Surface Of Cabbage Research Articles

Antiviral activity of Polygonum aviculare extract against murine norovirus as norovirus surrogate and its application in model food

Norovirus is a major cause of acute gastroenteritis, with vaccines or antiviral therapy yet to be approved. Polygonum aviculare is a medicinal plant with various physiological properties. In this study, the antiviral activity of Polygonum aviculare extract (PAE) was examined against murine norovirus (MNV-1), a human norovirus surrogate. Pre-treatment with PAE suppressed MNV-1, achieving a half-maximal inhibitory concentration (IC50) of 78.4 μg/mL. TEM images revealed viral morphological changes following PAE treatment, indicating the antiviral effect of PAE. Treatment with 100 and 200 μg/mL PAE for 1 h significantly reduced the temperature-dependent antiviral PAE activity at all temperatures. Time-of-addition test results also demonstrated PAE antiviral activity in cell pre-, co-, and post-treatments, with slightly higher activity detected upon cell pre-treatment. HPLC analysis identified avicularin and myricitrin peaks, and LC-QTOF/MS determined phenolic acids and flavonoids as the main constituents. Our findings confirmed the antiviral efficacy of myricetin and quercetin at concentrations of 50 and 100 μM in co-treatment experiments. Upon inoculating the cabbage surface with MNV-1, PAE treatment at 4 or 25 °C reduced MNV-1 plaque formation. Collectively, our findings suggest that PAE could effectively inactivate norovirus and demonstrate promising potential as a natural antiviral agent for food safety.

A study on antibiotic resistance gene degradation in fresh produce using peracetic acid combined with an ultraviolet-C light-emitting-diode

This study investigates the effects of peracetic acid (PAA)/ultraviolet-C light-emitting-diode (UVC-LED) treatment on the deactivation and degradation of the antibiotic-resistance gene (ARG). The deactivation rate constant for the ampicillin-resistance ( amp R ) gene encoded in plasmid pUC19 was measured using the transformation assay. The deactivation rate constant of pUC19 treated by PAA (10–50 ppm)/UVC-LED grew with an increasing concentration of PAA. At a PAA of 50 ppm, the deactivation rate constant reached its maximum: 0.16 cm 2 /mJ. Degradation rate constants for four amp R amplicons (192, 400, 603, and 851 bp) were obtained via the quantitative polymerase chain reaction (qPCR). The average degradation rate constant for the pUC19 plasmid was 1.45 × 10 −1 cm 2 /mJ with UVC-LED treatment, and 1.17 cm 2 /mJ with the PAA/UVC-LED treatment. Using PAA/UVC-LED, the deactivation rates for the amp R gene on the tomato and cabbage surfaces were 2.69 × 10 −2 cm 2 /mJ and 2.48 × 10 −2 cm 2 /mJ, respectively. Through color quality evaluation for each fresh produce confirmed that ARG could be effectively controlled using the PAA/UVC-LED treatment without affecting the color quality of fresh produce. In this study, the ARG control effect using the PAA/UVC-LED treatment was identified both in water and on fresh produce surfaces, which have a high risk of ARG exposure. • Deactivation effect of ARG in water by PAA/UVC-LED treatment according to PAA concentration was determined. • ARG degradation in water by PAA/UVC-LED treatment was measured using qPCR with different lengths of target amplicon. • Kinetics of deactivation and degradation of ARG treated by PAA/UVC-LED were analyzed and compared. • Control effect of PAA/UVC-LED treatment on ARG at the surface of fresh produce was determined.

Surface Defect Detection of Cabbage Based on Curvature Features of 3D Point Cloud

The dents and cracks of cabbage caused by mechanical damage during transportation have a direct impact on both commercial value and storage time. In this study, a method for surface defect detection of cabbage is proposed based on the curvature feature of the 3D point cloud. First, the red-green-blue (RGB) images and depth images are collected using a RealSense-D455 depth camera for 3D point cloud reconstruction. Then, the region of interest (ROI) is extracted by statistical filtering and Euclidean clustering segmentation algorithm, and the 3D point cloud of cabbage is segmented from background noise. Then, the curvature features of the 3D point cloud are calculated using the estimated normal vector based on the least square plane fitting method. Finally, the curvature threshold is determined according to the curvature characteristic parameters, and the surface defect type and area can be detected. The flat-headed cabbage and round-headed cabbage are selected to test the surface damage of dents and cracks. The test results show that the average detection accuracy of this proposed method is 96.25%, in which, the average detection accuracy of dents is 93.3% and the average detection accuracy of cracks is 96.67%, suggesting high detection accuracy and good adaptability for various cabbages. This study provides important technical support for automatic and non-destructive detection of cabbage surface defects.

Nano-EMB-SP improves the solubility, foliar affinity, photostability and bioactivity of emamectin benzoate.

Emamectin benzoate (EMB), a frequently used biopesticide, is poorly soluble in water, making it difficult to wet the leaf surface, is prone to degrade in sunlight and readily loses its bioactivity. Traditional methods such as organic solvent application, pH adjustment and addition of photoprotectants either increase the economic and environmental costs or barely achieve the desired goal. We hypothesized that nanotechnology could improve the solubility, foliar affinity, photostability and bioactivity of EMB. This research set out to prepare a nano-EMB solid powder (nano-EMB-SP) and test this hypothesis. Nano-EMB-SP was prepared using a self-emulsifying method combined with carrier solidification. The mean particle size and Polydispersity index (PDI) of nano-EMB-SP were 14.64 nm and 0.24, respectively. A scanning electron microscopy image showed that EMB nanoparticles were mainly spherical or ellipsoidal in shape. Without organic solvent, the aqueous solubility of EMB in nano-EMB-SP was 4500 mg L-1 , at least 14-fold that of the EMB soluble granule (EMB-SG), which is solubilized by pH adjustment. Excellent foliar affinity of EMB was achieved by nano-EMB-SP, which completely wet and penetrated the superhydrophobic surface of cabbage (Brassica oleracea L.) leaf. Without photoprotectants, up to 82% of EMB content can be protected from ultraviolet (UV) damage in nano-EMB-SP. The combined effects of excellent photostability and foliar affinity of nano-EMB-SP led to the bioactivity of EMB being almost unchanged before and after UV radiation. Nano-EMB-SP is an eco-friendly and efficient way to improve the solubility, foliar affinity, photostability and bioactivity of EMB. This research provides a good approach to improving the efficacy of poorly soluble and UV-sensitive pesticides. © 2022 Society of Chemical Industry.

Analysis of Growth Characteristics of Kimchi Cabbage Using Drone-Based Cabbage Surface Model Image

Cultivation soil is the basis for cabbage growth, and it is important to assess not only to provide information on how it affects the growth of vegetable crops but also for cultivation management. Until now, field cabbage surveys have measured size and growth variations in the field, and this method requires a lot of time and effort. Drones and sensors provide opportunities to accurately capture and utilize cabbage growth and variation data. This study aims to determine the growth stages based on drone remote estimation of the cabbage height and evaluate the impact of the soil texture on cabbage height. Time series variation according to the growth of Kimchi cabbage exhibits an S-shaped sigmoid curve. The logistic model of the growth curve indicates the height and growth variation of Kimchi cabbage, and the growth rate and growth acceleration formula of Kimchi cabbage can thus be derived. The curvature of the growth parameter can be used to identify variations in Kimchi cabbage height and its stages of growth. The main research results are as follows. (1) According to the growth curve, Kimchi cabbage growth can be divided into four stages: initial slow growth stage (seedling), growth acceleration stage (transplant and cupping), heading through slow growth, and final maturity. The three boundary points of the Kimchi cabbage growth curve are 0.2113 Gmax, 0.5 Gmax, and 0.7887 Gmax, where Gmax is the maximum height of Kimchi cabbage. The growth rate of cabbage reaches its peak at 0.5 Gmax. The growth acceleration of cabbage forms inflection points at 0.2113 Gmax and 0.7887 Gmax, and shows a variation characteristic. (2) The produced logistic growth model expresses the variation in the cabbage surface model value for each date of cabbage observation under each soil texture condition, with a high degree of accuracy. The accuracy evaluation showed that R2 was at least 0.89, and the normalized root-mean-square error (nRMSE) was 0.09 for clay loam, 0.06 for loam, and 0.07 for sandy loam, indicating a very strong regression relationship. It can be concluded that the logistic model is an important model for the phase division of cabbage growth and height variation based on cabbage growth parameters. The results obtained in this study provide a new method for understanding the characteristics and mechanisms of the growth phase transition of cabbage, and this study will be useful in the future to extract various types of information using drones and sensors from field vegetable crops.

Employing a fluorescent and colorimetric picolyl-functionalized rhodamine for the detection of glyphosate pesticide

The ongoing poisoning of agricultural products has pushed the security problem to become an important issue. Among them, exceeding the standard rate of pesticide residues is the main factor influencing the quality and security of agricultural products. Monitoring pesticide residues and developing simple, yet ultrasensitive detection systems for pesticide residues are urgently needed. In this study, we successfully developed a novel rhodamine derivative as fluorescent and colorimetric chemosensor R-G for the rapid, selective and ultrasensitive detection of glyphosate pesticide residue in aqueous solution. Through a Cu2+-indicator displacement strategy, glyphosate can displace an indicator (R-G) from a Cu2+-indicator complex due to its strong affinity to bind with Cu2+ to give a turn-on fluorescence and distinct color change. Moreover, a test strip was also fabricated to achieve a facile detection of glyphosate pesticide. To demonstrate the possibility of practical applications, glyphosate was detected on the surface of cabbage and in a spiked soil sample. The detection limit of 4.1 nM and the response time of 2 min indicate that the method is enough sensitive and rapid to detect the glyphosate residue at or below levels that pose a health risk.

Suppression of norovirus by natural phytochemicals from Aloe vera and Eriobotryae Folium

Human norovirus (HuNoV) is the major cause of viral foodborne diseases, but no effective medication is currently available. This study reported the anti-norovirus activity of the natural extracts of Aloe vera (AV) and Eriobotryae Folium (EF). Murine norovirus 1 (MNV-1), a surrogate virus of HuNoV, was preincubated with AV or EF extracts and then subjected to plaque assays in RAW 264.7 cells. Pretreatment of AV and EF extracts effectively suppressed the infectivity of MNV-1 with an estimated half-maximal inhibitory concentration (IC50) of 0.778 and 1.196 mg/mL, respectively. Cytotoxicity of AV and EF was not observed in RAW 264.7 cells. Anthraquinone compounds found in AV, aloin and aloe-emodin showed moderate antiviral effects. When fresh cabbage was inoculated with MNV-1 on the surface, AV and EF treatments as well as aloin and aloe-emodin at 25 °C for 30 min suppressed the MNV-1 infectivity on cabbage surface as effectively as in solution, suggesting the antiviral activity of AV and EF can be applied on food surface. These results showed AV and EF may serve as potentially effective and safe norovirus inhibitors due to their relatively low cytotoxicity, which allows them to be prepared as food-safe formulations.

Nanopartículas de prata: método alternativo de sanitização para couve minimamente processada1

RESUMO O processamento mínimo de hortaliças visa, basicamente, a estender a vida útil dos alimentos, o que depende de uma série de fatores, como, por exemplo, a sanitização, a qual é considerada etapa fundamental para a qualidade microbiológica do alimento. No entanto, os agentes antimicrobianos usuais reduzem a população microbiana em, no máximo, dois ciclos logarítmicos. Dessa forma, existe a necessidade de desenvolvimento de sanitizantes alternativos. O presente trabalho objetivou aumentar a inocuidade de couve minimamente processada, por meio de sanitização com nanopartículas de prata. Observou-se que as nanopartículas promoveram três reduções logarítmicas, ou seja, 99,9 % de redução, na população de Escherichia coli inoculada na superfície da couve. Quando comparadas com outros agentes antimicrobianos (dicloroisocianurato de sódio e hipoclorito de sódio), as nanopartículas mostraram-se mais eficientes na sanitização da couve minimamente processada, apresentando menor contagem de mesófilos aeróbios. Observou-se, também, que a superfície da couve apresenta características hidrofóbicas, resultando em maior propensão para adesão bacteriana, o que foi confirmado na avaliação da termodinâmica de adesão favorável para Staphylococcus aureus, Escherichia coli e Listeria innocua.

Effects of various pretreatments and drying methods on Salmonella resistance and physical properties of cabbage

The combined effects of pretreatment and drying methods on the resistance of Salmonella attached to vegetable surfaces as well as some physical properties, in terms of color and shrinkage, were investigated. Cabbage was used as a test vegetable and Salmonella Anatum was used as a test microorganism. Cabbage leaves were pretreated either by soaking in 0.5% (v/v) acetic acid for 5min, blanching in hot water for 4min or blanching with saturated steam for 2min prior to either hot air drying, vacuum drying (10kPa) or low-pressure superheated steam drying (10kPa) at 60°C. Based on an initial Salmonella contamination level of approximately 6.4logCFU/g, soaking in acetic acid, hot-water and steam blanching resulted in 1.6, 3.8 and 3.6logCFU/g reduction in the number of Salmonella, respectively. Drying without pretreatment could not completely eliminate Salmonella attached on the cabbage surfaces, while no Salmonella was detected on the pretreated samples at the end of the drying process. Volumetric shrinkage was not affected by the pretreatment and drying methods. Dried blanched samples exhibited greener and darker color than the dried acetic acid pretreated and untreated samples.

The impact of liquid drops on purple cabbage leaves (Brassica oleracea l. Var. Capitata)

Liquid drop impact on solid surfaces has been well studied due to its wide industrial application; however, there are very few studies of liquid drop impact on vegetable surfaces. The present work determined the drop impact pattern on purple cabbage leaves' surface and evaluated the influence of water drop viscosity and surface tension. The pattern of fluid impact on cabbage surface was evaluated by using a high-speed camera (1250 frames/s) at different impact heights for Weber numbers ranging from 100-800. The results showed that greater maximum spread factor was achieved with higher impact speed and lower surface tension drops. Viscosity had great influence on maximum spread factor and on dynamic impact. Maximum scaled spread factor ξmax was We1/4 for low viscosity water drops (water and Tween20-water). Fluid viscosity could be increased or surface tension decreased to prevent droplet rebound and keep them on purple cabbage surface by spraying them with an edible coating.

Attachment strength and biofilm forming ability of Bacillus cereus on green-leafy vegetables: Cabbage and lettuce

The present study was designed to investigate the ability of six Bacillus cereus strains to attach and form biofilm on cabbage and lettuce surfaces. These six strains were; a reference strain DSMZ 345 and five biofilm-producing strains (aquatic strains; TUB8, TUB30, TUB31, TUB32 and TUB33) isolated from drinking-water distribution network. Hydrophobicity, biofilm formation ability, attachment strength (SR) of spores and vegetative cells of the six B. cereus strains were also determined. Due to their high hydrophobicity, spores of all strains had high ability to attach polystyrene and did not affect by dilution of tryptone soy broth (TSB, 1:20 v/v) in the in vitro experiment. Significant (p < 0.05) enhancement in vitro biofilm formation by vegetative cells of B. cereus was recorded in the diluted TSB. The highest biofilm formation on cabbage and lettuce surfaces was obtained by spores and vegetative cells of all tested strains on the 4th hour of the incubation period. These populations were significantly (p < 0.05) increased by elongating incubation time from 4 h to 24 h except DSMZ 345 and TUB8. Biofilm formation behavior obtained by B. cereus spores and vegetative cells on the polystyrene surface was different compared with that recorded on produce surface. The SR of both spores and vegetative cells of the studied strains to the lettuce surface was higher than that of the cabbage surface. The hydrophobicity, biofilm formation and SR of spores and vegetative cells of the biofilm-producing strains were higher than that of the reference strain DSMZ 345. Scanning electron microscopy (SEM) exposed random distribution of cells either on the surface or cut edge, without clear obvious affinity for the surface structures. Increasing in the presence of large clusters of cells on leaf surfaces was demonstrated after 4 and 24 h.In conclusion, use of aquatic environmental isolates is more useful for studying biofilm formation than the reference strain. Lettuce surface supported the attachment of B. cereus spores and vegetative cells compared with the cabbage surface. Further investigations are required to improve our knowledge of biofilm formation mechanisms by the human pathogenic microorganisms, especially by using the environmental and clinical isolates. To ensure safety level of green-leafy vegetables, biofilm formation after harvest should be considered as critical control point during handling of these vegetables.

Thermal resistance of Salmonella enterica serovar Anatum on cabbage surfaces during drying: Effects of drying methods and conditions

The effects of selected drying methods, i.e., hot air drying, vacuum drying and low-pressure superheated steam drying (LPSSD), on the heat resistance of Salmonella attached on vegetable surface, which are data that have never been reported elsewhere, were investigated at drying temperatures of 50-70 °C; vacuum drying and LPSSD were carried out at an absolute pressure of 10 kPa. The selected Salmonella serovar, i.e., S. Anatum, was used as a test organism. Cabbage was used as a vegetable model to represent uneven natural surface. The results showed that drying methods had a significant effect on the drying kinetics as well as the destruction rate of Salmonella. Higher drying temperatures resulted in higher destruction rates of S. Anatum. Hot air drying was noted to be the slowest drying process, while vacuum drying and LPSSD could be used to shorten the drying time. By considering the reduction in the number of Salmonella at the end of drying, LPSSD is recommended as it has proved to yield the highest degree of S. Anatum inactivation.

Differences in attachment of Salmonella enterica serovars to cabbage and lettuce leaves

This study investigated the ability of five Salmonella enterica serovars to attach to and colonize intact and cut lettuce (Iceberg, Romaine) and cabbage surfaces. Biofilm formation and attachment of Salmonella serovars to intact and cut leaves were determined. Populations of loosely and strongly attached Salmonella were obtained to calculate the attachment strength ( S R). Biofilm formation, as determined by microtiter plate assay, varied with strain and growth medium used. Salmonella Tennessee and S. Thompson produced stronger biofilms compared to S. Newport, S. Negev, and S. Braenderup. Biofilm formation was also stronger when Salmonella spp. were grown in diluted TSB (1:10). S. Tennessee, which produced strong biofilms, attached to produce surfaces at significantly higher numbers than the populations of S. Negev. Overall, S. Tennessee displayed more biofilm formation in vitro and attached more strongly to lettuce than other serovars. All Salmonella serovars attached rapidly on intact and cut produce surfaces. Salmonella spp. attached to Romaine lettuce at significantly higher numbers than those attached to Iceberg lettuce or cabbage. Salmonella attached preferentially to cut surface of all produce; however, the difference between Salmonella populations attached to intact and cut surfaces was similar ( P > 0.05). Salmonella attachment to both intact and cut produce surfaces increased with time. The overall attachment strength of Salmonella was significantly lower on cabbage (0.12) followed by Iceberg (0.23) and Romaine lettuce (0.34). Cabbage, intact or cut, did not support attachment of Salmonella as well as Romaine lettuce. Understanding the attachment mechanisms of Salmonella to produce may be useful in developing new intervention strategies to prevent produce outbreaks.

Effects of Acetic Acid Pretreatment and Hot Air Drying on Resistance of Salmonella on Cabbage Slices

The heat resistance of Salmonella anatum inoculated onto the surface of cabbage slices as affected by acetic acid pretreatment (0.5–1.5% v/v) and hot air drying at 50–60°C was investigated. Approximately 1.5 log10 of Salmonella numbers was reduced after soaking the vegetables in acetic acid solution. The inhibitory effect of acetic acid on the bacteria was more pronounced during drying. The heat resistance of Salmonella on the cabbage surface treated with acetic acid decreased considerably compared with untreated cabbage. Moreover, the vegetable treated with higher acetic acid concentration resulted in a higher degree of acid injury and hence increased the susceptibility to heat during drying. The results revealed that acetic acid pretreatment may be used as an additional processing step to increase the safety margin of dried vegetable products.

Effects of Drying Temperature and Surface Characteristics of Vegetable on the Survival of Salmonella

The heat resistance of Salmonella Anatum inoculated on the surface of a model vegetable as affected by hot-air drying temperature (50 to 70 degrees C) and surface characteristics was determined in this study. Cabbage was selected as a model vegetable to demonstrate the effect of topographical feature of vegetable surface on the Salmonella attachment ability. An image analysis technique was developed to monitor the change of cabbage surface during drying and the specific surface characteristics were described in terms of the roughness factor (R). It was found that the water activity of the vegetable decreased while R-value increased with longer drying time and higher drying temperature. However, the changes of both parameters during drying did not show a significant effect on the susceptibility of Salmonella attached on the cabbage surface. Drying temperature was found to be a major factor influencing the heat resistance of Salmonella during drying.

Determination of volatilization (dissipation) and secondary deposition of pesticides in a field study using passive dosimeters

The volatilization and secondary deposition of the herbicides prosulfocarb and pendimethalin were measured using passive dosimeters with Chinese cabbage and soil as collective material. Passive dosimeters were placed in the field before spraying and at three distances downwind after spraying. The volatilization of prosulfocarb and pendimethalin determined as dissipation was 80 and 60% of the applied amount from the cabbage surface, while no significant loss was measured from soil surfaces after 48 h. The secondary deposition of prosulfocarb and pendimethalin 25 m from the spray zone was 2 and 4% on the leaf surface as well as on the soil surface. At 5 m distance, 6 and 10% of the field dose of prosulfocarb and pendimethalin could be determined on dosimeters with leaves, and 4 and 8% of the field dose could be determined on soil surfaces.

Strain and growth temperature influence Listeria spp. attachment to intact and cut cabbage

Twenty four Listeria strains representing three different species and two serotypes of L. monocytogenes were investigated for their ability to attach to and colonize cabbage tissue. All strains exhibited a preference to attach to cut tissues compared to the intact leaf surfaces. Most strains attached to cut surfaces at levels 1.0 to 1.2 log CFU/cm 2 above numbers on intact tissue. Although all strains demonstrated the ability to colonize both intact and cut surfaces, some strains consistently exhibited higher levels of attachment. This attribute was independent of species or serotype. Scanning electron microscopy (SEM) revealed the presence of increased cell numbers on the cut edges with numerous cells located within folds and crevices. The distribution of cells found on the intact surfaces appeared to be randomly distributed with no apparent affinity for specialized surface structures such as stomata. SEM analysis also revealed the increased presence of large clusters of cells on leaf surfaces after 4 and 24 h. These cell aggregates appeared to be in the early stages of biofilm development. L. moncytogenes strain Scott A was used to examine the effect of prior growth temperature on attachment at 10 °C. Cells attached to intact cabbage surfaces within 5 min of exposure, with numbers reaching 4.3 log CFU/cm 2 for cells grown at 22 °C and 37 °C, and 3.8 log CFU/cm 2 for 10 °C cultures. The culture growth temperature was shown to significantly ( P < 0.05) affect the strength of attachment ( S R values) during the first 4 h of exposure to intact surfaces, as cells cultivated at 37 °C were more easily removed from leaf surfaces than those cultivated at 10 °C or 22 °C. However, after 24 h binding was not significantly different between temperatures ( P > 0.05) where more than 80% of cells, regardless of cultivation temperature, remained attached to the leaf surfaces following successive washes. Irrespectively of prior growth temperature, increasing exposure time to the cabbage resulted in increased attached cell numbers as well as increased binding strength. The increase in development of cell clusters and early biofilm structures may explain the decreased efficiency over time in removal of cells from the cabbage surfaces. The information presented in this study may have important implications for produce handling practices and the implementation of wash regimes intended to remove microorganisms from edible plant surfaces.

Translocation and translaminar bioavailability of two neonicotinoid insecticides after foliar application to cabbage and cotton

A laboratory study was undertaken to investigate the leaf systemic properties and the translaminar aphicidal activity of two commercialised neonicotinoid (chloronicotinyl) insecticides. For that purpose [14C]imidacloprid was subjected to uptake and translocation studies in cabbage and cotton after foliar application. Foliar penetration and short-term translocation patterns of imidacloprid were similar in both plant species. Nevertheless imidacloprid penetrated twice as much into cabbage leaves as it did into cotton leaves. It showed a comparable translaminar behaviour and was entirely translocated acropetally, indicating its well-known xylem mobility. The translaminar and acropetal movement of imidacloprid and acetamiprid were quantified by simple laboratory bioassays using the green peach aphid, Myzus persicae (Sulzer), and the cotton aphid, Aphis gossypii (Glover), as typical homopteran pests for cabbage and cotton, respectively. A single dose (7.5 micrograms AI per leaf) applied to the upper leaf surface of cabbage and cotton was tested against aphids feeding on the lower leaf surface both close to and distant from the site of application 1, 5 and 12 days after treatment. The translaminar residual activity of imidacloprid on cabbage leaves was superior to that of acetamiprid, whereas its translaminar efficacy against A gossypii on cotton was inferior to that of acetamiprid. However, oral ingestion bioassays using an artificial double membrane feeding system revealed no significant differences in intrinsic activity between the two neonicotinoids tested.

NEONATE Plutella xylostella RESPONSES TO SURFACE WAX COMPONENTS OF A RESISTANT CABBAGE (Brassica oleracea)

Behavior of neonate Plutella xylostella was observed and quantified during the first 5 min of contact with cabbage surface waxes and surface wax components deposited as a film (60 μg/cm2) on glass. The time larvae spent biting was greater and the time walking was less on waxes extracted from the susceptible cabbage variety, Round-Up, than on an insect-resistant glossy-wax breeding line, NY 9472. The waxes of both cabbage types were characterized and some of the compounds present at higher concentrations in the glossy waxes were tested for their deterrent effects on larvae by adding them to the susceptible waxes. Adding a mixture of four n-alkane-1-ols or a mixture of α- and β-amyrins to wax from susceptible cabbage reduced the number of insects biting and, among those biting, reduced the time biting and increased the time walking in a dose-dependent manner. Among individual n-alkane-1-ols, adding C24 or C25 alcohols reduced the number of insects biting but only adding C25 alcohol reduced the time spent biting among those insects that initiated biting. Adding a mixture of five n-alkanoic acids did not affect biting, but increased the time spent palpating and decreased walking time. Among individual n-alkanoic acids, only adding C14 significantly increased the time palpating. If the observed responses were gustatory, the results indicate that some primary wax components, including specific long-chain alkyl components, have allelochemical activity influencing host acceptance behavior by a lepidopteran larva.

Leaf surface compound fromBrassica oleracea (Cruciferae) induces oviposition byPieris brassicae (Lepidoptera: Pieridae)

Chemicals present on the surface of cabbage (Brassica oleracea L.) leaves were extracted by dipping these leaves for 3 s in dichloromethane followed by a 3 s dip in methanol. When offered in dual choice bioassays using green paper cards as a substrate, the methanol extract stimulated oviposition activity byPieris brassicae L. (Lepidoptera: Pieridae) females. The oviposition stimulant was isolated using medium pressure liquid chromatography, reversed-phase HPLC, ion-pair HPLC and ion exchange chromatography. Using1H-NMR spectroscopy, the stimulant could be identified as glucobrassicin (3-indolyl-methyl-glucosinolate). When pure glucobrassicin was offered at a dose identical to that in the crude methanol extract, butterflies did not discriminate between these two substrates in a dual choice test. It is argued that a high sensitivity for indole glucosinolates as host recognition factors may confer an adaptive value for these specialist crucifer feeders. The nutritional significance of their precursor tryptophan and the non-volatile nature of the aglycones formed upon enzymic hydrolysis in damaged tissues are proposed as properties of indole glucosinolates that contribute to this possible adaptive advantage.