Screening of natural products in the laboratory and the field for control of pollen beetles

Pollen beetles, Meligethes spp. (Coleoptera: Nitidulidae), are among the most damaging pests of oilseed rape (Brassica napus L.). Increasing populations of pyrethroid‐resistant pollen beetles coupled with the prohibition of synthetic pest control products in organic farming means that other direct control methods are needed. A laboratory study was therefore conducted to evaluate the effect of natural products, combinations of natural products and additives as well as natural and synthetic insecticides on mortality of pollen beetles. In addition, field trials under both integrated and organic production were conducted to evaluate the efficacy of six natural products, nine combinations of natural products, two synthetic insecticides (integrated‐production trials only), two natural insecticides and two additives to reduce pollen beetles. The laboratory trial, using both a curative and preventive approach, showed that two of the eight natural products (lavender oil and stone meal) caused a mortality of over 98% within the first day of application. The other natural products were only partially effective compared with the untreated control. In the field trials, the natural products reduced the number of pollen beetles 1 day after application compared with the untreated control in both trial years and production systems. Promising substances were stone meal, Silico‐Sec and liquid manure. Nevertheless, the efficacy was not consistent, and no effect on oilseed rape yield was observed. In spite of this, these products have the potential to control pollen beetles under field conditions with comparable effects to synthetic insecticides. Further research should therefore focus on timing and frequency of applications as well as on the formulation of the natural products to increase the persistency of the products under field conditions.     

A review of sources of resistance to turnip yellows virus (TuYV) in Brassica species

Turnip yellows virus (TuYV; previously known as beet western yellows virus) causes major diseases of Brassica species worldwide resulting in severe yield-losses in arable and vegetable crops. It has also been shown to reduce the quality of vegetables, particularly cabbage where it causes tip burn. Incidences of 100% have been recorded in commercial crops of winter oilseed rape (Brassica napus) and vegetable crops (particularly Brassica oleracea) in Europe. This review summarises the known sources of resistance to TuYV in B. napus (AACC genome), Brassica rapa (AA genome) and B. oleracea (CC genome). It also proposes names for the quantitative trait loci (QTLs) responsible for the resistances, Tu rnip Y ellows virus R esistance (TuYR), that have been mapped to at least the chromosome level in the different Brassica species. There is currently only one known source of resistance deployed commercially (TuYR1). This resistance is said to have originated in B. rapa and was introgressed into the A genome of oilseed rape via hybridisation with B. oleracea to produce allotetraploid (AACC) plants that were then backcrossed into oilseed rape. It has been utilised in the majority of known TuYV-resistant oilseed rape varieties. This has placed significant selection pressure for resistance-breaking mutations arising in TuYV. Further QTLs for resistance to TuYV (TuYR2-TuYR9) have been mapped in the genomes of B. napus, B. rapa and B. oleracea and are described here. QTLs from the latter two species have been introgressed into allotetraploid plants, providing for the first time, combined resistance from both the A and the C genomes for deployment in oilseed rape. Introgression of these new resistances into commercial oilseed rape and vegetable brassicas can be accelerated using the molecular markers that have been developed. The deployment of these resistances should lessen selection pressure for resistance-breaking isolates of TuYV and thereby prolong the effectiveness of each other and extant resistance.     

Exploitation of host plant preferences in pest management strategies for oilseed rape (Brassica napus)

New control strategies for insect pests of arable agriculture are needed to reduce current dependence on synthetic insecticides, the use of which is unsustainable. We investigated the potential of a simple control strategy to protect spring‐sown oilseed rape, Brassica napus L. (Brassicaceae), from two major inflorescence pests: the pollen beetle, Meligethes aeneus (Fabricius) (Coleoptera: Nitidulidae), and the seed weevil, Ceutorhynchus assimilis (Paykull) (Coleoptera: Curculionidae), through exploitation of their host plant preferences. The strategy comprised, for the main crop, Starlight [an oilseed rape cultivar with relatively low proportions of alkenyl glucosinolates in the leaves (thereby releasing lower levels of attractive isothiocyanates than conventional cultivars)] and turnip rape, Brassica rapa (L.) (Brassicaceae), as a trap crop. We tested the system in laboratory, polytunnel semifield arena, and field experiments. The odours of Starlight were less attractive in olfactometer tests to both pests than those from a conventional cultivar, Canyon, and the plants were less heavily colonized in both polytunnel and field experiments. Turnip rape showed good potential as a trap crop for oilseed rape pests, particularly the pollen beetle as its odour was more attractive to both pests than that of oilseed rape. Polytunnel and field experiments showed the importance of relative growth stage in the system. As turnip rape flowers earlier than oilseed rape, beetles would be maintained on turnip rape past the damage‐susceptible growth stage of oilseed rape. The development of a pest control regime based on this strategy is discussed.     

Potato proteins, and other plant proteins, as potential transgenic resistance factors to pollen beetles in oilseed rape

Proteinase inhibitors (PIs), lectin and patatin purified from potato tubers were tested in no‐choice feeding assays with pollen beetle larvae (Meligethes spp.). The idea was to search for resistance factors possible to introduce into oilseed rape (Brassica napus) by genetic engineering. The larval diet was prepared by soaking oilseed rape anthers in protein solutions of known concentrations. Potato lectin was the most potent in that it was the only of these proteins that reduced both larval survival and growth rate, while cysteine, aspartic and metallo PIs and patatin only reduced larval growth rate. Serine PIs had no significant effect on larval performance. Subsequently, the effect of potato lectin was compared to that of lectins from other food or feed crops, resulting in the following mortality‐ based ranking of activity: Con A from jackbean > wheat germ lectin > potato lectin > peanut lectin. In choice tests, larvae did not discriminate between Con A‐ and control‐diets. These results suggest that the effect of Con A on larvae is toxic, not deterrent. Adult response was stronger to Con A than to potato lectin in no‐choice tests, just as it was in larvae. However, adult survival rate and weight was not affected by Con A but the lectin significantly reduced adult feeding as well as oviposition rates. A resistance factor that suppresses adult feeding on flower buds is important for reduced impact of the pollen beetle on the Brassica oilseed crop.     

Performance of cabbage stem flea beetle larvae (Psylliodes chrysocephala) in brassicaceous plants and the effect of glucosinolate profiles

The cabbage stem flea beetle (CSFB), Psylliodes chrysocephala L. (Coleoptera: Chrysomelidae), is one of the most important pests in European winter oilseed rape production. Adult beetles feed on young leaves whereas larvae mine within the petioles and stems. Larval infestation can cause significant crop damage. In this study, the host quality for CSFB of four oilseed rape (Brassica napus L.) cultivars and seven other brassicaceous species with different glucosinolate (GSL) profiles was assessed under controlled conditions. Larval instar weights and mortality were measured after 14 and 21 days of feeding in the petioles of test plants. To study the impact of GSL on the performance of larvae, the GSL contents in petioles from non-infested and infested plants were analysed before, and 21 days after, the start of larval infestation. Larval performance was not significantly different between the four cultivars of oilseed rape, but differed considerably among the other brassicaceous species tested. In comparison to the weight of larvae in the standard B. napus cv. Robust, the larval weight was higher in turnip rape (Brassica rapa L. var. silvestris) and significantly reduced in white mustard (Sinapis alba L.), oil radish (Raphanus sativa L. var. oleiformis), and cabbage (Brassica oleracea L. convar. capitata var. alba). The duration of larval development increased in white mustard and oilseed radish. The GSL profiles of the petioles showed little difference between non-infested and infested plants of oilseed rape whereas the content of aliphatic GSL increased in the infested turnip rape plants. In contrast, the aliphatic and benzenic GSL decreased in infested Indian rape (B. rapa subsp. dichotoma Roxb.). Larval weight was not correlated with the total GSL content of plants, neither before infestation nor 21 days after. Larval weight was positively correlated with progoitrin and 4-hydroxyglucobrassicin. White mustard, which provides inferior host quality for larval development, has the potential to introduce insect resistance into high-yielding oilseed rape cultivars in breeding programmes.     

Environmental burdens of producing bread wheat,oilseed rape and potatoes in England and Wales using simulation and system modelling

Background, aims and scope  

Food production is essential to life. Modern farming uses considerable resources to produce arable crops. Analysing the environmental burdens of alternative crop production methods is a vital tool for policymakers. The paper describes the production burdens (calculated by life cycle analysis) of three key arable crops: bread wheat, oilseed rape and potatoes as grown in England and Wales using organic and non-organic (contemporary conventional) systems. Resource use (e.g. abiotic and energy) and burdens from emissions are included (e.g. global warming potential on a 100-year basis, global warming potential (GWP), and eutrophication and acidification potentials).     

Effect of flower traits and hosts on the abundance of parasitoids in perennial multiple species wildflower strips sown within oilseed rape (<Emphasis Type="Italic">Brassica napus</Emphasis>) crops

Reducing the use of insecticides is an important issue for agriculture today. Sowing wildflower strips along field margins or within crops represents a promising tool to support natural enemy populations in agricultural landscapes and, thus, enhance conservation biological control. However, it is important to sow appropriate flower species that attract natural enemies efficiently. The presence of prey and hosts may also guide natural enemies to wildflower strips, potentially preventing them from migrating into adjacent crops. Here, we assessed how seven flower traits, along with the abundance of pollen beetles (Meligethes spp., Coleoptera: Nitidulidae) and true weevils (Ceutorhynchus spp., Coleoptera: Curculionidae), affect the density of parasitoids of these two coleopterans in wildflower strips sown in an oilseed rape field in Gembloux (Belgium). Only flower traits, not host (i.e. pollen beetles and true weevils) abundance, significantly affected the density of parasitoids. Flower colour, ultraviolet reflectance and nectar availability were the main drivers affecting parasitoids. These results demonstrate how parasitoids of oilseed rape pests react to flower cues under field conditions. Similar analyses on the pests and natural enemies of other crops are expected to help to develop perennial flower mixtures able to enhance biological control throughout a rotation system.     

Efficient Detection of Leptosphaeria maculans from Infected Seed lots of Oilseed Rape

An efficient DNA extraction protocol and polymerase chain reaction (PCR) assay for detecting Leptosphaeria maculans from infected seed lots of oilseed rape were developed. L. maculans, the causal agent of blackleg, a damaging disease in oilseeds rape/canola worldwide, was listed as a quarantine disease by China in 2009. China imports several millions of tons of oilseeds every year. So there is a high risk that this pathogen will be introduced to China via contaminated seeds. Seed contamination is one of the most significant factors in the global spread of phytopathogens. Detection of L. maculans in infected seed lots by PCR assay is difficult due to the low level of pathogen mycelium/spores on seeds and PCR inhibitors associated with the seeds of oilseed rape. In our study, these two major obstacles were overcome by the development of a two‐step extraction protocol combined with a nested PCR. This extraction protocol (kit extraction after CTAB method) can efficiently extract high‐quality DNA for PCR. Amplification results showed that the detection threshold for conventional PCR and nested PCR was, respectively, 1 ng and 10 fg of DNA per μl in mycelia samples. On contaminated seed lots of oilseed rape, the detection threshold of conventional and nested PCR was 709 fg/μl and 709 ag/μl of DNA, respectively. The DNA extraction protocol and PCR assay developed in this study can be used for rapid and reliable detection of L. maculans from infected seeds of oilseed rape .     

Effects of non‐host plant odour on Meligethes aeneus during immigration to oilseed rape

The use of semiochemicals for the manipulation of the pollen beetle, Meliethes aeneus (Fabricius) (Coleoptera: Nitidulidae), is being investigated for potential incorporation into a push‐pull strategy for this pest, which damages oilseed rape, Brassica napus L. (Brassicaceae), throughout Europe. Previous laboratory behavioural studies using volatiles from non‐host plants showed that M. aeneus is repelled by the odour of lavender, Lavendula angustifolia Mill. (Lamiaceae), essential oil. This article reports on semi‐field and field trials to investigate this behaviour under more realistic conditions. Semi‐field experiments were conducted to assess the relative importance of olfaction at different points in host location behaviour by M. aeneus. The results showed that oilseed rape plants treated with lavender odour were less colonised by M. aeneus in comparison with an untreated control, but that the treatment effect was much reduced if the lavender odour was applied after colonisation. The field experiment demonstrated that lavender odour caused a significant reduction in the number of adult M. aeneus infesting the oilseed rape plants in the treatment plots compared to the control plots. Overall, these findings are very encouraging for the future development of a push‐pull pest control system.     

Interaction of Anthonomus grandis and cotton genotypes: biological and behavioral responses

The boll weevil, Anthonomus grandisBoheman (Coleoptera: Curculionidae), is a key pest of cotton, Gossypium hirsutumL. (Malvaceae). Knowledge about boll weevil feeding and oviposition behavior and its response to plant volatiles can underpin our understanding of host plant resistance, and contribute to improved monitoring and mass capture of this pest. Boll weevil oviposition preference and immature development in four cotton genotypes (CNPA TB90, TB85, TB15, and BRS Rubi) were investigated in the laboratory and greenhouse. Volatile organic compounds (VOCs) produced by TB90 and Rubi genotypes were obtained from herbivore‐damaged and undamaged control plants at two phenological stages – vegetative (prior to squaring) and reproductive (during squaring) – and four collection times – 24, 48, 72, and 96 h following herbivore damage. The boll weevil exhibited similar feeding and oviposition behavior across the four tested cotton genotypes. The chemical profiles of herbivore‐damaged plants of both genotypes across the two phenological stages were qualitatively similar, but differed in the amount of volatiles produced. Boll weevil response to VOC extracts was studied using a Y‐tube olfactometer. The boll weevil exhibited similar feeding and oviposition behavior at the four tested cotton genotypes, although delayed development and production of smaller adults was found when fed TB85. The chemical profile of herbivore‐damaged plants of both genotypes at the two phenological stages and time periods (24–96 h) was similar qualitatively, with 30 identified compounds, but differed in the amount of volatiles produced. Additionally, boll weevil olfactory response was positive to herbivory‐induced volatiles. The results help to understand the interaction between A. grandis and cotton plants, and why it is difficult to obtain cotton genotypes possessing constitutive resistance to this pest.     

Behavioural responses in three ichneumonid pollen beetle parasitoids to volatiles emitted from different phenological stages of oilseed rape

Pollen beetles (Meligethes spp.; Coleoptera: Nitiduliae) are a major pest of oilseed rape, Brassica napus L. (Brassicaceae) in northern Europe. Phradis interstitialis Thomson, P. morionellus Holmgr., and Tersilochus heterocerus Thomson (Hymenoptera: Ichneumonidae) are among the most frequent pollen beetle parasitoids. These three species differ in temporal occurrence, as well as in preferred host stage. The behavioural responses of female parasitoids to odours from oilseed rape at bud and flowering stage were evaluated in two‐choice experiments. The role of visual stimuli was examined by combining green and yellow colours with odour stimuli. All three species were attracted to odours from the bud stage of oilseed rape. Tersilochus heterocerus was attracted to odours of flowering rape, but the two Phradis species avoided the flower odours. However, when the odours of flowering rape were combined with yellow, and odours of the bud stage were combined with green, P. interstitialis was equally attracted to both stimuli, and T. heterocerus showed an increased preference for flower odours, while no effect of colours could be found in P. morionellus. The observed differences in responses between the parasitoids may reflect differences in their biology and may be involved in the niche segregation of these often coexisting species. The volatile blends released from the two phenological stages were identified and compared. Clearly, odours can be reliable cues for differentiating between oilseed rape in the bud and flowering stage. Of 20 identified compounds, 18 were released at a significantly higher rate from flowering plants. The terpenes sabinene, myrcene, limonene, and (E,E)‐α‐farnesene were the dominant volatiles in the bud and flower headspace. A group of aromatic compounds including benzaldehyde, methyl benzoate, and phenyl acetaldehyde were mainly released from flowering rape.     

Crop–noncrop spillover: arable fields affect trophic interactions on wild plants in surrounding habitats

Ecosystem processes in agricultural landscapes are often triggered by resource availability in crop and noncrop habitats. We investigated how oilseed rape (OSR; Brassica napus, Brassicaceae) affects noncrop plants in managed systems and semi-natural habitat, using trophic interactions among wild mustard (Sinapis arvensis, Brassicaceae), rape pollen beetles (Meligethes aeneus, Nitidulidae) and their parasitoids (Tersilochus heterocerus, Ichneumonidae). We exposed wild mustard as phytometer plants in two cropland habitat types (wheat field, field margin) and three noncrop habitat types (fallow, grassland, wood margin) across eight landscapes along a gradient from simple to complex (quantified as % arable land). Both landscape and local factors affected the abundance of rape pollen beetles and parasitoids. Rape pollen beetle infestation and parasitism rates on these plants were lower in noncrop habitats and higher in wheat fields and field margins, whereas beetles and parasitoids responded differently to landscape scale parameters. We found the hypothesized spillover from OSR crop onto wild plants in surrounding habitats only for parasitoids, but not for pollen beetles. Parasitism rates were not related to landscape simplification, but benefited from increasing proportions of OSR. In contrast, rape pollen beetles benefited from simple landscape structures, presumably due to multi-annual population build-ups resulting from long-term OSR planting (as part of the crop rotation). In conclusion, we showed that spillover from cropland affects parasitism rates on related wild plants outside cropland, which has not been shown so far, but can be expected to be a widespread effect shaping noncrop food webs.     

Injury to oilseed rape caused by mirid bugs (Lygus) (Heteroptera: Miridae) and its effect on seed production

Injury by Lygus spp. to oilseed rape, Brassica napus L. and Brassica campestris L., was assessed based on laboratory and field studies in Alberta, Canada. The visible injuries consisted of lesions on the surfaces of stems, buds, flowers and pods similar to those described for other crops. They caused buds and flowers to abscise and seeds to collapse, and reduced the weight of healthy seeds produced per pod. The plants compensated for bud loss so that no net reduction in the number of pods occurred. However, in some situations the damage to buds resulted in a reduced seed yield that increased with the amount of injury. The plants also compensated for flower loss so that no net reduction in the number of pods occurred, but seed yield declined as injury increased. Plants did not compensate for seeds that collapsed as a result of lygus feeding. The feeding activity of lygus bugs reduced seed yield in oilseed rape.     

Studies on the taro leaf blight fungus Phytophthora colocasiae in Solomon Islands: control by fungicides and spacing

Surveys in 1974–75 in which 20 plants were examined in each of 105 fields showed that cabbage stem weevil was widespread on spring oilseed rape in the south of England, the larvae sometimes infesting a large percentage of plants and reducing vigour and yield. In replicated field trials during 1974–77, infestations were reduced by seed treatments of gamma-HCH or sprays of gamma-HCH, azinphos-methyl, azinphos-methyl + demeton-S-methyl sulphone, chlorpyrifos or triazophos. In some experiments treatments significantly improved plant growth or yield, or both. Granules of carbofuran or phorate also reduced larval infestations and damage, but both thiofanox granules and dimethoate sprays were ineffective. Sprays of gamma-HCH or azinphos-methyl + demeton-S-methyl sulphone which were effective against stem weevil could also in some years give improved control of blossom beetles (Meligethes spp.)     

Integrated Control of Clubroot

Clubroot caused by Plasmodiophora brassicae affects the Brassicaceae family of plants, including many important vegetable and broadacre crops. In the last 20 years increasing intensity of vegetable production and the rapid growth in popularity of oilseed rape as a broadacre or arable break crop have increased the severity of clubroot and the area of land affected in both the vegetable and broadacre industries. Resting spores of P. brassicae are long-lived in soil, but the number of spores can be reduced through crop rotation, fallowing, chemical application, and management of brassica weeds. The host-pathogen system is responsive to a range of control measures, including calcium and boron amendments, manipulation of soil pH, and fungicide application. Molecular tests have been developed to predict disease and resistant cultivars are available for some crops. Increasingly, a multifaceted or integrated approach is being used to manage clubroot. This approach has been particularly successful in vegetable production systems.     

Ground-dwelling predators can affect within-field pest insect emergence in winter oilseed rape fields

We investigated, (i) whether the emergence from pupation of two coleopteran pest insect groups in oilseed rape (OSR, Brassica napus L.)—pollen beetles (Meligethes spp. F., Nitidulidae) and stem weevils (Ceutorhynchus pallidactylus Marsh and C. napi Gyll., Curculionidae)—is affected by the exclusion of ground-dwelling predatory arthropods, and (ii) the role for pest control of the widely abundant carabid beetles Anchomenus dorsalis Pontop. and Poecilus cupreus L. Densities of ground-dwelling arthropods were manipulated using enclosures; emerging pest adults were assessed using emergence traps. Where arthropods had been excluded, between two (June sampling) and tenfold (August sampling) more stem weevils emerged than where predators had free access. The addition of 25 adult A. dorsalis m⁻² to formerly predator-free enclosures showed similar stem weevil emergence than plots where predators had free access; the addition of 25 adult P. cupreus m⁻² did not reduce stem weevil emergence. In August, both A. dorsalis and P. cupreus additions marginally significantly reduced pollen beetle emergence. Handling editor: Patrick De Clercq.     

Glucosinolates in oilseed rape (Brassica napus) and the incidence of pollen beetles (Meligethes aeneus)

During an early stage of migration into a field of oilseed rape in the spring of 1988, more pollen beetles were observed on the double-low variety, Ariana, than on the adjacent single-low varieties, Bienvenu and Mikado. More beetles were found on open flowers on terminal racemes than on yellow and green flower buds on lateral racemes. Five alkenyl, three indolyl and two aromatic glucosinolates were identified in the floral tissues of oilseed rape. The major compounds were progoitrin (2-OH, 3-butenyl) and glucobrassicanapin (4-pentenyl). There were no differences in the types and concentrations of glucosinolates present in the terminal and lateral racemes of any variety, and only small differences between single- and double-low varieties. Concentrations of glucosinolates in floral tissues of crops grown with a little nitrogen were twice those of well-fertilised crops. There was no association between the number and distribution of pollen beetles on plants and the amounts or types of glucosinolates present in floral tissues.     

Valuable New Resistances Ensure Improved Management of Sclerotinia Stem Rot (Sclerotinia sclerotiorum) in Horticultural and Oilseed Brassica Species

Field resistances against Sclerotinia rot (SR) (Sclerotinia sclerotiorum) were determined in 52 Chinese genotypes of Brassica oleracea var. capitata, 14 Indian Brassica juncea genotypes carrying wild weedy Brassicaceae introgression(s) and four carrying B‐genome introgression, 22 Australian commercial Brassica napus varieties, and 12 B. napus and B. juncea genotypes of known resistance. All plants were individually inoculated by securing an agar disc from a culture of S. sclerotiorum growing on a glucose‐rich medium to the stem above the second internode with Parafilm tape. Mean stem lesion length across tested genotypes ranged from <1 to >68 mm. While there was considerable diversity within the germplasm sets from each country, overall, 65% of the B. oleracea var. capitata genotypes from China showed the highest levels of stem resistance, a level comparable with the highest resistance ever recorded for oilseed B. napus or B. juncea from China or Australia. One Indian B. juncea line carrying weedy introgression displayed a significant level of both stem and leaf resistance. However, the vast majority of commercial Australian oilseed B. napus varieties fell within the most susceptible 40% of genotypes tested for stem disease. There was no correlation between expressions of stem versus leaf resistance, suggesting their independent inheritance. A few Chinese B. oleracea var. capitata genotypes that expressed combined extremely high‐level stem (≤1 mm length) and leaf (≤0.5 mean number of infections/plant) resistance will be particularly significant for developing new SR‐resistant horticultural and oilseed Brassica varieties.     

Studies on beet western yellows virus in oilseed rape (Brassica napus ssp. oleifera) and sugar beet (Beta vulgaris)

Oilseed rape (Brassica napus L. ssp. oleifera) was studied as a potential overwintering host for the sugar-beet yellowing viruses, beet yellows virus (BYV) and beet mild yellowing virus (BMYV), and their principal vector, Myzus persicae. In spring 1982, plants infected with a virus which reacted positively in enzyme-linked immunosorbent assay (ELISA) with BMYV antibody globulin were found in oilseed-rape crops; none of the plants contained virus which reacted with BYV antibody globulin. This virus was subsequently identified as beet western yellows virus (BWYV). No leaf symptoms could be consistently associated with infection of oilseed rape, but the virus was reliably detected by sampling any leaf on an infected oilseed-rape plant. Some isolates from oilseed rape did infect sugar beet in glasshouse tests, but the proportions of inoculated plants which became infected were low. Apparently there is therefore little danger of much direct transmission of BWYV by M. persicae from oilseed rape to sugar beet in spring. BWYV was introduced to and spread within oilseed-rape crops in autumn by M. persicae, and autumn-sown oilseed rape proved to be a potentially important overwintering host for M. persicae. In a survey of 80 autumn-sown crops of oilseed rape in East Anglia, northern England and Scotland in spring 1983, 78 were shown to be extensively infected with BWYV. Experimental plots of oilseed rape with 100% BWYV-infection yielded approximately 13.4% less oil than plots with 18% virus infection, the result of a decrease in both seed yield and oil content.     

Assays of the production of harmful substances by genetically modified oilseed rape (<Emphasis Type="Italic">Brassica napus</Emphasis> L.) plants in accordance with regulations for evaluating the impact on biodiversity in Japan

Environmental risk assessment of transgenic crops is implemented under the Cartagena Protocol domestic law in accordance with guidelines for implementing the assessment established by the Ministry of Agriculture, Forestry and Fisheries (MAFF) and the Ministry of Environment (MOE) in Japan. Environmental risk assessments of transgenic crops are implemented based on the concept of ‘substantial equivalence’ to conventional crops. A unique requirement in Japan to monitor the production of harmful substances, or allelochemicals, is unparalleled in other countries. The potential for allelochemicals to be secreted from the roots of transgenic crops to affect other plants or soil microflora or for substances in the plant body to affect other plants after dying out must be evaluated. We evaluated the allelopathic potential of seven transgenic oilseed rape (Brassica napus L.) lines that express glufosinate tolerance in terms of substantial equivalence to conventional oilseed rape lines, and established evaluation methods. Our results indicate no potential production of allelochemicals for any of the seven transgenic oilseed rape lines compared with conventional oilseed rape lines.