Development of a low input system for growing wheat (Triticum vulgare) in a permanent understorey of white clover (Trifolium repens)

In three field experiments carried out during 1989-91, a permanent sward of pure white clover (Trifolium repens) was established to provide a source of N for winter or spring wheat crops (Triticum vulgare) directly drilled into the legume. Spring-sown wheat failed to compete with the clover, but wheat sown in the autumn established successfully. N fertiliser was applied to all three experiments at rates of 0, 50 and 100 kg N ha“¹ measurements of grain and whole-crop silage yields were made. Yields were low for all treatments, probably because of the dry conditions prevailing and the low soil N status of the site used. Yield responses to fertiliser were significant, despite the contribution to plant nutrition that the clover was intended to make. A key feature of the work was that the clover survived successive cereal crops and could be grazed and used as an understorey for later crops. Further, response to fertiliser N diminished with a successive crop implying a build-up of available soil N, which measurements confirmed had occurred. Use of the system obviated the need to use pesticides, although reasons for the lack of pest damage were not clear.     

Changes in wheat bulb fly (Delia coarctata) populations in East Anglia in relation to crop rotations, climatic data and damage forecasting

Records of wheat bulb fly egg (Delia coarctata) population densities in fields sampled throughout East Anglia in the autumns of 1953–1990 are presented. In descending order of risk, fallow, potato, pea (mainly vining), sugar beet and oilseed rape are the main crops preceding wheat or barley which attract oviposition. A declining trend of egg populations observed over the study period may be associated with climatic changes as well as with the elimination of fallow in the rotation and the dramatic increase in the use of insecticides against the pest. Negative correlations (P < 0.05) in mean annual egg numbers were found with departures from average of July temperature and January air or soil temperature; positive correlations (P<0.05) with departure from average of August raindays. Stepwise regression analysis was used to identify the most important relationships of meteorological variables with mean annual egg numbers, or the proportion of fields sampled with egg numbers in excess of the action threshold of 2.5 million eggs/ha. Up to 59% of the variation in the annual proportion of fields above threshold was accounted for in a regression equation using departures from average of July temperature, August raindays and the percentage of average of October (preceding year) rainfall. Estimated mean annual egg populations and the proportion of fields above threshold showed a good fit with the observed values. The findings are discussed and compared with previous work. The forecasting model may be readily incorporated as a regional risk-prediction component of a knowledge-based system for the management of wheat bulb fly control. Regional forecasts of wheat bulb fly oviposition from this work should be tested and modified as necessary according to experience or changing climatic or agricultural factors.     

Anomalous segregations at the Sr6 locus for stem rust resistance in wheat

The action of the gene Sr6 for stem rust resistance in wheat is affected by temperature, light, and the particular susceptible parent with which a line carrying Sr6 has been crossed. Two experiments were carried out to determine whether the effect of the susceptible parents was due to modifier genes, the general genetic background, or interallelic interactions. The data indicated that the susceptible parents carried different sr6 alleles that interacted with Sr6, possibly in a paramutation-like process. In the course of the study, a number of anomalous results were obtained that may be due to the action of transposable elements. Received: 18 February 2000 / Accepted: 31 October 2000     

Genetic characterisation of a further homoeoallelic series of grain esterase loci,Est-6, in wheat

Summary Isoelectric focussing in alkaline pH gels has permitted the identification of a new homoeoallelic series of genes,Est-6, encoding grain esterases in bread wheat,Triticum aestivum. Nullisomic analysis located these genes to the short arms of the homoeologous group 2 chromosomes. A search for polymorphism withinEst-6 revealed null alleles at each ofEst-A6,Est-B6 andEst-D6. A further homoeolocus,Est-M6, is present on chromosome arm2MS ofAegilops comosa.     

A biophysical characterization of the iron coordination environment in wheat germ peroxidase

 The heme protein wheat germ peroxidase (isoenzyme C₂) and its cyanide-inhibited form have been investigated by means of electronic, CD and paramagnetic NMR spectroscopy. The data indicate a protein environment of the active site distinct from that of horseradish peroxidase (HRP), with a larger solvent accessibility. The iron is pentacoordinated at neutral and low pH, whereas a hydroxyl anion may be bound at alkaline pH. The fifth axial ligand is a His residue with a partial anionic character, as found in other peroxidases. A spin equilibrium is observed at high enzyme concentrations. Received: 17 September 1996 / Accepted: 10 January 1997     

Determinants of resistant starch accumulation in wheat endosperm

A part of the big three cereal crops in the world, wheat has become a major constituent of the everyday food chain and is grown at a massive scale to meet global demands. This makes it an important crop from an economic as well as food security perspective. Selection of high-quality cultivars and consistent trait enhancement for such cultivars is crucial, and in light of new challenges from climate change, this has become an absolute necessity of time. In this regard, we conducted a detailed qualitative and quantitative trait analysis for multiple commercially viable varieties of wheat, and corresponding results were subjected to a series of critical statistical analyses. Final results have shown that five cultivars including Uqaab-2000, Faisalabad- 85, Anmol-19, NARC-2009, and Pirsabak-2004 depicts higher levels of various essential qualitative and quantitative traits (including Starch content, grain weight, RS content, Protein content, etc.) and are most viable varieties for further growth and trait enhancements to meet regional and global food challenges.     

Effect of psyllium husk and wheat mill bran fractions on the microstructure and mixograph characteristics of Arabic bread

When psyllium husk, wheat bran and germ was added, Incorporation of psyllium and wheat bran may affect the dough structure, dough rheology as well as the final quality of baked Arabic flat bread, which, thus, became important for this study. Scanning Electron Micrographs (SEM) taken on Arabic bread, depicted both intact small and the large starch granules on the outer crust area. This was mainly due to the rapid loss of moisture from the Arabic bread surface during intense baking operation leaving less moisture for gelatinization to take place. With psyllium added to WWF at 0, 3, and 5 % level, the peak time was increased from 3 to 4.5 min. The ascending and descending angle values were more or less identical in all the samples except with wheat germ addition, whereas much lower values (51 to 58°) for these parameters were observed, indicating a faster rate of dough breakdown. With psyllium, fine- and coarse bran addition to WWF, a corresponding increase in peak time was observed. Ascending and descending angles showed similar trends to that of the WWF and psyllium combinations. Use of falling number apparatus is an indirect method of measuring the diastatic enzyme activity in cereal flours. WGF showed lower falling-number values (502 s) than the WWF (607 s). Addition of fine bran to WWF lowered the falling number (607 to 563 s) whereas with coarse wheat bran and germ, these values were increased.     

Organ/tissue-specific changes in the mitochondrial genome organization of in-vitro cultures derived from different explants of a single wheat variety

Summary We have previously shown that the mitochondrial genome of long-term tissue cultures prepared from immature embryos of several varieties of cultivated wheat underwent variety-specific rearrangements resulting from either changes in the relative amounts of subgenomic components or from the appearance of novel genomic configurations. In the present work, both categories of rearrangements were studied in long-term tissue cultures initiated from other explants (shoot meristem, young leaf base, young root tip, immature inflorescence) of the same wheat variety (Chinese Spring) and were compared to those previously obtained with immature embryo cultures. Two main patterns of reorganization were found in a region of the mitochondrial genome known to be hypervariable in structure. In addition, some of the novel subgenomic configurations were obviously organ/tissue-specific whereas others were present in more than one type of organ. In several instances, the age of culture was found to determine the degree of mitochondrial DNA rearrangement. The data presented in this study strengthen the hypothesis of an association between a particular organization of the mitochondrial genome in tissue culture and its regeneration capacity.     

Effects of lignin content on the properties of lignocellulose-based biocomposites

The paper is focused on the analysis of the behaviour of biocomposites (biodegradable composites) which are reinforced with different fillers fractions, with varying lignin contents. These materials have been carried-out by extrusion and injection moulding. The matrix, an aromatic copolyester (polybutylene adipate-co-terephthalate), is biodegradable. The lignocellulose fillers are a by-product of an industrial fractionation process of wheat straw. From the raw agro-material and by lignin extractions, various fillers fractions have been obtained by varying the fractionation conditions, both on the liquid media (aqueous or organic) and on the temperature. The fillers lignin contents vary from 30 to 14 wt% with a resultant increase of the cellulose content. We have analysed the impact of the different extraction conditions on the fillers surface and size distribution, and also on the final thermal and mechanical properties of the biocomposites. These materials present significant differences of behaviour which can fulfil some requirements for applications, such as non-food packaging or other short-lived applications (agriculture, sport …) where long-lasting polymers are not entirely adequate.