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1.
Oilseed rape (OSR) genes can escape fields in space via pollen and seeds and in time via volunteers resulting from seeds lost before or during oilseed rape harvests. Previous simulation studies and field observations showed that co-existence at the landscape level of contrasting OSR varieties such as genetically modified (GM) and non-GM varieties require costly measures that are difficult to implement, such as isolation distances between OSR fields and stringent volunteer control in all fields and road margins. In the present study, two local strategies, non-GM buffer zones around GM fields and discarding the harvest of boundary plants of non-GM fields, were tested in a simulation study using the GENESYS model. This model, which was modified here to improve the prediction of volunteer reproduction and pollen dispersal, quantifies the effects of cropping system on gene flow in landscapes over the years. The evaluation of the improved model version with independent field observations showed that cross-pollination of fields was accurately predicted up to 50 m and systematically underestimated above that distance, though fields were still ranked correctly. A corrective factor should therefore be applied to predictions in case of low regional OSR and GM proportions (which result into large distances between fields). To study the effects of the two local strategies, simulations were carried out in four contrasted case studies, based on different landscapes, regional OSR and GM proportions, cropping systems and OSR varieties. In these situations, harvest discarding was needless when volunteers were well controlled because the GM impurity in non-GM harvests was well below the EU labelling thresholds; it was useless when OSR contained male-sterile plants or when the landscape was infested by volunteers because large parts of the fields had to be discarded to respect impurity thresholds, which is financially unacceptable. Buffer zones were useful if the non-GM varieties comprised male-sterile plants or if the non-GM fields were small, but only if volunteers were well controlled and harvest impurity was already close to the labelling threshold. Buffer zones appeared considerably more efficient in reducing harvest impurity than harvest discarding because they not only increase the distance between GM and non-GM fields but also diminish the proportion of GM pollen in the total pollen cloud over landscapes. Harvest discarding could possibly be interesting for isolated OSR crops surrounded by bare ground or small crops, an effect that was not tested here. The present study showed that efforts should be dedicated to characterizing and modelling of gene flow at the landscape level, as well as the collection of datasets for the evaluation of these models in many landscapes and configurations. Local measures tested here are insufficient for ensuring harvest purity. Therefore, future work should focus on finding additional measures are necessary to manage OSR volunteers which constitute the major risk factor for OSR harvest purity. 相似文献
2.
The European Commission have established the concept of coexistence, according to which, farmers should be able to grow whatever type of agricultural crops they wish (genetically modified (GM), conventional or organic), provided that they comply with the legal obligations for labeling and/or purity standards. In the case of maize, the main factor conditioning the feasibility of coexistence is gene flow from GM fields to other types of production. The distance between fields has been identified as a key factor governing this gene flow. As a consequence, the existing regulations mostly concern the maintenance of a fixed isolation distance between GM fields and the closest non-GM field. However, other factors, such as temporal dynamics of pollen shedding, wind, relative field sizes and shapes and the spatial distribution of the different types of fields, may greatly modulate the effect of distance. Moreover, uniform distance-based rules create a “domino effect”, in which it is difficult for GM crops and non-GM crops to co-exist at the landscape scale. In this study, we hypothesized that the use of a spatially explicit gene-flow model, MAPOD®, would result in a significant gain in proportionality and freedom of choice for the farmer over uniform distance-based rules. To test this hypothesis, we performed a global sensitivity analysis on this process-based model but, instead of exploring a random set of situations, the sensitivity analysis was carried out on a subset of realistic scenarios based on farmers’ strategies. To select those scenarios, we constructed a multicriteria decision-making model describing the decision process used by farmers when deciding whether or not to grow GM maize, and used this model to generate realistic allocation scenarios for GM, non-GM conventional and organic maize cultivation. We showed that the coexistence method based on the MAPOD® model allowed the presence of a higher percentage of GM maize in the landscape than the distance-based method. This made it possible to follow the farmer’s field intended allocations more closely, whilst complying with the legal threshold requirements. This gain in proportionality was greater at high maize densities, for which the distance-based method allowed almost no cultivation of GM crops. However, in case of high proportions of organic fields, our study indicated that coexistence between GM maize and organic maize at the landscape level is difficult, if not impossible in case of farm-saved seeds, without a spatial aggregation of fields, leading de facto to separate non-GM and GM zones. Finally, the use of MAPOD® resulted in better discrimination between acceptable and risky situations, and greater flexibility, which is crucial for the implementation of an efficient coexistence strategy. 相似文献
3.
Gene flow between coexisting oilseed rape varieties and rape volunteers cannot be solely studied on field experiments. Previously, a model (GeneSys: [Colbach, N., Clermont-Dauphin, C., Meynard, J.M., 2001. GeneSys: A model of the inluence of croping system on gene escape from herbicide-tolerant rapeseed crops to rape volunteers. I. Temporal evolution of a population of rapeseed volunteers in a field. Agric. Ecosyst. Environ. 83, 235–253; Colbach, N., Clermont-Dauphin, C., Meynard, J.M., 2001. GeneSys: A model of the inluence of croping system on gene escape from herbicide-tolerant rapeseed crops to rape volunteers. II. Genetic exchanges among volunteer and cropped populations in a small region. Agric. Ecosyst. Environ. 83, 255–270]) was therefore developed to quantify the effects of cropping systems on gene flow from rapeseed varieties to rape volunteers in time and in space. In the present work, the model was improved to simulate simultaneously the spread of three different genes. Four different regions were then surveyed from 1995 to 2001: one region comprised only farmers’ fields with frequent rape crops in the rotations; the three remaining regions comprised the French experimental GMO platforms with 2–3 GM and one non-GM rape variety as well as neighbour farmers’ fields. For all these fields, cropping history was recorded during the study and for at least three previous years. In the first region, rapeseed volunteers were assessed in crops as well as on road and field margins in 1 year. In the three remaining regions, volunteer densities and genotypes were assessed each year after harvest and rape harvest genotypes determined during 2 years. The comparison of simulated and observed data showed that the model usually satisfactorily predicts volunteer densities and genotype proportions as well as harvest genotype proportions. Several problem areas were identified: volunteers in road and field margins were usually badly predicted; the model frequently underestimated volunteer densities in spring crops; gene flow via pollen dispersal was underestimated when the distance from the pollen source increased. The model was then used to simulate the spread of herbicide-tolerant rape volunteers in a region grown with one or several GM herbicide-tolerant varieties and more particularly the stacking of several resistance genes in individuals. The simulations also showed the contamination of the harvest of non-GM rape varieties by GM seeds resulting from gene flow. 相似文献
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5.
Potato is a critical crop to European growers, both economically and agronomically as a break crop in the standard cereal rotation. As studies investigating the agronomic performance and environmental impact of disease resistant, GM potatoes come to an end across several sites in Europe, past discussions on achieving the effective coexistence of GM and equivalent non-GM crops have too often focussed on the purported risk of excessive pollen-mediated gene flow. Dependent on the crop in question, the impact of seed loss pre- and/or post-harvest presents a greater challenge to securing efficient coexistence practises. To examine this issue for potato, a total of 51 fields that had been commercially cultivated with potatoes were surveyed in two separate cohorts for post-harvest tuber loss and/or volunteer emergence. Across 17 fields studied, the average post-harvest tuber loss was recorded at 141,758 ± 911 tubers ha−1, with volunteer establishment in the following crop ranging from 400 ± 59 ha−1 to 55,698 ± 47 ha−1. In parallel, by surveying a separate cohort of 34 commercial fields an average of 30,789 ± 2658 volunteer ha−1 was recorded in the subsequent cereal crop, with a repeat survey made after an additional year indicating an 87.2% reduction in this mean number of volunteers across the 34 fields (P < 0.001). Of the additional variables studied only location (P < 0.001), herbicide application (P = 0.037) and potato variety used (P = 0.045) significantly influenced volunteer proliferation. Volunteer fecundity was confirmed with upto 3 tubers produced per 1st generation volunteer, with tuber yield from the 2nd generation volunteers reduced significantly (P < 0.001). Assessments of the tuber lots from these 2nd generation volunteers confirmed their ability to sprout post-dormancy, therefore, indicating the potential for 3rd generation volunteers to emerge. Combined, the datasets confirm the potential for significant seed-mediated gene flow from commercial potato systems; indicating that the regulated 0.9% coexistence threshold would in all probability be compromised if GM potatoes were grown in rotations of 1:4 years or less, in the absence of a comprehensive tuber loss and/or volunteer management system. 相似文献
6.
Identifying indicator species for post-release monitoring of genetically modified,herbicide resistant crops 总被引：1，自引：1，他引：0
In Europe, regulations for release and placing-on-the-market of genetically modified (GM) crops require post-release monitoring
of their impact on the environment. Monitoring potential adverse effects of GM crops includes direct effects as well as indirect
effects, e.g. GM crop specific changes in land and pest management. Currently, there is a gap in the pre-release risk assessments
conducted for regulatory approval of GM herbicide resistant (HR) crops. Since the relevant non-selective herbicides have been
registered many years ago, in current dossiers requesting regulatory approval of GM HR crops, the environmental impacts of
the corresponding non-selective herbicides are either entirely omitted or the applicant simply refers to the eco-toxicological
safety assessments conducted for its original pesticide approval that do not address environmental issues arising in conjunction
with the cultivation of GM HR crops. Since the ‘Farm-scale Evaluations’, it is clear that consequences for farmland biodiversity
can be expected. The objective of this project was to identify relevant indicator species for the long-term impact of GM HR
maize cultivation and the application of their corresponding non-selective herbicides, glyphosate and glufosinate. In this
article, we describe the outcome of a modified Event Tree Analysis, essentially a funnel-like procedure allowing to reduce
the large number of potentially affected non-target species to those with greatest ecological relevance and highest risk to
be adversely affected based on a number of ecological criteria. This procedure allowed us to identify a total of 21 weed-Lepidoptera
associations that we proposed for post release monitoring of GM HR maize in Germany. 相似文献
7.
Charles Njontie Xavier Foueillassar Nikolai K. Christov Alexandra Hüsken 《Euphytica》2011,180(2):163-172
Recently, the introduction of GM maize in agricultural production in the EU and elsewhere has raised the issue of adventitious
presence of GM seeds in conventional seed lots. Adventitious presence may occur in all arable farming, and at any step in
the production of seeds or grain, or in processing of harvested product in the food/feed chain. As of today, there are no
official thresholds governing the adventitious presence of GM seeds in conventional seed lots in Europe. However, it is assumed
that GM admixture in seed lots could have a considerable influence on the level of adventitious presence in the non-GM harvested
product. The experiments highlighted in this paper aim at the consequences of adventitious presence of GM maize seeds in conventional
seed lots. It is shown for varieties belonging to the same maturity group that the final GM rate (% seeds) in the harvest
product is nearly same as the initial seed admixture (% seeds). This corresponds to Hardy–Weinberg expectations. The variation
depends mainly on the flowering coincidence, the site and climatic conditions. In cases where the admixed seeds are of different
maturity group, the level of cross-pollination in the harvest product is reduced. Furthermore a comparison between the visual
GM seed detection and real-time PCR detection was done. It is evident that the result of the real-time PCR detection method
has a more variable uncertainty associated with its results than the visual seed testing method. The accuracy of prediction
from % GM seed to % GM DNA depends on the reference material used for calibration curves. 相似文献
8.
乙酰乳酸合成酶及ALS基因研究概述 总被引：2，自引：0，他引：2
乙酰乳酸合成酶抑制剂类除草剂以其独有的优点,20世纪90年代以来一直占领世界除草剂市场。抗草甘膦转基因作物的问世,草甘膦的销售量大幅增加,乙酰乳酸合成酶抑制剂类除草剂销量不断减少。然而,大量抗草甘膦杂草的产生,使得人们期望培育出抗不同类型除草剂转基因作物,抗ALS抑制剂类除草剂成为人们的首选。笔者概述了乙酰乳酸合成酶的结构、功能、除草剂作用机理、抗ALS基因的研究现状。期望对抗ALS抑制剂基因的筛选,利用提供参考。 相似文献
9.
Volunteer oilseed rape (OSR, Brassica napus L.) causes various agronomic problems in crop rotations and can contribute to gene dispersal by pollen and by seed admixture. A 4-year field experiment (2008–2011) was set up in south-west Germany to investigate the performance of volunteers derived from two OSR cultivars with different levels of seed dormancy. Volunteers of a high-dormancy (HD) and a low-dormancy (LD) OSR cultivar were deliberately generated by spreading 10,000 seeds m−2 on a field in August 2008 and 2009. Four different crops were grown on that area in the first year following the seed rain: winter wheat (Triticum aestivum L.), winter turnip rape (Brassica rapa L.), spring barley (Hordeum vulgare L.) and field pea (Pisum sativum L.). In the second year, maize (Zea mays L.) was sown uniformly across all plots. Numbers of OSR seedlings emerging in early autumn shortly after seed rain were not connected with the size of the soil seed bank in early spring of the following year. The seeds of the HD-cultivar formed a much greater soil seed bank (up to 14% of the initially spread seed number) compared with the LD-cultivar (up to 1.3%) in the soil layer of 0 to 30 cm in early spring 2009 and 2010). Across all crops, considerably more volunteers of the HD-cultivar than of the LD-cultivar were present at several survey dates in the first year following seed rain. The highest number of volunteers originated from the HD-cultivar with up to 11 volunteers m−2 in winter turnip rape compared with a maximum of 0.48 plants m−2 in the other crops. Cultivar-specific differences in volunteer density were observed as well in maize two years after OSR seed rain. Flowering and seed setting volunteers were only present in 2010 and the flowering time was crucially overlapping with that of sown winter OSR. The reproductive ability (seeds produced m−2) of the LD-volunteers was five times lower in winter turnip rape than of the HD-volunteer; a similar trend was observed for the OSR volunteers in the other host crops.Strategies to definitely reduce unwanted effects of OSR volunteers, such as gene flow, should include the use of LD-cultivars with a low potential to form a soil seed bank, particularly if selective herbicides are not available, for instance in broad-leaved crops, or if the volunteers are herbicide-tolerant. 相似文献
10.
Oilseed rape has been modified extensively by conventional breeding for the production of varieties useful for human consumption (blended vegetable oil and margarine) and industrial processes (rubber additives and high‐temperature lubricants). Because much is now known about its genetic and biochemical composition, it has been an obvious choice for genetic modification and is now at the forefront of the commercial development of genetically modified (GM) or transgenic crops. Around the world, the increase in commercial plantings of all transgenic crops has been rapid. In 1996, 1.7 million hectares were planted, but by 1998 this figure had jumped to 27.8 million ha. The area in the year 2001 is likely to be about 50 million ha. With the possible introduction of transgenic varieties into European agriculture, it is essential that the associated farming practices employed are appropriate for their growth, both from a commercial and an environmental viewpoint. Some of the first transgenic crops are those carrying agronomic traits, e.g. herbicide tolerance transgenes. However, before full commercialization occurs, important agronomic and environmental questions need to be answered. How are these new crops to be incorporated into existing cropping practices? How will this change the current herbicide use profile for a given crop? Do herbicide‐tolerant varieties enhance or impede integrated pest management schemes? What is the likely uptake of such crops in agriculture? What are the ecological implications of their introduction? Are there effective measures to control the spread of transgenes to wild relatives? This paper addresses these questions, with special emphasis on oilseed rape production in the UK, but includes examples from other crops and countries where appropriate. 相似文献
11.
The reduction of pesticide use intensity is a societal and political ambition. Crop rotation is one important method to control pests and diseases in arable farming. We investigated the contribution of crop rotation to the variability of herbicide and fungicide use of 60 farms in four regions of Northern Germany. Our study aimed at answering the question: do diverse crop sequences lead to reduced herbicide and fungicide use in arable farming?Ten-year data on chemical plant protection measures and field management were examined for six field crops. We classified crop sequences (triplets of three succeeding crops) according to their susceptibility for weeds and diseases (= ’riskiness’). The Treatment Frequency Index (TFI) of the last crop in the triplet was set in relation to the crop triplet riskiness, additionally also in combination with tillage.In general, herbicide and fungicide use intensities were smaller in more diverse crop sequences. Diversified cereal sequences, involving roots and tubers, maize or spring cereals were less dependent on herbicides. Cultivation of maize in three subsequent years increased herbicide use. Crop sequences including high proportion of winter cereals increased fungicide use in cereals, while roots and tubers, winter oilseed rape and set-aside in the crop sequence decreased it. In winter oilseed rape, sequences with roots and tubers also increased fungicide use. In sugar beets, sequences with maize or a high concentration of sugar beets led to increasing fungicide use. If farmers chose riskier crop sequences tillage by plough decreased the need for herbicide and fungicide use.To reduce herbicide and fungicide use intensities we recommend increasing the diversity of crop rotations, including a higher number of crops per rotation together with ploughing. Simplifying both crop sequence diversity and tillage intensity implies higher use of herbicides and fungicides. Results will be useful for convincing farmers to diversify crop sequences. 相似文献
12.
Modern plant breeding is highly dependent on new technologies to master future problems. More traits have to be combined, frequently originating from wild species. Traditional breeding is connected with linkage drag problems. The crop plant itself and its crossable species represent the traditional breeders gene pool. GM-breeding is a new way of improving existing varieties. Transgenes originate from non-crossable species and are representing a new gene pool. For release of GM-plants into the environment and onto the market in Europe Directive 2001/18/EC has been developed, primarily based on GM-technology and not on gene source. In society, opposition against GM crops is complicating the implementation of GM crops. In this paper, it is shown that not only transgenes, representing a new gene pool but also cisgenes and intragenes are available, representing the breeders gene pool. Cisgenes are natural genes and intragenes are composed of functional parts of natural genes from the crop plant itself or from crossable species. Cisgenesis is the combined use of only cisgenes with marker-free transformation, mimicking linkage drag free introgression breeding in one step. Therefore, cisgenesis is a new sub-invention in the traditional breeding field and indicates the need for reconsideration of GM Directives. Inventions are frequently containing not only hardware elements, but also software and orgware elements. For cisgenesis it is foreseen that the technical (hardware) and bioinformatic (software) elements will develop smoothly, but that implementation in society is highly dependent on acceptance and regulations (orgware). It could be made in a step by step approach by specific crop-gene derogations from the Directive, followed by adding cisgenesis to annex 1b of Directive 2001/18/EC for exemption. At present GM crops can only be introduced by large companies. An open innovation approach for cisgenesis by public private partnership including traditional SMEs has been discussed. Cisgenesis has been exemplified for resistance breeding of potato to Phytophthtora infestans. 相似文献
13.
《European Journal of Agronomy》2005,22(1):71-84
Different preceding crops interact with almost all husbandry and have a major effect on crop yields. In order to quantify the yield response of winter wheat, a field trial with different preceding crop combinations (oilseed rape (OSR)–OSR–OSR–wheat–wheat–wheat), two sowing dates (mid/end of September, mid/end of October) and 16 mineral nitrogen (N) treatments (80–320 kg N ha−1) during 1993/1994–1998/1999, was carried out at Hohenschulen Experimental Station near Kiel in NW Germany. Single plant biomass, tiller numbers m−2, biomass m−2, grain yield and yield components at harvest were investigated. During the growing season, the incidence of root rot (Gaeumannomyces graminis) was observed. Additionally, a bioassay with Lemna minor was used to identify the presence of allelochemicals in the soil after different preceding crops.Averaged over all years and all other treatments, wheat following OSR achieved nearly 9.5 t ha−1, whereas the second wheat crop following wheat yielded about 0.9 t ha−1 and the third wheat crop following 2 years of wheat about 1.9 t ha−1 less compared with wheat after OSR. A delay of the sowing date only marginally decreased grain yield by 0.2 t ha−1. Nitrogen fertilization increased grain yield after all preceding crop combinations, but at different levels. Wheat grown after OSR reached its maximum yield of 9.7 t ha−1 with 210 kg N ha−1. The third wheat crop required a N amount of 270 kg N ha−1 to achieve its yield maximum of 8.0 t ha−1.Yield losses were mainly caused by a lower ear density and a reduced thousand grain weight. About 4 weeks after plant establishment, single wheat plants following OSR accumulated more biomass compared to plants grown after wheat. Plants from the third wheat crop were smallest. This range of the preceding crop combinations was similar at all sampling dates throughout the growing season.Root rot occurred only at a low level and was excluded to cause the yield losses. The Lemna bioassay suggested the presence of allelochemicals, which might have been one reason for the poor single plant development in autumn.An increased N fertilization compensated for the lower number of ears m−2 and partly reduced the yield losses due to the unfavorable preceding crop combination. However, it was not possible to completely compensate for the detrimental influences of an unfavorable preceding crop on the grain yield of the subsequent wheat crop. 相似文献
14.
In intensive farming systems, farmers split up and apply the N fertilization to winter cereals and oilseed rape (OSR) at several dates to meet the need of the crop more precisely. Our objective was to determine how prior fertilizer N application as slurry and/or mineral N affects contributions of fertilizer‐ and soil‐derived N to N uptake of barley (1997), oilseed rape (OSR; 1998) and wheat (1999). In addition, residual fertilizer N effects were observed in the subsequent crop. Since autumn 1991, slurry (none, slurry in autumn, in spring, in autumn plus in spring) and mineral N fertilizer (0, 12 and 24 g N m−2) were applied annually. Each year, the treatments were located on the same plots. In 1997–1999, the splitting rates of the mineral N fertilization were labelled with 15N. Non‐fertilizer N uptake was estimated from the total N uptake and the fertilizer 15N uptake. All three crops utilized the splitting rates differently depending on the time of application. Uptake of N derived from the first N rate applied at the beginning of spring growth was poorer than that from the second splitting rate applied at stem elongation (cereals) or third splitting rate applied at ear emergence or bud formation (all three crops). In contrast, N applied later in the growing season was taken up more quickly, resulting in higher fertilizer N‐use efficiency. Mineral N fertilization of 24 g N m−2 increased significantly non‐fertilizer N uptake of barley and OSR at most of the sampling dates during the growing season. In cereals, slurry changed the contribution of non‐fertilizer N to the grain N content only if applied in spring, while OSR utilized more autumn slurry N. In OSR and wheat, only small residual effects occurred. The results indicate that 7 years of varying N fertilization did not change the contribution of soil N to crop N uptake. 相似文献
15.
The benefits of improving nitrogen use efficiency (NUE) in crops are typically studied through the performance of the individual crop. However, in order to increase yields in a sustainable way, improving NUE of the cropping systems must be the aim. We did a model simulation study to investigate how improvement of NUE traits of individual crops affects the succeeding crops and the NUE of the crop rotation. Based on experimental results parameterization was altered for different types of improved NUE in the EU-Rotate_N model, e.g. through higher N harvest index, reduced litter loss or improved root depth penetration rate. The different ways of improving NUE have different effects on the cropping system, affecting either N uptake, the ability of the crop to hold on to N already taken up, or the fraction of crop N being harvested. Due to the different modes of action, the model simulations show that these changes in NUE traits will also have different effects on N leaching loss and on N availability and N loss in the following years. Simulations also show that the effect of genotypes with improved NUE depend on environment and crop management. This is true for the improved crop itself and when its effect is analyzed for the whole cropping system. The environmental conditions, crop choices and management will all affect the fate of the N left in the soil, and whether this will contribute mainly to leaching loss or be used for production in later crops. As an example, increasing pre-crop fertilization was shown to affect the leaching after the following oilseed rape crop with up to 50 kg N ha?1 taken up before it was lost to the environment when pre-crop fertilization as well as root depth penetration rate was high. All in all, the simulations illustrate the concept of NUE as the result of interactions between genotype, environment and crop management (G×E×M). 相似文献
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17.
Genetically modified, herbicide-tolerant (GMHT) Brassica napus plants originating from seed spill have recently been found along roadsides leading from Japanese ports that unload oilseed rape. Such introductions have potential biodiversity effects (as defined by the Cartagena Protocol): these include replacement of native elements in the biota through competitive suppression or hybridization. We conducted surveys in the period 2006–2011 to assess such threats. We examined shifts in the population distribution and occurrence of GMHT plants in 1,029 volunteer introduced assemblages of B. napus, 1,169 of B. juncea, and 184 of B. rapa around 12 ports. GMHT B. napus was found around 10 of 12 ports, but its proportion in the populations varied greatly by year and location. Over the survey period, the distributions of a pure non-GMHT population around Tobata and a pure GMHT population around Hakata increased significantly. However, there was no common trend of population expansion or contraction around the 12 ports. Furthermore, we found no herbicide tolerant B. juncea and B. rapa plants derived from crosses with GMHT B. napus. Therefore, GMHT B. napus is not invading native vegetation surrounding its populations and not likely to cross with congeners in Japanese environment. 相似文献
18.
绿盲蝽危害对棉花防御性酶活性及丙二醛含量的诱导 总被引：11，自引：3，他引：8
以2种转基因棉品种国抗22、sGK321及其亲本泗棉3号、石远321为材料,研究受绿盲蝽危害胁迫后,其叶片防御性酶活性及丙二醛含量等生理指标的动态。结果表明:接种绿盲蝽前后,2种转基因棉花品种叶片防御性酶活性及丙二醛含量与其亲本棉花相比差异均不显著,说明外源基因的导入对棉花各项生理指标的变化无影响。同一棉花品种在绿盲蝽不同刺吸诱导的时间中,叶片防御性酶活性及丙二醛含量差异均达到极显著水平;在品种和接虫时间互作效应中,SOD、MDA、PAL活性或含量差异达显著或极显著水平,说明品种与接虫时间在这几个指标水平上存在真实的交互作用,而其余生理指标的差异不显著。 相似文献
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Agriculture generates important impacts on the environment, which can be evaluated with agri-environmental indicators. A key element of environment protection in agriculture is the maintenance of a dense soil cover for the longest possible period. Notably, soil cover is known to diminish erosion risks and nitrate leaching. In this study, an agri-environmental indicator for soil cover is presented, which integrates data from the crop model STICS to quantify vegetation growth dynamics. Simulations were conducted with STICS for the major crops cultivated in Switzerland across several contrasting pedoclimatic situations. They were then integrated with data for crop residue cover to evaluate soil cover at the field and farm levels in the framework of a farm network survey. At the field level, for the period from the harvest of the previous crop through the harvest of the main crop, the highest soil cover was achieved by silage maize and winter barley. A high variability between fields was observed, due to the diversity of cultural practices during the period preceding the seeding of the main crops. Some crops, winter wheat in particular, showed a high number of days with insufficient soil cover (under 30%), leading to potential environmental risks. This shows the crucial need of promoting conservation agriculture principles (permanent soil cover, minimum soil disturbance, diversification of crop rotation) in arable systems to better protect the soils and the environment. The soil cover indicator presented here provided a continuous quantification of soil cover, whereas most of the currently used indicators provide qualitative or roughly quantitative results. 相似文献