Chinese Cabbage Leaf Research Articles

Transcriptomic analyses to summarize gene expression patterns that occur during leaf initiation of Chinese cabbage.

In Chinese cabbage, rosette leaves expose their adaxial side to the light converting light energy into chemical energy, acting as a source for the growth of the leafy head. In the leafy head, the outer heading leaves expose their abaxial side to the light while the inner leaves are shielded from the light and have become a sink organ of the growing Chinese cabbage plant. Interestingly, variation in several ad/abaxial polarity genes is associated with the typical leafy head morphotype. The initiation of leaf primordia and the establishment of leaf ad/abaxial polarity are essential steps in the initiation of marginal meristem activity leading to leaf formation. Understanding the molecular genetic mechanisms of leaf primordia formation, polar differentiation, and leaf expansion is thus relevant to understand leafy head formation. As Brassica's are mesa-hexaploids, many genes have multiple paralogues, complicating analysis of the genetic regulation of leaf development. In this study, we used laser dissection of Chinese cabbage leaf primordia and the shoot apical meristem (SAM) to compare gene expression profiles between both adaxial and abaxial sides and the SAM aiming to capture transcriptome changes underlying leaf primordia development. We highlight genes with roles in hormone pathways and transcription factors. We also assessed gene expression gradients along expanded leaf blades from the same plants to analyze regulatory links between SAM, leaf primordia and the expanding rosette leaf. The catalogue of differentially expressed genes provides insights in gene expression patterns involved in leaf development and form a starting point to unravel leafy head formation.

PLS-DA model for accurate identification of Chinese cabbage leaf color based on multispectral imaging

PLS-DA model for accurate identification of Chinese cabbage leaf color based on multispectral imaging

Single-cell transcriptome reveals dominant subgenome expression and transcriptional response to heat stress in Chinese cabbage

BackgroundChinese cabbage (Brassica rapa ssp. pekinensis) experienced a whole-genome triplication event and thus has three subgenomes: least fractioned, medium fractioned, and most fractioned subgenome. Environmental changes affect leaf development, which in turn influence the yield. To improve the yield and resistance to different climate scenarios, a comprehensive understanding of leaf development is required including insights into the full diversity of cell types and transcriptional networks underlying their specificity.ResultsHere, we generate the transcriptional landscape of Chinese cabbage leaf at single-cell resolution by performing single-cell RNA sequencing of 30,000 individual cells. We characterize seven major cell types with 19 transcriptionally distinct cell clusters based on the expression of the reported marker genes. We find that genes in the least fractioned subgenome are predominantly expressed compared with those in the medium and most fractioned subgenomes in different cell types. Moreover, we generate a single-cell transcriptional map of leaves in response to high temperature. We find that heat stress not only affects gene expression in a cell type-specific manner but also impacts subgenome dominance.ConclusionsOur study highlights the transcriptional networks in different cell types and provides a better understanding of transcriptional regulation during leaf development and transcriptional response to heat stress in Chinese cabbage.

Uptake and translocation of both legacy and emerging per- and polyfluorinated alkyl substances in hydroponic vegetables

The extensive use of per- and polyfluorinated alkyl substances (PFASs) and their substitutes has resulted in their frequent detections in environmental matrices. However, limited information is known about their uptake into vegetables and health risk through diet, particularly for those emerging alternatives. In this study, a total of 17 PFASs (namely 12 legacy PFASs and 5 of their alternatives) were compared for their accumulation into four staple vegetables (lettuce, Chinese cabbage, chrysanthemum coronarium, and cucumber) in hydroponic system with single PFAS concentration being 10 μg/L, except for 8:2 chlorinated polyfluoroalkyl ether sulfonate (Cl-PFESA) as 0.5 μg/L. The sum concentrations of 17 PFASs in edible parts were in the order of Chinese cabbage leaf (13,456 ng/g) > lettuce leaf (5996 ng/g) > cucumber fruit (4115 ng/g) >chrysanthemum coronarium stem (3999 ng/g). For perfluorooctanoate acid (PFOA) and its alternatives, hexafluoropropylene oxide trimer acid (HFPO-TA) preferentially accumulated in roots than PFOA with root concentration factors being 35.7–99.9. Translocation to edible parts was more remarkable for hexafluoropropylene oxide dimer acid (HFPO-DA) compared with PFOA in lettuce and cucumber. For perfluorooctanesulfonate acid (PFOS) and its alternatives, roots of all the four vegetables were found to more readily accumulate 8:2 Cl-PFESA than PFOS, but 8:2 Cl-PFESA was hardly translocated to the aerial parts. Significantly (p < 0.05) higher edible concentrations of 8:2 and 6:2 fluorotelomer sulfonic acids (FTSA) than that of PFOS were observed for cucumber.

Transcriptome sequencing and gas chromatography–mass spectrometry analyses provide insights into β-caryophyllene biosynthesis in Brassica campestris

Sesquiterpenes are important defensive secondary metabolites and aroma components. However, limited information is available on the mechanism of sesquiterpene formation and composition in the non-heading Chinese cabbage (NHCC) leaf. Therefore, headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC–MS) combined with transcriptome analysis was used to study the mechanism of volatile organic compound formation. A total of 26 volatile organic compounds were identified in two NHCC cultivars ‘SZQ’ and ‘XQC’ and their F1 hybrids. Among these, sesquiterpene β-caryophyllene was identified only in ‘XQC’ and F1. Five genes encoding caryophyllene synthase were identified. The candidate β-caryophyllene synthase genes BcTPSa11 and BcTPSa21 had high expression levels only in ‘XQC’ and F1. In addition, several transcription factors of MYB-related, MYB, bHLH, and AP2/ERF families were identified by co-expression, suggesting that they regulate β-caryophyllene biosynthesis. Our results provide a molecular basis for sesquiterpene biosynthesis as well as insights into the regulatory network of β-caryophyllene in NHCC.

The Adaxial/Abaxial Patterning of Auxin and Auxin Gene in Leaf Veins Functions in Leafy Head Formation of Chinese Cabbage.

Leaf curling is an essential prerequisite for the formation of leafy heads in Chinese cabbage. However, the part or tissue that determines leaf curvature remains largely unclear. In this study, we first introduced the auxin-responsive marker DR5::GUS into the Chinese cabbage genome and visualized its expression during the farming season. We demonstrated that auxin response is adaxially/abaxially distributed in leaf veins. Together with the fact that leaf veins occupy considerable proportions of the Chinese cabbage leaf, we propose that leaf veins play a crucial supporting role as a framework for heading. Then, by combining analyses of QTL mapping and a time-course transcriptome from heading Chinese cabbage and non-heading pak choi during the farming season, we identified the auxin-related gene BrPIN5 as a strong candidate for leafy head formation. PIN5 displays an adaxial/abaxial expression pattern in leaf veins, similar to that of DR5::GUS, revealing an involvement of BrPIN5 in leafy head development. The association of BrPIN5 function with heading was further confirmed by its haplo-specificity to heading individuals in both a natural population and two segregating populations. We thus conclude that the adaxial/abaxial patterning of auxin and auxin genes in leaf veins functions in the formation of the leafy head in Chinese cabbage.

Analysis of Glucosinolate Content and Metabolism Related Genes in Different Parts of Chinese Flowering Cabbage.

Glucosinolates (GSLs) are important secondary metabolites that play important defensive roles in cruciferous plants. Chinese flowering cabbage, one of the most common vegetable crops, is rich in GSLs and thus has the potential to reduce the risk of cancer in humans. Many genes that are involved in GSL biosynthesis and metabolism have been identified in the model plant Arabidopsis thaliana; however, few studies investigated the genes related to GSL biosynthesis and metabolism in Chinese flowering cabbage. In the present study, the GSL composition and content in three different organs of Chinese flowering cabbage (leaf, stalk, and flower bud) were determined. Our results showed that the total GSL content in flower buds was significantly higher than in stalks and leaves, and aliphatic GSLs were the most abundant GSL type. To understand the molecular mechanisms underlying the variations of GSL content, we analyzed the expression of genes encoding enzymes involved in GSL biosynthesis and transport in different tissues of Chinese flowering cabbage using RNA sequencing; the expression levels of most genes were found to be consistent with the pattern of total GSL content. Correlation and consistency analysis of differentially expressed genes from different organs with the GSL content revealed that seven genes (Bra029966, Bra012640, Bra016787, Bra011761, Bra006830, Bra011759, and Bra029248) were positively correlated with GSL content. These findings provide a molecular basis for further elucidating GSL biosynthesis and transport in Chinese flowering cabbage.

A NAC transcription factor BrNAC087 is involved in gibberellin-delayed leaf senescence in Chinese flowering cabbage

Phytohormone gibberellins (GAs) regulate leaf senescence. A global view of the regulatory pathways associated with GA-mediated inhibition of leaf senescence, especially in economically important leafy vegetables such as Chinese flowering cabbage, remains unclear. In this study, exogenous supply of gibberellin (GA3) delayed postharvest Chinese flowering cabbage leaf senescence. By comparative transcriptome analysis of leaf tissue, a total of 4682, 5059, and 2362 differentially expressed genes (DEGs) were identified between the comparison of 0d (cabbages at the harvest day) and CK3d (control cabbages at day 3 post-harvest), 0d and GA3d (GA3-treated cabbages at day 3 post-harvest), and CK3d and GA3d, respectively. Further analysis of identified DEGs involved in chlorophyll and GA degradation during leaf senescence, and the activity of chlorophyll catabolic genes (CCGs) BrPPH and BrRCCR, and bioactive GA degradation gene BrGA2ox1, was greatly reversed with GA3 application during leaf senescence. More importantly, a NAC transcription factor (TF), BrNAC087, was found to be associated with leaf senescence. BrNAC087 is a nuclear localized gene with transcriptional activity, highly expressed during senescence but downregulated by GA3. Significantly, BrNAC087 positively regulated BrPPH, BrRCCR and BrGA2ox1 expression by binding to NAC-binding sequences in their promoters in vitro and in vivo. These findings collectively provide evidence for a new molecular regulatory pathway explaining, at least in part, a mechanistic basis for gibberellin-mediated leaf senescence inhibition in postharvest Chinese flowering cabbage.

Qualitative Analysis of Lambda-Cyhalothrin on Chinese Cabbage Using Mid-Infrared Spectroscopy Combined with Fuzzy Feature Extraction Algorithms

Excess pesticide residues on cabbage are harmful to humans. In this study, we propose an innovative strategy for a quick and nondestructive qualitative test of lambda-cyhalothrin residues on Chinese cabbage. Spectral profiles of Chinese cabbage leaf samples with different concentrations of surface residues of lambda-cyhalothrin were collected with an Agilent Cary 630 FTIR Spectrometer. Standard normal variate (SNV), multiplicative scatter correlation (MSC), and principle component analysis (PCA) were utilized to preprocess the spectra. Then, fuzzy Foley-Sammon transformation (FFST), fuzzy linear discriminant analysis (FLDA), and fuzzy uncorrelated discriminant transformation (FUDT) were employed to extract features from the spectra data. Finally, k-nearest neighbor (kNN) was applied to classify samples according to the concentration of lambda-cyhalothrin residue. The highest identification accuracy rates of FFST, FLDA, and FUDT were 100%, 97.22%, and 100%, respectively. FUDT performed the best considering the combination of accuracy rate and required computing time. We believe that mid-infrared spectroscopy combined with fuzzy uncorrelated discriminant analysis is an effective method to accurately and quickly conduct qualitative analyses of lambda-cyhalothrin residues on Chinese cabbages. This method may have applications in other crops and other pesticide residues.

Involvement of BrNAC041 in ABA-GA antagonism in the leaf senescence of Chinese flowering cabbage

Abstract Phytohormone abscisic acid (ABA) and gibberellins (GAs) are well-known to be antagonistic in mediating plant development processes. However, the underlying molecular mechanism of this antagonism in leaf senescence of economically important leafy vegetables is largely unclear. In this study, we report that a Chinese flowering cabbage NAC transcription factor BrNAC041, mediated the ABA-antagonized GA accumulation in ABA-induced leaf senescence. Exogenous ABA treatment accelerated Chinese flowering cabbage leaf senescence, with decreasing maximum quantum yield (Fv/Fm) and total chlorophyll content, as well as up-regulating the expressions of senescence-associated genes. Notably, ABA treatment enhanced endogenous ABA accumulation and reduced GA3 level in senescing leaves. Consistently, down-regulation of one ABA catabolism gene BrCYP707A3 and two GA biosynthesis genes BrKAO2 and BrGA20ox2 was observed following ABA application. Furthermore, a NAC transcription factor, BrNAC041, a homolog of Arabidopsis ANAC041, was isolated and characterized. BrNAC041 was senescence-/ABA-up regulated and localized in the nucleus acting as a transcriptional repressor. Further in vitro and in vivo experiments demonstrated that BrNAC041 repressed BrCYP707A3, BrKAO2 and BrGA20ox2 transcription by targeting their promoters via the NAC-binding sequence (NACBS). Collectively, our findings reveal BrNAC041 as a novel regulator involved in the antagonism of ABA on GA in the leaf senescence of Chinese flowering cabbage, through the transcriptional repression of ABA catabolic and GA biosynthetic genes.

Identification of source-sink tissues in the leaf of Chinese cabbage (Brassica rapa ssp. pekinensis) by carbohydrate content and transcriptomic analysis.

A leaf of Chinese cabbage (Brassica rapa ssp. pekinensis) is composed of a photosynthetic blade and a non-photosynthetic large midrib; thus each leaf contains both source and sink tissues. This structure suggests that, unlike in other plants, source-sink metabolism is present in a single leaf of Chinese cabbage. This study was designed to identify the transport route of photosynthetic carbon and to determine whether both source and sink tissues were present in a leaf. Plant samples were collected diurnally. Their carbohydrate contents were measured, and a genome-wide transcriptome analysis was performed using the Br300K microarray. Expression profiles of selected genes were validated using qRT-PCR analysis. The presence of two contrasting tissues (blade as source and midrib as sink) in a leaf was demonstrated by (1) diurnal distribution patterns of starch and sucrose content; (2) Gene Ontology (GO) enrichment analysis of microarray data; (3) expression profiles of photosynthetic and sucrose biosynthetic genes; and (4) expression patterns of a variety of sugar transporter genes. Source and sink tissues were both present in Chinese cabbage leaves, but the midrib functioned as a sink tissue as well as a site exporting to roots and other sink tissues. Function of most genes discriminating between source and sink tissue appeared to be regulated largely at the post-transcriptional level, not at the transcriptional level.

Transcriptome-Wide Identification and Characterization of Circular RNAs in Leaves of Chinese Cabbage (Brassica rapa L. ssp. pekinensis) in Response to Calcium Deficiency-Induced Tip-burn

Circular RNA (circRNA) is a newly discovered non-coding RNA, which play significant roles in the function and transcriptional regulation of microRNA. To date, in Chinese cabbage, the functional characteristic of circRNAs in response to calcium deficiency-induced tip-burn have not been reported. In this study, 730 circRNAs were isolated from Chinese cabbage leaves, of which 23 and 22 were differentially expressed in different calcium deficiency stages compared with the control. Forty-six host genes of the differentially expressed circRNAs were identified, and one circRNA was found to act as miRNAs sponges. Based on the functional analysis of host genes and target mRNAs of the corresponding miRNAs, the identified circRNAs might participated in response to stimulus, electron carrier activity, ATPase activity, cell wall metabolism, transcription factors and plant hormone signal transduction. ABF2, a positive regulator of the abiotic stress response in the abscisic acid (ABA) pathway, may play a role in calcium deficiency tolerance through a circRNA regulatory pathway. Correspondingly, the concentration of ABA is also increased during the Ca2+ deficiency stress. Our results suggest that circRNAs participate in a broad range of biological processes and physiological functions in the response to calcium deficiency-induced tip-burn and provide a basis for further studies of the biological roles that circRNAs play in the plant stress response.

耐热青梗小白菜和黑叶小白菜品种筛选

耐热青梗小白菜和黑叶小白菜品种筛选

Transfer of a cyanobacterial neurotoxin, β-methylamino-l-alanine from soil to crop and its bioaccumulation in Chinese cabbage

Most cyanobacteria can synthesize the notorious neurotoxin β-methylamino-l-alanine (BMAA) that is transferred and bioaccumulated through natural food webs of aquatic ecosystems and ultimately arises the potential human health risks by the consumption of BMAA-contaminated aquatic products. Fertilization of cyanobacterial composts in farmlands may also lead to BMAA contamination in soil and its possible transfer and bioaccumulation within major crops, thereby threatening human health. In this study, we first detected a high level of BMAA (1.8–16.3 μg g−1) in cyanobacterial composts. In order to assess the health risks from cyanobacterial composts, we planted Chinese cabbage, a favourite vegetable in China, in BMAA-contaminated soil (4.0 μg BMAA/g soil) and detected the levels of free and protein-associated BMAA in soil and crop organs during the whole growth cycle by HPLC-MS/MS, respectively. Our results demonstrated that BMAA indeed transferred from soil to root, stem and leaf of Chinese cabbage during the growth cycle. The BMAA level finally accumulated in the edible portions was much higher than the initial level in soil, including 13.82 μg g−1 in leaf and 4.71 μg g−1 in stem. The discovery of the neurotoxin BMAA in this vegetable, an ending in human consumption, not only provides a BMAA transfer pathway in farmland ecosystems, but also is alarming and requires attention due to the potential risk of cyanobacterial composts to human health.

Effect of Fertilizers Using Ferro-Nickel Slag on Chinese Cabbage Growth and Soil Chemical Properties

This study was conducted to investigate the application effect of fertilizer using ferro-nickel slag on Chinese cabbage cultivations in upland field. Field experiments were designed with control (Cn), ferronickel slag soil conditioner fertilizer (FNS SCF), ferronickel magnesium fertilizer (FNS MGF), and conventional silicate fertilizer (CSF) treatments. Chinese cabbage fresh weight, length, leaf width, and leaf number during the harvest period showed high growth at the FNS SCF and FNS MGF treatment area. Compared to the control group, the FNS SCF and CSF treatment areas showed 26% heavier fresh weight. During the harvest period, compared to the growing period, the contend of inorganic components in Chinese cabbage seemed to decrease, but Na2O was increasing in the root. The T-N showed pretty high in the outer leaf at the CSF and FNS MGF treatment areas. Heavy metal content of Chinese cabbage during the harvest period, compared to the growth period, showed overall decrease. During the harvest, the Ni content in the outer leaf showed highest at FNS MGF, in the inner leaf highest at Cn treatment area, and in the root highest at the FNS SCF treatment area. Growth properties of Chinese cabbage in harvest period. Treatment† Fresh weight (g plant-1) Head width Head height Head tightness Plant weight Head weight (cm) (cm) Cn 3.92a‡ 2.41a 17.0a 27.6ab 10.73a FNS SCF 4.88b 3.12b 18.7b 28.9b 13.00b CSF 4.94b 3.10b 18.7b 28.4ab 12.97b FNS MGF 4.33ab 2.73ab 18.0ab 26.8a 11.95ab †Cn, control; FNS SCF, ferronickel slag soil conditioner fertilizer; CSF, conventional silicate fertilizer; FNS MGF, ferronickel magnesium fertilizer.

A Method to Forecast the Combustion Characteristics of Biomass Waste: Based on a Custom-Designed Macro-TGA

The combustion characteristics of five model biomass components (cellulose, hemicellulose, lignin, pectin and starch) and four real biomass waste (poplar stem, Chinese cabbage, orange peel and ginkgo leaf) were evaluated in a custom-designed macro-TGA at three different heating rates. With the increase in the heating rates, the peaks of the various samples in DTG curves shifted to the high temperature region. All main peaks temperature of 20 °C/min were 40–55 °C higher than that of 10 °C/min and 30–40 °C lower than that of 30 °C/min in the combustion on macro-TGA, except for lignin. Furthermore, the pseudo-component model based on the macro-TG curves simulation was analyzed and three/five components simulating results were compared. The overlap ratios between actual macro-TG curves and fitting curves by different methods and heating rates were all higher than 0.979 to suggest that biomass waste combustion characteristics could be well simulated by its components, and the three and five components fitting effects differed for the specific material because of its composition. The TG curves of real biomasses at one heating rate were used to gain the fitting TG curves of other heating rates and forecast their combustion characteristics. The forecast method showed good results but they varied among the biomasses. It might be due to their composition and the interactions among the biomass model components. The pseudo-component model provides a potential method to forecast the combustion characteristics of biomass waste in the MSW incineration.

Characterization of a Transcriptional Regulator, BrWRKY6, Associated with Gibberellin-Suppressed Leaf Senescence of Chinese Flowering Cabbage.

Phytohormone gibberellin (GA) and plant-specific WRKY transcription factors (TFs) are reported to play important roles in leaf senescence. The association of WRKY TFs with GA-mediated leaf senescence of economically important leafy vegetables like Chinese flowering cabbage, however, remains largely unknown. In this study, we showed that exogenous application of GA3 suppressed Chinese flowering cabbage leaf senescence, with GA3-treated cabbages maintaining a higher level of maximum quantum yield (Fv/Fm) and total chlorophyll content. GA3 treatment also led to lower electrolyte leakage and expression level of a series of senescence-associated genes (SAGs) including BrSAG12 and BrSAG19, and chlorophyll catabolic genes (CCGs) BrPPH1, BrNYC1, and BrSGRs. In addition, higher transcription levels of GA biosynthetic genes BrKAO2 and BrGA20ox2 were found after GA3 treatment. More importantly, a GA-repressible, nuclear-localized WRKY TF, BrWRKY6, a homologue of the Arabidopsis AtWRKY6, was identified and characterized. BrWRKY6 was GA-repressible and localized in the nucleus. Further experiments revealed that BrWRKY6 repressed the expression of BrKAO2 and BrGA20ox2, while it activated BrSAG12, BrNYC1, and BrSGR1, through binding to their promoters via the W-box cis-element. Together, the novel GA-WRKY link reported in our study provides new insight into the transcriptional regulation of GA-suppressed leaf senescence in Chinese flowering cabbage.

Influence of Road Proximity on the Concentrations of Heavy Metals in Korean Urban Agricultural Soils and Crops.

The urban agricultural (UA) environment near active roadways can be degraded by traffic-related particles (i.e., exhaust gases and road dust), which may contain heavy metals. The current study investigated changes in heavy-metal [cadmium (Cd), copper (Cu), chromium (Cr) nickel (Ni), lead (Pb) and zinc (Zn)] concentrations in soils located near highly trafficked roads in Korea and the subsequent uptake of these metals by Chinese cabbage. Heavy-metal plant concentrations were determined in both washed and unwashed plant leaves to determine whether foliar deposition played any role in plant metal uptake. Soil concentrations of Cd, Cu, Pb, and Zn were all lower than the Korean standard soil limits and showed no significant influence from road traffic. In contrast, both Ni and Cr concentrations in soils collected within 10m of the road were 4 and 5 times greater, respectively, than those in soils collected 70m from the road. Heavy-metal concentrations in unwashed Chinese cabbage leaf collected at 5m from the road were consistently greater than those of washed leaf samples, thus indicating the deposition of traffic-related particles on the plant surface. With the exception of Cu, all heavy-metal concentration in washed plant samples collected at 5m also showed greater accumulation compared with samples collected further away. This was mainly attributed to increased total soil heavy-metal concentrations and increased metal phytoavailability induced by decreases in soil pH near the road. However, overall heavy-metal soil concentrations were well lower than the allowable concentrations, and the levels observed in plants collected in this study were considered not to currently pose a significant risk to human health. However, some traffic-related heavy metals, in particular Cr and Ni, were being accumulated in the roadside UA environment, which may warrant some caution regarding the environment and/or health issues in the future.

Molecular Characterization of a Leaf Senescence-Related Transcription Factor BrWRKY75 of Chinese Flowering Cabbage

WRKY is a plant-specific transcription factor (TF) involved in the regulation of many biological processes; however, its role in leaf senescence of leafy vegetables remains unknown. In the present work, a WRKY TF, termed BrWRKY75 was isolated from Chinese flowering cabbage [Brassica rapa L. ssp. chinensis (L.) Mokino var. utilis Tsen et Lee]. Analysis of deduced amino acid sequence and the phylogenetic tree showed that BrWRKY75 has high homology with WRKY75 from Brassica oleracea and Arabidopsis thaliana, and belongs to the II c sub-group. Sub-cellular localization and transcriptional activity analysis revealed that BrWRKY75 is a nuclear protein with transcriptional repression activity, and was up-regulated during leaf senescence. Electrophoretic mobility shift assay confirmed that BrWRKY75 directly bound to the W-box (TTGAC) cis-element. Collectively, these results provide a basis for further investigation of the transcriptional regulation of Chinese flowering cabbage leaf senescence.

Relative toxicity of insecticides to the crucifer pests Plutella xylostella and Myzus persicae and their natural enemies

The widespread and intensive use of conventional pesticides, particularly insecticides, presents a major risk to natural enemies of target pests, as well as to the environment in general. The aim of this study was to investigate the differential intrinsic toxicity of insecticides to two key pests of crucifers, Plutella xylostella and Myzus persicae and their respective hymenopteran parasitoids, Cotesia vestalis and Aphidius colemani. Such knowledge can help inform effective integration of insecticides and biological control in IPM systems. Three insecticides generally regarded as being compatible with natural enemies (abamectin, spinosad and indoxacarb) and one compound regarded as harmful to natural enemies (lambda-cyhalothrin) were examined. A comparative measure of the intrinsic toxicity of fresh deposits of insecticides on Chinese cabbage leaf discs was determined for both pest and parasitoids species after exposure to insecticide for 24 h and 120 h, and after 24 h exposure to insecticide plus 96 h on untreated leaf discs. Differences in the susceptibility of pests and parasitoids to different insecticides were marked for P. xylostella and C. vestalis, LC50 values being significantly lower for the pest species. Such differences were not observed for M. persicae and A. colemani. There was a direct relationship between dose, exposure time and toxicity for all insecticides tested. All insecticides tested showed lower toxicity to both parasitoids compared with P. xylostella, which suggests that for this pest species side-effects on parasitoids can be minimised through IPM practices that reduce exposure time to such non-target organisms.