Optimisation of a solvent for the complete extraction of prolamins from heated foods

Wheat bread was lyophilised, ground, extracted and centrifuged. The supernatants were analysed for gluten content by RP-HPLC and a commercial sandwich ELISA. Prolamin extraction solvents contained tris(2-carboxyethyl)phosphine (TCEP; 1, 2, 5, 10, 20, 50 mmol/L), guanidine hydrochloride (GUA; 0 or 2 mol/L) and a buffered salt solution. A commercial cocktail solution (250 mmol/L mercaptoethanol (ME), 2 mol/L GUA, buffered salt solution) as well as 60% (v/v) ethanol were used as control solvents. Wheat flour was the control for the extractability of the native prolamins. 60% ethanol only extracted 37% of the prolamins from wheat bread (cocktail = 100%). When ME was replaced by TCEP the protein yield increased from 35% at the lowest TCEP-level to 95% when 20–50 mmol/L TCEP were used. The use of GUA was essential to extract prolamins quantitatively. Comparative protein analysis using RP-HPLC and ELISA showed that both methods provided comparable prolamin (gliadin) concentrations of the wheat flour (40.3–45.7 mg/g), when 60% ethanol was used as extraction solvent. The extraction yields from bread were considerably lower (16.7–24.7 mg/g). Cocktail and TCEP extracted almost the same amount of protein from flour and bread with TCEP showing slightly lower yields. Total extractable protein (gliadin + glutenin) as determined by RP-HPLC was 70.5–75.3 mg/g, and total gliadin as determined by ELISA was 42.7–44.2 mg/g. Thus, the study has shown that TCEP in combination with GUA extracts proteins from heated, gluten-containing foods as effective as the commercial cocktail solution.     

Phosphorus efficiency in long-term (15 years) wheat–maize cropping systems with various soil and climate conditions

Long-term (over 15 years) winter wheat (Triticum aestivum L.)–maize (Zea mays L.) crop rotation experiments were conducted to investigate phosphorus (P) fertilizer utilization efficiency, including the physiological efficiency, recovery efficiency and the mass (the input–output) balance, at five sites across different soil types and climate zones in China. The five treatments used were control, N, NP, NK and NPK, representing various combinations of N, P and K fertilizer applications. Phosphorus fertilization increased average crop yield over 15 years and the increases were greater with wheat (206%) than maize (85%) across all five sites. The wheat yield also significantly increased over time for the NPK treatments at two sites (Xinjiang and Shanxi), but decreased at one site (Hunan). The P content in wheat was less than 3.00 g kg⁻¹ (and 2.10 g kg⁻¹ for maize) for the N and NK treatments with higher values for the Control, NP and NPK treatments. To produce 1 t of grain, crops require 4.2 kg P for wheat and 3.1 kg P for maize. The P physiological use efficiency was 214 kg grain kg⁻¹ P for wheat and 240 kg grain kg⁻¹ P for maize with over 62% of the P from P fertilizer. Applying P fertilizer at 60–80 kg P ha⁻¹ year⁻¹ could maintain 3–4 t ha⁻¹ yields for wheat and 5–6 t ha⁻¹ yields for maize for the five study sites across China. The P recovery efficiency and fertilizer use efficiency averaged 47% and 29%, respectively. For every 100 kg P ha⁻¹ year⁻¹ P surplus (amount of fertilizer applied in excess of crop removal), Olsen-P in soil was increased by 3.4 mg P kg⁻¹. Our study suggests that in order to achieve higher crop yields, the long-term P input–output balance, soil P supplying capacity and yield targets should be considered when making P fertilizer recommendations and developing strategies for intensively managed wheat–maize cropping systems.     

Chemical control of weeds in wheat (Triticum aestivum L.) in Iran

Experiments were conducted in 2006–2007 at six research stations of the Iranian Plant Protection Research Institute to study the efficacy of different herbicides to control weeds in wheat. Treatments included mesosulfuron-methyl plus iodosulfuron-methyl-sodium plus mefenpyr-diethyl (WG) at 45 + 45 + 135 g a.i./ha, respectively, sulfosulfuron at 21, 31.5, 42 and 51 g a.i./ha, chlorsulfuron at 15 g a.i./ha, bromoxynil plus MCPA at 600 g a.i./ha with clodinafop propargyl at 64 g a.i./ha, sulfosulfuron plus metsulfuron-methyl at 36 g a.i./ha, mesosulfuron-methyl plus iodosulfuron-methyl-sodium plus mefenpyr-diethyl (OD) at 15 + 3 + 45 g a.i./ha, respectively, and a full season weed-free control. Herbicides were applied at wheat tillering. Results showed that sulfosulfuron plus metsulfuron-methyl, and bromoxynil plus MCPA with clodinafop propargyl resulted in satisfactory weed control and wheat grain yield at most locations. Weed control efficacy of both formulations of mesosulfuron-methyl plus iodosulfuron-methyl-sodium was variable across locations. Efficacy of the OD formulation appears to depend upon location, so that application of this herbicide at Shiraz and Gorgan resulted in better weed control compared to use of the WG. Satisfactory performance of the OD formulation at Gorgan and Shiraz could be attributed in part to the even pattern of rainfall distribution during the growing season and wheat cultivar used, respectively. With respect to grain yield, however, the OD formulation was better than WG formulation at most of the locations.     

Reciprocal influence of crops and shallow ground water in sandy landscapes of the Inland Pampas

In regions with shallow water tables, ground water may have a positive (water supply) or negative (waterlogging or salinization) impact on crops. Reciprocally, crops can influence ground water, altering water table depth and chemical composition. We quantified these reciprocal influences along natural gradients of groundwater depth in flat sedimentary landscapes of the Inland Pampas occupied by wheat, soybean, and maize during two growing seasons (2006/2007 and 2007/2008). We correlated crop yield and groundwater depth maps at the field level and made direct plant, soil and groundwater observations at the stand level across topographic gradients. Water table level largely accounted for spatial crop yield variation, explaining 20–75% of their variance. An optimum groundwater depth range, where crop yields were highest, was observed for all three crop species analyzed (1.40–2.45 m for maize, 1.20–2.20 m for soybean, and 0.70–1.65 m for wheat). The areas within these optimum bands had yields that were 3.7, 3 and 1.8 times larger than those where the water table was below 4 m for wheat, maize, and soybean, respectively. As groundwater levels become shallower than these depth bands, crop yields declined sharply (∼0.05 kg m⁻² on average for every 10 cm increase in water table level), suggesting negative effects of waterlogging, root anoxia and/or salinity. Groundwater levels below these depth bands were associated with gradually declining yields, likely driven by poorer groundwater supply.     

Effects of soil compaction in the sub-humid cropping environment in Pakistan on uptake of NPK and grain yield in wheat (Triticum aestivum): II: Alleviation

Alleviation of soil compaction can be achieved through application of appropriate measures which will vary from soil to soil and with the socio-economic factors of the farmers. The effects of alleviation measures applied to artificially compacted soil on yield components, grain yield, dry matter and nutrient uptake by wheat was studied at the Agriculture Research Institute, Mingora, Pakistan, in two separate experiments in 2002–2003 and 2003–2004. The improvement measures included deep ploughing (DP), farmyard manure (FYM) and gypsum (GYP), and comprised a compacted control and four treatments T1 (control), T2 (DP), T3 (DP + FYM), T4 (DP + gypsum) and T5 (DP + FYM + GYP), arranged in completely randomized block design replicated four times. Improvement measures applied to compacted soil significantly decreased soil bulk density and increased total porosity. Bulk density decreased in the range of 12–15% while total porosity showed an increase of 16–23% over the control. Improvement measures significantly increased concentration and uptake of NPK in both years. Higher concentration and uptake was recorded during the second year as compared to the first year, probably as a result of higher seasonal rainfall in the second year. The uptake of NPK by wheat plants increased in the range of 43–51, 25–94 and 11–28%, respectively, over plants in the compacted control. Similarly, improvement treatments increased grains spike⁻¹, thousand grain weight, dry matter accumulation and grain yield in the range of 14–21, 5–14, 3–10 and 21–37% respectively, over the control. This work demonstrates that it is possible to overcome the deleterious effects of compaction induced by wheeled traffic, and improve crop yields and nutrient uptake in intensive cropping systems in rainfed environments in Pakistan and similar environments.     

Using stress tolerance indicator (STI) to select high grain yield iron-deficiency tolerant wheat genotypes in calcareous soils

Despite large variation among crop genotypes in response to Fe fertilization, there is no reliable indicator for identifying Fe-deficiency tolerant wheat genotypes with high grain yield. The aim of this investigation was to compare the grain yield response of 20 spring and 30 winter bread wheat genotypes to Fe fertilization under field conditions and to select high grain yield Fe-deficiency tolerant genotypes using a stress tolerance indicator (STI). Two individual trials, each one consisting two field plot experiments, were conducted during 2006–2007 and 2007–2008 growing seasons. Spring wheat genotypes (Trial l) and winter wheat genotypes (Trial 2) were planted at two different locations. Two Fe rates (0 and 20 kg Fe ha⁻¹ as Fe-EDTA) were applied. Spring and winter wheat genotypes differed significantly (P < 0.01) in the grain yield both with and without added Fe treatments. Application of Fe fertilizer increased grain yield of spring wheat genotypes by an average of 211 and 551 kg ha⁻¹ in Karaj and Isfahan locations, respectively. By Fe application, the mean grain yield of winter wheat genotypes increased 532 and 798 kg ha⁻¹ in Karaj and Isfahan sites, respectively. Iron efficiency (Fe-EF) significantly differed among wheat genotypes and ranged from 65% to 113% for spring wheat and from 69% to 125% for winter wheat genotypes. No significant correlation was found between Fe-EF and grain yield of spring wheat genotypes under Fe deficient conditions. For winter wheat genotypes grown in Mashhad, Fe-efficiency was not significantly correlated with the grain yield produced without added Fe treatment. The STI was significantly (P < 0.01) varied among spring and winter wheat genotypes. The interaction between location and genotype had no significant effect on the STI. According to these results, the STI should be considered as an effective criterion for screening programs, if a high potential grain yield together with more stable response to Fe fertilization in different environments is desired.     

Effect of high-pressure treatment on rheological,thermal and structural changes in Basmati rice flour slurry

Rheological, thermal and structural changes in high pressure (HP) treated Basmati rice flour dispersions were studied as function of pressure level (350–650 MPa), slurry concentration (with 1:5, 1:3 and 1:2 flour-to-water ratios) and holding time (7.5–15 min). Rice flour dispersions exhibited a gradual liquid–solid gel transformation as they gelatinized and/or denatured and behaved as viscoelastic fluid following HP treatment. Mechanical strength (G′) of pressurized gel increased with applied pressure and rice concentration. Differential scanning calorimeter (DSC) thermograms of rice slurry measured after pressure treatment indicated a reduction in peak enthalpy in proportion with the extent of gelatinization and/or denaturation of starch and proteins. Pressure-treated rice samples had a progressively lower gelatinization temperature. A 15 min pressure treatment at 550 MPa was found sufficient to complete gelatinization of protein free isolated rice starch while the slurry required 650 MPa. The presence of proteins might have been responsible for the slower starch gelatinization in the rice slurry during pressure treatment. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier-transform infrared (FTIR) spectroscopy results indicated some minor changes in protein subunits and secondary structure of rice protein. This study has provided complementary information on pressure-induced changes in physical (thermal stability, overall structure) and molecular level (secondary structure) of rice protein.     

Analysis of polyphenols in cereals may be improved performing acidic hydrolysis: A study in wheat flour and wheat bran and cereals of the diet

Most analytical studies on polyphenols in cereals refer to compounds determined in aqueous-organic extracts and alkali hydrolysates, but an appreciable amount of polyphenols bound to cell wall constituents may remain insoluble in the residues of extraction and alkali hydrolysis. The main objective of this work was to determine if sulphuric acid hydrolysis may release significant amounts of polyphenols to be considered for analytical and nutritional studies. HPLC/MS analyses of polyphenols were performed in methanol–acetone extracts, alkali and sulphuric acid hydrolysates of wheat flour, bran and a pool of cereals of the diet. The amount of polyphenols found in the acidic hydrolysates (200–1600 mg/100 g) was higher than in alkali hydrolysates (0.2–372 mg/100 g). Lower amount of polyphenols were found in the methanol–acetone extracts (44–160 mg/100 g). Hydroxybenzoic, caffeic, cinammic, ferulic and protocatechuic acids were the main constituents of the hydrolysates. The contribution of cereals to the intake of dietary polyphenols in Spain was estimated around 360 mg/person/day (65 mg of extractable and 295 mg nonextractable polyphenols).     

Evaluation of alternative tillage and crop establishment methods in a rice–wheat rotation in North Western IGP

The rice–wheat rotation covering 13.5 million ha in the Indo-Gangetic Plains is vital for food security. Its sustainability is at risk as the current production practices are inadequate resulting in high cost of cultivation and inefficient use of inputs (i.e. water, labor and energy). In a field study, we evaluated resource conserving and cost-saving alternative tillage and crop establishment options with an aim to improve system productivity and efficiency. Treatments included transplanting and direct-seeding of rice after reduced and no-tillage, followed by wheat after no-tillage. Conventional-tilled (puddled) transplanted rice followed by conventional-tilled wheat was included as a current practice. Rice yields of transplanted rice were similar irrespective of tillage/puddling. However, both dry and wet direct-seeded rice yielded 0.45–0.61 Mg ha⁻¹ lower than puddled transplanted rice. Wheat yield after no-tillage was either higher or equivalent to conventional practice. Wheat provided more economic return (US $35 ha⁻¹) than rice. No-till wheat was 6% more profitable than the conventional practice (T1). Rice transplanting with or without puddling had similar water application but dry direct-seeded rice had 10–12% lower and wet direct-seeded rice 20–24% higher. Machine labor without tillage was lower by maximum of 51 and 43% in rice and wheat, respectively. Similarly, human labor was also 9–16% lower in no-till rice compared to other practices. Two years results consistently showed $35 more net income when rice was transplanted without puddling than that of conventional practice. Direct-seeded/un-tilled rice had variable response in 2 years; US $16 more in year 1 and similar in year 2 to the puddled transplanted rice. Direct-seeded or transplanted rice after no-tillage can be more efficient and profitable alternatives to current practice (puddled transplanted rice), however, require further refinement in areas of cultivar development for no-till direct-seeding condition, nutrient, water and weed management to harness maximal potential.     

Ultra-fast separation of wheat glutenin subunits by reversed-phase HPLC using a superficially porous silica-based column

A relatively new, unique column packing material for reversed-phase high-performance liquid chromatography (RP-HPLC) was evaluated for rapid separation of wheat glutenin protein subunits. The product named “Poroshell” by the manufacturer consists of a solid core and a porous coat instead of solid silica spheres used in conventional RP-HPLC column packing. This architecture favours rapid mass transfer, facilitating faster reversed-phase separations of biomolecules compared to conventional silica columns. The main objective of this study was to evaluate the quality of separations of glutenin subunits (GS), as well as to optimize conditions to produce the fastest possible run times without sacrificing resolution using a Poroshell 300SB-C₈ 2.1×75 mm column. The stability of GS separations over time was also assessed. Two different bread wheat genotypes were used for optimization of separation conditions and six more common and durum wheat genotypes possessing different subunit combinations were used for further evaluation. Glutenin protein was extracted with 0.08 M Tris–HCl buffer (pH 7.5) containing 50% 1-propanol under reducing conditions after pre-extraction of soluble proteins with 50% 1-propanol. Optimization of GS resolution and sample throughput by RP-HPLC was assessed in response to variation in eluent flow rate, acetonitrile (ACN) gradient, and column temperature. The best resolution of both HMW- and LMW-GS was obtained in 13 min using a 23–44% ACN gradient with a flow rate of 0.7 mL/min at 65 °C. Subunit elution times and integrated areas were highly repeatable even after several hundred injections. Highly satisfactory separation of HMW-GS and quantification of ratio of HMW- to LMW-GS were achieved in less than 4 min per sample using a modified HPLC gradient. Ratio of HMW- to LMW-GS was unaffected by the speed of the separations. As well, the elution order of HMW- and LMW-GS was unaffected by the rapid analysis, compared to conventional RP-HPLC separations, so no new learning was required for interpreting chromatograms and classification of subunits. The rapid RP-HPLC method using the Poroshell column appears to be very well suited for routine quantification of HMW-GS and LMW-GS especially for purposes of wheat quality screening and wheat cultivar development activities where large numbers of samples are typically encountered.     

Starch granule size distribution of hard red winter and hard red spring wheat: Its effects on mixing and breadmaking quality

Starch was isolated from 98 hard red winter (HRW) wheat and 99 hard red spring (HRS) wheats. Granule size/volume distributions of the isolated starches were analyzed using a laser diffraction particle size analyzer. There were significant differences in the size distribution between HRW and HRS wheats. The B-granules (<10 μm in diameter) occupied volumes in the range 28.5–49.1% (mean, 39.9%) for HRW wheat, while HRS wheat B-granules occupied volumes in the range 37.1–56.2% (mean, 47.3%). The mean granule sizes of the distribution peaks less than 10 μm in diameter also showed a significant difference (HRW, 4.32 vs. HRS, 4.49 μm), but the mean sizes of the distribution peaks larger than 10 μm were not significantly different (21.54 vs. 21.47 μm). Numerous wheat and flour quality traits also showed significant correlation to starch granule size distributions. Most notably, protein content was inversely correlated with parameters of B-granules. Crumb grain score appeared to be affected by starch granule size distribution, showing significant inverse correlations with B-granules. Furthermore, the linear correlations were improved when the ratio of B-granules to protein content was used, and the polynomial relation was applied. There also appeared to be an optimum range of B-granules for different protein content flour to produce bread with better crumb grain.     

Clover cover crops under-sown in winter wheat increase yield of subsequent spring barley—Effect of N dose and companion grass

Four two-year field trials, arranged in randomised split-plots, were carried out in southern Sweden with the aim of determining whether reduced N fertiliser dose in winter wheat production with spring under-sown clover cover crops, with or without perennial ryegrass in the seed mixture, would increase the clover biomass and hence the benefits of the cover crops in terms of the effect on the wheat crop, on a subsequent barley crop and on the risk of N leaching. Four doses of nitrogen (0, 60, 120 or 180 kg N ha⁻¹) constituted the main plots and six cover crop treatments the sub-plots. The cover crop treatments were red clover (Trifolium pratense L.), white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) in pure stands and in mixtures. The winter wheat (Triticum aestivum L.) was harvested in August and the cover crops were ploughed under in November. The risk of N leaching was assessed in November by measuring the content of mineral N in the soil profile (0–30, 30–90 cm). In the following year, the residual effects of the cover crops were investigated in spring barley (Hordeum distichon L.) without additional N. Under-sowing of cover crops did not influence wheat yield, while reduced N fertiliser dose decreased yield and increased the clover content of the cover crops. When N was applied, the mixed cover crops were as effective in depleting soil mineral nitrogen as a pure ryegrass cover crop, while pure clover was less efficient. The clover content at wheat harvest as well as the amount of N incorporated with the cover crops had a positive correlation with barley yield. Spring barley in the unfertilised treatments yielded, on average, 1.9–2.4 Mg DM ha⁻¹ more in treatments with clover cover crops than in the treatment without cover crops. However, this positive effect decreased as the N dose to the preceding wheat crop increased, particularly when the clover was mixed with grass.     

Phytate and mineral elements concentration in a collection of Italian durum wheat cultivars

Mineral deficiencies are prevalent in human populations and the improvement of the mineral content in cereal products represents a possible strategy to increase the human mineral intake. Nevertheless, most of the inorganic phosphorus (P_i) present in mature cereal seeds (40–80%) is stored as phytate, an anti-nutritional factor that forms complexes with minerals such as Ca, Mg, Zn and Fe reducing their bioavailability. The present study was undertaken: (i) to determine the variation in phytate and mineral concentrations in the whole grains of 84 Italian durum wheat (Triticum durum Desf.) cultivars representative of old and modern germplasm; (ii) to estimate the magnitude of genotype × environment interaction effects; and (iii) to examine the interrelationships among mineral concentrations in durum wheat with the final aim to identify superior durum wheat cultivars that possess low phytate content and high concentration of mineral elements in their whole-wheat flour. The cultivars were grown in field trials during 2004–2005 at Foggia, Italy and during 2005–2006 at Foggia and Fiorenzuola d’Arda—Southern and Northern Italy. The phytate content was estimated indirectly by using a microtitre plate assay evaluating the P_i absorbance at 820 nm, while the Cu, Fe, Mn, Ca, K, Mg, Na and Zn mineral contents were determined by ICP/OES. The contents of Zn and Fe across years and locations ranged from 28.5 to 46.3 mg/kg for Zn with an average of 37.4 mg/kg and from 33.6 to 65.6 mg/kg for Fe with an average of 49.6 mg/kg. P_i grain content was between 0.46 and 0.76 mg/g showing a positive correlation with all minerals except Cu and Zn. Although breeding activity for Fe and Zn would be difficult because G × E interaction is prevalent, multi-location evaluation of germplasm collection help to identify superior genotypes to achieve this objective. The results here reported open the possibility of designing a specific breeding program for improving the nutritional value of durum wheat through the identification of parental lines with low-P_i and high minerals concentration in whole grains.     

Crop performance in permanent raised bed rice–wheat cropping system in Punjab,India

Raised beds are widely used in agriculture in developed countries and have proven to be an excellent option for wheat. Permanent raised beds may also offer benefits for rice–wheat (RW) systems in South Asia, in terms of both production and the possibility that furrow-irrigation may be more efficient than flood irrigation. The performance of a RW system on permanent raised beds (37 cm wide, 15 cm high, furrow width 30 cm) was compared with conventional cultivation on the flat on sandy loam and loam soils in replicated experiments in central Punjab, India. The experiments commenced with wheat sown in November 2002, and were continued for 8 crops.     

Analysis of starch swelling power in Australian breeding lines of hexaploid wheat (Triticum aestivum L.)

Starch is the major component of wheat (Triticum aestivum L.) grain and is composed of two large glucan molecules, amylose and amylopectin. The ratio between the two polymers types influences the water absorbing properties of starch upon heating, and thus affects the end-use of grain and purified starch. In this study, we evaluated the starch swelling power (SSP) values in seven wheat populations developed from crosses involving low-SSP lines. Analysis of starch produced by the F₂ generation plants showed that the largest SSP variation (11.4–16.2) and lowest SSP mean (13.9) was obtained for a population derived from doubled haploid lines SM1028 (SSP = 14.5) and VK306 (SSP = 13.6). The population of 360 lines was advanced by single seed descent to the following generations for further studies. Starch analysis of grain produced by F₄ generation lines in two field locations during 2006 and in a greenhouse environment during 2005 showed that SSP values were relatively stably inherited. The average broad-sense heritability was 73% and significant (P < 0.001) genotype × genotype and genotype × environment interactions were seen. Starches with the highest and lowest SSP values were inversely related to amylose concentration determined by high pressure liquid chromatography (HPLC)–size exclusion chromatography (SEC) of debranched starch. Developed lines with the lowest SSP values surpassed 40% in apparent amylose concentration. The study illustrates that screening for SSP in early generations can be used to develop wheat lines with desired starch swelling characteristics.     

Productivity and sustainability of a spring wheat–field pea rotation in a semi-arid environment under conventional and conservation tillage systems

A long-term rotation experiment was established in 2001 to compare conservation tillage techniques with conventional tillage in a semi-arid environment in the western Loess Plateau of China. We examined resource use efficiencies and crop productivity in a spring wheat (Triticum aestivum L.)–field pea (Pisum arvense L.) rotation. The experimental design included a factorial combination of tillage with different ground covers (complete stubble removal, stubble retained and plastic film mulch). Results showed that there was more soil water in 0–30 cm at sowing under the no-till with stubble retained treatment than the conventional tillage with stubble removed treatment for both field pea (60 mm vs. 55 mm) and spring wheat (60 mm vs. 53 mm). The fallow rainfall efficiency was up to 18% on the no-till with stubble retained treatment compared to only 8% for the conventional tillage with stubble removed treatment. The water use efficiency was the highest in the no-till with stubble retained treatment for both field pea (10.2 kg/ha mm) and spring wheat (8.0 kg/ha mm), but the lowest on the no-till with stubble removed treatment for both crops (8.4 kg/ha mm vs. 6.9 kg/ha mm). Spring wheat also had the highest nitrogen use efficiency on the no-till with stubble retained treatment (24.5%) and the lowest on the no-till with stubble removed treatment (15.5%). As a result, grain yields were the highest under no-till with stubble retained treatment, but the lowest under no-till with no ground cover treatment for both spring wheat (2.4 t/ha vs. 1.9 t/ha) and field pea (1.8 t/ha vs. 1.4 t/ha). The important finding from this study is that conservation tillage has to be adopted as a system, combining both no-tillage and retention of crop residues. Adoption of a no-till system with stubble removal will result in reductions in grain yields and a combination of soil degradation and erosion. Plastic film mulch increased crop yields in the short-term compared with the conventional tillage practice. However, use of non-biodegradable plastic film creates a disposal problem and contamination risk for soil and water resources. It was concluded that no-till with stubble retained treatment was the best option in terms of higher and more efficient use of water and nutrient resources and would result in increased crop productivity and sustainability for the semi-arid region in the Loess Plateau. The prospects for adoption of conservation tillage under local conditions were also discussed.     

Composition and molecular structure of polysaccharides released from barley endosperm cell walls by sequential extraction with water,malt enzymes,and alkali

Isolated and purified endosperm cell walls (CW), used in this study, were derived from a Canadian malting barley variety, AC Metcalfe, grown in three different environments in Canada in 2003, and varying in grain protein and β-glucan contents, as well as in grain hardness. The CW were initially extracted with water at 45 °C and subsequently digested with barley malt crude enzyme extract resulting in two fractions designated CW-WE45 and CW-MD, respectively. The remaining non-digested cell wall material (CW_ND) was further fractionated by sequential extraction with water at 95 °C (CW_ND-WE95), saturated barium hydroxide (CW_ND-BaE), and 1 N sodium hydroxide (CW_ND-NaE) at 25 °C. Composition and molecular structure analyses were carried out for all fractions including the remaining cell wall residue (CW_RES). Extraction of CW with water followed by digestion with malt crude enzyme extract solubilized the majority of β-glucans (∼55–70%) and glucomannans (∼60–80%) but only a small portion of arabinoxylans (∼20–30%) present in the intact CW. The CW-WE45 and CW_ND-WE95 fractions consisted mostly of β-glucans exhibiting high average molecular weights (M_w) (2–3 × 10⁶), whereas the CW_ND-BaE consisted mainly of arabinoxylans with M_w about 1–1.5 × 10⁶. The CW_ND-NaE contained almost equal amounts of β-glucans and arabinoxylans and a small amount of glucomannans, whereas the CW_RES contained approximately equal proportions of β-glucans, arabinoxylans and glucomannans. β-Glucans in CW_ND-WE95, CW_ND-NaE, and CW_RES exhibited a higher ratio of 3-O-β-d-cellobiosyl-d-glucose to 3-O-β-d-cellotriosyl-d-glucose (DP3/DP4) compared to β-glucans in CW-WE45 and CW-MD. β-Glucans in CW_ND-NaE showed the highest level of long cellulosic oligosaccharides with DP ≥ 5, whereas those in the CW_RES had the highest DP3/DP4 ratio. The CW-MD was fractionated by ultrafiltration into high (CW-MD_HMW) and low-molecular weight (CW-MD_LMW) sub-fractions, with weight-average M_w of ∼150–350 × 10³ and <10 × 10³, respectively, as confirmed by size-exclusion chromatography. The monosaccharide composition of the sub-fractions indicated a more extended enzymic degradation of β-glucans and glucomannans than arabinoxylans. Some differences in composition and molecular structure of the cell wall constituents among the three barley samples were related to their solubility and enzymic digestibility.     

Thermoplastic films from wheat proteins

We show that the wheat proteins gluten, gliadin and glutenin can be compression molded into thermoplastic films with good tensile strength and water stability. Wheat gluten is inexpensive, abundantly available, derived from renewable resource and therefore widely studied for potential thermoplastic applications. However, previous reports on developing thermoplastics from wheat proteins have used high amounts of glycerol (30-40%) and low molding temperature (90-120 °C) resulting in thermoplastics with poor tensile properties and water stability making them unsuitable for most thermoplastic applications. In this research, we have developed thermoplastic films from wheat gluten, gliadin and glutenin using low glycerol concentration (15%) but high molding temperatures (100-150 °C). Our research shows that wheat protein films with good tensile strength (up to 6.7 MPa) and films that were stable in water can be obtained by choosing appropriate compression molding conditions. Among the wheat proteins, wheat gluten has high strength and elongation whereas glutenin with and without starch had high strength and modulus but relatively low elongation. Gliadin imparts good extensibility but decreased the water stability of gluten films. Gliadin films had strength of 2.2 MPa and good elongation of 46% but the films were unstable in water. Although the tensile properties of wheat protein films are inferior compared to synthetic thermoplastic films, the type of wheat proteins and compression molding conditions can be chosen to obtain wheat protein films with properties suitable for various applications.     

Incorporation of soy proteins into the wheat–gluten matrix during dough mixing

Farinograph methodology was used to evaluate the possible incorporation of soy proteins into a glutenin–soy complex during mixing and to study the contribution of soy proteins to the chemical and physical properties of the dough. To facilitate the interaction of soy and wheat proteins, a redox process was used, which allowed the partial reduction (using dithiothreitol, DTT) and subsequent reoxidation (using potassium iodate) of glutenin without changing its functionality in the dough (a composite of equal parts of wheat and soy flours, 300 g in total). Either raw soy flour (RSF) or physically modified soy flour (PMSF) was used as the soy component. Dough samples were taken at peak mixing time and at break time during mixing, and these were freeze dried for SE-HPLC analysis and capillary electrophoresis (Lab-on-a-chip).     

Mineral fertilizer response and nutrient use efficiencies of East African highland banana (Musa spp., AAA-EAHB,cv. Kisansa)

Poor yields of East African highland bananas (Musa spp., AAA-EAHB) on smallholder farms have often been attributed to problems of poor soil fertility. We measured the effects of mineral fertilizers on crop performance at two sites over two to three crop cycles; Kawanda in central Uganda and Ntungamo in southwest Uganda. Fertilizers were applied at rates of 0N–50P–600K, 150N–50P–600K, 400N–0P–600K, 400N–50P–0K, 400N–50P–250K and 400N–50P–600K kg ha⁻¹ yr⁻¹. In addition 60Mg–6Zn–0.5Mo–1B kg ha⁻¹ yr⁻¹ was applied to all treatments, with the exception of the control plots which received no fertilizer. Fresh bunch mass and yield increased with successive cycles. Yield increases above the control ranged from 3.1 to 6.2 kg bunch⁻¹ (average bunch weight for all treatments 11.5 kg bunch⁻¹) and 2.2–11.2 Mg ha⁻¹ yr⁻¹ (average yield for all treatments 15.8 Mg ha⁻¹ yr⁻¹) at Kawanda, compared with 12.4–16.0 kg bunch⁻¹ (average bunch weight for all treatments 14.7 kg bunch⁻¹) and 7.0–29.5 Mg ha⁻¹ yr⁻¹ (average yield for all treatments 17.9 Mg ha⁻¹ yr⁻¹) at Ntungamo. The limiting nutrients at both sites were in the order K > P > N. Potassium, N and P foliar nutrient mass fractions were below previously established Diagnosis and Recommendation Integrated System (DRIS) norms, with the smallest K mass fractions observed in the best yielding plots at Ntungamo. Total nutrient uptakes (K > N > P) were higher at Ntungamo as compared with Kawanda, probably due to better soil moisture availability and root exploration of the soil. Average N, P and K conversion efficiencies for two crop cycles at both sites amounted to 49.2 kg finger DM kg⁻¹ N, 587 kg finger DM kg⁻¹ P and 10.8 kg finger DM kg⁻¹ K. Calibration results of the model QUEFTS using data from Ntungamo were reasonable (R² = 0.57, RMSE = 648 kg ha⁻¹). Using the measured soil chemical properties and yield data from an experiment at Mbarara in southwest Uganda, the calibrated QUEFTS model predicted yields well (R² = 0.68, RMSE = 562 kg ha⁻¹). We conclude that banana yields can be increased by use of mineral fertilizers, but fertilizer recovery efficiencies need to improve substantially before promoting wide-scale adoption.