Availability of different forms of sulphur fertilisers to wheat and oilseed rape

A pot experiment was conducted to compare the availability and efficiency of three sulphur (S) fertilisers to wheat in the first year and oilseed rape in the second year, using six agricultural soils. Four treatments were applied in the initial year: control (no S), two forms of elemental S (either micronised S° particles or a bentonite + S° mixture) and a sulphate fertiliser (ammonium sulphate). In the first year, the micronised S° was as effective as the sulphate fertiliser, both producing similar increases of wheat grain yield (on average 36%) and S uptake (on average 164%) over the control. In contrast, responses to the bentonite + S° form were minimal, indicating a limited S supply. In the second year the control treatment failed to produce seeds in most soils, whereas the micronised S° and sulphate treatments increased seed yields of oilseed rape to an average of 13.4 and 12.9 g pot^-1, respectively. The performance of the bentonite + S° varied between soils: two soils produced yields similar to those of the other S fertilisers, while the remaining soils had low yields. To test whether the poor performance of the bentonite clay + S° fertiliser was due to the lack of exposure of the prills to physical weathering in the glasshouse, the effect of freeze-thaw action on the fertilisers performance was assessed in a separate pot experiment. The responses in wheat yield and S uptake showed that freeze-thaw did not enhance the physical disruption of the prills or fertiliser effectiveness. These results suggest that the release of available S from the bentonite + S° mixture was too slow to meet the requirement of wheat and oilseed rape. This revised version was published online in June 2006 with corrections to the Cover Date.     

Comparative assessment of the sensitivity of oilseed rape and wheat to limited water supply

The drought‐sensitivity of oilseed rape (OSR, Brassica napus cv. SW Landmark) was investigated, using the more widely studied crop species wheat (Triticum aestivum cv. Tybalt) as a benchmark. The water relations of OSR and wheat were compared in lysimeter and controlled environment experiments to test the hypothesis that the growth of OSR is restricted to a greater extent by soil drying than wheat and to determine whether the greater sensitivity results from differences in root or shoot traits. Plants were grown, with or without irrigation, in 1.2 m tall lysimeters packed with a sandy clay loam soil. The experiment was conducted in an open‐sided glasshouse to encourage air flow and to resemble a field environment as far as possible; plant population densities were equivalent to commercial crops. Irrigated OSR (evapo)transpired more water than wheat (498 vs. 355 mm), but had a comparable water use efficiency (WUE; 4.1 vs. 4.4 g DW mm^?1 H₂O). Oilseed rape showed a greater reduction in above‐ground growth (52% vs. 21%) and a smaller increase in WUE (27% vs. 45%) when water was withheld. Oilseed rape also responded to soil drying at a lower soil moisture deficit than wheat; transpiration rates fell below the potential of irrigated plants when plant available water remaining in the soil profile declined from 54 to 23% compared to 38 to 9% for wheat. The root hydraulic conductivity of young OSR plants, measured on root surface area basis, was about twice that of wheat, and was comparable on a root length basis. The results show that OSR was more sensitive to a restricted water supply than the benchmark species wheat and that the greater sensitivity resulted from differences in shoot, rather than root, characteristics. The root system of OSR was at least as efficient as wheat at extracting water from soil.     

The impact of zearalenone and thidiazuron on indirect plant regeneration of oilseed rape and wheat

The aim of the study was to test the synergistic activity of zearalenone and thidiazuron with commonly used regulators (6-benzylaminopurine, 2,4-dichlorophenoxyacetic acid) in callus tissue growth and the regeneration processes of winter oilseed rape and winter wheat. Oilseed rape callus was obtained from the upper fragments of seedling hypocotyls. Wheat callus tissue was obtained from immature embryos. Zearalenone, in combination with 6-benzylaminopurine, stimulated the regeneration of oilseed rape and, in combination with 2,4-dichlorophenoxyacetic acid, the regeneration of wheat. An additional application of thidiazuron to these media increased the percentage of shoot regeneration from callus in both species tested. Zearalenone is proposed as a new regulator in in vitro plant cultures for use in protocols of plant regeneration.     

Surveys of diseases of winter wheat in England and Wales, 1976–1988

Samples from 300 – 400 randomly selected winter wheat crops were taken annually at growth stage 73 – 75 from 1976 to 1988 with the exception of 1983 and 1984. The number of samples from each region was proportional to the area of wheat grown in each region. The percentage of the area of the top two leaves affected by diseases, the severity of ear and stem base diseases and, in 6 years, the severity of take-all were recorded. Septoria tritici and Septoria nodorum were, on average, the most severe of the foliar diseases and eyespot (Pseudocercosporella herpotrichoides) was the most severe of the stem base diseases. Regional differences in levels of S. tritici, brown rust, sharp eyespot and nodal fusarium were significant. Cultivar resistance affected disease severity, and previous cropping patterns particularly affected take-all and eyespot. Eyespot and sharp eyespot were less severe in late- than in early-sown crops. The percentage of crops treated with a fungicidal spray increased from 14% in 1976 to over 90% between 1983 and 1985. Use of benzimidazole fungicides applied at growth stage 31 declined, while use of morpholines from flag leaf emergence onwards increased between 1985 and 1988.     

Environmental temperatures and the incidence of food poisoning in England and Wales

The incidence of food poisoning in England and Wales has been increasing for many years and it is now a major public health problem. Superimposed on this general rising trend is a well-established tendency for the number of cases of food poisoning to rise during the summer when warm weather favours the multiplication of pathogenic micro-organisms. This paper shows that weekly notifications of food poisoning in England and Wales are strongly associated with environmental temperatures, but that there are some important time lags in this relationship. The number of cases of food poisoning in a given week was only weakly correlated with the temperature of that week and the one preceding it. This suggests that factors operating close to the point of consumption within or outside the home are not the principal cause of the rise in food poisoning associated with warm summer conditions. There was a much stronger association with temperatures 2–5 weeks earlier, pointing to the importance of factors operating earlier in the food production or distribution system. The results of this study suggest that the food poisoning problem requires action by food producers and distributors as well as by consumers. Received: 15 May 2000 / Revised: 17 October 2000 / Accepted: 18 October 2000     

Glucosinolate biosynthesis in oilseed rape (Brassicanapus L.): studies with 35SO2-4 and glucosinolate precursors using oilseed rape pods and seeds

³⁵SO^2–₄ and glucosinolate precursors were administeredto investigate the capacity of oilseed rape intact whole pods,isolated pod walls and seeds to carry out reactions of the glucosinolatebiosynthetic pathway. Pod walls incorporated ³⁵S-label from³⁵SO^2–₄ into both the thio-glucose and sulphonate-sulphurof glucosinolates. Pulse-labelling experiments showed that podwalls were the predominant source of the glucosinolates accumulatedby the seeds. Isolated immatureseeds were capable of reductiveassimilation of ³⁵SO^2–₄ and incorporated ³⁵S into sulphur-containingamino acids and the sulphonate moiety of glucosinolates, butwere not able to incorporate ³⁵S into the thio-glucose of glucosinolates. Key words: Biosynthesis, glucosinolates, oilseed rape, pod walls, seeds     

Genetic manipulation in cultivars of oilseed rape (Brassica napus) using Agrobacterium

Summary The response of oilseed rape cultivars to infection with Agrobacterium tumefaciens and A. rhizogenes and the possibility of regenerating genetically transformed oilseed rape plants were examined. The frequency at which Agrobacterium induced galls or hairy-roots on in vitro cultured plants ranged from 10% to 70%, depending on the cultivar. From galls induced by the tumorigenic strain T37, known to be strongly shoot inducing on tobacco, roots developed frequently. Occasionally, shoots formed and some of these produced tumour cell specific nopaline. Attempts to grow the transformed shoots into plants have so far been unsuccessful. Whole plants transformed with Ri-T-DNA, however, were regenerated. These had crinkled leaves and abundant, frequently branching roots that showed reduced geotropism, similar to previously isolated Ri T-DNA transformed tobacco and potato plants. The transformed oilseed rape plants flowered, but failed to form seeds.     

Temperature and heterogeneity of emergence time in oilseed rape

Emergence of oilseed rape cultivars with known differences in germination profile was examined by controlled sowings in the field at mean temperatures between 2 and 10°C. Early percentiles, up to the 50th in two cultivars (Rocket and Martina) and up to the 20th in a third (Comet), responded to temperature similarly at all sowings, in that 1/time to emergence of a percentile (emergence rate) increased exponentially with temperature above an intercept of-1°C. For these percentiles, emergence occurred at a similar thermally weighted time over the whole range of temperature, indicating the peak of the first flush of seedlings is predictable. Percentiles higher than those cited above displayed increasing non-germination (probably secondary dormancy) as temperature declined towards winter. The maximum non-germination ranged between 50% and 80% among the cultivars. In sowings during and just after winter, the emergence rate of these higher percentiles was lower than at a comparable temperature before winter. A portion of non-germinating seeds of the two most heterogeneous cultivars overwintered and emerged synchronously in April from a range of pre- and post-winter sowings, probably stimulated by increasing diurnal temperature amplitude from 7 to 15K. At low temperature, therefore, cultivars exhibited great heterogeneity in the emergence profile, those with more heterogeneity being more likely to give rise to temporally separate weed or feral populations. The findings are discussed in the context of weediness and transgene movement in the oilseed rape metapopulation.     

Phytohormonal changes in intact shoots of wheat and oilseed rape treated with the acylcyclohexanedione growth retardant prohexadione calcium

The effects of the acylcyclohexanedione-type growth retardant prohexadione calcium on seedling growth and endogenous levels of immunoreactive phytohormone-like substances in shoots of wheat ( Triticum aestivum L. cv. Kanzler) and oilseed rape ( Brassica napus L. ssp. napus cv. Lirajet) were studied. After treatment of seedlings with increasing retardant concentrations in hydroponics, plant height and fresh weight of shoots were reduced by up to 40%. Concomitantly, the amount of immunoreactive gibberellins decreased, on a fresh weight basis, when compared with levels in the shoots of control plants. In contrast, the levels of abscisic acid and dihydrozeatin riboside and isopentenyladenosine-type cytokinins were considerably elevated by the growth retardant. The content of 3-indoleacetic acid decreased slightly. These results suggest that, in addition to its effect on gibberellin content, prohexadione calcium also influences the levels of endogenous abscisic acid and cytokinins.     

Development of an assay for Mg-dechelatase of oilseed rape cotyledons, using chlorophyllin as the substrate

Chlorophyllin (Chlin), the Mg-chlorin obtained from chlorophyll (Chl) was employed as substrate of Mg-dechelatase. The release of Mg²⁺ was associated with a shift of absorption from 644 to 687 nm. Changes of absorption at 687 nm were taken as a measure of Mg-dechelatase activity present in preparations of oilseed rape thylakoids. Absorption changes were correlated linearly with enzyme dose. The pH optimum of Mg release from Chlin was ca 9 with a broad flank down to pH 7. The reaction showed saturation kinetics with an apparent K_m value of ca 17 n M . The activity was inhibited in the presence of cysteamine or reduced glutathion. There was no effect of the thiol reagent N-ethyl maleimide. The bulk of dechelatase activity was associated with the chloroplast membranes. The enzyme is partially latent and the appearance of full activity requires the solubilization of thylakoids with detergent. The highest activities were detected in mature green rape cotyledons. During dark-induced senescence the activity declined at roughly the same rate as Chl was lost in the leaf tissue.     

Insect pollination enhances seed yield, quality, and market value in oilseed rape

The relationships between landscape intensification, the abundance and diversity of pollinating insects, and their contributions to crop yield, quality, and market value are poorly studied, despite observed declines in wild and domesticated pollinators. Abundance and species richness of pollinating insects were estimated in ten fields of spring oilseed rape, Brassica napus var. SW Stratos?, located along a gradient of landscape compositions ranging from simple landscapes dominated by arable land to heterogeneous landscapes with extensive cover of semi-natural habitats. In each field, we assessed the contribution of wind and insect pollination to seed yield, seed quality (individual seed weight and oil and chlorophyll contents), and market value in a block experiment with four replicates and two treatments: (1) all flowers were accessible to insects, self and wind pollination, and (2) flowers enclosed in tulle net bags (mesh: 1 × 1 mm) were accessible only to wind and self pollination. Complex landscapes enhanced the overall abundance of wild insects as well as the abundance and species richness of hoverflies. This did not translate to a higher yield, probably due to consistent pollination by honey bees across all fields. However, the pollination experiment showed that insects increased seed weight per plant by 18% and market value by 20%. Seed quality was enhanced by insect pollination, rendering heavier seeds as well as higher oil and lower chlorophyll contents, clearly showing that insect pollination is required to reach high seed yield and quality in oilseed rape. Our study demonstrates considerable and previously underestimated contributions from pollinating insects to both the yield and the market value of oilseed rape.     

Diagnosing sulfur deficiency in field-grown oilseed rape (Brassica napus L.) and wheat ( Triticum aestivum L.)

The effects of increasing sulfur applications on field-grown oilseed rape (Brassica napus L.) and wheat (Triticum aestivum L.) were investigated in 1998 and 1999, and the critical values and efficiency of several diagnostic indicators for S deficiency were determined. Critical values for leaf concentrations of total S, sulfate and glutathione changed over time and were not suitable for diagnosing S deficiency early in the growth season. The N:S ratio was more reliable but involved two analytical measurements. A practical and reliable indicator for S deficiency was the malate:sulfate peak area ratio as measured by ion chromatography, which required only a single analysis and was independent of the time of sampling or calibration of the samples. A malate:sulfate ratio ≤ 1 indicated S sufficiency at the time of sampling, whereas a ratio > 1 suggested S deficiency at the time of sampling. The malate:sulfate ratio was reliable at growth stage 3.6–3.7 (flower stalks extending to first flowers yellow) for oilseed rape and at growth stage 22–25 (main stem and 2–5 tillers) for wheat, which was sufficiently early in the growth season to apply remedial sulfur fertilizer, if necessary. This revised version was published online in June 2006 with corrections to the Cover Date.     

5-Aminolevulinic acid enhances photosynthetic gas exchange, chlorophyll fluorescence and antioxidant system in oilseed rape under drought stress

This study evaluates the role of exogenous foliar application of 5-aminolevulinic acid (ALA) on water relations, gas exchange, chlorophyll fluorescence, and the activities and gene expression patterns of antioxidant enzymes in leaves of oilseed rape under drought stress and recovery conditions. Seedlings at four-leaf stage were imposed to well-watered condition (80 % of water-holding capacity) or drought stress (40 % of water-holding capacity) and subsequently foliar sprayed with water or ALA (30 mg l^?1). Drought suppressed the accumulation of plant biomass and decreased chlorophyll content and leaf water status (relative water content and water potential). The actual quantum yield of photosystem II and electron transport rates were hampered in parallel to net photosynthetic rate. However, drought stress induced the accumulation of malondialdehyde (MDA) and hydrogen peroxide, enhanced the activities of catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR) and superoxide dismutase and up-regulated the expression of APX and GR. After rehydration for 4 days, the growth of drought-treated seedlings was restored to normal level for most of the physiological parameters. Foliar application of ALA maintained relatively higher leaf water status and enhanced chlorophyll content, net photosynthetic rate, actual quantum yield of photosystem II, photochemical quenching, non-photochemical quenching and electron transport rates in stressed leaves. Exogenous ALA also alleviated the accumulation of MDA and hydrogen peroxide, increased the activities of antioxidant enzymes and enhanced the expression of CAT and POD in drought-treated plants. These results indicate that ALA may effectively protect rapeseed seedlings from damage induced by drought stress.     

长期不同施肥方式对稻油两熟制油菜田杂草群落多样性的影响

为揭示长期不同施肥管理措施下农田生态系统生物多样性的变化规律,作者于2006年4月在太湖地区一个长期肥料试验定位监测田,运用群落生态学方法研究了7种长期不同施肥处理持续20年后对水稻-油菜两熟制油菜田杂草群落多样性的影响。试验区共记录到杂草17种,隶属于11科。不同施肥处理小区中杂草种类以单施化肥区（6种）和施化肥＋全年秸秆区（5种）最少,纯氮肥区最高（12种）;以看麦娘（Alopecurus aequalis）、日本看麦娘（A.japonicus）、菵草（Beckmannia syzigachne）、牛繁缕（Malachium aquaticum）、野老鹳草（Geranium carolinianum）等5种发生密度较大,它们分别在不同施肥小区中占据优势。长期不同施肥措施下,田间杂草群落的物种多样性有明显差异：纯氮肥区Shannon-Wiener指数显著大于其他小区,但Simpson优势度指数最低;不施肥区（对照区）和纯氮肥区Pielou均匀度指数显著高于其他施肥处理区;施化肥＋秸秆还田显著提高了田间杂草的优势度。田间杂草群落的优势种组成也发生了一定变化,Whittaker指数表明施化肥＋夏季秸秆还田和单施化肥的影响最显著,常规施肥和施化肥＋秋季秸秆还田次之,而施化肥＋全年秸秆还田和单施氮肥没有显著影响。Sφrenson群落相似性指数及聚类分析结果也得到同样的结论。本文研究结果表明,单施化肥（平衡施用N、P、K肥）、常规施肥和化肥配施秸秆处理均能显著改变田间杂草群落的组成,降低某些优势杂草在群落中的优势地位,从而抑制其发生危害程度。