Herbicide-tolerant crops in agriculture: oilseed rape as a case study

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.     

Variation of prezygotic barriers in the interspecific hybridization between oilseed rape and wild radish

Escape of transgenes from genetically modified oilseed rape, Brassica napus, into wild radish, Raphanus raphanistrum, depends on sexual compatibility. The variation in prezygotic barriers of two different cultivars for interspecific hybridization with a population of wild radish was investigated by hand crossing and fluorescence microscopy of pistils. Significant differences were observed between oil seed rape cultivars in their ability to accept wild radish pollen germinating onto their stigma and the rate of fertilization of ovules. Some differences among the pollen donor plants were also detected. These results suggest that the rate of interspecific hybridization in the field would depend upon the oilseed rape cultivar and the genotype composition of the local wild populations. The implication of S-related genes, as revealed through identification by pistil tissue prints of class I and II S-types of SLG (S-Locus Glycoprotein) and SLR1 (S-Locus Related),and immuno-IEF, was not significant. This revised version was published online in August 2006 with corrections to the Cover Date.     

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.     

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.     

蜂蜜中主要转基因蜜源植物花粉形态学鉴别方法的研究

目前已批准大面积商业化种植的最主要转基因蜜源植物是棉花和油菜。通过对棉花和油菜花粉显微形态的研究,建立标准花粉图谱,以显微镜检的方式快速排除不含上述作物花粉的蜂蜜;也可在蜜种鉴定中发挥作用。     

Status and perspectives of breeding for enhanced yield and quality of oilseed crops for Europe

Vegetable oils are a high-value agricultural commodity for use in refined edible oil products and as renewable industrial or fuel oils, and as the world population increases demand for high-quality seed oils continues to grow. Worldwide the oilseed market is dominated by soybean (Glycine max), followed by oilseed rape/canola (Brassica napus). In Europe the major oilseed crop is oilseed rape (B. napus), followed some way behind by sunflower (Helianthus annuus) and other minor crops like linseed (Linum usitatissimum) or camelina (Camelina sativa). The seed oil of these crops is characterized by a specific quality, i.e. fatty acid composition and other fat-soluble compounds: Camelina and linseed oils are characterised by high contents of linolenic acid (C18:3); in sunflower very high-oleic (up to 90% C18:1) types exist in addition to classical high-linoleic (C18:2) oilseeds; in B. napus a broad diversity of oil-types is available in addition to the modern 00 (canola) type, e.g. high-erucic acid rapeseed or high-oleic and low-linolenic cultivars. Moreover, vegetable oils contain valuable minor compounds such as tocopherols (vitamin E). Increases of such contents by breeding have lead to value-added edible oils. After oil extraction, oilseed meals—such as rapeseed extraction meal—contain a high-quality protein that can be used as a valuable animal feed. However, in comparison to soybean the meal from oilseed rape also contains relatively high amounts of anti-nutritive fibre compounds, phenolic acids, phytate and glucosinolates. Breeding efforts with respect to meal quality are therefore aimed at reduction of anti-nutritive components, while increasing the oil content, quality and yield also remains a major aim in oilseed rape breeding. This review article provides a general overview of the status of oilseed production in Europe and uses examples from winter oilseed rape to illustrate key breeding aims for sustainable and high-yielding production of high-quality vegetable oil. Emphasis is placed on analytical tools for high-throughput selection of overall seed quality.     

An overview of general features of risk assessments of genetically modified crops

The intentional introduction into the environment or market of genetically modified organisms (GMOs) is nearly always governed by a framework of science-based risk assessment and risk management measures. This is usually implemented through the integration of hazard identification and characterisation of all of the elements of risk associated with a new GM crop or derived product. Typical categories of hazards arising from the introduction of transgenic crops include: possible unintended negative health effects in a susceptible subgroup of the consumer (target) population; the evolution of resistance in the targeted pest/pathogen populations when the transgene confers resistance to a pest or pathogen; non-target hazards associated directly or indirectly with the transgenic plant or transgene product outside the plant; and those associated with the integration and subsequent expression of the transgene in a different organism or species following gene flow. The consequences of likely exposure to these and other hazards are considered in this introduction to the main issues raised when evaluating the possible risks arising from the importation or cultivation of genetically modified crops.     

玉米转基因技术研究及其应用

随着植物转基因技术的深入发展,大豆、玉米、油菜和棉花等转基因作物大面积商品化生产为全球的粮食安全做出了巨大贡献。玉米是全球第一大粮食作物,自1986年以来玉米的转基因技术发展较快,其主要的遗传转化方法包括农杆菌介导法、基因枪法和花粉管通道法等,农艺性状改良涉及抗除草剂、抗虫、抗病、抗旱、抗盐和品质改良等,其中抗除草剂和抗虫玉米已成为主要的商业化转基因作物。本文综述了玉米转基因技术的研究进展及应用,展望了玉米转基因研究的发展方向。     

Identification of QTLs for phenolic compounds in oilseed rape (<Emphasis Type="Italic">Brassica napus L.</Emphasis>) by association mapping using SSR markers

Association mapping identifies quantitative trait loci (QTLs) by examining the marker-trait associations that can be attributed to the strength of linkage disequilibrium between markers and functional polymorphisms across a set of diverse germplasm. In this study, association mapping was performed to detect QTL-linked and genome wide SSR markers linked to phenolic compounds of extraction meal in a population of 49 genetically diverse oilseed rape cultivars of dark-seeded, winter-type oilseed rape accessions. Correction for population structure was performed using 559 genome wide SSR markers. Results showed that seed colour is an important contributor to seed meal quality. Totally, 52 SSR markers linked to phenolic compounds were detected, five of them being QTL linked markers. Some of these markers were already mapped on Brassica napus chromosomes that contain known QTL controlling oilseed rape meal quality traits. Our results demonstrate that association mapping is a useful approach to complement and enhance previous QTL information for marker-assisted selection.     

The Effect of A Genome Substitution on the Resistance of Brassica napus to Infection by Leptosphaeria maculans

Six accessions belonging to four subspecies of Brassica rapa, including three accessions of B. rapa subsp. sylvestris, were crossed with B. oleracea subsp. alboglabra in order to develop a series of synthetic B. napus lines with a common C genome but contrasting A genomes. Different A genomes had significant effects on the efficiency of B. napus resynthesis and the sexual compatibility of the synthetic lines with oilseed rape cultivars. The synthetic lines were used to investigate the effect of A genome substitution on the resistance of B. napus to infection by Leptosphaeria maculans, and to explore the potential for the use of wild forms of B. rapa in oilseed rape breeding programmes. Synthetic lines derived from two wild accessions of B. rapa, and their F₁ hybrids with oilseed rape cultivars, expressed high levels of resistance to L. maculans in glasshouse experiments. One of these lines also expressed high levels of resistance in field experiments in England and Australia when exposed to a genetically diverse pathogen population. All other synthetic lines and cultivars were highly susceptible in both glasshouse and field experiments. F₁ hybrids between oilseed rape cultivars and synthetic lines derived from B. rapa subsp. chinensis were significantly more susceptible than either parent.     

油菜野芥NSa细胞质雄性不育系的特异性分子鉴定

常规细胞质类型鉴定方法花费时间长、工作量大、鉴定效率低、应用性较差。基于基因组重复序列的PCR技术(rep-PCR)在重复序列丰富的线粒体和原核生物的基因组鉴定中效果较好, 本研究对8份油菜资源的细胞质进行分子鉴定,结果表明rep-PCR可以明确区分甘蓝型油菜中常见的6种雄性不育细胞质。同时对甘蓝型油菜和野芥(Sinapis arvensis)体细胞杂交创建的、育性较为稳定的NSa野芥雄性不育胞质进行了分子特异性鉴定,获得了两条NSa不育胞质的特征DNA条带。但波里马和萝卜质不育细胞质的特异性引物在NSa中不能扩增出特异性片段,说明NSa不属于这两种细胞质类型。本研究结果为该不育胞质系统的利用和知识产权保护提供了理论依据和技术支撑。     

Morphological differences among Raphanus raphanistrum populations and their relationship to related crops

Wild radish (Raphanus raphanistrum) has developed introgressed populations after hybridization with its cultivated counterpart (R. sativus) in California. Hybridization with various Brassica and Sinapis species is also possible. To determine if hybridization is responsible of the genetic diversity of European populations, six wild radish populations with distinct morphological traits were sampled from geographically distant regions in Europe. Plants were cultivated in an oilseed rape field and in insect‐proof cages. Silique and flower morphology, growth, and reproductive traits were measured. The wild radish populations could be discriminated by the morphological traits, but not related to geographic regions. In particular, populations of one region showed wide variability in terms of silique shape and growth behaviour, and small‐sized flowers. Although the origin of morphological diversity in wild radish is unclear, i.e. native or due to gene flow from the cultivated radish or other Brassicaceae, significant morphological divergence was found that could have relevant effects on plant ecology and adaptation.     

冬油菜苗期化学除草效果和经济效益研究

为筛选出经济、高效、安全的化学除草方法,有效控制油菜田间杂草危害,提高油菜产量和种植效益,通过试验,研究了2种化学除草剂不同使用浓度的安全性和苗期化学除草效果,并以人工除草和不除草方法为对照,对比分析不同除草方法的投入和产出情况。结果表明：不同除草方法间油菜产量差异显著;化学除草方法对油菜田间杂草有较好的防除效果,并可显著降低油菜生产的劳动力和生产成本投入,进而提高经济效益;不同化学除草方法均于施药35天后表现出较好的除草效果;每公顷用21.2%喹·胺·草除灵悬浮剂900 mL于油菜4—5叶期、杂草3—4叶期兑水900 kg及时喷施的方法除草效果好,对油菜生长安全,可以作为冬油菜田的苗期化学除草方法在生产上应用。     

Predictive study of the advantages of cleistogamy in oilseed rape in limiting unwanted gene flow

Summary The aim of this study was to evaluate the interest of beginning the selection process on a new genetic characteristic, cleistogamy, to manage gene flow in oilseed rape. The first step was to introduce this characteristic in an existing model of gene flow between oilseed rape populations in time and space, GeneSys-Rape. The second step was to evaluate the parameters of the model linked to this characteristic using field experimentations. Cleistogamous oilseed rape was shown to have an autogamy rate as high as 94% and to emit 10 times less pollen than an open-flowered oilseed rape in the same conditions. But the cleistogamous character was also shown to be unstable in the genotypes tested. The third step was to evaluate the interest of cleistogamy using simulations comparing several genotypes with or without cleistogamy in two different cropping systems. These simulations showed that an oilseed rape both dwarf and cleistogamous was interesting to limit gene escape and that a 99%-autogamous oilseed rape was interesting to limit both gene escape from and harvest contamination of the 99%-autogamous oilseed rape.     

Hybridization of radish (Raphanus sativus L.) and oilseed rape (Brassica napus L.) through a flower-culture method

Summary Hybridization between radish and oilseed rape has been cumbersome, requiring elaborate embryo rescue techniques. With a modified flower culture method, we have achieved successful hybridization between radish and (transgenic) oilseed rape without the laborious and technically demandingin vitro ovule or embryo rescue techniques.The hybrid nature of the intergeneric hybrids was demonstrated using morphological traits, and DNA analyses. The described method will facilitate the generation ofRaphanobrassica hybrids useful for biosafety studies of the potential for transgenes to spread in weedyCruciferae as well as for breeding programs aimed at introducing useful radish genes, e.g. nematode resistance genes, into oilseed rape.     

蜜蜂授粉在油菜生产中的作用研究

为探明蜜蜂授粉在油菜生产中作用和经济重要性,采用蜜蜂授粉依赖度模型,从蜜蜂对油菜授粉服务价值、油菜生产对授粉蜂群需求量2个方面评价蜜蜂授粉在油菜生产中作用。结果表明,2018年蜜蜂对国内油菜的授粉服务价值约104.19亿元,相当于油菜年产值661.41亿元的15.75%。蜜蜂对四川省、湖北省、湖南省油菜生产的授粉价值均在10亿元以上。国内油菜生产对授粉蜂群的需求量较大,约需1637.65万群以上蜜蜂授粉,该数量已超国内目前蜂群总量908.84万群,其中,湖南省和四川省油菜生产对授粉蜂群的需求量最大,约占国内现有蜂群总量的1/3以上。由此可见,蜜蜂授粉是油菜生产重要的生产投入,应当逐步提高民众对蜜蜂授粉经济价值的认识,大力推广油菜蜜蜂授粉技术。     

油菜抗根肿病资源创新与利用的研究进展与展望

根肿病是原生动物界根肿菌门根肿菌属芸薹根肿菌( Plasmodiophora brassicae Wor.)侵染引起, 并专性危害十字花科作物的一种传染性强的土传病害。近些年来, 加拿大和我国油菜的安全生产均受到根肿病的严重威胁。本文简要介绍了根肿菌的生物学特性、分类及主要防治途径, 重点总结了在根肿病抗性资源发掘、抗病基因遗传定位和克隆以及抗病育种等方面的进展, 分析了目前我国油菜根肿病综合防控过程中存在的主要问题, 并探讨与展望了相应的对策, 旨在为油菜抗根肿病遗传育种的高效顺利开展提供技术支持, 进而保障油菜产业的可持续发展。     

Molecular characterization of novel resynthesized rapeseed (Brassica napus) lines and analysis of their genetic diversity in comparison with spring rapeseed cultivars*

Resynthesized (RS) rapeseed generated from interspecific hybridization between suitable forms of Brassica rapa L. (syn. campestris; genome AA, 2n = 20) and B. oleracea L. (CC, 2n = 18) represents a potentially important resource to expand genetic diversity in the narrow gene pool of oilseed rape (B. napus L., AACC, 2n = 38). In this study 165 RS rapeseed lines originating from crosses between an Indian Yellow Sarson (B. rapa ssp. trilocularis) and five different cauliflower (B. oleracea convar. botrytis) cultivars were studied using amplified fragment length polymorphism (AFLP) markers and their genetic diversity was compared in relationship to an assortment of 40 diverse spring oilseed and fodder rape varieties. Using three AFLP primer combinations, a total of 467 polymorphic bands were scored. Cluster analysis allowed differentiation among the different RS lines, which, as expected, were genetically highly divergent from the cultivars. The genetic diversity of the material is discussed in relation to its morphological variability with a view to the implementation of RS lines in oilseed rape breeding.     

Marker-assisted increase of genetic diversity in a double-low seed quality winter oilseed rape genetic background

Generation of novel genetic diversity for maximization of heterosis in hybrid production is a significant goal in winter oilseed rape breeding. Here, we demonstrate that doubled haploid (DH) production using microspore cultivation can simultaneously introgress favourable alleles for double‐low seed quality (low erucic acid and low‐glucosinolate content) into a genetically diverse Brassica napus genetic background. The DH lines were derived from a cross between a double‐low quality winter rapeseed variety and a genetically diverse semisynthetic B. napus line with high erucic acid and high glucosinolates (++ quality). Twenty‐three low‐glucosinolate lines were identified with a genome component of 50–67% derived from the ++ parent. Four of these lines, with a genome component of 50–55% derived from the ++ parent, also contained low erucic acid. Heterosis for seed yield was confirmed in test‐crosses using these genetically diverse lines as pollinator. The results demonstrate the potential of marker‐assisted identification of novel genetic pools for breeding of double‐low quality winter oilseed rape hybrids.     

A mutant of Brassica napus with increased palmitic acid content

An induced mutant from European winter oilseed rape with increased palmitic acid content was phenotypically characterized and genetically analysed. The mutant showed a palmitic acid content of 9.2% compared with 4.5% in the parental cultivar. The oleic acid content decreased from 61.6% to 44.2%, whereas the linoleic and linolenic acid contents increased. The mutant plants grew poorly and their seed oil content was only 31.2% compared with 42.8% in the parental cultivar. The inheritance of the mutant was oligogenic and determined by at least four genes. In the F₂ generation, palmitic acid content was negatively correlated with oil content. This mutant may be useful to improve understanding of the genetic regulation of storage lipid synthesis, but has no immediate value for oilseed rape improvement.