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.     

Weed seed banks in arable fields under contrasting pesticide regimes

Viable weed seed banks on a clay soil were estimated for five years from 11 arable fields receiving one of three levels of pesticide application. Low seed densities, averaging 2000 m^-2, were recorded, but dicotyledonous weed seed numbers usually increased following oilseed rape crops, reaching 26 000 m^-2 in one field. Field-to-field variability was large. Samples could be grouped using multivariate techniques into those dominated by grass weed seeds and those containing mainly dicotyledonous weed seeds. Within TWINSPAN classifications, most fields maintained similar seed banks during the study period, indicating relative stability of communities. Differences present at the outset of the experiment, including variation between fields in the same treatment area, were maintained for the five years. Patterns were not associated with straw disposal or spring herbicide application. Oilseed rape crops did not cause qualitative change in seed bank communities, but allowed certain species, notably Stellaria media and Sonchus asper, to increase seed numbers. Smaller and less diverse seed banks in the area receiving most herbicide were not statistically significant. Seed banks gave poor predictions of following weed populations.     

抗草丁膦和抗草甘膦转基因油菜的抗性基因向野芥菜的流动

通过人工去雄授粉和田间隔行种植试验,研究了抗草丁膦和抗草甘膦转基因油菜(Brassica napus)中的bar基因和EPSPS基因向野芥菜(B. juncea var. gracilis)流动的可能性。结果表明在人工授粉的情况下,以野芥菜为母本,分别以两种转基因油菜为父本,亲和性指数都很高,达13以上,与野芥菜自交或开放授粉条件下的亲和性指数没有明显差异,说明两种转基因油菜和野芥菜的亲和性较好。经两次除草剂筛选,人工杂交获得的所有F₁对相应的除草剂都表现出了明显的抗性,且经PCR检测扩增出了各自的特异性条带,说明人工杂交获得的所有F₁都携带了相应的抗性基因。F₁的适合度研究表明,两种F₁种子萌发率和母本都没有明显差异,营养生长明显好于母本。但花粉活力和结实率明显下降,携带抗草丁膦基因F₁的花粉活力和每角果粒数分别是32.4%和0.59粒,携带抗草甘膦基因F₁的花粉活力和每角果粒数分别是35.1%和0.58粒。经两次除草剂筛选和PCR检测,表明野芥菜和抗草丁膦油菜或与抗草甘膦油菜田间隔行种植分别能产生0.02%和0.014%的携带抗性基因的F₁杂种。以上结果表明抗除草剂转基因油菜的抗性基因具有向野芥菜流动的可能性,且bar和EPSPS基因向野芥菜流动的可能性类似,但对其可能引起的环境后果需要做进一步地深入研究。     

Glucosinolate changes in developing pods of single and double low varieties of autumn-sown oilseed rape (B. napus)

Single and double low varieties of oilseed rape were grown in the 1987/88 and 1988/89 seasons to study changes in the concentrations of total and individual glucosinolates within pods during development. Total glucosinolate concentration in seeds of all varieties increased during development when expressed on a fresh weight basis. The levels of the major alkenyl glucosinolates present in the seed; 2–hydroxy-3–butenyl, 3–butenyl and 4–pentenyl had been reduced in the transition from single to double low varieties. The major indole glucosinolates in the seed, 4–hydroxy-3–indolylmethyl and 3–indolylmethyl were present in the same amounts in single and double low varieties but in the latter represented a greater proportion of the total seed glucosinolate content. A decline in the total glucosinolate concentration in the pod walls with time together with the analogous profile of individual glucosinolates in the seeds and pod walls suggests that the pod wall is a major site of seed glucosinolate synthesis. Other plant parts may also have an important role to play in provision of intact glucosinolates or precursors to the pod walls for glucosinolate biosynthesis.     

Molecular markers for low-glucosinolate alleles in oilseed rape (Brassica napus L.)

Two recent studies have mapped QTLs associated with the level of seed glucosinolates in oilseed rape (Brassica napus L.). It was likely that the two most significant QTLs identified in each study were the same, as they were linked to RFLP alleles identified by common DNA probes. To investigate the utility of these probes in breeding programmes, they were used to study RFLPs in a range of low- and high-glucosinolate cultivars and breeding lines. It was shown that all low glucosinolate spring and winter cultivars possessed a specific RFLP fragment identified by probe wg3f7 which is linked to theGSL-1 QTL, and all high-glucosinolate cultivars possessed a specific RFLP fragment identified by probe wg7a8, which is linked to theGSL-2 QTL. Cultivar Ariana, which has intermediate levels of glucosinolates possessed the low-glucosinolate fragment atGSL-1 but the high-glucosinolate fragment atGSL-2. A similar result was found with the cvs. Martina and Bronowski which have intermediate and variable levels of glucosinolates. There were no other RFLP fragments identified by other DNA probes which were specific to either the low- or high-glucosinolate phenotypes. The use of probes wg3f7 and wg7a8 in selection of low-glucosinolate lines in breeding programmes is discussed.     

Quantification of ammonia exchange between agricultural cropland and the atmosphere: Measurements over two complete growth cycles of oilseed rape,wheat, barley and pea

The exchange of ammonia between the atmosphere and the canopy of barley, wheat, oilseed rape and pea crops was studied over two growing seasons by use of a modified aerodynamic gradient technique in which passive horizontal flux samplers were applied with a wind profile in gradient configuration. The crop foliage was a net source of NH₃ to the atmosphere, with NH₃ emissions on a seasonal basis between 1 and 5 kg NH₃–N ha^–1. The amount of NH₃ lost constituted between 1 and 4% of the applied nitrogen and between 1 and 4% of the actual amount of nitrogen present in the mature shoots. The volatile NH₃ losses depended on seasonal variations in climatic conditions affecting the growth and nitrogen economy of the crops and increased under conditions with excessive N absorption by roots and a high N concentration in the foliage. The accumulated NH₃ loss was positively correlated with the above-ground crop N content at anthesis, but not with that at final maturity. There were no indications that NH₃ emissions were larger under conditions unfavourable for nitrogen remobilization from vegetative plant parts (low N harvest index). Nevertheless, a distinct peak in NH₃ emission occurred during senescence. It is concluded that crops in many areas will represent a significant input of ammonia to the atmosphere and that NH₃ losses may become large enough to significantly affect crop N budgets.     

Comparative response of wheat and oilseed rape to nitrogen supply: absorption and utilisation efficiency of radiation and nitrogen during the reproductive stages determining yield

We investigated the response of spring wheat and oilseed rape to nitrogen (N) supply, focusing on the critical period for grain number definition and grain filling. Crops were grown in containers under a shelter and treated with five combinations of applied N. Wheat and oilseed rape produced comparable amounts of biomass and yield when corrected for the costs of biomass synthesis (SC). From the responses of biomass and yield to late N applications and the apparent contribution of mobilised biomass to yield, it seems that the yield of oilseed rape was more source-limited during grain filling than that of wheat, particularly at the medium and high N levels. Both species recovered equal amounts of N from the total available N in the soil and had similar N use efficiencies, expressed as yield per unit of N absorbed. However, oilseed rape had higher efficiency to convert absorbed N in biomass, but lower harvest index of N than wheat. Oilseed rape had similar or lower root biomass than wheat, depending on N level, but higher root length per unit soil volume and specific root length. The specific uptake rate of N per unit root dry weight during the critical period for grain number determination was higher in oilseed rape than in wheat. In wheat, N limitation affected growth through a similar or lower reduction in radiation use efficiency corrected for synthesis costs (RUE_SC) than in the cumulative amount of intercepted photosynthetically active radiation (IPARc). In oilseed rape, lower growth due to N shortage was associated more with RUE_SC than IPARc, during flowering while during grain filling both components contributed similarly to decreased growth. RUE_SC and the concentration of N in leaves and inflorescence (LIN%) decreased from flowering to maturity and were curvilinearly related. Oilseed rape tended to have higher RUE_SC than wheat at high N supply during the critical period for grain number determination, and generally lower during grain filling. The reasons for these differences and possibilities to increase yield potential are discussed in terms of the photosynthetic efficiency of the different organs and changes in source–sink ratio during reproductive stages. This revised version was published online in June 2006 with corrections to the Cover Date.     

不同水旱轮作体系稻田土壤剖面N2O的分布特征

通过原位采集淹水和排水状态下土壤剖面4个层次的气体,研究氧化亚氮（N₂O）在水旱轮作体系稻田土壤剖面中的动态分布特征.试验设置小麦-单季稻和油菜-双季稻两种轮作体系,包括施N和不施N两种施肥方式.结果表明:施用N肥极显著促进了土壤剖面N₂O的产生（P<0.01）,不同层次间N₂O浓度相关性极显著（P<0.01）,小麦、油菜生长期施N和无N处理下层30 cm和50 cm处N₂O浓度均高于表层7 cm和15 cm处;早稻无N处理则为表层7 cm和15 cm处高于下层30 cm和50 cm处（P<0.05）,其他水稻处理各层次间无显著差异.无N处理土壤N₂O峰值出现在旱作向水稻的转变期,施N处理则出现在旱作第2次追肥后,季节转变期也有较高的N₂O浓度.     

Chloroplast Transformation in Oilseed Rape

The chloroplast transformation vector pNRAB carries two expression cassettes for the spectinomycin resistance gene aadA and the insect resistance gene cry1Aa10. The two cassettes are sited between the rps7 and ndhB targeting fragments. Biolistic delivery of the vector DNA, followed by spectinomycin selection, yielded chloroplast transformants at a frequency of four in 1000 bombarded cotyledon petioles. PCR analysis and Southern blot of PCR products confirmed the site-specific integration of aadA and cry1Aa10 into the chloroplast genomes of transgenic oilseed rape. When transgenic oilseed rape leaves were fed to second instar Plutella xylostera larvae, 47% mortality was observed against this insect and the surviving larvae had significantly lower weight than the control. This is the first report of chloroplast transformation in oilseed rape and the introduction of novel genes between the rps7 and ndhB genes in the chloroplast genome. This offers an opportunity for improvement of oilseed rape by chloroplast genetic engineering.     

不同水旱轮作体系稻田土壤剖面N2O的分布特征

通过原位采集淹水和排水状态下土壤剖面4个层次的气体,研究氧化亚氮(N2O)在水旱轮作体系稻田土壤剖面中的动态分布特征.试验设置小麦-单季稻和油菜-双季稻两种轮作体系,包括施N和不施N两种施肥方式.结果表明:施用N肥极显著促进了土壤剖面N2O的产生(P＜0.01),不同层次间N2O浓度相关性极显著(P＜0.01),小麦、油菜生长期施N和无N处理下层30 cm和50 cm处N2O浓度均高于表层7 cm和15 cm处;早稻无N处理则为表层7 cm和15 cm处高于下层30 cm和50 cm处(P＜0.05),其他水稻处理各层次间无显著差异.无N处理土壤N2O峰值出现在旱作向水稻的转变期,施N处理则出现在旱作第2次追肥后,季节转变期也有较高的N2O浓度.     

HPLC分析油菜籽油中维生素E的组成与含量

本文利用ＨＰＬＣ法分析了５０份遗传背景丰富的白菜型油菜、甘蓝型油菜、芥菜型油菜和芸芥种子油中维生素E的组成与含量,研究结果显示,油菜种子油中主要含α-生育酚和? -生育酚,且α-生育酚、? -生育酚和维生素E总量均存在明显的基因型差异,甘蓝型油菜种子油中维生素E含量总体水平最高,平均总量较高,为123.11 mg/100g油, 维生素E含量最高的Omega,总量为144.73 mg/100g油, α/ ? -生育酚比值最高可达0.77。α-生育酚、? -生育酚和维生素E总量与类胡萝卜素含量均呈现显著以上负相关,种子油中α-生育酚与含油量呈现显著正相关,α-生育酚、? -生育酚和维生素E总量与生育期均呈现显著或极显著正相关,α-生育酚和维生素E总量与株高均呈现显著正相关,维生素E总量与千粒重呈显著正相关,而α-生育酚、? -生育酚和维生素E总量与全株角果数和每角粒数相关不显著。     

基于高通量测序分析大豆和油菜根际微生物群落结构的差异

根肿病是由芸薹根肿菌侵染引起的专性寄生性土传病害,严重制约着油菜等十字花科作物的可持续生产.前期研究发现,大豆作为前茬作物可以显著降低后茬油菜根肿病的发生和危害,\"豆-油轮作\"模式是一种值得探索和应用的根肿病防治新途径.为了解开大豆作为前茬防治根肿病发生的机理,本研究基于扩增子测序技术探究大豆与油菜根际土壤微生物的群落结构差异.结果表明:大豆和油菜根际土壤微生物类群在门水平的优势类群相同,包括变形菌门、拟杆菌门、酸杆菌门、放线菌门、子囊菌门、接合菌门、担子菌门和壶菌门等丰度都较高.但相比于油菜根际土壤,大豆根际土壤富含具有生防作用和促进植物生长的微生物,如黄杆菌属、鞘脂单胞菌属、芽孢杆菌属、链霉菌属、假单胞菌属、木霉属和盾壳霉属等;而一些植物病原细菌(如肠杆菌、黄单胞菌)和真菌(炭疽菌和尾孢菌)含量则低于油菜根际土壤;另外,大豆根际土壤中还富含具有固氮功能的根瘤菌属、慢生根瘤菌属和丛枝菌根真菌(如球囊霉属).可见,大豆根际土壤利于有益微生物生长并可抑制病原菌繁殖.大豆和油菜根际微生物组差异为大豆-油菜轮作防治根肿病提供了理论依据,并为根肿病的防治提供了一些潜在的生物防治资源.     

Growth responses in oilseed rape (Brassica napus L.) to combined applications of the triazole chemicals triapenthenol and tebuconazole and interactions with gibberellin

Crop height in the oilseed rape cv. Ariana was reduced more by the triazole retardant triapenthenol at 490 g ai ha^–1, applied as a combined spray with the triazole fungicide tebuconazole at 250 g ai ha^–1, than when triapenthenol was applied alone. The growth responses following combined treatment appeared to be additive of the component effects.Initial inhibition of stem extension and leaf expansion by tebuconazole was followed by compensatory growth; the pattern of responses was similar to that with triapenthenol applied at approximately one tenth of the rate. However, different mechanisms of effects on growth were indicated by competitive interaction with gibberellic acid.     

Polyethylene glycol and electric field treatment of plant protoplasts: characterization of some membrane properties

Petiolar protoplasts of a dihaploid line of winter oilseed rape Brassica napus L. ssp. oleifera were exposed to fusogenic polyethylene glycol (PEG) and electric field treatments. The surface properties and stability of membrane components of the treated protoplasts were investigated by contact angle measurements in aqueous two-phase systems and differential scanning calorimetry, respectively. The leakage of intracellular components was estimated with respect to amino acids, proteins and DNA. Both fusogenic treatments resulted in the same apparent changes in membrane surface hydrophobicity and the same destabilization of membrane components. However, the PEG-treated protoplasts were more leaky than both the control and the electric field-treated protoplasts. The results indicate that the molecular mechanisms of PEG- and electrical field-induced fusion are similar. However, the effects of the latter appear to be less harmful presumably because the parameters for electric field treatment are more easily controlled.