Ecological aspects of transgenic sugar beet: transfer and expression of herbicide resistance in hybrids with wild beets

Summary An increasing number of genetically engineered cultivars of several crops is being experimentally released into the environment. In future, crops with new transgenic traits will probably play an important role in agricultural practice. The long-term effect of transgenes on community ecology will depend on the distribution and establishment of transgenic plants in the wild, on the sexual transfer of their new genes to the environment and on the potential ecological impact of the transgenic trait. The starting point was the use of transgenic sugar beet lines, Beta vulgaris subspec. vulgaris var. altissima DÖLL (Helm 1957), with transgenes coding for rhizomania and herbicide (BASTA^®) resistance. The first two questions to answer were: Can the transgenes be transferred via pollen to wild beets, Beta vulgaris subspec. maritima (L.) ARCANG. or cultivated relatives such as red beet or spinach beet and are they expressed in the hybrids? Can transgenes be monitored in young Beta vulgaris-hybrids? The experimental transfer of transgenes was conducted in 1993 at a field location in northern Germany. The beets were hand-pollinated with transgenic pollen. In a non destructive biotest, the hybrid seedlings were tested for herbicide resistance. Transgenic plants showed no noxious phenotypic effects whereas control plants developed leaf necroses. All herbicide resistant hybrids within the biotest were assumed to be transgenic.     

Occasional loss of expression of phosphinothricin tolerance in sexual offspring of transgenic oilseed rape (Brassica napus L.)

The commercial and economic value of genetically modified crops is determined by a predictable, consistent and stable transmission and expression of the transgenes in successive generations. No gene inactivation is expected after selfings or crosses with non-transformed plants of homozygous transgenic oilseed rape plants if the expression of the transgene in homozygous or hemizygous nature in such plants is stable. The segregation ratios of phosphinothricin (PPT) tolerance in successive generations of selfings and mutual crosses of a few independent transgenic PPT-tolerant oilseed rape plants indicated a dominant, monogenic inheritance. In within-variety and between-variety crosses no transgene inactivation was observed. However, after selfings and backcrosses with non-transgenic oilseed rape infrequent loss of the expression of the PPT tolerance transgene was observed independent from its homozygous or hemizygous nature. Molecular analysis of PPT-susceptible plants showed that the loss of expression was due to gene inactivation and not to the absence of the transgene. Methylation and co-suppression are mechanisms that might cause reduced or even loss of expression of the transgene in later generations. The implications of this observation for seed multiplication of varieties and breeding activities with transgenic oilseed rape are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Rapid and efficient screening of phosphinothricin tolerant oilseed rape (Brassica napus) with a novel germination test

A novel screening test is described for the discrimination of transgenic phosphinothricin tolerant oilseed rape from non transgenic rape seedlings. The method is based on the germination of rape seeds on filter paper soaked with a 0.005% phosphinothricin solution. Under these conditions inhibition of seedling development by the herbicide can be observed after 10 days. The germination test gains an advantage over the routinely used herbicide spraying, because it is rapid, needs little space and allows efficient screening of huge numbers of seeds. The assay has been successfully applied to the screening of different transgenic and non transgenic rapeseed varieties/lines and has been compared to other methods such asBasta® spray test, drop test, ELISA-technique and PCR-amplification of the pat gene. This test allows on one hand large screening programmes to monitor the foreign gene in the environment and on the other quality control of seedlots before market introduction of herbicide tolerant oilseed rape.     

Novel Traits in Novel Crops： Fueling the Growth of Agrobiotechnology

Biotechnology has contributed greatly to improvements in agriculture during the past decades. Advances have been most spectacular in the fi eld of herbicide and insect resistance and have benefi ted primarily four major crops,     

The Experimental and Commercial Release of Transgenic Crop Plants

With advances in recombinant DNA methods and transformation procedures, it is possible to transfer genes into crop plants from unrelated plants, microbes and animals. Many of the modifications being carried out, or envisaged, are for disease and pest resistance, product quality and tolerance to environmental stress, but there are additional opportunities to modify crops to give specialized products for industrial or pharmaceutical use. Some of the characteristics of transgenic plants are considered, including: transgene copy number, position, expression, stability, pleiotropy, selectable marker genes and somaclonal variation. There have been several hundreds of field trials with transgenic plants, and the first transgenic varieties are likely to be approved for commercial production in 1993. Before releasing transgenic plants, it is necessary to carry out a risk assessment to determine whether the transgenic variety will behave differently from a conventionally bred variety. Assessment procedures are being harmonized internationally by various organizations. There is a growing commitment to apply these genetic modification methods to crops in developing countries, as genes relevant to their crops and environments become available.     

Breeding for yield, in mixtures of common beans (Phaseolus vulgaris L.) and maize (Zea mays L.)

Summary Despite the growing industrialization, technification and transformation that is happening in the agriculture around the world, and despite that agricultural research has always concentrated its effort on sole crops, multiple cropping systems have historically been important for common bean production in tropical countries. The reasons for this fact, are economical and social, as well as biological. Bean breeders have always been questioned on their work, because the development of new varieties is usually done in sole crop, but the varieties are grown in either systems. This paper addresses a set of questions that are usually presented to the breeders, in light of the evidence obtained from many trials conducted in Brazil and in the U.S.A.: Will the genotypes bred for sole crop conditions, perform well when grown in intercrop; How different should a genotype be, for cultivation in intercropping compared to genotypes developed for sole crop conditions; Is there a need for special breeding programs for intercropping and How could a breeding program focus the question of multiple (associated) cropping?     

Selecting the optimum genetic background for transgenic varieties, with examples from Brassica

Summary The performance of transgenic varieties depends not only upon the stable and correctly-regulated expression of specific transgenes but also upon the agronomic potential of the background genotype. Ideally, transgenes should be introduced into agronomically-superior cultivars and transgenic varieties will become out-classed if their agronomic properties are not continually improved. It will often prove desirable to use conventional breeding techniques, as opposed to new cycles of transformation, to carry out this process of varietal improvement.Continuing advances in marker-assisted selection have made possible the selection and manipulation of an entire genetic background. This means that transgenes can be transferred to new and often untransformable varieties with relative ease. To carry out this process efficiently requires the correct choice of male and female parents, the use of appropriate marker-systems and the concentration of selection on the most appropriate generations.Efficient, phenotypically-neutral marker-systems have revolutionised the identification and manipulation of quantitative trait loci (QTLs). The loci which modify the expression of transgenes are a form of QTL. Desirable alleles at modifier QTLs can be transferred to new varieties along with the transgenes themselves, using marker-assisted breeding.The strategies for maker-assisted selection are becoming ever more sophisticated. A range of complementary marker systems allows the selection of desirable genotypes. In addition, the meiotic reassortment and recombination of chromosomes which produces new genotypes is becoming better understood. The most efficient plant breeding methods and the most powerful genetics will make optimal use of both markers and meiosis.     

GAFP基因导入对彩色棉抗病性和农艺及经济性状的影响

通过对转GAFP基因品系ZB-1-31、ZB-1-49、LB-7-8与原受体品种新彩棉1号、绿9903进行了抗枯、黄萎病性的对比和农艺、经济性状方面的对比研究,结果表明,3个转GAFP基因品系对枯、黄萎病的抗性显著高于受体品种,生育期有所提前,产量均明显高于受体品种,纤维品质也有不同程度的提高。     

Comparison of genetically modified and conventionally derived herbicide tolerance in oilseed rape: A case study

Oilseed rape (Brassica napus) is animportant source of oils for industrial andfood processes. Agriculturally it is auseful break crop in cereal rotations butsuffers from competition from broad-leavedweeds that can be difficult to control. Toextend the range and efficacy of weedcontrol options, herbicide-tolerant oilseedrape cultivars have been developed throughboth conventional and transgenic geneticmodification processes. Here we compare thesuccess of these approaches and discuss theimplications of the new herbicide tolerancetraits in agricultural production ofoilseed rape. We conclude that the impactof HT traits on the agri-environment willbe dependent on the nature of the trait andthe management strategies under which it isemployed. We find no evidence that thetechnology used in the production of HTcultivars has any influence on theirperformance as crops. In fact transgenic HTcultivars are simpler to monitor foragricultural and environmental impact thanare conventional HT cultivars.     

Outcrossing frequencies from multiple high erucic acid oilseed rape fields to a central receptor field

Genetically modified oilseed rape is currently grown on about 23 % of the global oilseed rape acreage. In order to separate transgenic and non-transgenic oilseed rape production and to ensure co-existence of different agricultural cultivation schemes, as is specified by the European legislation, confinement measures have to be defined. Pollen-mediated gene flow is the most important means by which transgenes are dispersed between fields. In contrast to the majority of the previous investigations the objective of this study was to assess the extent of gene flow in the case of multiple pollen-donor fields. A high erucic acid rape genotype was used as biochemical marker for the quantification of outcrossing into a low erucic acid oilseed rape variety. Outcrossing data were obtained from two experimental locations. As expected, multiple pollen sources in a fragmented landscape can result in high gene transfer frequencies, thus requiring larger isolation distances than a field design with a single pollen donor source. The results of the study are transferable to homozygous transgenic oilseed rape varieties.     

Assessing genetic diversity in the cassava (Manihot esculenta Crantz) germplasm collection in Brazil using PCR-based markers

Knowledge of the origin, organization and nature of the cassava (Manihot esculenta Crantz) germplasm collection in Brazil is incomplete due to lack of critical information on several aspects of the collection. This study verifies the utility of SSR-primed PCR markers for germplasm assessment and then utilizes these markers as well as RAPD's to characterize the Brazilian collection. We specifically address the following questions: 1)what is the relationship of morphologically closely related species to cultivated cassava? 2) What is the genetic diversity of cultivars within and between different habitats in Brazil? 3) Do agronomic traits and molecular markers reveal the same relationship among cassava accessions? 4) How complete is the Brazilian cassava collection and how well is it represented in the Word Core Collection of cassava, maintained by CIAT? Results of the interspecific studies of cassava and its wild relatives confirms the close relationship of cassava, Manihot esculenta ssp. esculenta to Manihot esculenta ssp. flabellifolia as well identifying several other closely related wild species. Next, PCR-based markers indicate a strong grouping of varieties related to the region of cultivation in Brazil. Moreover, important regions such as Cerrados and Amazon are relatively poorly represented in germplasm collections. Interestingly, the relationships of accessions based on agronomic traits are not fully congruent with relationships revealed with RAPD markers. Finally, the genetic diversity of the Brazilian cassava collection is not fully represented in the Core of the Word Core Collection of CIAT.     

RNAi技术在作物中的应用及安全评价研究

RNA干扰（RNAi）技术在基因功能研究方面应用广泛。近年来,RNAi被认为是具有应用潜力的育种新方法。具有良好抗虫性状的RNAi转基因作物已研究成功,预示其商业化应用成为可能。RNAi转基因作物如何监管成为人们关注的新问题。本文介绍了RNAi转基因作物的发展现状,分析了RNAi技术与传统育种技术及传统转基因技术之间的不同点,总结了RNAi转基因作物的潜在风险,并以美国和欧盟为代表总结了RNAi转基因作物的监管态度,最后分析了RNAi转基因作物存在的监管问题并提出了相关建议,为我国对RNAi转基因作物的监管提供参考。     

Management of Broomrape (Orobanche spp.) – A review

Broomrapes ( Orobanche spp.) are phanerogamic holoparasites that subsist upon the roots of many important crops thus causing considerable yield losses, especially in the drier and warmer areas of Europe, Africa and Asia.
The major principles of reducing the seed bank and controlling the weed in the germination and parasitic/ reproductive phases are critically reviewed. Practices to control broomrape include physical methods (weeding, soil tillage, flooding, irrigation, solarization, flaming), chemical methods (soil fumigation, herbicide application, use of germination stimulants) and biological methods (use of resistant or tolerant varieties, cropping systems with trap and catch crops, intercropping, biological control with insects or fungi). Cultural practices which help to avoid germination, infection or strong reproduction of the weed or improve the crop's tolerance should be optimized.
However, no single cheap method can control the weed, so integrated management practices are required. Integrated control strategies are site- and cropping-system specific but have in common that measures are taken to kill part of the seed bank, induce the conditioned seeds to germinate in the absence of the commercial crop, kill emerging Orobanche shoots before seed set during growth of the commercial crop and further reduce or avoid damage to the commercial crop.     

The influence of crop sequence on fungicide and herbicide use intensities in North German arable farming

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.     

不同熟期“川油”系列甘蓝型油菜品种主要性状与产量的相关分析

探讨在成都地区气候条件下不同熟期甘蓝型油菜产量的主要影响因素,以期为油菜抗性育种提供理论基础。采用相关分析、通径分析和主成分分析等方法,分析不同熟期甘蓝型油菜主要农艺性状、茎秆抗折力和菌核病发病率等与产量的关系。相关分析结果表明,早熟品种产量与单株有效角果数、每果粒数和茎秆中上部抗折力均呈显著或极显著正相关,中熟品种产量与株高、一次分枝高度、单株有效角果数、茎秆下部和茎秆中下部抗折力均呈极显著正相关。通径分析结果表明,早熟和中熟品种主要性状中,单株有效角果数对产量的直接作用最大。主要性状中,每果粒数对早熟品种产量的间接综合效应最大,中熟品种间接综合效应最大的是茎秆下部抗折力。主成分分析结果表明,早熟品种主要性状分为抗倒性状、株型性状、产量构成性状和抗病性状等4类性状。中熟品种为产量构成性状、株型性状和抗倒性性状等3类性状。研究表明,在四川省自然气候条件下,无论是早熟品种还是中熟品种选育,应在保证产量性状的同时,加强植株株型、抗倒性和抗病性的选择。     

Stickstoffaufnahme und Stickstoffrückstände von Hauptfrucht-und Ausfallrapsbeständen

Nitrogen Uptake and Nitrogen Residuals of Winter Oil-Seed Rape and Fallout Rape
The objective of the investigation was a study of the relationship between seed dry-matter production and vegetative dry-matter production in oil-seed rape crops and their dependence on the production conditions. In addition to the relationship between the N-uptake during the vegetation period and the N-residue after harvest was of major interest. Furthermore the potential for N-uptake in fallout rape was measured. Over two vegetation periods factorial field experiments with winter oil-seed rape, cv. Lirabon, different drilling techniques and different nitrogen fertilization levels were tested. Measured traits were: the dry-matter accumulation including root mass and fall-off leaf-material mass, the N-uptake of both the oil-seed crops and the fallout rape stands, and, simultaneously, the soil NO₃-N content. Finally the harvest indices and the N-harvest indices were calculated.
Combined with a N-uptake of up to 330 kg N/ha, oil-seed rape crops produced up to 200 dt dry matter/ ha. At seed yield levels of 33dt/ha (d.m.), harvest indices varied from 0.14—0.23 and N-harvest indices varied from 0.30–0.50. As a result of the residue of vegetative plant material at harvest, leaf losses before harvest and the soil NO₃-N-contents at harvest up to 275 kg N/ha remained in the field. After the harvest of oil-seed rape, the soil NO₃-N-contents were quickly reduced by emerging and growing fallout rape stands. However, following soil-preparation measures in the autumn, a continuous rise in the soil NO₃-N-content was observed.     

Variability in Namibian landraces of watermelon (Citrullus lanatus)

An on-station experiment was carried out in northern Namibia to compare local landraces of watermelon to modern varieties. Three groups of local watermelon are distinguished by farmers in Namibia: watermelons for fresh consumption, cooking melons used for porridge, and seed melons for oil pressing. The present study was carried out to estimate agronomic potential of the local landraces and verify whether agronomic characteristics would justify the local groupings. Important agronomic and fruit-quality traits (yield, earliness, fruit weight, fruit number, rind thickness, soluble solids, seed weight, and tolerance to biotic and abiotic stress) were measured in seven landraces (three watermelons, three cooking melons and one seed melon)and compared to three modern cultivars frequently grown in Namibia. The study revealed that well-adapted, productive Citrullus lanatuslandraces are available, and cultivated by local farmers throughout the northern regions of Namibia. Based on a combination of agronomic characteristics these local varieties could be grouped into three distinct types: watermelons, cooking melons, and seed melons, in agreement with farmers classification. Landrace water melons were characterized by smaller, less sweet fruits with larger seed and a thicker rind compared to modern varieties. Yield level was comparable but development was later and fruit number in some cases higher. Cooking water melons were less sweet than local water melon with large fruits comparable in size to modern cultivars. The only included seed watermelon had small fruits with large seeds and low soluble sugars. Yield varied from 118 t/ha for a giant cooking melon, out yielding all other accessions, to only 10t/ha for the seed melon type, but with considerable variation within groups. The earliness of commercial varieties maybe of interest in developing a mixed portfolio of short- and long-cycle landraces, whereas plant vigour, resistance and seed characters in some of the Namibian landraces may be important traits for breeding for both local purposes and for commercial varieties. This revised version was published online in July 2006 with corrections to the Cover Date.     

A methodology for multi-objective cropping system design based on simulations. Application to weed management

Weeds are harmful for crop production but important for biodiversity. In order to design cropping systems that reconcile crop production and biodiversity, we need tools and methods to help farmers to deal with this issue. Here, we developed a novel method for multi-objective cropping system design aimed at scientists and technical institutes, combining a cropping system database, decision trees, the “virtual field” model FlorSys and indicators translating simulated weed floras into scores in terms of weed harmfulness (e.g. crop yield loss, weed-borne parasite risk, field infestation), weed-mediated biodiversity (e.g. food offer for bees) and herbicide use intensity. 255 existing cropping systems were simulated with FlorSys, individual indicator values were aggregated into a multi-performance score, and decision trees were built to identify combinations of management practices and probabilities for reaching performance goals. These trees are used to identify the characteristics of existing cropping systems that must be changed to achieve the chosen performance goals, depending on the user's risk strategy. Alternative systems are built and simulated with FlorSys to evaluate their multi-criteria performance. The method was applied to an existing oilseed rape/wheat/barley rotation with yearly mouldboard ploughing from Burgundy which was improved to reconcile weed harmfulness control, reduced herbicide use and biodiversity promotion, based on a risk-minimizing strategy. The best alternative replaced a herbicide entering plants via shoot tips (during emergence) and roots after barley sowing by a spring herbicide entering via leaves, introduced crop residue shredding before cereals and rolled the soil at sowing, which reduced the risk of unacceptable performance from 90% to 40%. When attempting to reconcile harmfulness control and reduced herbicide use, the best alternative changed the rotation to oilseed rape/wheat/spring pea/wheat, replaced one herbicide in oilseed rape by mechanical weeding, delayed tillage before rape and applied the PRE herbicide before oilseed rape closer to sowing. This option reduced the risk of unacceptable performance to 30%. None of the initial or alternative cropping systems succeeded in optimal performance, indicating that more diverse cropping systems with innovative management techniques and innovative combinations of techniques are needed to build the decision trees. This approach can be used in workshops with extension services and farmers in order to design cropping systems. Compared to expert-based design, it has the advantage to go beyond well-known options (e.g. plough before risky crops) to identify unconventional options, with a particular focus on interactions between cultural techniques.     

数量性状基因定位研究中若干常见问题的分析与解答

QTL作图是基因精细定位、克隆以及有效开展分子育种的基础,在利用QTL作图开展数量性状基因定位研究的过程中经常会碰到一些问题,与统计方法有关的一些问题包括LOD的统计学意义是什么？检测QTL的可信度和LOD临界值的关系是什么？如何评价不同的QTL作图方法？提高QTL检测效率的途径有哪些？与遗传参数估计有关的一些问题包括QTL的贡献率是如何计算出来的？如何确定QTL有利等位基因的来源？选择基因型分析的有效性如何？复合性状是否适宜于QTL作图？与作图群体及遗传图谱有关的一些问题包括QTL作图群体中表型数据是否要求服从正态分布？加密标记是否可以显著提高QTL检测功效？缺失分子标记对QTL作图有什么影响？奇异分离标记对QTL作图有什么影响？文章试图结合笔者多年研究工作对这12个有共性的常见问题做出分析和解答,以供科研工作者参考。     

抗除草剂转基因水稻的研究进展及其安全性问题

近年来,抗除草剂转基因作物的研究取得了一些进展。本文简述了抗除草剂转基因作物的发展历史以及除草剂的作用机理,分别介绍了抗EPSPS抑制剂基因、抗ALS抑制剂基因、乙酰CoA转移酶基因、阿特拉津氯水解酶基因、细胞色素P450基因和原卟啉原氧化酶基因这6类抗除草剂基因的来源,抗性机理以及目前它们在转基因水稻上的应用。最后,对转基因水稻的食用安全性,转基因释放、飘移对生态的影响进行了探讨,并对转基因水稻的未来发展进行了展望。