The responses of the cabbage seed weevil Ceutorhynchus assimilis to volatile compounds from oilseed rape in a linear track olfactometer

The cabbage seed weevil, Ceutorhynchus assimilis Payk. [syn. Ceutorhynchus obstrictus (Marsham)] (Coleoptera: Curculionidae), a crucifer-feeding insect, is a pest of oilseed rape (Brassica napus L.). It is known to be attracted by isothiocyanates, crucifer-specific volatiles that are metabolites of the glucosinolates. The responses of this insect to other electrophysiologically-active volatiles from rape were tested in a linear track olfactometer. Attraction was demonstrated to nitriles (phenylacetonitrile, 4-pentenenitrile and 5-hexenenitrile), which are also glucosinolate metabolites, and to volatiles emitted by a wider spectrum of plant families ((Z)-3-hexen-1-ol and methyl salicylate). Combination of an isothiocyanate mixture with phenylacetonitrile increased attraction, but there was no such increase when the isothiocyanate mixture was combined with methyl salicylate. A mixture of 23 volatiles, emulating an attractive air-entrainment extract of oilseed rape, was not significantly attractive, although a high proportion of weevils (60%) turned towards it. The potential of these volatiles for inclusion into an isothiocyanate-based monitoring system is discussed.     

Prediction model for cabbage stem weevil Ceutorhynchus pallidactylus Mrsh. occurrence on winter rape based on an artificial neural network

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Distant olfactory response of the cabbage seed weevil, Ceutorhynchus assimilis, to oilseed rape odour in the field

Abstract. The olfactory orientation of adult cabbage seed weevils (Ceutorhynchus assimilis Payk.) from a distance of 20 m to extracts of oilseed rape (Brassica napus L.) was studied in the field using mark–release–recapture experiments. Male and female weevils dispersed upwind from the centre of a circular array of traps baited with Oilseed rape extracts. In the absence of host-plant odour, female weevils dispersed randomly, and male weevils downwind. Percentage recapture of weevils was significantly greater in traps baited with rape flower than rape leaf extracts. Significantly fewer weevils were recaptured in unbaited traps compared to traps baited with rape flower or leaf extracts. We suggest that seed weevils can use odour-mediated upwind anemotaxis to locate their host-plants from distances of at least 20 m.     

Importance of long-term research in classical biological control: an analytical review of a release against the cabbage seedpod weevil in North America

Abstract:  Cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Col., Curculionidae), is an invasive alien pest that is spreading in North America. To aid with planning for introductions of European parasitoids in North America, we examined the status of the only classical biological control release against this pest in North America, which in 1949 introduced Mesopolobus morys , Stenomalina gracilis and Trichomalus perfectus (Hym., Pteromalidae). Weevils and parasitoids were reared in 2005 from mass collections of seedpods of Brassica napus , Brassica rapa and Raphanus raphanistrum (Brassicaceae) from 18 sites in the Fraser Valley, near Vancouver, British Columbia, Canada. Of the three European parasitoid species that were originally released, only S. gracilis was found. The predominant hymenopterous parasitoid species were Trichomalus lucidus , S. gracilis , Mesopolobus moryoides (Pteromalidae), Necremnus tidius (Eulophidae) and Eupelmus vesicularis (Eupelmidae). These constituted over 97% of the parasitoids reared, although overall parasitism was low. Only M. moryoides is clearly North American in distribution; other than S. gracilis , the remaining species were either accidentally introduced or are Holarctic in distribution. Based on these results, re-releases of M. morys and T. perfectus in North America should be considered as part of a classical biological control programme. However, redistribution of S. gracilis is not recommended at present because of potential conflicts with biological control programmes against weeds. Ongoing re-examination of classical biological control programmes can further our understanding of failure of release programmes, particularly when re-examination can be made in the light of improved taxonomy and systematics of the target and agent species.     

Identification of the gland secreting oviposition-deterring pheromone in the cabbage seed weevil,Ceutorhynchus assimilis,and the mechanism of pheromone deposition

After laying an egg into a pod of Brassica napus, the female cabbage seed weevil, Ceutorhynchus assimilis, brushes the caudal setae of the eighth abdominal tergite (VIII UT) on the host pod as she walks along it, depositing oviposition-deterring pheromone (ODP). The VIII UT is periodically extended and withdrawn, thus repeatedly rubbing against the posterior fold of the seventh urotergite (VII UT) which bears the individual outlets of glandular epidermal cells. In post-diapause, sexually mature, gravid (i.e. oviferous) females (virgin or mated) the cells of this VII UT gland were hypertrophic, showing intense secretory activity. Extracts of VII UT from these individuals elicited strong electrophysiological responses from antennal club gustatory sensilla and deterred oviposition. In pre-diapause (sexually immature) females, the cells of the VII UT gland were neither hypertrophic nor active and an extract of their VII UT elicited no significant electrophysiological or behavioural response. Extract of female rectum was a less potent oviposition deterrent than VII UT extract and elicited an electrophysiological response similar to male rectum extract. An extract of ovarian calyces and ovaries elicited no behavioural response. We conclude that ODP is secreted by the epidermal cells of the VII UT posterior fold.     

Morphological and electrophysiological mapping of tarsal chemoreceptors of oviposition-deterring pheromone in Rhagoletis pomonella flies

Light microscopy and S.E.M. observations revealed that Rhagoletis pomonella female tarsi, bearing the principal receptors of oviposition-deterring fruit marking pheromone (ODP), have 3 types of chemosensilla: B, C and D. Using electrophysiological hair tip-recording techniques, we found that D chemosensilla located in pairs on distal ventrolateral portions of the 2nd, 3rd and 4th tarsomeres of each leg were highly sensitive to stimulation by the pheromone. D chemosensilla located in pairs on the 5th tarsomere of each leg were moderately sensitive to the pheromone, while the B and C chemosensilla of all tarsi were nearly or completely insensitive to it. For reasons discussed, the D chemosensilla on the prothoracic tarsi may be the most important in providing sensory input eliciting oviposition deterrence.     

The responses of the cabbage seed weevil (Ceutorhynchus assimilis) to the odour of oilseed rape (Brassica napus) and to some volatile isothiocyanates

The responses of the cabbage seed weevil,Ceutorhynchus assimilis Payk. (Coleoptera: Curculionidae) to volatiles from oilseed rape (Brassica napus L.) were tested using a linear track olfactometer. Weevils were attracted towards the odour of rape during a short period before diapause and for most of their postdiapause life. Odours from both the flowering and green parts of the plant were attractive, but the odour of a non-host plant (Bellis perennis L.) was not. An entrainment extract of flowering rape volatiles in pentane was attractive, but significantly less so than the odour of flowering rape itself. Attraction was found to 3-butenyl and 4-pentenyl isothiocyanate (NCS), but not to 2-phenylethyl isothiocyanate. A mixture of the three NCSs was more attractive than the individual NCSs. However, the concentration required to produce a response was still relatively high. Isothiocyanates, along with other volatiles from rape, probably play a role in host plant recognition by the seed weevil.     

Screening of oilseed rape and other brassicaceous genotypes for susceptibility to Ceutorhynchus pallidactylus (Mrsh.)

Production of oilseed rape, Brassica napus L., is affected by various insect pests. The cabbage stem weevil, Ceutorhynchus pallidactylus (Mrsh.) (Col.: Curculionidae), is one of the most damaging pests in Northern and Central Europe that requires regular control measures. Host plant resistance is a key factor in integrated pest management systems. To evaluate a large number of genotypes for their susceptibility to infestation by C. pallidactylus, new screening techniques were developed for testing both, the amount of feeding and the number of eggs deposited by adult C. pallidactylus on accessions of Brassicaceae under controlled conditions. In no‐choice screening tests, the leaf area consumed by adult cabbage stem weevil was quantified on a wide spectrum of 107 brassicaceous genotypes (B. napus, Brassica rapa L. and Brassica oleracea L. cultivars, breeding lines, resynthesized rapeseed lines and wild Brassicaceae). In comparison to feeding on the standard cultivar ‘Express’, the average leaf area consumed by C. pallidactylus on nine oilseed rape cultivars, four resynthesized rapeseed lines and five other accessions [B. oleracea, Camelina alyssum (Mill.) and Lunaria annua L.] was significantly reduced by 44–90%. In dual‐choice screening tests for the evaluation of oviposition preferences on 42 genotypes, female C. pallidactylus laid significantly fewer eggs into plants of two oilseed rape cultivars, five resynthesized rapeseeds and three accessions of B. oleracea and Brassica fruticulosa Cyrillo, respectively, than into plants of the standard cv ‘Express’. Results of both laboratory screening tests were confirmed by results of additional field testing.     

Glucosinolate profile and oviposition behavior in relation to the susceptibilities of Brassicaceae to the cabbage seedpod weevil

Understanding how host‐plant characteristics affect behavioral and physiological responses of insect herbivores is of considerable importance in the development of resistant crop germplasm. Feeding, oviposition preference, larval development, and oviposition behavior of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (= Ceutorhynchus assimilis Payk.) (Coleoptera: Curculionidae), were investigated on eight Brassicaceae species that differed in their glucosinolate profiles. The least preferred host plants for feeding and oviposition were the Sinapis alba L. lines while the Brassica carinata L. line was most preferred. Larval development occurred most rapidly on Brassica rapa L. and slowest on S. alba. Larval weight was highest on B. napus L. and lowest on S. alba. Total glucosinolate levels did not influence C. obstrictus larval growth or development; however high levels of specific glucosinolates such as p‐hydroxybenzyl and 3‐butenyl glucosinolate were associated with increased developmental time or reduced weight. The time required for oviposition behavioral events was measured on different host‐plant species: B. rapa, B. napus, B. napus×S. alba, B. tournefortii Gouan., B. juncea (L.) Czern, B. carinata, B. nigra (L.) Koch., and S. alba. The early steps in the sequence were completed faster on more susceptible host plants (B. carinata, B. napus, and B. rapa) than on relatively resistant ones (B. tournefortii and B. juncea). Females explored pods of B. nigra and S. alba, but oviposition occurred only rarely on these species. There was no significant difference in the location on the pod on which oviposition occurred among the different plant species. Mean eggs laid per female weevil were highest on the B. napus×S. alba hybrid and lowest on B. nigra and S. alba.     

Effect of marking pheromone on clutch size in the Mediterranean fruit fly

Abstract Using acridine orange to selectively stain eggs, we showed that wild-collected female Mediterranean fruit flies (Ceratitis capitata Wiedemann) laid fewer eggs per clutch in fruit previously infested with eggs than in uninfested fruit. This effect is apparently attributable to marking pheromone deposited by females after oviposition: clutch size on fruit infested with eggs but free of marking pheromone was not statistically different from that on uninfested fruit. Clutch size on uninfested fruit on which marking pheromone was artificially transferred was significantly lower than that on uninfested and untreated fruit. Marking pheromone had a comparable though not statistically significant effect on the clutch size of females originating from a strain maintained in the laboratory for several hundred generations.     

Fine-tuning the composition of the cranberry weevil (Coleoptera: Curculionidae) aggregation pheromone

The cranberry weevil Anthonomus musculus Say is a key pest of highbush blueberries (Vaccinium corymbosum L.) and cranberries (Vaccinium macrocarpon Aiton) in the northeastern United States. Previous studies have reported A. musculus adult attraction to traps baited with the aggregation pheromone of the pepper weevil Anthonomus eugenii Cano, likely because these two weevils share similar pheromone blends that differ only in two components. The A. musculus aggregation pheromone contains (Z)-2-(3,3-dimethylcyclohexylidene) ethanol (Z grandlure II), (Z)-(3,3-dimethylcyclohexylidene) acetaldehyde (grandlure III), (E)-(3,3-dimethylcyclohexylidene) acetaldehyde (grandlure IV) and (E)-3,7-dimethyl-2,6-octadien-1-ol (geraniol); whereas A. eugenii produces a pheromone blend that includes (E)-2-(3,3-dimethylcyclohexylidene) ethanol (E grandlure II) and (E)-3,7-dimethyl-2,6-octadienoic acid (geranic acid) in addition to the four A. musculus pheromone components. Here, we hypothesized that differences in pheromone composition between these two species influence A. musculus adult attraction to its aggregation pheromone. To test this, we studied the response of A. musculus to its pheromone blend with and without E grandlure II and geranic acid, a commercial A. eugenii pheromone lure and a no-lure control in highbush blueberry and cranberry fields in New Jersey and Massachusetts, respectively. Regardless of crop type, A. musculus adults were more attracted to their four-component pheromone blend and the blend plus geranic acid than the commercial A. eugenii pheromone and the no-lure controls. The A. musculus pheromone blend plus E grandlure II and the A. eugenii pheromone blend also captured more A. musculus adults than the no-lure control but not compared to the commercial A. eugenii pheromone. Further analysis showed that A. musculus adults are significantly (~27%) less attracted to their pheromone blend if it contains E grandlure II, although the addition of geranic acid did not affect their response. These findings may help guide future efforts towards the development of behaviour-based tools to monitor and manage A. musculus.     

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

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

油菜烯醇酶基因的克隆与分析(英文)

烯醇酶(enolase)是糖酵解途径中的一个重要酶类,它能够催化磷酸甘油酸酯(2-PGA)生成磷酸烯醇丙酮酸酯(PEP)。我们通过RACE-PCR方法从油菜(Brassica napus L. )中克隆到了编码烯醇酶的全长基因。序列分析表明该基因全长cDNA为1624bp,拥有一个由444个氨基酸组成的开放读码框,所编码的蛋白质分子量为47.38kD,等电点为5.78。比较发现,油菜烯醇酶与已分离出的其他烯醇酶氨基酸序列有较高的同源性。Southern杂交结果显示烯醇酶以低拷贝形式在油菜基因组中存在。RT-PCR和Northern分析表明烯醇酶基因在100mmol/L盐浓度胁迫条件下表达量上升,而在低温诱导时表达量下降。该研究表明所克隆基因是植物烯醇酶基因家族的新成员。     

油菜烯醇酶基因的克隆与分析

烯醇酶(enolase)是糖酵解途径中的一个重要酶类,它能够催化磷酸甘油酸酯(2-PGA)生成磷酸烯醇丙酮酸酯(PEP).我们通过RACE-PCR方法从油菜(Brassica napus L.)中克隆到了编码烯醇酶的全长基因.序列分析表明该基因全长cDNA为1 624bp,拥有一个由444个氨基酸组成的开放读码框,所编码的蛋白质分子量为47.38 kD,等电点为5.78.比较发现,油菜烯醇酶与已分离出的其他烯醇酶氨基酸序列有较高的同源性.Southern杂交结果显示烯醇酶以低拷贝形式在油菜基因组中存在.RT-PCR和Northern分析表明烯醇酶基因在100 mmol/L盐浓度胁迫条件下表达量上升,而在低温诱导时表达量下降.该研究表明所克隆基因是植物烯醇酶基因家族的新成员.     

Phenotypic alterations and component analysis of seed yield in transgenic Brassica napus plants expressing the tzs gene

Cytokinins play an important role in plant development. We investigated the possibility that the nopaline Ti plasmid gene ( tzs ) from Agrobacterium tumefaciens could encode a protein able to participate in plant cytokinin production and lead to alterations in plant phenotype as a result of the expression of endogenous tzs . tzs was placed under the control of a heat‐inducible promoter from the Zea mays hsp70 gene. The expression of this fused gene was examined in transgenic Brassica napus plants. The tzs gene, which encodes the enzyme dimethylallyl transferase, was used as a cytokinin biosynthetic gene. The expression of the tzs gene was monitored by RNA hybridization and analysis of cytokinin content. Overproduction of cytokinin was observed even when the plants had not been heat‐shocked, and the plants displayed a reduced root system, increased height and branching, and delayed flowering. In addition, a significant increase in seed yield was observed in the transgenic plants, accounted for by increased number of seeds per silique and seed weight. The results suggest that increased levels of cytokinins, through the expression of tzs , are correlated with growth rather than with differentiation processes.     

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.     

One gene‐one name: the AvrLmJ1 avirulence gene of Leptosphaeria maculans is AvrLm5

Leptosphaeria maculans, the causal agent of blackleg disease, interacts with Brassica napus (oilseed rape, canola) and other Brassica hosts in a gene‐for‐gene manner. The avirulence gene AvrLmJ1 has been cloned previously and shown to interact with an unidentified Brassica juncea resistance gene. In this study, we show that the AvrLmJ1 gene maps to the same position as the AvrLm5 locus. Furthermore, isolates complemented with the AvrLmJ1 locus confer avirulence towards B. juncea genotypes harbouring Rlm5. These findings demonstrate that AvrLmJ1 is AvrLm5 and highlight the need for shared resources to characterize accurately avirulence and/or resistance genes.     

Effects of the triazole plant growth retardant BAS 111¨W on gibberellin levels in oilseed rape, Brassica napus

Three-week-old shoots of the spring oilseed rape cv. Petranova ( Brassica napus L. ssp. napus ) were found by combined gas chromatography-mass spectrometry to contain GA₁, GA₈, GA₁₅, GA₁₇, GA₁₉, GA₂₀, GA₂₄, GA₂₉, 3-epi-GA₁ and a previously uncharacterised C₁₉ dicarboxylic acid that is probably structurally related to GA₂₄. Shoots of the winter cultivar Belinda, harvested at the early flowering stage, contained the same GAs with the exception of the C₁₉ dicarboxylic acid and, in addition, GA₃₄ and GA₅₁ were identified. All material contained higher levels of GA₂₀ than of GA₁; the ratio of GA₁ to GA₂₀ was highest in shoots containing the largest proportion of young immature tissues. Soil treatment of cv. Petranova seedlings with the growth retardant BAS 111¨W [1-phenoxy-5,5-dimethyl-3-(1,2,4-triazol-1-yl)-hexan-4-ol] caused 80% reduction in height 18 days after treatment and the levels of all GAs were 20% or less that of control plants. Foliar treatment at the same dosage reduced height by 50% and caused an 85% or greater reduction in the concentrations of the GA₁ precursors GA₂₀, GA₁₉ and GA₄₄. However, the levels of GA₁, GA₈ and GA₂₉ were affected to a much smaller extent. Foliar application of BAS 111¨W to cv. Belinda 1 month after sowing resulted in only a 20% height reduction at flowering, but no uniform decrease in the concentrations of endogenous GAs at this stage.