Plant genetic diversity, irrigation and nutrient cycling in traditional mountain oases of northern Oman

Little is known about plant biodiversity, irrigation management and nutrient fluxes as criteria to assess the sustainability of traditional irrigation agriculture in eastern Arabia. Therefore interdisciplinary studies were conducted over 4 yrs on flood-irrigated fields dominated by wheat (Triticum spp.), alfalfa (Medicago sativa L.) and date palm (Phoenix dactylifera L.) in two mountain oases of northern Oman. In both oases wheat landraces consisted of varietal mixtures comprising T. aestivum and T. durum of which at least two botanical varieties were new to science. During irrigation cycles of 6-9 days on an alfalfa-planted soil, volumetric water contents ranged from 30-13%. For cropland, partial oasis balances (comprising inputs of manure, mineral fertilizers, N2-fixation and irrigation water, and outputs of harvested products) were similar for both oases, with per hectare annual surpluses of 131 kg N, 37 kg P and 84 kg K at Balad Seet and of 136 kg N, 16 kg P and 66 kg K at Maqta. Respective palm grove surpluses, in contrast were with 303 kg N, 38 kg P, and 173 kg K ha^-1 yr^-1 much higher at Balad Seet than with 84 kg N, 14 kg P and 91 kg K ha^-1 yr^-1 at Maqta. The results show that the sustainability of these irrigated landuse systems depends on a high quality of the irrigation water with low Na but high CaCO3, intensive recycling of manure and an elaborate terrace structure with a well tailored water management system that allows adequate drainage.

Entwicklung und Validierung einer elektrochemischen Methode zur Differenzierung von Weizenproben und elektrochemische Unterschungen an Möhren

Eine Methode zur Differenzierung von Weizenproben (Triticum aestivum L.) mittels elektrochemischer Parameter wurde entwickelt und validiert. Die Methode wurde auf die wichtigsten Einfluss- und Verfahrensgrößen hin untersucht. Als eine Voraussetzung zur Validierung wurden alle Laborprozesse in normativen Dokumenten beschrieben. Dies ist zum ersten Mal überhaupt für die Methode in diesem Umfang durchgeführt worden. Mit der Methode wurden Messungen durchgeführt, um Weizenproben aus fünf verschiedenen Anbausystemen (DOK-Versuch) am Produkt zu differenzieren. Eine Anbauvariante konnte anhand der Messungen statistisch signifikant abgetrennt werden. Das Validierungsziel, alle Varianten des DOK-Versuches statistisch signifikant mit elektrochemischen Parametern zu trennen, wurde demnach noch nicht erreicht. Weiterhin wurde versucht, Möhren (Daucus carota L.), die sich hinsichtlich der gedüngten Stickstoffmenge unterschieden, elektrochemisch zu differenzieren. Mit der eingesetzten Methode konnte eine statistisch signifikante Trennung erfolgen.

Charakterisierung von Möhren und Weizen aus ökologischem und konventionellem Anbau anhand ihrer Carotinoid- und Polyphenolkonzentration

Kurzfassung: Der Markt für ökologische Lebensmittel wächst stark. Verbraucher kaufen Produkte aus ökologischem Landbau aus einer Vielzahl von Gründen. Ein Teil dieser Gründe lässt sich nicht auf die Produktqualität zurückführen, sondern beruht auf der Annahme, dass sich der Produktionsprozess des Ökologischen Landbaus hinsichtlich der Schonung von Umweltressourcen, der Nachhaltigkeit der Produktion und sozialen Komponenten vom konventionellen Anbau unterscheidet. Daneben spielt der Wunsch nach einer gesunden Ernährung eine Rolle. Ökologische Lebensmittel können als Vertrauensgüter verstanden werden. Lebensmittelskandale machten in den vergangenen Jahren auch vor ökologischen Lebens¬mitteln nicht Halt. Folgerichtig erschütterte dies das Vertrauen der Verbraucher in ökologische Produkte. Mit steigender Produktion könnte die Gefahr, das weitere solche Ereignisse auftreten, steigen. Daher besteht Bedarf für Methoden, die die ökologische Produktqualität im Sinne einer Authentizitätsprüfung prüfen. Eine solche Prüfung könnte sich auf die Analyse sekundärer Pflanzenstoffe stützen. Diese Gruppe von Pflanzeninhaltsstoffen spielt bei der Diskussion um die besondere Qualität ökologischer Pflanzenprodukte eine große Rolle. Postuliert wird, dass ökologisch angebaute Pflanzen mangels mineralischer Düngung und mangels Schädlingsbekämpfung mit synthetischen Pestiziden einem erhöhten Stress ausgesetzt sind. Dies soll sich in einem höheren Niveau der mit den Selbstverteidigungsmechanismen der Pflanze eng verbundenen sekundären Pflanzenstoffe ausdrücken. Wichtige Untergruppen der sekundären Pflanzenstoffe sind Carotinoide und Polyphenole. An Weizen (Triticum aestivum L. und Triticum durum L.) und Möhre (Daucus carota L.) als für den ökologischen Landbau wichtigen Produkten wurden Messungen der Carotinoid- und Polyphenolkonzentration mit dem Ziel durchgeführt, die potentielle Eignung dieser Pflanzenstoffe als Biomarker zur Authentizitätsprüfung ökologischer Produkte zu evaluieren. Dazu wurden Proben aus ökologischem und konventionellem Anbau (Paarvergleich) untersucht. Diese stammten aus Langzeit-Feldversuchen (Weizen aus dem DOK- und dem MASCOT-Versuch), Feldversuchen und von Betriebspaaren untersucht. Ein generell höheres Niveau sekundärer Pflanzenstoffe in Möhren bzw. Weizen aus ökologischem Anbau gegenüber Proben aus konventionellem Anbau wurde nicht gefunden. Die Carotinoide waren weder bei der Möhre noch beim Weizen zur Authentizitätsprüfung geeignet. Die Konzentration der Carotinoide wurde stark durch die nicht dem Anbau¬verfahren zuzuordnenden Faktoren Klima, Sorte und Standort beeinflusst. Die Luteinkonzentration war das einzige durch das Anbauverfahren systematisch beeinflusste Carotenoid bei Weizen und Möhre. Die Unterschiede der Luteinkonzentration waren aber im Paarvergleich von Proben (ökologischer versus konventioneller Anbau) nicht durchgängig signifikant. Die Eignung von Polyphenolen als potentielles Authentizitätskriterium wurde nur an Möhren geprüft. Im Paarvergleich unterschieden sich die Konzentrationen einzelner Polyphenole signifikant und konsistent über Probenjahre und Standorte, nicht jedoch über Sorten hinweg. Wie bei den Carotinoiden konnte auch hier ein starker Einfluss von Probenjahr, Standort und Sorte gezeigt werden. Trotz der Variation durch diese nicht dem Anbau zuzuordnenden Faktoren war eine korrekte Klassifizierung der Proben nach Anbauverfahren möglich. Dies wurde mittels Diskriminanzanalyse getestet. Die Polyphenole sind daher potentiell als Authentizitätskriterium geeignet.

Discrimination between organically and conventionally grown winter wheat by means of holistic and selected analytical methods

Die Verordnung des Europäischen Rates (EC) 834/2007 erkennt das Recht des Konsumenten auf eine Entscheidung basierend auf vollständiger Information bezüglich der enthaltenen Zutaten im Produkt und deren Herkunft (Qualität der Verarbeitung). Die primäre Kennzeichnungsverordnung betont „organische“ Produktionsstandards ebenso wie die Notwendigkeit zur Kontrolle und Aufsicht. Jedoch ist zurzeit keine validierte Methode zur analytischen Diskriminierung zwischen „organischer“ und „konventioneller“ Herkunft von angebotenen Lebensmitteln verfügbar. Das Ziel der Dissertationsarbeit war die Überprüfung der Möglichkeit mit ausgewählten analytischen und holistischen Methoden zwischen organisch und konventionell angebautem Weizen objektiv zu unterscheiden. Dies beinhaltete die Bestimmung des Gesamtstickstoff (Protein) nach Dumas, zweidimensionale Fluoreszenzdifferenz Gelelektrophorese (2D DIGE) und die Kupferchloridkristallisation. Zusätzlich wurde die Anzahl der Körner pro Ähre (Kornzahl) bestimmt. Alle Bestimmungen wurden an rückverfolgbaren in den Jahren 2005 – 2007 in Belgien gesammelten Proben des Winterweizen (Triticum aestivum L. cv. Cubus) durchgeführt. Statistisch signifikante (p < 0.05) Unterschiede wurden innerhalb der untersuchten Probengruppen sowohl in der Kornzahl, dem Gesamtsticksoff (Eiweißgehalt), als auch in der Gesamtausbeute gefunden, wobei in den meisten Fällen die konventionellen Proben höhere Kornzahlen und Gesamtsticksoff (Eiweißgehalte) aufwiesen. Eine mit der 2D DIGE kompatible Probenvorbereitungsmethode für Winterweizen wurde entwickelt und auf einen internen Winterweizenstandard sowie die entsprechenden Proben angewendet. Die organischen Proben waren im Vergleich mit den konventionellen Gegenstücken in allen Fällen durch eine kleinere Anzahl von signifikant (p < 0.05) stärker exprimierten Proteinspots gekennzeichnet. Gewisse Tendenzen in Richtung der Bevorzugung bestimmter Regionen von stärker ausgeprägten Proteinspots auf aufeinanderfolgenden 2D Abbildungen in Abhängigkeit von der landwirtschaftlichen Methode konnten zwar beobachtet werden, jedoch konnte kein universelles Markerprotein zur Unterscheidung von konventionell und biologisch angebautem Winterweizen identifiziert werden. Die rechnergestützte Verarbeitung der digitalisierten Kristallisierungsbilder mittels multivariater statistischer Analyse und der Regression partieller kleinster Quadrate ermöglichte eine 100%ig korrekte Vorhersage der landwirtschaftlichen Methode unbekannter Proben sowie der Beschreibung der Kristallisierungsbilder. Diese Vorhersage bezieht sich nur auf den hier verwendeten Datensatz (Proben einer Sorte von drei Standorten über zwei Jahre) und kann nicht ohne weiteres übertragen (generalisiert) werden. Die Ergebnisse deuten an, dass die Quantifizierung der beschriebenen Parameter ein hohes Potential zur Lösung der gestellten Aufgabe besitzt.

Egyptian wheat

Wheat as the major cereal crop in Egypt is the core of the government's food security policy. But there are rapid losses of the genetic resources of the country as a result of ongoing modernization and development. Thus we compiled the largest possible number of Egyptian accessions preserved in the world gene banks. In the present study we collected nearly 1000 Egyptian wheat accessions. A part from the Triticum species of the Egyptian flora four species have been found, which were recorded for the first time T. turanicum, T. compactum, T. polonicum and T. aethiopicum. To classify the Egyptian wheat species using morphological studies, 108 accessions were selected. Thereafter, these accessions were cultivated and evaluated morphologically to confirm the validity of the classified species. During the morphological evaluation study, a new case was noticed for the number of glumes in one of the Egyptian wheat accessions. Three glumes per spikelet were observed in a branched spike. This led us to assess the phenomenon in all varieties with branching spikes within the genus Triticum. All varieties which have branching spikes at least in some spikletes have three glumes. We considered the case of the third glume as indicator for the domestication syndrome. Also, a new case of other forms of branching in the genus Triticum was investigated, which was a compromise between true and false-branching. We called it true-false branching. Comparative anatomical studies were carried out between Egyptian Triticum species to investigate the possibility of using anatomical features to classify the Egyptian wheat species. It was concluded that it is difficult to use anatomical features alone to differentiate between two Triticum species, especially when they belong to the same ploidy level. A key for the identification of Egyptian Triticum taxa was established.

Bedeutung der C- und N-Rhizodeposition für das mikrobielle Wachstum und den mikrobiellen Umsatz von C und N in der Rhizosphäre in Abhängigkeit von der Entfernung zur Wurzel

Ziel dieser Arbeit war es, die Bedeutung des C und N mit Herkunft aus der Rhizodeposition für das mikrobielle Wachstum und den C- und N-Umsatz in der Rhizosphäre in Abhängigkeit von der Entfernung zur Wurzel zu untersuchen. Dazu wurde als wesentliche methodische Voraussetzung ein künstliches Rhizosphärensystem entwickelt, um die durch die Rhizodeposite induzierten Prozesse an der Grenzfläche zwischen Wurzeloberfläche und Boden zu untersuchen. Dieses eingesetzte Rhizosphärensystem wurde nach einem Vorbild eines in schon vielfältigen Untersuchungen der Rhizosphäre eingesetzten Systems von GAHOONIA und NIELSEN (1991) konzipiert. Zur Verfolgung der pflanzlichen C- und N-Rhizodeposition im Boden wurden 13C- und 15N-Tracer-Isotopen-Techniken zur Isotopenmarkierung der Testpflanzen eingesetzt. Zur Probenahme des Rhizosphärenbodens in räumlichen Abstand zur künstlichen Rhizoplane wurde eine Schneidvorrichtung nach FITZ et al. (2003) eingesetzt, die es ermöglicht frische Bodenproben in definiertem Abstand zur künstlichen Rhizoplane zu schneiden. Das Rhizosphärensystem wurde in 13C- und 15N-Doppelmarkierungsexperimenten mit Lolium perenne, Triticum aestivum und Avena sativa eingesetzt.Das unterschiedliche Ansprechen der mikrobiellen Gemeinschaft auf den Substrateintrag in unterschiedlicher Entfernung zur Wurzel zeigte komplexe Wechselwirkungen in Bezug auf das mikrobielle Wachstum, den mikrobiellen Umsatz, den Substrateintrag aus der Rhizodeposition und den stimulierten Abbau der nativen organischen Bodensubstanz. Der Eintrag von Rhizodepositen stellt daher eine bedeutende Funktion in der Regulation der mikrobiellen Biomasse und der Prozesse des Umsatzes der organischen Bodensubstanz während und wahrscheinlich bis nach der Vegetationsperiode dar. Die simultane Verfolgung von Rhizodepositions-C und -N im Boden und deren Funktionen innerhalb der Rhizosphäre, gerade im Hinblick auf die mikrobielle Biomasse und den Umsatz der organischen Substanz im Boden, führt zu einem besseren Verständnis der komplexen wechselseitigen Prozesse zwischen Pflanze und Boden.

Effects of different tillage treatments on labile soil organic matter pools and stabilization processes

An improved understanding of soil organic carbon (Corg) dynamics in interaction with the mechanisms of soil structure formation is important in terms of sustainable agriculture and reduction of environmental costs of agricultural ecosystems. However, information on physical and chemical processes influencing formation and stabilization of water stable aggregates in association with Corg sequestration is scarce. Long term soil experiments are important in evaluating open questions about management induced effects on soil Corg dynamics in interaction with soil structure formation. The objectives of the present thesis were: (i) to determine the long term impacts of different tillage treatments on the interaction between macro aggregation (>250 µm) and light fraction (LF) distribution and on C sequestration in plots differing in soil texture and climatic conditions. (ii) to determine the impact of different tillage treatments on temporal changes in the size distribution of water stable aggregates and on macro aggregate turnover. (iii) to evaluate the macro aggregate rebuilding in soils with varying initial Corg contents, organic matter (OM) amendments and clay contents in a short term incubation experiment. Soil samples were taken in 0-5 cm, 5-25 cm and 25-40 cm depth from up to four commercially used fields located in arable loess regions of eastern and southern Germany after 18-25 years of different tillage treatments with almost identical experimental setups per site. At each site, one large field with spatially homogenous soil properties was divided into three plots. One of the following three tillage treatments was carried in each plot: (i) Conventional tillage (CT) with annual mouldboard ploughing to 25-30 cm (ii) mulch tillage (MT) with a cultivator or disc harrow 10-15 cm deep, and (iii) no tillage (NT) with direct drilling. The crop rotation at each site consisted of sugar beet (Beta vulgaris L.) - winter wheat (Triticum aestivum L.) - winter wheat. Crop residues were left on the field and crop management was carried out following the regional standards of agricultural practice. To investigate the above mentioned research objectives, three experiments were conducted: Experiment (i) was performed with soils sampled from four sites in April 2010 (wheat stand). Experiment (ii) was conducted with soils sampled from three sites in April 2010, September 2011 (after harvest or sugar beet stand), November 2011 (after tillage) and April 2012 (bare soil or wheat stand). An incubation study (experiment (iii)) was performed with soil sampled from one site in April 2010. Based on the aforementioned research objectives and experiments the main findings were: (i) Consistent results were found between the four long term tillage fields, varying in texture and climatic conditions. Correlation analysis of the yields of macro aggregate against the yields of free LF ( ≤1.8 g cm-3) and occluded LF, respectively, suggested that the effective litter translocation in higher soil depths and higher litter input under CT and MT compensated in the long term the higher physical impact by tillage equipment than under NT. The Corg stocks (kg Corg m−2) in 522 kg soil, based on the equivalent soil mass approach (CT: 0–40 cm, MT: 0–38 cm, NT: 0–36 cm) increased in the order CT (5.2) = NT (5.2) < MT (5.7). Significantly (p ≤ 0.05) highest Corg stocks under MT were probably a result of high crop yields in combination with reduced physical tillage impact and effective litter incorporation, resulting in a Corg sequestration rate of 31 g C-2 m-2 yr-1. (ii) Significantly higher yields of macro aggregates (g kg-2 soil) under NT (732-777) and MT (680-726) than under CT (542-631) were generally restricted to the 0-5 cm sampling depth for all sampling dates. Temporal changes on aggregate size distribution were only small and no tillage induced net effect was detectable. Thus, we assume that the physical impact by tillage equipment was only small or the impact was compensated by a higher soil mixing and effective litter translocation into higher soil depths under CT, which probably resulted in a high re aggregation. (iii) The short term incubation study showed that macro aggregate yields (g kg-2 soil) were higher after 28 days in soils receiving OM (121.4-363.0) than in the control soils (22.0-52.0), accompanied by higher contents of microbial biomass carbon and ergosterol. Highest soil respiration rates after OM amendments within the first three days of incubation indicated that macro aggregate formation is a fast process. Most of the rebuilt macro aggregates were formed within the first seven days of incubation (42-75%). Nevertheless, it was ongoing throughout the entire 28 days of incubation, which was indicated by higher soil respiration rates at the end of the incubation period in OM amended soils than in the control soils. At the same time, decreasing carbon contents within macro aggregates over time indicated that newly occluded OM within the rebuilt macro aggregates served as Corg source for microbial biomass. The different clay contents played only minor role in macro aggregate formation under the particular conditions of the incubation study. Overall, no net changes on macro aggregation were identified in the short term. Furthermore, no indications for an effective Corg sequestration on the long term under NT in comparison to CT were found. The interaction of soil disturbance, litter distribution and the fast re aggregation suggested that a distinct steady state per tillage treatment in terms of soil aggregation was established. However, continuous application of MT with a combination of reduced physical tillage impact and effective litter incorporation may offer some potential in improving the soil structure and may therefore prevent incorporated LF from rapid decomposition and result in a higher C sequestration on the long term.

Vigilancia tecnológica de los tres principales productos agrícolas base de alimentación y cultivados en Brasil y Argentina

La seguridad agroalimentaria debe ser prioridad para los gobiernos de Brasil y Argentina, debido a que deben garantizar la producción y el abastecimiento de los alimentos básicos para las futuras generaciones, entendido como alimentos básicos aquellos que más se consumen, ya sea en su forma original o por medio de sus subproductos, estos productos son el trigo, el maíz y el arroz. El garantizar la producción y el abastecimiento de estos productos en el corto y largo plazo, implica entender cuáles de los procesos productivos aplicados en la realización de los productos base de alimentación no son compatibles con el medio ambiente, generando impactos negativos sobre este. Estos impactos ambientales generados a partir de la agricultura, son identificados como el uso excesivo de recursos naturales entre ellos el agua, así como su contaminación por agentes toxico como los agroquímicos y fertilizantes. Asimismo, el uso de estos agentes tóxicos, genera la infertilidad de los suelos afectando directamente la producción en el largo plazo. Entender los impactos ambientales, implica desarrollar estrategias transversales que le permitan a los garantizar un desarrollo sostenible a lo largo de todo el ciclo del producto; estas estrategias deben estar acompañadas por un rendimiento y eficiencia de los cultivos, de nada sirve implementar estrategias compatibles con el medio ambiente si no se cumple con el principal objetivo de la producción de estos producto, que es garantizar el abastecimiento y alimentación para las generaciones presentes y futuras.

Modelled soil organic carbon stocks and changes in the Indo-Gangetic Plains, India from 1980 to 2030

The Global Environment Facility co-financed Soil Organic Carbon (GEFSOC) Project developed a comprehensive modelling system for predicting soil organic carbon (SOC) stocks and changes over time. This research is an effort to predict SOC stocks and changes for the Indian, Indo-Gangetic Plains (IGP), an area with a predominantly rice (Oryza sativa) - wheat (Triticum aestivum) cropping system, using the GEFSOC Modelling System and to compare output with stocks generated using mapping approaches based on soil survey data. The GEFSOC Modelling System predicts an estimated SOC stock for the IGP, India of 1.27, 1.32 and 1.27 Pg for 1990, 2000 and 2030, respectively, in the top 20 cm of soil. The SOC stock using a mapping approach based on soil survey data was 0.66 and 0.88 Pg for 1980 and 2000, respectively. The SOC stock estimated using the GEFSOC Modelling System is higher than the stock estimated using the mapping approach. This is due to the fact that while the GEFSOC System accounts for variation in crop input data (crop management), the soil mapping approach only considers regional variation in soil texture and wetness. The trend of overall change in the modelled SOC stock estimates shows that the IGP, India may have reached an equilibrium following 30-40 years of the Green Revolution. This can be seen in the SOC stock change rates. Various different estimation methods show SOC stocks of 0.57-1.44 Pg C for the study area. The trend of overall change in C stock assessed from the soil survey data indicates that the soils of the IGP, India may store a projected 1.1 Pg of C in 2030. (C) 2007 Elsevier B.V. All rights reserved.

Evaluating the century C model using long-term fertilizer trials in the Indo-Gangetic Plains, India

The GEFSOC Project developed a system for estimating soil carbon (C) stocks and changes at the national and sub-national scale. As part of the development of the system, the Century ecosystem model was evaluated for its ability to simulate soil organic C (SOC) changes in environmental conditions in the Indo-Gangetic Plains, India (IGP). Two long-term fertilizer trials (LTFT), with all necessary parameters needed to run Century, were used for this purpose: a jute (Corchorus capsularis L.), rice (Oryza sativa L.) and wheat (Triticum aestivum L.) trial at Barrackpore, West Bengal, and a rice-wheat trial at Ludhiana, Punjab. The trials represent two contrasting climates of the IGP, viz. semi-arid, dry with mean annual rainfall (MAR) of < 800 mm and humid with > 1600 turn. Both trials involved several different treatments with different organic and inorganic fertilizer inputs. In general, the model tended to overestimate treatment effects by approximately 15%. At the semi-arid site, modelled data simulated actual data reasonably well for all treatments, with the control and chemical N + farm yard manure showing the best agreement (RMSE = 7). At the humid site, Century performed less well. This could have been due to a range of factors including site history. During the study, Century was calibrated to simulate crop yields for the two sites considered using data from across the Indian IGP. However, further adjustments may improve model performance at these sites and others in the IGP. The availability of more longterm experimental data sets (especially those involving flooded lowland rice and triple cropping systems from the IGP) for testing and validation is critical to the application of the model's predictive capabilities for this area of the Indian sub-continent. (C) 2007 Elsevier B.V. All rights reserved.

An X-ray micro-tomography system optimised for the low-dose study of living organisms

An X-ray micro-tomography system has been designed that is dedicated to the low-dose imaging of radiation sensitive living organisms and has been used to image the early development of the first few days of plant development immediately after germination. The system is based on third-generation X-ray micro-tomography system and consists of an X-ray tube, two-dimensional X-ray detector and a mechanical sample manipulation stage. The X-ray source is a 50 kVp X-ray tube with a silver target with a filter to centre the X-ray spectrum on 22 keV.A 100 mm diameter X-ray image intensifier (XRII) is used to collect the two-dimensional projection images. The rotation tomography table incorporates a linear translation mechanism to eliminate ring artefact that is commonly associated with third-generation tomography systems' Developing maize seeds (Triticum aestivum) have been imaged using the system with a cubic voxel linear dimension of 100 mum, over a diameter of 25 mm and the root lengths and volumes measured. The X-ray dose to the plants was also assessed and found to have no effect on the plant root development. (C) 2003 Elsevier Science Ltd. All rights reserved.

Characterisation of an s-type low molecular weight glutenin subunit of wheat and its proline and glutamine-rich repetitive domain

The low molecular weight glutenin subunits (LMW-GS) are major components of the glutenin polymers which determine the elastomeric properties of wheat (Triticum aestivum L.) gluten and dough. They comprise a complex mixture of components and have proved to be difficult to purify for detailed characterisation. The mature LMW subunit proteins comprise two structural domains, with one domain consisting of repeated sequences based on short peptide motifs. DNA sequences encoding this domain and a whole subunit were expressed in Escherichia coli and the recombinant proteins purified. Detailed comparisons by spectroscopy (CD, FT-IR) and dynamic light scattering indicated that the repetitive and non-repetitive domains of the proteins formed different structures with the former having an extended conformation with an equilibrium between poly-L-proline II-like structure and type II’ b-turns, and the latter a more compact globular structure rich in a-helix. Although the structures of these two domains appear to form independently, dynamic light scattering of the whole subunit dissolved in trifluoroethanol(TFE) suggested that they interact, leading to a more compact conformation. These observations may have relevance to the role of the LMW-GS in gluten structure and functionality.

Down-regulation of the CSLF6 gene results in decreased (1,3;1,4)-beta-D-glucan in endosperm of wheat

(1,3;1,4)-beta-d-Glucan (beta-glucan) accounts for 20% of the total cell walls in the starchy endosperm of wheat (Triticum aestivum) and is an important source of dietary fiber for human nutrition with potential health benefits. Bioinformatic and array analyses of gene expression profiles in developing caryopses identified the CELLULOSE SYNTHASE-LIKE F6 (CSLF6) gene as encoding a putative beta-glucan synthase. RNA interference constructs were therefore designed to down-regulate CSLF6 gene expression and expressed in transgenic wheat under the control of a starchy endosperm-specific HMW subunit gene promoter. Analysis of wholemeal flours using an enzyme-based kit and by high-performance anion-exchange chromatography after digestion with lichenase showed decreases in total beta-glucan of between 30% and 52% and between 36% and 53%, respectively, in five transgenic lines compared to three control lines. The content of water-extractable beta-glucan was also reduced by about 50% in the transgenic lines, and the M(r) distribution of the fraction was decreased from an average of 79 to 85 x 10(4) g/mol in the controls and 36 to 57 x 10(4) g/mol in the transgenics. Immunolocalization of beta-glucan in semithin sections of mature and developing grains confirmed that the impact of the transgene was confined to the starchy endosperm with little or no effect on the aleurone or outer layers of the grain. The results confirm that the CSLF6 gene of wheat encodes a beta-glucan synthase and indicate that transgenic manipulation can be used to enhance the health benefits of wheat products.

Analysis of wheat SAGE tags reveals evidence for widespread antisense transcription

BACKGROUND: Serial Analysis of Gene Expression (SAGE) is a powerful tool for genome-wide transcription studies. Unlike microarrays, it has the ability to detect novel forms of RNA such as alternatively spliced and antisense transcripts, without the need for prior knowledge of their existence. One limitation of using SAGE on an organism with a complex genome and lacking detailed sequence information, such as the hexaploid bread wheat Triticum aestivum, is accurate annotation of the tags generated. Without accurate annotation it is impossible to fully understand the dynamic processes involved in such complex polyploid organisms. Hence we have developed and utilised novel procedures to characterise, in detail, SAGE tags generated from the whole grain transcriptome of hexaploid wheat. RESULTS: Examination of 71,930 Long SAGE tags generated from six libraries derived from two wheat genotypes grown under two different conditions suggested that SAGE is a reliable and reproducible technique for use in studying the hexaploid wheat transcriptome. However, our results also showed that in poorly annotated and/or poorly sequenced genomes, such as hexaploid wheat, considerably more information can be extracted from SAGE data by carrying out a systematic analysis of both perfect and "fuzzy" (partially matched) tags. This detailed analysis of the SAGE data shows first that while there is evidence of alternative polyadenylation this appears to occur exclusively within the 3' untranslated regions. Secondly, we found no strong evidence for widespread alternative splicing in the developing wheat grain transcriptome. However, analysis of our SAGE data shows that antisense transcripts are probably widespread within the transcriptome and appear to be derived from numerous locations within the genome. Examination of antisense transcripts showing sequence similarity to the Puroindoline a and Puroindoline b genes suggests that such antisense transcripts might have a role in the regulation of gene expression. CONCLUSION: Our results indicate that the detailed analysis of transcriptome data, such as SAGE tags, is essential to understand fully the factors that regulate gene expression and that such analysis of the wheat grain transcriptome reveals that antisense transcripts maybe widespread and hence probably play a significant role in the regulation of gene expression during grain development.

The effects of irrigation, nitrogen fertilizer and grain size on Hagberg falling number, specific weight and blackpoint of winter wheat

The effects of irrigation and nitrogen (N) fertilizer on Hagberg falling number (HFN), specific weight (SW) and blackpoint (BP) of winter wheat (Triticum aestivum L) were investigated. Mains water (+50 and +100 mm month(-1), containing 44 mg NO3- litre(-1) and 28 mg SO42- litre(-1)) was applied with trickle irrigation during winter (17 January-17 March), spring (21 March-20 May) or summer (24 May-23 July). In 1999/2000 these treatments were factorially combined with three N levels (0, 200, 400 kg N ha(-1)), applied to cv Hereward. In 2000/01 the 400 kg N ha(-1) treatment was replaced with cv Malacca given 200 kg N ha(-1). Irrigation increased grain yield, mostly by increasing grain numbers when applied in winter and spring, and by increasing mean grain weight when applied in summer. Nitrogen increased grain numbers and SW, and reduced BP in both years. Nitrogen increased HFN in 1999/2000 and reduced HFN in 2000/01. Effects of irrigation on HFN, SW and BP were smaller and inconsistent over year and nitrogen level. Irrigation interacted with N on mean grain weight: negatively for winter and spring irrigation, and positively for summer irrigation. Ten variables derived from digital image analysis of harvested grain were included with mean grain weight in a principal components analysis. The first principal component ('size') was negatively related to HFN (in two years) and BP (one year), and positively related to SW (two years). Treatment effects on dimensions of harvested grain could not explain all of the effects on HFN, BP and SW but the results were consistent with the hypothesis that water and nutrient availability, even when they were affected early in the season, could influence final grain quality if they influenced grain numbers and size. (C) 2004 Society of Chemical Industry