High Concentrations Of Glucosinolates Research Articles

Genotypes of Eruca vesicaria subsp. sativa grown in contrasting field environments differ on transcriptomic and metabolomic levels, significantly impacting nutritional quality.

Rocket (Eruca vesicaria subsp. sativa) is a source of sulfur-containing glucosinolates (GSLs). GSLs and their breakdown hydrolysis products (GHPs) are responsible for health-related benefits, such as anti-cancer and anti-neurodegenerative properties. Understanding how phytochemical composition changes between cultivation environments is key to developing cultivars with improved nutritional quality. Two consecutive harvests (first and second regrowth) of crops, grown in both Italy and the UK, were used to determine the phytochemical and transcriptomic differences between six lines of Eruca. Samples were taken upon delivery from field sites (D0) and after five days of cold storage (D5) for each location. Leaves were analysed for sulfur content, volatile organic compounds (VOCs), GSLs, GHPs, and sugars. Transcriptome data were associated with metabolite profiles to identify differentially expressed genes between plants grown in the two environments. VOC compounds (carbon disulfide, methyl thiocyanate) were associated with growth environment and with differences in sulfur metabolism gene expression (APR2, LSU2, LSU3, SDI1, SiR), GSL biosynthesis (MYB28, FMOGS-OX2) and GHP formation (ESM1, TGG1, TGG2). The concentrations of sugars were an order of magnitude greater in UK grown samples (up to 29.9 mg g-1 dry weight; dw). Sulfur content was significantly higher in the Italy plant samples (11.4 - 20.1 mg g-1 dw), which was in turn associated with higher concentrations of GSLs (pentyl GSL, up to 15.8 μmol g-1 dw; sinigrin, up to 0.005 μmol g-1 dw; glucoraphanin, up to 5.1 μmol g-1 dw; glucorucolamine, up to 23.6 μmol g-1 dw; neoglucobrassicin, up to 5.3 μmol g-1 dw) and hydrolysis products (sativin, up to 13.5 μmol g-1 dw; erucin, up to 1 μmol g-1 dw; sulforaphane, up to 34.7 μmol g-1 dw). VOC profiles of plants cultivated in the UK were distinct from Italy grown plants, with higher relative abundances of alkanes and esters in second cut and shelf-life (D5) samples. The data indicate a significant interaction of cultivar response with environment, highlighting the difficulty of producing Eruca crops with consistent phytochemical and postharvest traits. Genes with differential expression between plants grown in Italy and the UK could be used as markers of phytochemical quality and composition.

The Impact of Organic, Inorganic Fertilizers, and Biochar on Phytochemicals Content of Three Brassicaceae Vegetables

The need for soil fumigants of natural origin such as glucosinolates (GSLs) has increased due to the general prevention of manmade soil fumigants. GSLs and other phytochemicals (vitamin C and phenols) present in Brassica vegetables such as turnips, arugula, and mustard have antioxidant properties, and hence have important health attributes. The study examined how different soil amendments (chicken manure CM, vermicompost Vermi, horse manure HM, sewage sludge SS, elemental inorganic fertilizer Inorg, organic fertilizer Org, and biochar) impact the concentrations of glucosinolates (GSLs), vitamin C, phenols, and reducing sugars in three varieties of turnips (Purple Top White Globe PTWG, Scarlet Queen Red SQR, and Tokyo Cross TC), arugula, and mustard greens grown under field conditions. The results showed that mustard greens contained higher concentrations of GSLs (974 µg g−1 fresh shoots) than arugula (651 µg g−1 fresh shoots), and the TC variety of turnip had the highest concentrations of GSLs, vitamin C, and sugars. Additionally, amending the soil with SS, CM, and HM significantly increased the vitamin C content in mustard shoots by 82%, 90%, and 31%, respectively, and the total phenols by 77%, 70%, and 36%, respectively, compared to the control treatment. The increased inorganic fertilizers cost, and availability of large amounts of animal manure made animal manure application to cropland an attractive disposal option.

Plant species with higher chemical defences enhance herbivore cellular immunity with differential effectiveness against two parasitoid species

Abstract Insect herbivores simultaneously experience bottom‐up effects of plant defensive chemistry and the top‐down effects of natural enemies. At the intersection of these effects are herbivore immune systems, herbivore traits that have largely been overlooked in studies of plant‐insect interactions. Most previous studies have demonstrated compromised immunity of herbivores that feed on plants with higher defensive chemistry. Many studies have used embedded microfilaments or silica beads as proxies for parasitoid eggs. Yet, parasitoids may evade or suppress host immune responses by injecting venom and calyx fluid, or through modifications of their egg surface structure, necessitating studies that include all three trophic levels to obtain a complete picture of how plant traits may modulate herbivore immunity. Here, we examined the effect of host plant species that differ in glucosinolate (anti‐herbivore compounds produced by plants in the Brassicaceae) concentrations on the immune status of an herbivore and its consequences for two species of parasitoids with different life history traits. We found that larvae of the butterfly Pieris rapae that fed on field mustard Brassica rapa, which contain 52‐fold higher glucosinolate concentrations than collards B. oleracea, attained lower body weights and experienced prolonged development to adulthood. Yet, caterpillars that fed on B. rapa had enhanced cellular immunity, as measured by total and differential haemocyte counts as well as melanization capacity, compared to larvae that fed on B. oleracea. In turn, the likelihood that at least some eggs in clutches of the gregarious endoparasitoid Cotesia glomerata would be encapsulated, leading to a reduction in brood size, were three times greater when their host caterpillars fed on B. rapa compared to B. oleracea. Interestingly, eggs of the solitary endoparasitoid Cotesia rubecula were rarely encapsulated irrespective of the host plant on which their host caterpillar fed. Therefore, our results suggest that plant defence metabolites can influence the expression of herbivore immunity, but the effectiveness of this response strongly depends on the identity of the parasitoid and its ability to evade the caterpillar immune response, and possibly the evolution of these trophic interactions in non‐native systems. Read the free Plain Language Summary for this article on the Journal blog.

Biofumigation for the Management of Fusarium graminearum in a Wheat-Maize Rotation.

Fusarium graminearum is the most important causal agent of head blight in wheat, and stalk and ear rot in maize. A field experiment was conducted to investigate the effect of incorporation of Brassicaceae cover crops on Fusarium graminearum in a wheat-maize rotation. Five species belonging to Brassicaceae (Brassica juncea, Eruca sativa, Raphanus sativus, B. carinata, B. oleracea var. caulorapa L.) were used in the field experiment to investigate their potential to suppress F. graminearum inoculum in soil, disease incidence in maize and to reduce subsequent mycotoxin contamination in maize. Brassica juncea was found to contain the highest glucosinolate concentration in shoots (31 µmol g-1). Severity of ear rot and stalk rot in maize was not significantly reduced in the amended plots. Incorporation of R. sativus 'Terranova' significantly decreased the amount of F. graminearum DNA by 58% compared with the cultivated fallow treatment, however the DNA concentration was not significantly different to fallow uncultivated. Fusarium graminearum DNA and deoxynivalenol in maize was 50% lower after incorporation of B. oleracea var. caulorapa L. compared to after fallow treatment but the difference was not significant. The brassica crops used in the present field experiment were not effective in suppressing F. graminearum, therefore further studies to optimise the current approach are recommended.

Studies on exogenous elicitors promotion of sulforaphane content in broccoli sprouts and its effect on the MDA-MB-231 breast cancer cell line

Broccoli (Brassica oleracea var. italica) belongs to the Brassicaceae family and is one of the most important cruciferous vegetables. It has gained popularity due to its high glucosinolate concentrations that have positive potential in cancer treatment. In this study, the effects of two elicitors; methyl jasmonate (MeJA) and salicylic acid (SA), on the production of sulforaphane from broccoli 7-days old seedlings, its antiapoptotic activity and its gene expression have been studied. Real-time PCR was used to quantify myrosinase (MY) gene expression associated with sulforaphane production. The antiapoptotic activity of sulforaphane treatments was evaluated and tested using MDA-MB-231 breast cancer cell line. The highest amount of sulforaphane was produced at 80 μM SA and 40 μM MeJA after 24 h of elicitation. Increased production of sulforaphane was found to be associated with over-expression of myrosinase gene. The sulforaphane extract obtained from broccoli seedlings treated with MeJA exerted a higher inhibitory effect on the MDA-MB-231 breast cancer cell line than sulforaphane extract obtained from broccoli seedlings treated with SA. The inhibitory effect increased by using purified sulforaphane. Studies on apoptosis gene transcription showed that all sulforaphane treatments down-regulated the B-cell lymphoma 2 (Bcl-2) gene (antiapoptotic) transcription while up-regulating the pro-apoptotic Bcl2 Associated X, Apoptosis Regulator (Bax) gene, Caspase-3, Caspase-8 and Caspase-9. It may be concluded that increased sulforaphane production could increase its antiapoptotic activity as indicated by induction of more apoptosis in MDA-MB-231 breast cancer cells.

Effect of continuous white light illumination on glucosinolate metabolism during postharvest storage of broccoli

Broccoli is a vegetable consumed globally due to its important nutritional properties, including high concentrations of glucosinolates. Light treatment can be an important tool to delay postharvest senescence. In this work it was evaluated the effect of postharvest continuous white light illumination on glucosinolate metabolism of broccoli heads. Five glucosinolates were identified, one aliphatic (glucoraphanin) and four indolics (glucobrassicin, neoglucobrassicin, 4-methoxyglucobrassicin and 4-hydroxyglucobrassicin). Level of total glucosinolates decreased from 10.1 μmol/g dry tissue to 1.4 μmol/g dry tissue in control samples after five days of storage, while the decrement was only until 3.0 μmol/g dry tissue in treated samples. The expression of genes associated with glucosinolate metabolism decreased during the first three days but this decrease was greater in illuminated samples. After five days, treated samples showed a higher expression (more than twice) in most of these genes with respect to the controls, coinciding with the higher glucosinolate content. Storage of broccoli heads under continuous white light allows to keep higher values of glucosinolate contents while maintaining at the same time the visual quality.

A comprehensive Vis-NIRS equation for rapid quantification of seed glucosinolate content and composition across diverse Brassica oilseed chemotypes

The globally cultivated Brassica crops contain high deliverable concentrations of health-promoting glucosinolates. Development of a Visible-Near InfraRed Spectroscopy (Vis-NIRS) calibration to profile different glucosinolate components from 641 diverse Brassica juncea chemotypes was attempted in this study. Principal component analysis of HPLC-determined glucosinolates established the distinctiveness of four B. juncea populations used. Subsequently, modified partial least square regression based population-specific and combined Vis-NIRS models were developed, wherein the combined model exhibited higher coefficient of determination (R2; 0.81–0.97) for eight glucosinolates and higher ratio of prediction determination (RPD; 2.42–5.35) for seven glucosinolates in B. juncea populations. Furthermore, range error ratio (RER > 4) for twelve and RER > 10 for eight glucosinolates make the combined model acceptable for screening and quality control. The model also provided excellent prediction for aliphatic glucosinolates in four oilseed Brassica species. Overall, our work highlights the potential of Vis-NIR spectroscopy in estimating glucosinolate content in the economically important Brassica oilseeds.

High Glucosinolate Content in Rocket Leaves (Diplotaxis tenuifolia and Eruca sativa) after Multiple Harvests Is Associated with Increased Bitterness, Pungency, and Reduced Consumer Liking.

Rocket (Diplotaxis tenuifolia and Eruca sativa) leaves delivered to the UK market are variable in appearance, taste, and flavour over the growing season. This study presents sensory and consumer analyses of rocket produce delivered to the UK over the course of one year, and evaluated the contribution of environmental and cultivation factors upon quality traits and phytochemicals called glucosinolates (GSLs). GSL abundance was positively correlated with higher average growth temperatures during the crop cycle, and perceptions of pepperiness, bitterness, and hotness. This in turn was associated with reduced liking, and corresponded to low consumer acceptance. Conversely, leaves with greater sugar content were perceived as more sweet, and had a higher correlation with consumer acceptance of the test panel. First cut leaves of rocket were favoured more by consumers, with multiple leaf cuts associated with low acceptance and higher glucosinolate concentrations. Our data suggest that the practice of harvesting rocket crops multiple times reduces consumer acceptability due to increases in GSLs, and the associated bitter, hot, and peppery perceptions some of their hydrolysis products produce. This may have significant implications for cultivation practices during seasonal transitions, where leaves typically receive multiple harvests and longer growth cycles.

A new pest management strategy: transforming a non-host plant into a dead-end trap crop for the diamondback moth Plutella xylostella L.

The use of trap crops can reduce the egg production of female Plutella xylostella in cruciferous vegetables and is an effective method for controlling this pest. To date, most of the trap plants that have been studied are cruciferous plants containing high concentrations of glucosinolates, which are more attractive to P. xylostella female adults. However, the application of these trap plants also has some limitations. Studies have shown that aqueous extracts of cruciferous plants can attract P. xylostella to lay eggs. In this study, we utilized the extract of Chinese kale to treat a non-host plant, the faba bean, and evaluated the possibility of using it as a dead-end trap plant for P. xylostella control. Plutella xylostella females laid significantly more eggs on faba beans that had been sprayed with the extract of Chinese kale rather than on Chinese kale itself. The first instar larvae of P. xylostella failed to survive on faba beans. Notably, the faba beans with the Chinese kale extract had the strongest attraction effect on P. xylostella females when placed 3 m away from the Chinese kale. Moreover, this attraction effect of faba beans on P. xylostella for oviposition lasted for up to 15 days. Faba bean plants sprayed with the aqueous extract of Chinese kale represent a potential dead-end trap plant for P. xylostella adults and their oviposition while being invariably deadly for their offspring. The present study provides a new proof of concept of using a non-cruciferous trap plant for P. xylostella management.

Harvesting at the end of the day extends postharvest life of kale (Brassica oleracea var. sabellica)

The contribution of Brassica vegetables to health improvement is related to their antioxidant capacity. Kale, as a member of Brassicaceae family, has high concentrations of antioxidants and glucosinolates. The main problem of harvested kale leaves is their accelerated senescence that leads to yellowing and a decline in nutritional quality.Previous reports indicate that daytime cycle strongly influenced different metabolic and physiological processes of plants, so the aim of this research was to determine if postharvest shelf life was influenced by the time of day in which kale leaves were harvested.In this study, we harvested kale leaves at 8:00, 13:00 and 18:00 h (in spring crop) and analysed their postharvest behaviour during storage for 9 days at 20 °C in darkness. We measured the yellowing and senescence metabolism during postharvest storage. Results show that leaves harvested at 8:00 h present earlier symptoms of yellowing, higher chlorophyll degradation and lower sugar content. On the other hand, the samples obtained at 18:00 h barely showed senescence symptoms with a delay in yellowing. Additionally, leaves harvested at 18:00 h present higher protein and sugar content giving evidence of the fact that harvest at 18:00 h contributes to delay kale leaves yellowing and senescence metabolism during storage.

Growth temperature influences postharvest glucosinolate concentrations and hydrolysis product formation in first and second cuts of rocket salad.

Rocket salad species (Diplotaxis tenuifolia and Eruca sativa; also known as E. vesicaria) are known for their high concentrations of health-related isothiocyanates, which are derived from secondary metabolites called glucosinolates. Increases in temperature due to climate change and extreme weather event frequencies over the coming decades are likely to influence not only the growth of leafy vegetables, but also their nutritional density. It is therefore essential to determine the impacts of these in order to mitigate crop losses and nutritional decline in future. Our data show there is a strong influence of pre-harvest growth temperatures on glucosinolate biosynthesis and formation of glucosinolate hydrolysis products postharvest, and that this is genotype dependent. High growth temperature (40 °C) severely retarded germination, growth, regrowth, and survival of rocket plants. Highest glucosinolate concentrations were observed in first and second cuts at 40 °C, but did not correspond to highest isothiocyanate concentrations (observed at 30 °C, second cut). Hydrolysis product formation is proportionately not as great as glucosinolate increases at 40 °C, possibly due to inhibition of enzyme function(s) at higher temperatures. These data indicate that high growth temperatures increase glucosinolate accumulation, but growth and productivity is significantly reduced. Much greater emphasis is needed for breeding cultivars tolerant to high growth temperatures in order to maximise nutritional benefits imparted by temperature stress.

Canola-quality white mustard: Agronomic management and seed yield

Modern white mustard (Sinapis alba L.) cultivars have high concentrations of erucic acid and glucosinolates. The progress in the breeding and cultivation of oilseed crops has contributed to the development of canola-quality white mustard, a variety without erucic acid and with low glucosinolate content, which was released for commercial production in 2012. The introduction of a new variety of white mustard could require partial or complete modification of the relevant production technology. The agricultural requirements of new crop cultivars can be rapidly assessed in experiments with fractional factorial design. In 2016–2018, a field experiment with mixed 2m3k−1 factorial design, where five factors were tested at two and three levels, was carried out in the Agricultural Experiment Station in Bałcyny in north-eastern Poland. Two white mustard cultivars, including the traditional cultivar Radena and the canola-quality cultivar Warta, were sown on three dates: the optimal date (4–10 April), as well as 7 and 14 days past the optimal date. White mustard cultivars were grown at three levels of agricultural inputs (0, 1, 2) with different rates of nitrogen (80, 120 and 160 kg ha-1), sulfur (0, 20 and 40 kg ha-1) and boron fertilizers (0, 150 and 300 g ha-1). The yields of the traditional cultivar exceeded those of the canola-quality cultivar by 0.53 Mg ha-1 on average. Both cultivars produced the highest yields when sown on the optimal date. Delayed sowing (by 7 and 14 days) contributed to the greatest decrease in yield (32 % and 42 %, respectively) in a dry year (2018). The traditional cultivar was more sensitive to delayed sowing than the canola-quality cultivar. In both analyzed cultivars, nitrogen fertilizer delivered yield-forming effects up to the rate of 80 kg ha-1 (in the dry year) or 120 kg ha-1 (in the year with above-average precipitation, 2016–2017). In both cultivars, a significant increase in seed yield was observed in response to 20 kg S ha-1. Foliar application of boron fertilizer did not increase white mustard yields.

Effective methods of biofumigation: a meta-analysis

Biofumigation, the burying of Brassicaceaous plant tissues to suppress soil pests, is an increasingly practiced technique. However, the efficiency of biofumigation varies considerably and motivated our meta-analysis on the topic. We meta-analyzed data from 46 publications where 934 experiments used 363 unique controls, in order to determine effectiveness of this practice compared with untreated controls, and to identify which aspects of treatment regimens were most important for ensuring success. Biofumigation generally reduced pest abundance, reduced incidence of disease, and increased crop yield by 30% over values seen in untreated controls. Neither the plant part incorporated, nor the method used to incorporate it, were important predictors of success. Contrary to our expectations, we found no evidence that solarization was beneficial, and only treatment regimens without solarization were generally effective. While treatment regimens varied, the most effective treatment combination that we identified was the incorporation of young Eruca and Raphanus plants, with high glucosinolate concentrations, applied at high doses with short exposure times to suppress the nematode Globodera in Solanaceous plants. Each component of this regimen would likely increase the effectiveness of biofumigation efforts aimed at other soil pests.

Bioherbicidal activity of Eruca sativa fresh shoot aqueous extract for the management of two annual weeds associating Pisum sativum plants

BackgroundBrassica species have been established to have very high concentrations of glucosinolates, flavonols, and other secondary metabolites that achieved good results in weed management strategy. So, this study highlights how to investigate the allelopathic potential of Eruca sativa fresh shoot aqueous extract as a natural bioherbicide to control Phalaris minor and Beta vulgaris weeds beside its effect on Pisum sativum growth as well as yield traits. Two pot experiments were conducted in the greenhouse of the National Research Centre, Dokki, Giza, Egypt, in the two successive winter seasons of (2016–2017, 2017–2018). Treatments were applied by spraying E. sativa fresh shoot aqueous extract once at 14 days after sowing and twice at 14 and 21 days after sowing at rates of 20, 40, 60, and 80% w/v.ResultsE. sativa fresh shoot aqueous extract at 80% achieved the maximum inhibition effect on the growth of both weeds. This in turn was reflected on P. sativum plant and gave the observable highest growth and yield parameters. Chemical analysis of E. sativa shoot powder approved the presence glucosinolates (9.6 μmol/g) and phenolic compounds (46.5 mg/g) which may be responsible for the allelopathic effect.ConclusionSpraying of aqueous fresh shoot extract of E. sativa at 80% (w/v) can be applied as natural selective bioherbicide in controlling the two annual grassy and broad-leaved weeds associated with P. sativum plants.

Effects of Developmental Stages and Reduced UVB and Low UV Conditions on Plant Secondary Metabolite Profiles in Pak Choi (Brassica rapa subsp. chinensis).

Pak choi (Brassica rapa subsp. chinensis) is rich in secondary metabolites and contains numerous antioxidants, including flavonoids; hydroxycinnamic acids; carotenoids; chlorophylls; and glucosinolates, which can be hydrolyzed to epithionitriles, nitriles, or isothiocyanates. Here, we investigate the effect of reduced exposure to ultraviolet B (UVB) and UV (UVA and UVB) light at four different developmental stages of pak choi. We found that both the plant morphology and secondary metabolite profiles were affected by reduced exposure to UVB and UV, depending on the plant's developmental stage. In detail, mature 15- and 30-leaf plants had higher concentrations of flavonoids, hydroxycinnamic acids, carotenoids, and chlorophylls, whereas sprouts contained high concentrations of glucosinolates and their hydrolysis products. Dry weights and leaf areas increased as a result of reduced UVB and low UV. For the flavonoids and hydroxycinnamic acids in 30-leaf plants, less complex compounds were favored, for example, sinapic acid acylated kaempferol triglycoside instead of the corresponding tetraglycoside. Moreover, also in 30-leaf plants, zeaxanthin, a carotenoid linked to protection during photosynthesis, was increased under low UV conditions. Interestingly, most glucosinolates were not affected by reduced UVB and low UV conditions. However, this study underlines the importance of 4-(methylsulfinyl)butyl glucosinolate in response to UVA and UVB exposure. Further, reduced UVB and low UV conditions resulted in higher concentrations of glucosinolate-derived nitriles. In conclusion, exposure to low doses of UVB and UV from the early to late developmental stages did not result in overall lower concentrations of plant secondary metabolites.

Testing the optimal defense hypothesis in nature: Variation for glucosinolate profiles within plants.

Plants employ highly variable chemical defenses against a broad community of herbivores, which vary in their susceptibilities to specific compounds. Variation in chemical defenses within the plant has been found in many species; the ecological and evolutionary influences on this variation, however, are less well-understood. One central theory describing the allocation of defenses in the plant is the Optimal Defense Hypothesis (ODH), which predicts that defenses will be concentrated in tissues that are of high fitness value to the plant. Although the ODH has been repeatedly supported within vegetative tissues, few studies have compared vegetative and reproductive tissues, and the results have not been conclusive. We quantified variation in glucosinolate profile and tissue value between vegetative and reproductive tissues in Boechera stricta, a close relative of Arabidopsis. B. stricta manufactures glucosinolates, a set of defensive compounds that vary genetically and are straightforward to quantify. Genetic diversity in glucosinolate profile has been previously demonstrated to be important to both herbivory and fitness in B. stricta; however, the importance of glucosinolate variation among tissues has not. Here, we investigate whether allocation of glucosinolates within the plant is consistent with the ODH. We used both clipping experiments on endogenous plants and ambient herbivory in a large-scale transplant experiment at three sites to quantify fitness effects of loss of rosette leaves, cauline leaves, and flowers and fruits. We measured glucosinolate concentration in leaves and fruits in the transplant experiment, and asked whether more valuable tissues were more defended. We also investigated within-plant variation in other aspects of the glucosinolate profile. Our results indicated that damage to fruits had a significantly larger effect on overall fitness than damage to leaves, and that fruits had much higher concentrations of glucosinolates, supporting the ODH. This is, to the best of our knowledge, the first study to explicitly compare both tissue value and chemical defense concentrations between vegetative and reproductive tissues under natural conditions.

Zinc hyperaccumulation substitutes for defense failures beyond salicylate and jasmonate signaling pathways of Alternaria brassicicola attack in Noccaea caerulescens.

The hypothesis of metal defense as a substitute for a defective biotic stress signaling system in metal hyperaccumulators was tested using the pathosystem Alternaria brassicicola-Noccaea caerulescens under low (2 µM), medium (12 µM) and high (102 µM) Zn supply. Regardless the Zn supply, N. caerulescens responded to fungal attack with the activation of both HMA4 coding for a Zn transporter, and biotic stress signaling pathways. Salicylate, jasmonate, abscisic acid and indoleacetic acid concentrations, as well as biotic stress marker genes (PDF1.2, CHIB, LOX2, PR1 and BGL2) were activated 24 h upon inoculation. Based on the activation of defense genes 24 h after the inoculation an incompatible fungal-plant interaction could be predicted. Nonetheless, in the longer term (7 days) no effective protection against A. brassicicola was achieved in plants exposed to low and medium Zn supply. After 1 week the biotic stress markers were even further increased in these plants, and this compatible interaction was apparently not caused by a failure in the signaling of the fungal attack, but due to the lack of specificity in the type of the activated defense mechanisms. Only plants receiving high Zn exhibited an incompatible fungal interaction. High Zn accumulation in these plants, possibly in cooperation with high glucosinolate concentrations, substituted for the ineffective defense system and the interaction turned into incompatible. In a threshold-type response, these joint effects efficiently hampered fungal spread and, consequently decreased the biotic stress signaling.

Distribution of glucosinolates in camelina seed fractions by HPLC‐ESI‐MS/MS

High glucosinolate concentrations were detected and identified in camelina (Camelina sativa L. Crantz.) seed fractions using reversed phase high performance liquid chromatography‐electrospray ionization‐mass spectrometry (HPLC‐ESI‐MS) in multiple reaction monitoring mode. Total glucosinolate quantitation was performed using proton nuclear magnetic resonance spectrometry using N,N‐dimethylformamide as an internal standard. Individual glucosinolate concentrations were determined by analysis on extracted ion chromatograms generated by a MS detector. Distribution of glucosinolates in C. sativa seed fractions during pressing is reported.Practical applications: HPLC‐ESI‐MS and HPLC‐ESI‐MS/MS using monolithic HPLC columns were used to detect, quantify, and identify the three major glucosinolates in Camelina sativa L. and fractions of C. sativa produced by processing. Quantitative extracted ion MS chromatograms afforded excellent quantitation of individual glucosinolates. The use of monolithic HPLC columns enabled rapid analysis of these samples.Schematic of a proposed dehulling system for Camelina sativa seed.

Effects of biofumigation using Brassica juncea and Raphanus sativus in comparison to disinfection using Basamid on apple plant growth and soil microbial communities at three field sites with replant disease

The effects of biofumigation with Brassica juncea ‘Terra Plus’ and Raphanus sativus ‘Defender’ in comparison to Basamid on apple plant growth and on soil microbial communities were studied at three sites affected by replant disease under field conditions. Apple rootstocks were planted on differently treated plots to evaluate the effect of the treatments on plant growth under field and greenhouse conditions. The glucosinolates in biofumigant plant organs and their breakdown products in soils were determined. Denaturing gradient gel electrophoresis fingerprints were performed with 16S rRNA gene and ITS fragments amplified from total community DNA extracted from different soils. The highest glucosinolate concentrations were found in inflorescences of both biofumigant plant species with no differences between sites. The most abundant degradation product in soil biofumigated with B. juncea was 2-propenyl isothiocyanate, while in soil treated with R. sativus only 4-(methylthio)-3-butenyl isothiocyanate was detected. Effects of biofumigation were recorded to be stronger on fungi than on bacteria. Growth of apple rootstocks was positively affected by the treatments in a site-dependent manner. The effects of biofumigation evaluated by the apple plant growth were site-dependent and might result from suppression of soil-borne pests and pathogens, changes in soil microbial community compositions, and additional nutrients from the incorporated biomass.

Effect of zinc and glucosinolates on nutritional quality of Noccaea caerulescens and infestation by Aleyrodes proletella

The Zn hyperaccumulating plant, Noccaea caerulescens, was grown under controlled conditions at a range of Zn concentrations (0–1000mgkg−1 dwt. soil) to determine the effectiveness of hyperaccumulation in deterring the cabbage whitefly, Aleyrodes proletella, and to establish the relationship between levels of foliar Zn and glucosinolates (organic defence compounds). Two weeks after introducing A. proletella adults to the plants, next generation nymphs were quantified. This sucking insect caused minimal damage to plant tissue and did not affect foliar glucosinolate levels. Foliar Zn concentrations increased with increasing soil Zn application and reached a maximum of ~7000mgkg−1. More whitefly nymphs were observed on plants as the foliar Zn concentration increased (up to ~3000mgkg−1) after which numbers declined. Zn was an explanatory variable in accumulated generalised linear regression after the variation in the data due to C/N ratio had been accounted for. Nymph numbers declined with increasing C/N ratio and increased with increasing N concentration. The highest glucosinolate concentrations were in shoots with the lowest Zn concentrations; this is consistent with the ‘trade-off’ hypothesis which states that elemental defence mechanisms allow for lowered organic defences.