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Wheat
Kinds of Wheat Terms modified by Wheat Selected AbstractsEFFECT OF COMPOSITION OF GLUTHNIN SUBFRACTIONS ON RHEOLOGICAL PROPERTIES OF WHEATJOURNAL OF FOOD BIOCHEMISTRY, Issue 4 2000S. JOOD ABSTRACT Gluten extracted from defatted flours of cv. Aubaine (extra-strong), Hereward (strong) and Riband (weak) was separated into five different fractions (R2 to R6) by sequential centrifugation and addition of sodium chloride. A seven-minute mixing time was used to carry out fractionation on the basis of depolymerization of glutenin macropolymers (GMP). Depolymerization of GMP occurred at much higher rates in dough of the weak cultivar compared to the strong and extra-strong cultivars. Polypeptide compositions of different ghttenin fractions were determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis under reduced and non-reduced conditions, followed by densitometric scanning of stained patterns. The amount of HMW-glutenin subunits decreased and LMW-glutenin subunits increased correspondingly in each cultivar with the fractionation from R2 to R6. The rheological behavior of the fractions was analyzed by small deformation rheological tests (strain sweep and frequency tests). The high molecular weight fraction (R2) from extra-strong wheat had a higher vahte of G' and a lower tan , value as compared to strong and weak bread-making wheats. The moduli of HMW glutenin fractions (R2 and R3) were frequency independent and promoted the network properties, whereas moduli of LMW glutenin fractions were frequency dependent and gave rise to a plasticizing effect. Therefore, it was concluded from the present studies that HMW-glutenin subunits are not the only factors governing good bread-making quality but their proportions in relation to low molecular weight glutenin subunits is equally important in sinking a balance between viscous and elastic properties essential for bread making performance. [source] MECHANICAL CHARACTERIZATION OF SHREDDED WHEATJOURNAL OF TEXTURE STUDIES, Issue 5 2008J.B. LAURINDO ABSTRACT The purpose of the study was to evaluate a methodology for mechanical characterization of brittle foods with strong anisotropy. Spoon-sized pieces of three commercial brands of dry shredded wheat were chosen for the demonstration. They were compressed along their three principal axes, individually and grouped in the same orientation. The force-displacement curves in the three directions were all irregular and irreproducible but had discernible features characteristic of the specimen's orientation. When tested as constrained groups, these features could change, depending on the compression direction, reflecting on the contribution of the broken structure's remnants to the specimen's mechanical resistance. The assemblies' force-displacement curves were all smoother than those of the individual particles, a result of the "averaging effect." The overall force level could not be predicted from the number of pieces because of differences in the specimens' post-failure response to added deformation. The jaggedness of the normalized (dimensionless) force oscillations record was quantified in terms of an apparent Kolmogorov (fractal) dimension, determined with the box counting algorithm. Its value strongly depended on the smoothing model's goodness fit if the fit was too close, but not if it only captured the general shape of the force-displacement curve. PRACTICAL APPLICATIONS Despite the irregular and irreproducible mechanical signature of shredded wheat and the dependence on the specimens' orientation, it is still possible to characterize the products' mechanical properties in a way that distinguishes between their overall strength and brittleness. The described method could help to quantify textural differences between these and other brittle food products, and probably identify the conditions under which crunchiness would be maintained or lost. [source] GLUTEN QUALITY PREDICTION AND CORRELATION STUDIES IN SPRING WHEATSJOURNAL OF FOOD QUALITY, Issue 4 2007IMRAN PASHA ABSTRACT Gluten, "cohesive, viscoelastic, proteinaceous material prepared as a by-product of the starch isolation from wheat flour" and the storage and dough-forming protein of wheat flour, is the key to the unique ability of wheat to suit the production of leavened products. Wet gluten was only affected by wheat varieties, while dry gluten was affected by wheat varieties, crop years and their interaction. The wet and dry gluten ranged 8.0,43.13% and 2.58,14.55%, respectively, and were positively correlated with Zeleny value, sodium dodecyl sulfate sedimentation value and falling number. The gluten content was higher in Pavon, SA 42 and Faisalabad 85, while Zeleny value was higher in GA 02 and C 518, resulting in better gluten quality. Zeleny value was negatively correlated with crude protein content (r = ,0.1857*). The lowest amount of wet and dry gluten was detected in Triticale and durum wheats as compared to common wheats. Zeleny value and sedimentation value may be used as indicators of gluten content and quality while working on wheats. The information thus collected will be valuable for cereal chemists and wheat breeders for improvements in their future breeding programs. PRACTICAL APPLICATIONS This research work will be a breakthrough and helpful for wheat breeders, growers, millers and bakers for their intended uses as every consumer demand specific wheat quality characteristics for their end products. [source] BAKING PERFORMANCE OF 1BL/1RS SOFT RED WINTER WHEATSJOURNAL OF FOOD QUALITY, Issue 2 2001WILLIAM E. BARBEAU ABSTRACT Baking performance of nine 1BL/1RS soft red winter wheat (SRWW) lines and six non-1BL/1RS lines was assessed during two crop years, 1995,96 and 1996,97, and at two locations, Blacksburg and Warsaw, Virginia. The 1BL/1RS flours produced cookies with significantly smaller diameters than non-1BL/1RS flours (p , 0.0026) across both growing years and locations. There was a highly significant negative correlation (r =,0.709) between cookie spread and alkaline water retention capacity (AWRC) of SRWW flours. Overall, there was no significant difference (p = 0.2552) in biscuit volume of 1BL/1RS and non-1BL/1RS flours. There were no significant differences in cake volumes of 1BL/1RS and non-1BL/1RS flours when data from both years and locations were combined, p = 0.0710; or when Blacksburg and Warsaw locations were considered separately, p = 0.2009 and 0.1882, respectively. Finally, there were no significant differences in the texture of cakes made from 1BL/1RS and non-1BL/1RS flours regardless of growing year or location. These results suggest that the 1BL/1RS translocation significantly reduces the cookie spread of SRWW flours but has no significant impact on biscuit or cake quality. [source] Lignan profile in seeds of modern and old Italian soft wheat (Triticum aestivum L.) cultivars as revealed by CE-MS analysesELECTROPHORESIS, Issue 22 2007Giovanni Dinelli Professor Abstract The health-promoting effects of whole-grain consumption have been attributed in part to their unique phytochemical contents and profiles. Wheat is an important component of the human diet; however, little is known about the phytochemical profiles of different wheat varieties, especially of old wheats. The objective of this study was to investigate the distribution of lignans, a class of phytochemicals with proved health benefit effects, of four modern and six old Italian soft wheat (Triticum aestivum L.) cultivars. In this work, we describe the first analytical method involving CE coupled to MS (CE-MS) used to identify and quantify lignan compounds in grains of different cultivars of wheat. Total lignan content determined by CE-ESI-MS was 2.60,±,0.21 and 5.00,±,1.30,,g/g dry seed weight for modern and old cultivars, respectively. Secoisolariciresinol and pinoresinol were detected in all ten investigated soft wheat cultivars, whereas arctigenin, hinokinin, and syringaresinol were exclusively detected in old genotypes. Significant differences between modern and old cultivars were also observed for the number of glycosidic forms. Results highlighted the high content and unique composition in lignans of old cultivars suggesting their uses into a wide range of regular and speciality food products naturally enriched with health-promoting compounds. [source] Soil,atmosphere exchange of CH4, CO, N2O and NOx and the effects of land-use change in the semiarid Mallee system in Southeastern AustraliaGLOBAL CHANGE BIOLOGY, Issue 9 2010IAN GALBALLY Abstract The semiarid and arid zones cover a quarter of the global land area and support one-fifth of the world's human population. A significant fraction of the global soil,atmosphere exchange for climatically active gases occurs in semiarid and arid zones yet little is known about these exchanges. A study was made of the soil,atmosphere exchange of CH4, CO, N2O and NOx in the semiarid Mallee system, in north-western Victoria, Australia, at two sites: one pristine mallee and the other cleared for approximately 65 years for farming (currently wheat). The mean (± standard error) rates of CH4 exchange were uptakes of ,3.0 ± 0.5 ng(C) m,2 s,1 for the Mallee and ,6.0 ± 0.3 ng(C) m,2 s,1 for the Wheat. Converting mallee forest to wheat crop increases CH4 uptake significantly. CH4 emissions were observed in the Mallee in summer and were hypothesized to arise from termite activity. We find no evidence that in situ growing wheat plants emit CH4, contrary to a recent report. The average CO emissions of 10.1 ± 1.8 ng(C) m,2 s,1 in the Mallee and 12.6 ± 2.0 ng(C) m,2 s,1 in the Wheat. The average N2O emissions were 0.5 ± 0.1 ng(N) m,2 s,1 from the pristine Mallee and 1.4 ± 0.3 ng(N) m,2 s,1 from the Wheat. The experimental results show that the processes controlling these exchanges are different to those in temperate systems and are poorly understood. [source] Contrasting infection frequencies of Neotyphodium endophyte in naturalized Italian ryegrass populations in Japanese farmlandsGRASSLAND SCIENCE, Issue 2 2010Masayuki Yamashita Abstract Neotyphodium endophytes often confer benefits to their host grasses and may enhance invasiveness of some grasses. The knowledge of infection frequencies of endophytes among invading weed populations is necessary to understand the relationships between endophyte infection and invasiveness. Here we present data on infection frequencies of Italian ryegrass (Lolium multiflorum Lam.), an important weed in some farmlands in Japan, persisting in contrasting farmlands: a terraced paddy field and a wheat-soybean double-cropped field in the western region of Shizuoka prefecture, Japan. The terraced paddy site is a mosaic of several landscape elements such as paddy fields, levees, fallow and abandoned fields, with a high percentage of non-crop area. Rice (Oryza sativa L.) has been cultivated for more than a decade with no application of chemical fertilizers, pesticides and fungicides. The wheat-soybean field is characterized by the aggregation of large-scaled fields that were originally reconstructed paddy fields, showing a low percentage of non-crop area. Wheat and soybean have been grown as winter and summer crops, respectively, using chemical fertilizers and herbicides. We examined the presence or absence of endophytes in a total of 1200 seeds sampled from the two Italian ryegrass populations. The terraced paddy population exhibited a markedly high infection frequency (91.0%), due possibly to selective feeding of non-infected seeds by insects. In contrast, the wheat-soybean farmland population showed almost no infection (1.1%), whereas the putative source of the invasion in the proximity exhibited a relatively high infection rate (64.4%). Such a micro-scale variation in infection frequencies may be attributable to a loss in endophyte viability within the wheat-soybean field. The findings suggest that endophyte infection frequency may markedly differ among the Italian ryegrass populations even within the same region, presumably depending on the abundance of the seed-eating insects, farmland management regimes and/or environmental conditions such as soil humidity. [source] Optimal Hedging Ratios for Wheat and Barley at the LIFFE: A GARCH ApproachJOURNAL OF AGRICULTURAL ECONOMICS, Issue 2 2000P. J. Dawson Over 100,000 futures contracts for cereals are traded annually on the London International Financial Futures Exchange. The proportion of the spot position held as futures contracts - the hedging ratio - is critical to traders and traditional estimates, using OLS, are constant over time. In this paper, we estimate time-varying hedging ratios for wheat and barley contracts using a multivariate generalised autoregressive conditional heteroscedasticity (GARCH) model. Results indicate that GARCH hedging ratios do change through time. Moreover, risk using the GARCH hedge is reduced significantly by around 4 per cent for wheat and 2 per cent for barley relative to the no hedge position, and significantly by around 0.2 per cent relative to the constant hedge. The optimal, expected utility-maximising, and the risk-minimising hedging ratios are equivalent. [source] Heat Shock Protein in Developing Grains in Relation to Thermotolerance for Grain Growth in WheatJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 1 2010P. Sharma-Natu Abstract Wheat (Triticum aestivum L.) cvs DL 153-2 and HD 2285 (relatively tolerant), HD 2329 and WH 542 (relatively susceptible), were grown under normal (27 November) and late (28 December) sown conditions. In another experiment, these cultivars were grown under normal sowing and at anthesis stage, they were transferred to control (C) and heated (H) open top chambers (OTCs). Under late sowing, wheat cultivars were exposed to a mean maximum temperature of up to 3.6 °C higher than normal sowing and in H-OTCs, mean maximum temperature was 3.2 °C higher than C-OTCs during grain growth period. Heat susceptibility index (S) for grain growth and grain yield was determined at maturity in both the experiments. The level of heat shock protein (HSP 18) in the developing grains was determined in C- and H-OTC grown plants and in normal and late sown plants by Western blot analysis. The moderately high temperature exposure increased the accumulation of HSP 18 in the developing grains. The relatively tolerant cultivars, as also revealed from S, showed a greater increase in HSP 18 compared with susceptible types in response to moderate heat stress. An association of HSP 18 with thermotolerance for grain growth in wheat was indicated. [source] Compensative Effects of Chemical Regulation with Uniconazole on Physiological Damages Caused by Water Deficiency during the Grain Filling Stage of WheatJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 1 2008L. Duan Abstract Chemical regulation using plant growth regulators has proved to be potentially beneficial in water-saving agriculture. This experiment was conducted with winter wheat (Triticum aestivum L. cv. ,Jingdong 6') to study the effect of chemical regulation on alleviation of water deficit stress during the grain filling stage. Uniconazole, a plant growth regulator, was foliar sprayed at 85 % (adequate irrigation) and 60 % (deficit irrigation) field capacity. Results showed that the distribution of 3H-H2O in roots and flag leaf, characteristics of vascular bundle in primary roots and internode below spike, roots activity, transpiration rate and stomatal conductance of flag leaf were negatively affected by deficit irrigation after flowering. Foliar spraying at the early jointing stage with 13.5 gha,1 uniconazole was able to relieve and compensate for the harmful effects of deficit irrigation. Both the area of vascular bundle in primary roots and internode below the ear were increased by uniconazole, while root viability and their ability to absorb and transport water were increased. In the flag leaf, stomatal conductance was reduced to maintain the transpiration rate and water use efficiency (WUE) measured for a single wheat plant was higher. Uniconazole increased WUE by 25.0 % under adequate and 22 % under deficit irrigations. Under adequate irrigations, the 14C-assimilates export rate from flag leaf in 12 h (E12h) was increased by 65 % and 36 % in early and late filling stages, while under deficit irrigations, the E12h of uniconazole-treated plants exceeded that of control plants by 5 % and 34 % respectively. Physiological damages caused by water deficiency during the grain filling stage of wheat was alleviated by foliar spraying with uniconazole. [source] Response of Weed Communities to Legume Living Mulches in Winter WheatJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 2 2007J. Hiltbrunner Abstract In order to obtain information about the impact of legume cover crops on the weed community in organic farming, winter wheat (Triticum aestivum L.) was directly drilled in rows 0.1875 and 0.3750 m apart in living mulches that consisted of Trifolium repens L. (TRFRE), T. subterraneum L. (TRFSU), Medicago truncatula Gaertner (MEDTR), and Lotus corniculatus L. (LOTCO). A control treatment without cover crops (NAT, the site-specific weed community) was also established. The vegetation between the wide rows was either mulched or left undisturbed. The effect of liquid farmyard manure (60 m3 ha,1) was also tested. TRFRE, TRFSU, and LOTCO effectively suppressed Poa annua L. and Matricaria recutita L. at site 1 and P. annua, Capsella bursa-pastoris (L.) Med., and Stellaria media (L.) Vill. at site 2 when compared with NAT. MEDTR, which died during the winter, provided little weed suppression. Mulching significantly suppressed dicotyledonous weed species, but favoured Poa trivialis L. No manure effect was observed. Winter hardy legume cover crops contribute to weed suppression in winter wheat. However, careful evaluation of cover crop × weed × management interactions is necessary to understand the risk for the establishment of problematic weeds. [source] Morphological Traits above the Flag Leaf Node as Indicators of Drought Susceptibility Index in Durum WheatJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 2 2007D. Villegas Abstract Selection criteria for drought tolerance would be helpful tools for wheat breeding programmes. To assess the usefulness of some morphological traits above the flag leaf node as indicators of yield and the susceptibility index (SI) of Fischer and Maurer, 10 durum wheat genotypes were used in experiments conducted under two water regimes at two latitudes in Spain during 3 years. Morphological traits were measured at anthesis, and yield, yield components and quality traits were evaluated at ripening. Principal components analysis showed associations between morphological traits and yield, yield components and quality, most of them caused by differences between environments. Peduncle weight, spike weight and length and awn length were significantly related to SI within environments. Spike and peduncle weight were the traits more related to yield and SI in all the experiments together and in the rainfed sites, while in the irrigated sites spike length was better. The spike weight and length were negatively associated with SI, while peduncle weight was positively associated to SI. Genotype means across all experiments were associated with SI values. These morphological traits could be selection criteria in breeding programmes to obtain varieties with good yield stability. The genetic variability found suggests opportunity for selection. [source] Effects of 15N Split-application on Soil and Fertiliser N Uptake of Barley, Oilseed Rape and Wheat in Different Cropping SystemsJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 1 2007K. Sieling Abstract In intensive farming systems, farmers split up and apply the N fertilization to winter cereals and oilseed rape (OSR) at several dates to meet the need of the crop more precisely. Our objective was to determine how prior fertilizer N application as slurry and/or mineral N affects contributions of fertilizer- and soil-derived N to N uptake of barley (1997), oilseed rape (OSR; 1998) and wheat (1999). In addition, residual fertilizer N effects were observed in the subsequent crop. Since autumn 1991, slurry (none, slurry in autumn, in spring, in autumn plus in spring) and mineral N fertilizer (0, 12 and 24 g N m,2) were applied annually. Each year, the treatments were located on the same plots. In 1997,1999, the splitting rates of the mineral N fertilization were labelled with 15N. Non-fertilizer N uptake was estimated from the total N uptake and the fertilizer 15N uptake. All three crops utilized the splitting rates differently depending on the time of application. Uptake of N derived from the first N rate applied at the beginning of spring growth was poorer than that from the second splitting rate applied at stem elongation (cereals) or third splitting rate applied at ear emergence or bud formation (all three crops). In contrast, N applied later in the growing season was taken up more quickly, resulting in higher fertilizer N-use efficiency. Mineral N fertilization of 24 g N m,2 increased significantly non-fertilizer N uptake of barley and OSR at most of the sampling dates during the growing season. In cereals, slurry changed the contribution of non-fertilizer N to the grain N content only if applied in spring, while OSR utilized more autumn slurry N. In OSR and wheat, only small residual effects occurred. The results indicate that 7 years of varying N fertilization did not change the contribution of soil N to crop N uptake. [source] Growth and Yield Response of Facultative Wheat to Winter Sowing, Freezing Sowing and Spring Sowing at Different Seeding RatesJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 1 2006A. Ozturk Abstract Growth and yield of wheat are affected by environmental conditions and can be regulated by sowing time and seeding rate. In this study, three sowing times [winter sowing (first week of September), freezing sowing (last week of October) and spring sowing (last week of April)] at seven seeding rates (325, 375, 425, 475, 525, 575 and 625 seeds m,2) were investigated during the 2002,03 and 2003,04 seasons, in Erzurum (Turkey) dryland conditions, using Kirik facultative wheat. A split-plot design was used, with sowing times as main plots and seeding rates randomized as subplots. There was a significant year × sowing time interaction for grain yield and kernels per spike. Winter-sown wheat produced a significantly higher leaf area index, leaf area duration, spikes per square metre, kernel weight and grain yield than freezing- and spring-sown wheat. The optimum time of sowing was winter for the facultative cv. Kirik. Grain yields at freezing and spring sowing were low, which was largely the result of hastened crop development and high temperatures during and after anthesis. Increasing seeding rate up to 525 seeds m,2 increased the spikes per square metre at harvest, resulting in increased grain yield. Seeding rate, however, was not as important as sowing time in maximizing grain yield. Changes in spikes per square metre were the major contributors to the grain-yield differences observed among sowing times and seeding rates. Yield increases from higher seeding rates were greater at freezing and spring sowing. We recommended that a seeding rate of 525 seeds m,2 be chosen for winter sowing, and 575 seeds m,2 for freezing and spring sowing. [source] Productivity and Sustainability of Cotton (Gossypium hirsutum L.),Wheat (Triticum aestivum L.) Cropping System as Influenced by Prilled Urea, Farmyard Manure and AzotobacterJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 5 2004A. Das Abstract Field experiments were conducted at Indian Agricultural Research Institute, New Delhi, during 2001,2002 and 2002,2003, to study the effect of inorganic, organic and Azotobacter combined sources of N on cotton (Gossypium hirsutum L.) and their residual effect on succeeding wheat (Triticum aestivum L.) crop. The results indicated considerable increase in yield attributes and mean seed cotton yield (2.33 Mg ha,1) with the combined application of 30 kg N and farmyard manure (FYM) at 12 Mg ha,1 along with Azotobacter (M4). The treatment in cotton that included FYM, especially when fertilizer N was also applied could either improve or maintain the soil fertility status in terms of available N, P and K. Distinct increase in yield attributes and grain yield of wheat was observed with the residual effect of integrated application of 30 kg N ha,1 + FYM at 12 Mg ha,1 + Azotobacter. Direct application of 120 kg N ha,1 resulted 67.4 and 17.7 % increase in mean grain yield of wheat over no N and 60 kg N ha,1, respectively. Integrated application of organic and inorganic fertilizer is therefore, recommended for higher productivity and sustainability of the cotton,wheat system. [source] Effect of Water Stress at Various Growth Stages on Some Quality Characteristics of Winter WheatJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 2 2004A. Ozturk Abstract A field experiment was carried out in Erzurum (Turkey) on winter wheat to analyse the effect of water stress at different growth stages , fully irrigated (FI), rainfed (R), early water stress (EWS), late water stress (LWS) and continuous water stress (CWS), on some quality characteristics , in the 1995,96 and 1996,97 cropping seasons. Water stress had a substantial effect on most of the quality characteristics. As averages of cropping seasons, CWS, EWS, R and LWS treatments decreased grain yields by 65.5, 40.6, 30.5 and 24.0 %, respectively, compared with the FI treatment. CWS increased grain protein content by 18.1 %, sedimentation volume by 16.5 %, wet gluten content by 21.9 % and decreased 1000-kernel weight by 7.5 g compared with FI treatment. LWS caused an increase of 8.3 % in grain protein content, 8.7 % in sedimentation volume, 10.8 % in wet gluten content and a reduction of 3.8 g in 1000-kernel weight compared with FI. EWS and R increased sedimentation volume and wet gluten content, but decreased 1000-kernel weight compared with FI. The effect of LWS on grain quality was more significant than that of EWS. The results suggest that soil moisture conditions increase grain yield and kernel weight of winter wheat but decrease its quality. [source] Lack of Interaction between Extreme High-Temperature Events at Vegetative and Reproductive Growth Stages in WheatJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2003B. Wollenweber Abstract Increased climatic variability and more frequent episodes of extreme conditions may result in crops being exposed to more than one extreme temperature event in a single growing season and could decrease crop yields to the same extent as changes in mean temperature. The developmental stage of the crop exposed to increased temperatures will determine the severity of possible damage experienced by the plant. It is not known whether or not the damaging effects of heat episodes occurring at different phenological stages are additive. In the present study, the interaction of high-temperature events applied at the stages of double ridges and anthesis in Triticum aestivum (L.) cv. Chablis was investigated. Biomass accumulation of control plants and that of plants experiencing high temperatures during the double-ridge stage were similar and were reduced by 40 % when plants were subjected to a heat event at anthesis. Grain number on the main and side tillers declined by 41 %, and individual grain weight declined by 45 % with heat stress applied at the double-ridge stage and anthesis or at anthesis alone. The harvest index was reduced from 0.53 to 0.33. Nitrogen contents in leaves were reduced by 10 % at the double-ridge stage and by 25 % at anthesis. The maximum rates of CO2 assimilation increased with heat stress at the double-ridge stage and higher rates were maintained throughout the growing season. The results clearly indicate that an extreme heat event at the double-ridge stage does not affect subsequent growth or the response of wheat to heat stress at anthesis. [source] Strategies to Improve the Use Efficiency of Mineral Fertilizer Nitrogen Applied to Winter WheatJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2002K. Blankenau Recovery of fertilizer nitrogen (N) applied to winter wheat crops at tillering in spring is lower than that of N applied at later growth stages because of higher losses and immobilization of N. Two strategies to reduce early N losses and N immobilization and to increase N availability for winter wheat, which should result in an improved N use efficiency (= higher N uptake and/or increased yield per unit fertilizer N), were evaluated. First, 16 winter wheat trials (eight sites in each of 1996 and 1997) were conducted to investigate the effects of reduced and increased N application rates at tillering and stem elongation, respectively, on yield and N uptake of grain. In treatment 90-70-60 (90 kg N ha,1 at tillering, 70 kg N ha,1 at stem elongation and 60 kg N ha,1 at ear emergence), the average values for grain yield and grain N removal were up to 3.1 and 5.0 % higher than in treatment 120-40-60, reflecting conventional fertilizer practice. Higher grain N removal for the treatment with reduced N rates at tillering, 90-70-60, was attributed to lower N immobilization (and N losses), which increased fertilizer N availability. Secondly, as microorganisms prefer NH4+ to NO3, for N immobilization, higher net N immobilization would be expected after application of the ammonium-N form. In a pot experiment, net N immobilization was higher and dry matter yields and crop N contents at harvest were lower with ammonium (ammonium sulphate + nitrification inhibitor Dicyandiamide) than with nitrate (calcium nitrate) nutrition. Five field trials were then conducted to compare calcium nitrate (CN) and calcium ammonium nitrate (CAN) nutrition at tillering, followed by two CAN applications for both treatments. At harvest, crop N and grain yield were higher in the CN than in the CAN treatment at each N supply level. In conclusion, fertilizer N use efficiency in winter wheat can be improved if N availability to the crops is increased as a result of reduced N immobilization (and N losses) early in the growth period. N application systems could be modified towards strategies with lower N applications at tillering compensated by higher N dressing applications later. An additional advantage is expected to result from use of nitrate-N fertilizers at tillering. Strategien zur Verbesserung der Effizienz von Düngerstickstoff in Winterweizen Aus früheren Versuchen mit Winterweizen ist bekannt, daß zur Ernte die Wiederfindung von im Frühjahr zur Bestokkung gedüngtem Stickstoff (N) geringer ist, als die von N aus Spätgaben. Die Ursachen liegen in einer höheren mikrobiell-bedingten Netto-N-Immobilisation, aber auch N-Verlusten zwischen Bestockung und Schoßbeginn im Vergleich zu späteren Wachstumstadien begründet. In den vorliegenden Versuchen wurden zwei Strategien getestet, um insbesondere die früh in der Vegetation auftretende Netto-N-Immobilisation zu vermindern. Die dadurch erwartete erhöhte N-Verfügbarkeit sollte zu einer erhöhten N-Effizienz (höherer N-Entzug/Ertrag bezogen auf die N-Düngung) führen. 1996 und 1997 wurden jeweils 8 Feldversuche mit Winterweizen durchgeführt, um den Einfluß einer reduzierten Andüngung bei gleichzeitig erhöhter Schossergabe im Vergleich zur konventionellen N-Düngung zu untersuchen. Tatsächlich wurden in dem Prüfglied 90-70-60 (N-Sollwertdüngung: 90 kg N ha,1, Schossergabe: 70 kg N ha,1, Ährengabe: 60 kg N ha,1) im Mittel bis zu 3.1 % höhere Erträge und 5.0 % höhere N-Abfuhren mit dem Korn im Vergleich zur konventionellen Variante 120-40-60 (N-Sollwertdüngung: 120 kg N ha,1, Schossergabe: 40 kg N ha,1 und Ährengabe: 60 kg N ha,1) erzielt. Die höhere N-Abfuhr kann auf eine erhöhte N-Verfügbarkeit infolge geringerer mikrobieller N-Festlegung zurückgeführt werden. Da die vornehmlich heterotrophen Bodenmikroorganismen bevorzugt NH4+ gegenüber NO3, immobilisieren, kann eine höhere N-Immobilisation bei Ammonium-Düngung erwartet werden. Tatsächlich wurden in einem Gefäßversuch nach Düngung von Ammoniumsulfat (+ Nitrifikationshemmer Dicyandiamid) geringere Trokkenmasseerträge und N-Aufnahmen von Weizenpflanzen erzielt als mit Calciumnitrat. Für die Ammoniumsulfatvariante ergab sich eine höhere Netto-N-Immobilisation. Danach wurde in fünf Feldversuchen mit Winterweizen der Einfluß einer Andüngung mit Nitrat (Calciumnitrat) im Vergleich zur Verwendung des ammoniumhaltigen Kalkammonsalpeters (KAS) auf die N-Aufnahme und den Kornertrag untersucht (beide Varianten erhielten KAS als Spätgaben). In der nitratangedüngten Variante wurden zum Teil signifikant höhere Ertäge und N-Aufnahmen in Korn und Stroh ermittelt. Aus den dargestellten Versuchen kann gefolgert werden, daß die Düngerstickstoff-Effizienz verbessert werden kann, wenn vor allem die N-Immobilisation (und eventuell auch N-Verluste) in frühen Wachstumsstadien zwischen Bestockung und Schoßbeginn verringert und so die N-Verfügbarkeit erhöht wird. Es kann empfohlen werden Winterweizenbestände mit geringeren N-Mengen , als nach N-Sollwert 120 kg N ha,1 vorgesehen , anzudüngen und die Schossergabe entsprechend zu erhöhen. Die Verwendung von nitrathaltigen Düngern bei der Andüngung ist von Vorteil. [source] Effects of Nitrogen on Dry Matter Accumulation and Productivity of Three Cropping Systems and Residual Effects on Wheat in Deep Vertisols of Central IndiaJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 2 2002P. Ramesh A field experiment was conducted on deep vertisols of Bhopal, India to study the effects of three levels of nitrogen (N), namely 0, 75 and 100 % of the recommended dose of nitrogen (RDN), on the dry matter accumulation (DMA) and productivity of three cropping systems (sole soybean, sole sorghum and soybean + sorghum intercropping) during the rainy season and their residual effect on the subsequent wheat crop during the post-rainy season. During the rainy season, sole sorghum was found to have significantly higher DMA and productivity in terms of soybean equivalent yield (SEY) than sole soybean or soybean + sorghum intercropping. Increasing the N dose from 0 to 100 % RDN significantly improved the DMA and SEY. At a low fertility level (N0), soybean + sorghum intercropping was found to be more productive, while at a high fertility level (100 % RDN), sole sorghum was more productive than the other two cropping systems. However, during the post-rainy season, sole soybean as the preceding crop gave the highest DMA and seed yield of wheat, which were similar to those found with soybean + sorghum intercropping. Sorghum followed by wheat gave the lowest DMA and seed yield of wheat. Application of 100 % RDN irrespective of cropping system during the preceding crop improved the DMA of wheat but not its seed yield. However, N applied to the wheat crop significantly increased its DMA and seed yield. Einfluss von Stickstoff auf Trockenmasseakkumulation und Produktivität von drei Anbausystemen und deren Rückstandswirkung auf Weizen in einem tiefen Vertisol Zentralindiens Ein Feldexperiment wurde durchgeführt auf einem tiefen Vertisol bei Bhopal, Indien, um den Einfluss von drei Stickstoffkonzentrationen 0, 75 und 100 % der empfohlenen Stickstoffmenge (RDN) auf die Trockenmasseakkumulation (DMA) und Produktivität von drei Anbausystemen (Reinanbau Sojabohne, Reinanbau Sorghum und Sojabohne + Sorghum Mischanbau) während der Regensaison und deren Nachwirkungen auf den folgenden Anbau von Weizen während der Nachregensaison zu untersuchen. Während der Regensaison war der Reinanbau von Sorghum signifikant höher in DMA und in der Produktivität in Form von Ertragsäquivalenten für Sojabohnen (SEY) im Vergleich zu einem Reinanbau von Sojabohne oder einem Mischanbau von Sojabohne + Sorghum. Eine Erhöhung der N-Anwendung von 0 bis 100 % RDN erhöhte Signifikanz DMA und SEY. Unter der niedrigen Düngung (N0) erwies sich Sojabohne + Sorghum Mischanbau als produktiver im Vergleich zu einer hohen Düngungeranwendung (100 % RDN), Reinanbau war produktiver als die anderen beiden Anbausysteme. Allerdings während der Nachregensaison erwies sich der Reinanbau von Sojabohnen vor Weizen als die höchste DMA und Ertragsmenge, was mit dem Sojabohnen + Sorghum Mischanbau vergleichbar war. Sorghum gefolgt von Weizen ergab den geringsten DMA und niedrigsten Weizenertrag. Die Anwendung von 100 % RDN erhöhte unabhängig von dem Anbausystem der vorhergehenden Kulturpflanzen DMA von Weizen aber nicht den Kornertrag. Allerdings erhöhte N im Weizenanbau signifikant sowohl DMA als auch Kornertrag. [source] Effect of Different Crop Densities of Winter Wheat on Recovery of Nitrogen in Crop and Soil within the Growth PeriodJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2001K. Blankenau Previous experiments have shown that, at harvest of winter wheat, recovery of fertilizer N applied in early spring [tillering, Zadok's growth stage (GS) 25] is lower than that of N applied later in the growth period. This can be explained by losses and immobilization of N, which might be higher between GS 25 and stem elongation (GS 31). It was hypothesized that a higher crop density (i.e. more plants per unit area) results in an increased uptake of fertilizer N applied at GS 25, so that less fertilizer N is subject to losses and immobilization. Different crop densities of winter wheat at GS 25 were established by sowing densities of 100 seeds m,2 (Slow), 375 seeds m,2 (Scfp= common farming practice) and 650 seeds m,2 (Shigh) in autumn. The effect of sowing density on crop N uptake and apparent fertilizer N recovery (aFNrec = N in fertilized treatments , N in unfertilized treatments) in crops and soil mineral N (Nmin), as well as on lost and immobilized N (i.e. non-recovered N = N rate , aFNrec), was investigated for two periods after N application at GS 25 [i.e. from GS 25 to 15 days later (GS 25 + 15d), and from GS 25 + 15d to GS 31] and in a third period between GS 31 and harvest (i.e. after second and third N applications). Fertilizer N rates varied at GS 25 (0, 43 and 103 kg N ha,1), GS 31 (0 and 30 kg N ha,1) and ear emergence (0, 30 and 60 kg ha,1). At GS 25 + 15d, non-recovered N was highest (up to 33 kg N ha,1 and up to 74 kg N ha,1 at N rates of 43 and 103 kg N ha,1, respectively) due to low crop N uptake after the first N dressing. Non-recovered N was not affected by sowing density. Re-mineralization during later growth stages indicated that non-recovered N had been immobilized. N uptake rates from the second and third N applications were lowest for Slow, so non-recovered N at harvest was highest for Slow. Although non-recovered N was similar for Scfp and Shigh, the highest grain yields were found at Scfp and N dressings of 43 + 30 + 60 kg N ha,1. This combination of sowing density and N rates was the closest to common farming practice. Grain yields were lower for Shigh than for Scfp, presumably due to high competition between plants for nutrients and water. In conclusion, reducing or increasing sowing density compared to Scfp did not reduce immobilization (and losses) of fertilizer N and did not result in increased fertilizer N use efficiency or grain yields. Einfluß unterschiedlicher pflanzendichten von Winterweizen auf die Wiederfindung von Stickstoff in Pflanze und Boden während der Vegetationsperiode Aus Wintergetreideversuchen ist bekannt, daß zur Ernte die Wiederfindung von Düngerstickstoff aus der Andüngung (Bestockung, [GS-Skala nach Zadok] GS 25) im Aufwuchs und in mineralischer Form im Boden (Nmin) niedriger ist als die von Düngerstickstoff der Schosser-und Ährengaben. Dies kann auf höhere Verluste bzw. eine höhere Immobilisation von Düngerstickstoff zwischen GS 25 und Schoßbeginn zurückgeführt werden, da hier die N-Aufnahme der Pflanzen im Vergleich zu späteren Wachstumsstadien gering ist. Daraus wurde abgeleitet, daß eine Erhöhung der Pflanzendichte zu einer erhöhten Aufnahme von früh gedüngtem N führen könnte, so daß weniger Dünger-N für Verlust- und Immobilisationsprozesse im Boden verbleibt. Unterschiedliche Pflanzendichten wurden durch unterschiedliche Aussaatstärken im Herbst erreicht (Slow= 100 Körner m,2, Scfp [herkömmliche Praxis]= 375 Körner m,2, Shigh= 650 Körner m,2). In der folgenden Vegetationsperiode wurde der Einfluß der verschiedenen Aussaatstärken auf die N-Aufnahme, die apparente Wiederfindung von Dünger-N (aFNrec = N in gedüngten , N in ungedüngten Prüfgliedern) in Pflanzen und Nmin, sowie auf potentielle Verluste und Immobilisation von Dünger-N (N-Defizit = N-Düngung , aFNrec) für zwei Phasen im Zeitraum zwischen der ersten N-Gabe (GS 25) und der Schossergabe zu GS 31 (d. h. zwischen GS 25 und 15 Tagen später [GS 25 + 15d] und von GS 25 + 15d bis GS 31), sowie zwischen GS 31 und der Ernte (d. h. nach der zweiten und dritten N-Gabe) untersucht. Die N-Düngung variierte zu den Terminen GS 25 (0, 43, 103 kg N ha,1), GS 31 (0, 30 kg N ha,1) und zum Ährenschieben (0, 30, 60 kg N ha,1). Unabhängig von der Aussaatstärke war das N-Defizit zum Termin GS 25 + 15d am höchsten (bis zu 33 kg N ha,1 und 74 kg N ha,1 bei einer N-Düngung von 43 bzw. 103 kg N ha,1), da die N-Aufnahme durch die Pflanzen während der Bestockungsphase am geringsten war. Das N-Defizit zeigt vornehmlich immobilisierten N an, da zu späteren Terminen eine Re-Mobilisation von N auftrat. Zwischen GS 31 und der Ernte wurden für die Aussaatstärke Slow die geringsten Aufnahmeraten von Düngerstickstoff aus der Schosser- und Ährengabe errechnet, so daß für Slow die höchsten N-Defizitmengen ermittelt wurden. Obwohl die N-Defizitmengen für Scfp und Shigh annähernd gleich waren, wurden bei N-Düngung von 43 + 30 + 60 kg N ha,1 für Scfp die höchsten Kornerträge erzielt. Diese Kombination von Aussaatstärke und N-Düngung kann als praxisüblich bezeichnet werden. Für Shigh wurden vermutlich niedrigere Kornerträge erzielt, weil die Konkurrenz um Nährstoffe und Wasser zwischen den Pflanzen aufgrund der hohen Pflanzendichte am intensivsten war. Die Ergebnisse lassen den Schluß zu, daß eine Verringerung oder Erhöhung der Pflanzendichte über entsprechende Aussaatstärken nicht zu einer Reduktion der Dünger-N-Immobilisation (oder von N-Verlusten) führt und demnach auch nicht die Dünger-N-Ausnutzung durch die Bestände erhöht wird. [source] Physiological and Biochemical Responses of Hexaploid and Tetraploid Wheat to Drought StressJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2000V. Chandrasekar An experiment was conducted to investigate the physiological and biochemical responses of two hexaploids viz., C 306 (water stress tolerant) and Hira (water stress susceptible), and two tetraploids, HW 24 (Triticum dicoccum) and A 9-30-1 (Triticum durum) wheat genotypes to water stress under pot culture condition. Water stress was imposed for a uniform period of 10 days at 50, 60 and 70 days after sowing (DAS) and observations were recorded at 60, 70 and 80 DAS. Total dry matter and plant height were recorded at harvest. Water stress caused a decline in relative water content (RWC), chlorophyll and carotenoid content, membrane stability and nitrate reductase activity and increased accumulation of proline at all stages and abscisic acid (ABA) at 80 DAS in all the genotypes. Both the tetraploids showed a lower reduction in RWC and highest ABA accumulation under water stress. Among the hexaploids Hira showed the most decline in RWC and the lowest ABA accumulation. The tetraploids also showed comparatively higher carotenoid content and membrane stability, closely followed by C 306, while Hira showed the minimum response under water stress. Nitrate reductase activity and chlorophyll content under irrigated conditions were highest in Hira but under water stress the lowest per cent decline was observed in C 306, followed by HW 24, A 9-30-1, and Hira. Proline accumulation under water stress conditions was highest in hexaploids C 306 and Hira and lowest in tetraploids HW 24 and A 9-30-1. Tetraploids HW 24, followed by A 9-30-1 maintained higher plant height and total dry matter (TDM) under water stress and also showed a lower per cent decline under stress than hexaploids C 306 and Hira. From the results it is clear that proline accumulation did not contribute to better drought tolerance of tetraploids than hexaploids. It is also apparent that water stress tolerance is the result of the cumulative action of various physiological processes, and all the parameters/processes may not be positively associated with the drought tolerance of a particular tolerant genotype. [source] Fate of inoculated Escherichia coli in hayJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007Z.G. Weinberg Abstract Aims:, To monitor the fate of inoculated Escherichia coli in dry and moist hay of various types, under laboratory conditions. Methods and Results:, Wheat, vetch and clover hay were used as received or wetted to 250,300 g kg,1 moisture. The hay was inoculated at about 106 CFU g,1 with a kanamycin-resistant E. coli strain that expresses the green fluorescence protein, and was stored in small open glass jars that were covered with aluminium foil. Three jars per treatment were sampled on days 1 and 3, or 4 and 7, or 8, 20 and 50, respectively, after the initiation of the experiments, and the numbers of E. coli in the hay were determined. The results indicated that E. coli disappeared from both dry and moist hay by 7,8 days after inoculation. However, in a few cases colonies that were presumed to be E. coli developed after incubation in Luria broth medium. Conclusions:, The tagged E. coli strain usually disappeared rapidly from both the dry and the moist hay, in spite of the high level of inocula used. However, in some cases a few, possibly injured E. coli might have persisted, and could be detected after incubation in a rich growth medium. Significance and Impact of the Study:, This study is part of a risk assessment associated with sewage irrigation of forage crops in Israel. The results indicate that E. coli added to the hay is not likely to pose a health risk to cattle or to humans. Nevertheless, more research with natural strains of E. coli and other enteric pathogens that might be more adapted to forage conditions is warranted in order to ensure the safety of sewage-irrigated crops. [source] REDUCED/OXIDIZED GLUTATHIONE INDEX AS A TOOL FOR FOOD MONITORITY OXIDATIVE STRESS DURING EXTRUSION COOKINGJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 3 2001H. ZIELINSKI Reduced and oxidized glutathione was assayed in wheat, barley, rye, oats and buckwheat before and after extrusion cooking. The results obtained indicate that GSH/GSSG ratio was decreased from 1.91 and 10.72 for raw oat and buckwheat grains to the 1.13, 1.01, 1.10 and 4.72, 3.89, 3.89 for extruded material, respectively, in temperature used of 120, 160 and 200C. These results indicate that the oxidative stress is least developed during extrusion cooking of oat and buckwheat grains. Wheat and barley grains were more prone to oxidative damage, and the observed decrease of the ratio ranged from 6.84 and 4.89 (wheat cv. Almari and barley cv. Mobek, raw material) to the 1.89 and 2.07 (after extrusion cooking at 200C, respectively). No significance differences were found between two cultivars of wheat and barley being used in the experiment. The most decreased ratio up to five times was found in rye grain extrudates. The extrusion performed under barrel temperature profile of 80,100,120,120,120C caused significant decrease in GSH content when compared to raw material. The next higher barrel temperature profiles of 100,130,160,160,120C and 120,160,200,200,120C led to further GSH decrease in extruded wheat grains. In contrast, the two high temperature profiles did not [source] Development and Evaluation of an Ozonated Water System for Antimicrobial Treatment of Durum WheatJOURNAL OF FOOD SCIENCE, Issue 7 2009B. Dhillon ABSTRACT:, Ozonated water is reported to be effective in reducing the microbial load in foods such as fruits, vegetables, and grains. Ozonated water may be an effective alternative to chlorinated water in treating durum wheat before milling. Therefore, durum wheat was washed with ozonated water and analyzed for yeast and mold count (YMC) and aerobic plate count (APC). A system for producing and monitoring ozonated water was developed. The effect of water quality (tap, distilled, and ultra-pure), temperature (7, 15, and 25 °C), and pH (2, 4, and 6.5) was evaluated on the following: steady-state dissolved ozone concentration, ozone decay constant, half-life, mass transfer coefficient, equilibrium ozone concentration, and solubility ratio. The study of these parameters was important to attain a stable, high dissolved ozone concentration at the outset of washing and to have information for system improvement and scale-up. A 1% acetic acid solution (pH 2) at 15 °C resulted in high dissolved ozone concentration (21.8 mg/L) and long half-life (9.2 min). Subsequently, wheat was washed with 5 wash water types: distilled water, ozonated water (16.5 mg/L), chlorinated water (700 mg/L), acetic acid solution (1%), and acetic acid + ozonated water (1%, 20.5 mg/L). The treated samples were analyzed for YMC and APC. The acetic acid + ozonated water treatment was the most effective, with a reduction of 4.1 and 3.2 log10 colony forming units/g in YMC and APC, respectively. Though ozonated water was not very effective alone, it was useful in combination with acetic acid. [source] Effects of Transglutaminase on SDS-PAGE Patterns of Wheat, Soy, and Barley Proteins and their BlendsJOURNAL OF FOOD SCIENCE, Issue 7 2002A. Basman ABSTRACT: Transglutaminase (TG) catalyzes the formation of nondisulfide covalent crosslinks between pep-tide-bound glutaminyl residues and ,-amino groups of lysine residues in proteins. TG can be used for polymerizing proteins from 1 or more sources through formation of intermolecular crosslinks. This study investigated, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, polymers created by the action of TG on proteins of wheat, soy, barley, wheat-soy, and wheat-barley blends. Electrophoretic results showed that with increasing incubation time, the crosslinking reaction is substantially increased, with progressive decrease or disappearance of some protein monomers. Densitometric results showed that soy proteins were the best substrates of TG while barley and wheat proteins were similar in reactivity. [source] The economic potential of precision nitrogen application with wheat based on plant sensingAGRICULTURAL ECONOMICS, Issue 4 2009Jon T. Biermacher Nitrogen fertilizer; Precision agriculture; Stochastic plateau; Wheat Abstract Plant-based precision nitrogen fertilizer application technologies have been developed as a way to predict and precisely meet nitrogen needs. Equipment necessary for precision application of nitrogen, based on sensing of growing wheat plants in late winter, is available commercially, but adoption has been slow. This article determines the expected profit from using a plant-sensing system to determine winter wheat nitrogen requirements. We find that plant-sensing systems have the potential to be more profitable than traditional nonprecise systems, but the existing system simulated was roughly breakeven with a traditional system. [source] The Characterization and Geographical Distribution of the Genes Responsible for Vernalization Requirement in Chinese Bread WheatJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 4 2009Qing-Ming Sun Abstract The frequency and distribution of the major vernalization requirement genes and their effects on growth habits were studied. Of the 551 bread wheat genotypes tested, seven allelic combinations of the three Vrn-1 genes were found to be responsible for the spring habit, three for the facultative habit and one for the winter habit. The three Vrn-1 genes behaved additively with the dominant allele of Vrn-A1 exerting the strongest effect. The allele combinations of the facultative genotypes and the discovery of spring genotypes with "winter" allele of Vrn-1 implied the presence of as yet unidentified alleles/genes for vernalization response. The dominant alleles of the three Vrn-1 genes were found in all ten ecological regions where wheat is cultivated in China, with Vrn-D1 as the most common allele in nine and Vrn-A1 in one. The combination of vrn-A1vrn-B1Vrn-D1 was the predominant genotype in seven of the regions. Compared with landraces, improved varieties contain a higher proportion of the spring type. This was attributed by a higher frequency of the dominant Vrn-A1 and Vrn-B1 alleles in the latter. Correlations between Vrn-1 allelic constitutions and heading date, spike length, plant type as well as cold tolerance were established. [source] Reproductive Allocation Patterns in Different Density Populations of Spring WheatJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 2 2008Jing Liu Abstract The effects of increased intraspecific competition on size hierarchies (size inequality) and reproductive allocation were investigated in populations of the annual plant, spring wheat (Triticum aestivum). A series of densities (100, 300, 1 000, 3 000 and 10 000 plants/m2) along a gradient of competition intensity were designed in this experiment. The results showed that average shoot biomass decreased with increased density. Reproductive allocation was negatively correlated to Gini coefficient (R2 = 0.927), which suggested that reproductive allocation is inclined to decrease as size inequality increases. These results suggest that both vegetative and reproductive structures were significantly affected by intensive competition. However, results also indicated that there were different relationships between plant size and reproductive allocation pattern in different densities. In the lowest density population, lacking competition (100 plants/m2), individual reproductive allocation was size independent but, in high density populations (300, 1 000, 3 000 and 10 000 plants/m2), where competition occurred, individual reproductive allocation was size dependent: the small proportion of larger individuals were winners in competition and got higher reproductive allocation (lower marginal reproductive allocation; MRA), and the larger proportion of smaller individuals were suppressed and got lower reproductive allocation (higher MRA). In conclusion, our results support the prediction that elevated intraspecific competition would result in higher levels of size inequality and decreased reproductive allocation (with a negative relationship between them). However, deeper analysis indicated that these frequency- and size-dependent reproductive strategies were not evolutionarily stable strategies. [source] Relationship between Carbon Isotope Discrimination and Grain Yield in Spring Wheat Cultivated under Different Water RegimesJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 10 2007Xing Xu Abstract In C3 plants, carbon isotope discrimination (,) has been proposed as an indirect selection criterion for grain yield. Reported correlations between , and grain yield however, differ highly according to the analyzed organ or tissue, the stage of sampling, and the environment and water regime. In a first experiment carried out in spring wheat during two consecutive seasons in the dry conditions of northwest Mexico (Ciudad Obregon, Sonora), different water treatments were applied, corresponding to the main water regimes available to spring wheat worldwide, and the relationships between , values of different organs and grain yield were examined. Under terminal (post-anthesis) water stress, grain yield was positively associated with , in grain at maturity and in leaf at anthesis, confirming results previously obtained under Mediterranean environments. Under early (pre-anthesis) water stress and residual moisture stress, the association between grain , and yield was weaker and highly depended on the quantity of water stored in the soil at sowing. No correlation was found between , and grain yield under optimal irrigation. The relationship between , and grain yield was also studied during two consecutive seasons in 20 bread wheat cultivars in the Ningxia region (Northern China), characterized by winter drought (pre-anthesis water stress). Wheat was grown under rainfed conditions in two locations (Guyuan and Pengyang) and under irrigated conditions in another two (Yinchuan and Huinong). In Huinong, the crop was also exposed to salt stress. Highly significant positive associations were found between leaf and grain , and grain yields across the environments. The relationship between , and yield within environments highly depended on the quantity of water stored in the soil at sowing, the quantity and distribution of rainfall during the growth cycle, the presence of salt in the soil, and the occurrence of irrigation before anthesis. These two experiments confirmed the value of , as an indirect selection criterion for yield and a phenotyping tool under post-anthesis water stress (including limited irrigation). [source] Quantitative Trait Loci Mapping for Chlorophyll Fluorescence and Associated Traits in Wheat (Triticum aestivum)JOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 5 2007De-Long Yang Abstract 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 (ChlC) and to map QTLs at the grain-filling 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 ChlC. 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 epistatic 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 ChlC were mapped on chromosomes 1A, 5A and 7A. The contributions of these QTLs for ChlC 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. (Handling editor: Yong-Biao Xue) [source] | |||||||||||||||||||||||||||||||||||||||||||