied. The straw was incorporated in the soil 2 or 4 weeks before a sowing of wheat and allowed to decompose at a moisture content of 60% or 200% of the water-holding capacity. The wheat plants were harvested at maturity and the roots, straw, and grains were analysed for total N and ¹⁵N. The soil was analysed for total N and ¹⁵N after the harvest to determine the recovery of fertilizer N in the soil-plant system and assess its loss. The dry matter and N yields of wheat were significantly retarded in the soil amended with rice straw. The availability of soil N to wheat was significantly reduced due to the straw application, particularly at high moisture levels during pre-incubation, and was assumed to cause a reduction in the dry matter and N yields of wheat. A significant correlation (r=0.89) was observed between the uptake of soil N and the dry matter yield of wheat with different treatments. In unamended soil 31.44% of the fertilizer N was taken up by the wheat plants while 41.08% of fertilizer N was lost. The plant recovery of fertilizer N from the amended soil averaged 30.78% and the losses averaged 45.55%     

Comparison of phenolic acids profile and antioxidant potential of six varieties of spelt (Triticum spelta L.)

Phenolic acids profile and antioxidant activity of six diverse varieties of spelt are reported. Antioxidant activity was assessed using eight methods based on different mechanism of action. Phenolic acids composition of spelt differed significantly between varieties and ranged from 506.6 to 1257.4 μg/g DW. Ferulic and sinapinic acids were the predominant phenolic acids found in spelt. Total ferulic acid content ranged from 144.2 to 691.5 μg/g DW. All analyzed spelt varieties possessed high antioxidant potential. In spite of the fact that bound phenolic acids possessed higher antioxidant activities, analysis of antioxidant potential and their relationship with phenolic acid content showed that free phenolics were more effective. Eight antioxidant methods were integrated to obtain a total antioxidant capacity index that may be used for comparison of total antioxidant capacity of spelt varieties. Total antioxidant potential of spelt cultivars were ordered as follows: Ceralio > Spelt INZ ≈ Ostro > Oberkulmer Rotkorn > Schwabenspelz > Schwabenkorn.     

Boron-Calcium Synergically Alleviates Aluminum Toxicity in Wheat Plants (Triticum aestivum L.)

The effects of B and Ca treatments on root growth, nutrient localization and cell wall properties in wheat ( Triticum aestivum L.) plants with and without Al stress were investigated. Seedlings were grown hydroponically in a complete nutrient solution for 7 d and then treated with B (0, 40 μM), Ca (0, 2,500 μM), and Al (0, 100 μM) in a 500 μM CaCl₂ solution for 8 d. The cell wall materials (CWM) were extracted with a phenol: acetic acid: water (2:1:1 w/v/v) solution and used for subsequent pectin extraction with trans -1,2-diami-nocyclohexane- N,N,N,N -tetraacetic acid (CDTA) and Na₂CO₃ solutions. Boron, Ca, and B + Ca treatments enhanced root growth by 19.5, 15.2, and 27.2%, respectively, compared to the control (pH 4.5). Calcium and B+Ca treatments enhanced root growth with Al stress by 43 and 54%, respectively, while B did not exert any effect. The amounts of CWM and pectin per unit of root fresh weight increased by Al treatment, whereas the Ca and B+Ca treatments slightly reduced the contents of these components. Seventy-four percent of total B, 69% of total Ca, and 85% of total Al were located in the cell wall in the B, Ca, and Al treatments, respectively and 32% of total B, 33% of total Ca, and 33% of total Al were located in the CDTA-soluble and Na₂CO₃-soluble pectin fractions. A more conspicuous localization of B was observed in the presence of Al. Aluminum treatment markedly decreased the Ca content in the cell wall as well as pectin fractions, mainly in the case of the CDTA-soluble pectin fraction. Boron + Ca treatment decreased the Al content in the cell wall and pectin fractions compared to the Ca treatment alone in the presence of Al. It is concluded that the B+Ca treatment enhanced root growth and, B and Ca uptake, and helped to maintain a normal B and Ca metabolism in the cell walls even in the presence of Al.     

Effects of sulphur application on grain yield and quality,and assessment of sulphur status in winter wheat (Triticum aestivum L.)

Abstract

Winter wheat was grown in 26 field trials in Norway during the period 2004–2006. The main aim was to determine the effect of various sulphur (S) fertilization strategies at two different nitrogen (N) levels on grain yield and quality of winter wheat. With the exception of four trials in central Norway, all the trials were located in the south-eastern part of the country.

Increasing the N fertilization from 170 to 210 kg N ha^?1 resulted in significantly higher grain protein content (GPC) and sodium dodecyl sulphate (SDS) sedimentation volume. On clayey soils in southeast Norway, increased N-fertilization also resulted in higher grain yield and lower test weight and thousand grain weight (tgw).

Omitting S fertilization significantly reduced grain yields on sandy soils in southeast Norway and on loam and silt loam in central Norway, whereas no yield reduction was found on clay soils. SDS sedimentation volume and specific SDS (sSDS = SDS/GPC) were significantly reduced when S-fertilization was omitted. GPC was reduced by S fertilization in central Norway. Generally there were no significant responses at application rates higher than 12 kg S ha^?1.

The malate:sulphate method is a field-based diagnostic test used to determine whether S deficiency is likely to occur. The results did not indicate that this test is reliable under Norwegian conditions. On the other hand, the use of a chlorophyll meter measurements to assess S status gave promising results.     

Effect of fungicides on three vesicular-arbuscular mycorrhizal fungi associated with winter wheat (Triticum aestivum L.)

Summary We studied the effects of field application rates of three fungicides on spore germination and root infection in three species of Glomus. Bavistin (carbendazim) prevented germination of spores of G. monosporum and G. mosseae whereas Calixin (tridemorph) had no effect. Tilt Turbo (propiconazole) inhibited spore germination less than Bavistin. Spores of G. geosporum germinated in the presence of all three fungicides. Foliar applications of Bavistin alone and in a triple-spray programme significantly reduced infection of all three Glomus species in wheat roots grown in conditions of low P availability (2 mg P 1^–1). Two fungicides with triazole derivatives, Sportak and Tilt Turbo, also decreased infection and the former significantly reduced spore production of all three Glomus species. Calixin-treated plants, however, showed increased infection levels, resulting in greater yields and greater foliar-P concentrations than control plants. Milgo (ethirimol) was not detrimental to the vesicular-arbuscular mycorrhizal (VAM) symbiosis when applied as a foliar spray.     

Crop growth and nitrogen transformations in wheat (Triticum aestivum L.) planted after wetland rice (Oryza sativa L.)

Summary A field study was undertaken to examine the effects of various management strategies on wheat (Triticum aestivum L.) performance and N cycling in an intensively cropped soil. Microplots receiving 100 kg N ha^–1 as¹⁵NH₄ ^{+ 15}NO₃ ^– at sowing, tillering or stem elongation were compared with unfertilized microplots. Stubble from the previous rice crop was either incorporated, burnt without tillage, burnt then tilled or retained on the surface of untilled soil. Wheat grain yield ranged from 1.5 to 5.1 t ha^– and was closely related to N uptake. Plant accumulation of soil N averaged 36 kg N ha^–1 (LSD 5% = 10) on stubble-incorporation plots and 54 kg N ha^–1 on stubble-retention plots. Fertilizer N accumulation averaged 18 kg N ha^–1 (LSD 51% = 6) on stubble-incorporation plots and 50 kg N ha^–1 on stubble-retention plots. Tillage had little effect on burnt plots. Delaying N application from sowing until stem elongation increased average fertilizer N uptake from 26 to 39 kg N ha^–1 (LSD 5% = 6), but reduced soil N uptake from 50 to 37 kg N ha^– (LSD 5% = 10).Immobilization and leaching did not vary greatly between treatments and approximately one-third of the fertilizer was immobilized. Less than 1% of the fertilizer was found below a depth of 300 mm. Incorporating 9 t ha^–1 of rice stubble 13 days before wheat sowing reduced net apparent mineralization of native soil N from 37 to 3 kg ha^–1 between tillering and maturity. It also increased apparent denitrification of fertilizer N from an average 34 to 53 kg N ha^–1 (LSD 5% = 6). N loss occurred over several months, suggesting that denitrification was maintained by continued release of metabolizable carbohydrate from the decaying rice stubble. The results demonstrate that no-till systems increase crop yield and use of both fertilizer and soil N in intensive rice-based rotations.     

Effect of nitrogen fertilizer levels and irrigation on quality characteristics in bread wheat (Triticum aestivum L.)

In order to evaluate irrigation regimes and nitrogen fertilization on quality characteristics of wheat cultivars, a field experiment was carried out using split-plot factorial design based on randomized complete block design with three replications in Quchan, Iran (2010–2012). Main plots were assigned with four irrigation regimes; I1, 90 mm; I2, 130 mm; I3, 170 mm based on evaporation from a class A pan; and I4, water deficit stress during post-anthesis stage; sub-plots were assigned with four levels of nitrogen (N1, 0; N2, 70; N3, 140; and N4, 210 kg ha^?1); and three wheat cultivars (V1, Mihan; V2, C-87-6; and V3, C-87-11) were used as factorial. The results showed that nitrogen fertilization increased some quality characteristics. Under water deficit (I4), gluten index, grain protein content, grain yield, and sedimentation volume decreased. Significant interactions between irrigation regimes and both nitrogen levels and cultivars were observed.     

Genetic diversity of HMW glutenin subunit in Chinese common wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) landraces from Hubei province

The high molecular weight (HMW) glutenin subunit composition of 111 common landraces of bread wheat collected from Hubei province, China has been determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Ninety six of the accessions were homogeneous for HMW glutenin subunit composition and 15 were heterogeneous. For the Glu-1 loci, 16 alleles were detected, 3 at the Glu-A1locus, 9 at the Glu-B1and 4 at the Glu-D1. Three novel alleles were identified, two at the Glu-B1 and one at the Glu-D1locus. Combination of these 16 alleles resulted in 14 different HMW subunit patterns. The distribution of HMW glutenin subunit alleles in a subset of 105 of the 111 accessions representing six populations was assessed both at the individual population and whole population levels. The results demonstrated that the distribution of allelic patterns varied among populations. Taken together, 62.5% of the alleles detected were considered to be rare alleles while the Glu-A1c (null), Glu-B1b (1Bx7 + 1By8) and Glu-D1a (1Dx2 + 1Dy12) alleles were found most frequently in the six populations. The subset exhibited relatively high genetic diversity (A = 5.33, P = 1.00, Ae = 1.352 and He = 0.238) with 81.5% of the diversity being within populations and 18.5% between populations.     

Aluminum inhibits growth and stability of cortical microtubules in wheat (Triticum aestivum) roots

Aluminum (Al) occurs abundantly in soil and solubilized aluminum ions in acid soil inhibit plant growth, in particular, root growth. Although several toxic effects of Al on plant growth have been reported, the mechanism of Al toxicity remains to be clarified.     

纳米氧化铜对小麦根系生理生化行为的影响

为阐明纳米金属材料暴露对植物生长的影响及其作用机制,采用模拟土壤的琼脂培养方法研究了纳米氧化铜(CuO NPs)对小麦(Triticum aestivum L.)根伸长及相关生理生化行为的影响。结果表明:小麦根伸长与CuO NPs暴露浓度之间存在指数相关关系,在低浓度CuO NPs(10 mg/L)暴露下得到一定程度促进,而在高浓度(100 mg/L)下受到强烈抑制。小麦根内超氧化物歧化酶(SOD)活性随CuO NPs暴露浓度的变化趋势与小麦根伸长具有一致性。另外,在1~100 mg/L范围内,随着CuO NPs暴露浓度的升高,小麦根内丙二醛(MDA)含量不断增加,但植物蛋白含量急剧降低。以上结果说明CuO NPs对根伸长抑制主要是由于纳米材料暴露造成植物细胞膜氧化损伤,小麦能通过提高根系活力对CuO NPs暴露作出适应性应激响应以减少纳米材料毒性的伤害。     

Mineral Uptake of Mycorrhizal Wheat (Triticum aestivum L.) under Salinity Stress

The hypothesis was that arbuscular mycorrhizal (AM) fungi are able to alleviate salt stress on plant growth by enhancing and adjusting mineral uptake. The objectives were to determine (1) the effects of soil salinity on mineral uptake by different wheat genotypes and (2) the effectiveness of different mycorrhizal treatments on the mineral uptake of different wheat (Triticum aestivum L.) genotypes under salinity. Wheat seeds of Chamran and Line 9 genotypes were inoculated with different species of AM fungi including Glomus mosseae, G. intraradices, and G. etunicatum and their mixture at planting using 100 g inoculum. Pots were treated with the salinity levels of 4, 8, and 12 dS/m before stemming. Different arbuscular mycorrhizal treatments, especially the mixture treatment, increased wheat mineral uptake for both genotypes. Although Line 9 genotype resulted in greater nutrient uptake under salinity stress, Chamran was more effective on adjusting sodium (Na⁺) and chloride (Cl^?) uptake under salt stress.     

Effects of herbicides on three vesicular-arbuscular fungi associated with winter wheat (Riticum aestivum L.)

Summary We studied the effects of field application rates of four herbicides (Avenge, Ceridor, Dicurane, and Harrier) on spore germination and infection of wheat roots by three species of Glomus grown under conditions of low P availability. Low concentrations of Ceridor (bifenox, mecoprop) and Harrier (mecoprop, ioxynil, clopyralid) inhibited spore germination while higher concentrations were stimulatory. Avenge (difenzoquat methyl sulphate) prevented spore germination completely, while Dicurane (chlortoluron) had no effect. The herbicide applications had no significant effect on the infection rates of any of the three fungi except Harrier on G. geosporum. The herbicide treatments did, however, affect plant growth and ear yields. Ceridor and Harrier increased ear yields, while Dicurane showed marked phytotoxic effects.