Glucosinolate Variation Research Articles

Variations of Major Glucosinolates in Diverse Chinese Cabbage (Brassica rapa ssp. pekinensis) Germplasm as Analyzed by UPLC-ESI-MS/MS.

In this study, the variability of major glucosinolates in the leaf lamina of 134 Chinese cabbage accessions was investigated using Acquity ultra-performance liquid chromatography (UPLC-ESI-MS/MS). A total of twenty glucosinolates were profiled, of which glucobrassicanapin and gluconapin were identified as the predominant glucosinolates within the germplasm. These two glucosinolates had mean concentration levels above 1000.00 μmol/kg DW. Based on the principal component analysis, accessions IT186728, IT120044, IT221789, IT100417, IT278620, IT221754, and IT344740 were separated from the rest in the score plot. These accessions exhibited a higher content of total glucosinolates. Based on the VIP values, 13 compounds were identified as the most influential and responsible for variation in the germplasm. Sinigrin (r = 0.73), gluconapin (r = 0.78), glucobrassicanapin (r = 0.70), epiprogoitrin (r = 0.73), progoitrin (r = 0.74), and gluconasturtiin (r = 0.67) all exhibited a strong positive correlation with total glucosinolate at p < 0.001. This indicates that each of these compounds had a significant influence on the overall glucosinolate content of the various accessions. This study contributes valuable insights into the metabolic diversity of glucosinolates in Chinese cabbage, providing potential for breeding varieties tailored to consumer preferences and nutritional demands.

Unveiling Glucosinolate Diversity in Brassica Germplasm and In Silico Analysis for Determining Optimal Antioxidant Potential.

This study explored the glucosinolate (GSL) content in Brassica plants and utilized in silico analysis approach to assess their antioxidant capabilities. GSLs, present abundantly in Brassica vegetables, offer potential health advantages, including antioxidant effects. Employing Ultra-Performance Liquid Chromatography (UPLC) coupled with tandem mass spectrometry (MS/MS), major GSLs were identified in 89 accessions from diverse species and subspecies. Statistical analysis and principal component analysis unveiled significant GSL variation and potential correlations among the Brassica germplasms. This study unveils the dominance of aliphatic GSLs over aromatic and indolyl compounds in all the accessions. Notably, Gluconapin (GNA) (33,049.23 µmol·kg-1 DW), Glucobrassicanapin (GBN) (9803.82 µmol·kg-1 DW), Progoitrin (PRO) (12,780.48 µmol·kg-1 DW) and Sinigrin (SIN) (14,872.93 µmol·kg-1 DW) were the most abundant compounds across the analyzed accessions. Moreover, in silico docking studies predicted promising antioxidant activity by evaluating the interactions of each GSL with antioxidant enzymes. Specifically, Sinigrin and Gluconapin exhibited a notably weaker influence on antioxidant enzymes. This provides key insights into the antioxidant potential of Brassica germplasm and highlights the importance of in silico analysis for evaluating bioactive properties. In general, the results of this study could be utilized in breeding programs to maximize GSL levels and antioxidant properties in Brassica crops and for developing functional foods with enhanced health benefits.

A Cold Case—Glucosinolate Levels in Kale Cultivars Are Differently Influenced by Cold Temperatures

Among the Brassica oleracea L. crops, kale has gained increased global recognition in recent years as a healthy food item due to its high nutritional value and versatility. Additionally, the diversity of different kale varieties has started to be explored across large latitudes from the Mediterranean to north temperate climates. Specifically, glucosinolates are the predominant phytochemicals found in kale leaves, contributing to the specific taste of this vegetable, and they are affected by environmental factors such as temperature. To date, no study has investigated the effect of chilling on glucosinolate diversity and, thus, the taste in genetically different kale cultivars at the same time. Given the variability of glucosinolates observed among cultivars, we evaluated the impact of acclimation to cold temperatures on glucosinolate levels in curly kale, Lacinato kale, and a feral type using high-performance liquid chromatography coupled with time-of-flight mass spectrometry (HPLC-ESI-qTOF-MS). We targeted the short-term impact (after 12 h) on glucosinolates as well as the longer-term effect (after seven days) of cold acclimation. Our results revealed different molecular patterns regarding the change in glucosinolates in the feral type compared to curly kale and Lacinato-type kale. In the latter ones, primary aliphatic glucosinolates were induced (the glucoraphanin in Lacinato kale increased by more than 200%). The indole glucobrassicin was not significantly affected. Conversely, in the feral type the indole glucobrassicin was reduced by 35% after cold acclimation, whereas aliphatic glucosinolates were hardly affected. The results indicate that both genetic and environmental factors are important for the composition of glucosinolate patterns in kale. In conclusion, to obtain plants with an improved nutritional value, considering both temperature and the choice of cultivar is crucial during kale cultivation. Future breeding attempts of kale should also emphasize the cultivar-dependent cold acclimation patterns reported here.

Glucosinolate Diversity Analysis in Choy Sum (Brassica rapa subsp. chinensis var. parachinensis) Germplasms for Functional Food Breeding.

The aim of this study was to analyze glucosinolates (GSLs) in germplasm that are currently conserved at the RDA-Genebank. The analysis focused on the glucosinolate diversity among the analyzed germplasms, with the goal of identifying those that would be most useful for future breeding efforts to produce nutritionally rich Choy sum plants. In total, 23 accessions of Choy sums that possessed ample background passport information were selected. On analyzing the glucosinolate content for 17 different glucosinolates, we observed aliphatic GSLs to be the most common (89.45%) and aromatic GSLs to be the least common (6.94%) of the total glucosinolates detected. Among the highly represented aliphatic GSLs, gluconapin and glucobrassicanapin were found to contribute the most (>20%), and sinalbin, glucoraphanin, glucoraphasatin, and glucoiberin were detected the least (less than 0.05%). We identified one of the accessions, IT228140, to synthesize high quantities of glucobrassicanapin and progoitrin, which have been reported to contain several therapeutic applications. These conserved germplasms are potential bioresources for breeders, and the availability of information, including therapeutically important glucosinolate content, can help produce plant varieties that can naturally impact public health.

Variation in glucosinolates and the formation of functional degradation products in two Brassica species during spontaneous fermentation

Vegetables from the Brassica species are excellent sources of glucosinolates (GLSs), the precursors of health-promoting isothiocyanates (ITCs). Fermentation enhances the biotransformation of GLSs into potential bioactive ITCs. To explore the biotransformation of GLSs during Brassica fermentation, the changes in GLSs during the fermentation of two Brassica species (i.e., cauliflower and broccoli); the formation of corresponding breakdown products; and the shifts in physicochemical parameters, bacterial communities, and myrosinase activities involved in GLSs degradation were systematically investigated. Nine aliphatic, three indolic, and two benzenic GLSs were identified in fermented cauliflower (FC) and fermented broccoli (FB). Aliphatic glucoiberin and glucoraphanin were the major forms of GLS in FC and FB, respectively; indolic glucobrassicin was also abundant in both FC and FB. The total GLS content decreased by 85.29% and 65.48% after 3 d of fermentation in FC and FB, respectively. After 2 d of fermentation, a significant increase in bioactive GLS degradation products (P < 0.05), including sulforaphane (SFN), iberin (IBN), 3,3-diindolylmethane (DIM), and ascorbigen (ARG), was observed in FC and FB compared to in fresh cauliflower and broccoli. Moreover, variations in pH value and titratable acidity in FC and FB correlated with Brassica fermentation and were accomplished by lactic acid bacteria, including Weissella, Lactobacillus-related genera, Leuconostoc, Lactococcus, and Streptococcus. These changes may enhance the biotransformation of GSLs to ITCs. Overall, our results indicate fermentation leads to the degradation of GLSs and the accumulation of functional degradation products in FC and FB.

Diversity of glucosinolates among common Brassicaceae vegetables in China

Brassicaceae vegetables are an important traditional daily food in China and around the world, which provide nutrients and phytochemicals that are beneficial for human health. Among them, Brassica and Raphanus are widely cultivated and eaten, have been evolved and/or bred for special characteristics during the long history of cultivation. Epidemiological studies suggest that the health benefits of Brassicaceae vegetables are mainly associated with glucosinolates (GSLs) and their hydrolytic products. In this review, we discuss the diversity of common consumed Brassicaceae vegetables and their GSL composition in edible parts. We also discuss the diversity factors affecting GSL content, and the diversity roles and functions of GSL. The information in this review provides guidance for consumers to select vegetables with a high GSL content, optimum edible stages, suitable edible methods, and provides a theoretical basis for crop molecular breeding and market development of GSL products.

Comparative responses of glucosinolates in Baemoochae and its parent plants, radish and Chinese cabbage, during development

Baemoochae ‘BB1’ is considered a suitable plant for elucidating comparative levels of glucosinolate metabolomics because it is bred by the inter-generic hybridization of radish ‘Taebaek’ and Chinese cabbage ‘Bulam3’. This present study was conducted to determine the developmental diversity of glucosinolates in Baemoochae and its parent plants. In Baemoochae leaf and radish, the primary glucosinolate was glucoraphasatin, and its content in Baemoochae increased as it grew from 450.1 to 2325.1 µmol kg−1. In addition, the content of gluconapin, glucobrassicanapin, and 4-methoxyglucobrassicin also increased to 106.8, 50.4, and 3.4 times, respectively, during the development of Baemoochae, an effect which was also observed in Chinese cabbage. In mature Baemoochae, the levels of glucoraphanin, glucoalyssin, and gluconapoleiferin increased in the leaves, and those of glucoerucin and glucoraphanin increased in the roots, as compared to those in radish and Chinese cabbage. Therefore, glucosinolates composition in Baemoochae is similar to that in its parent plants; however, Baemoochae exhibited discrete patterns of glucosinolate distribution during developmental stages. Based on these results, the present study provides basic information of glucosinolates in Baemoochae, and will aid the understanding of changes in these metabolites during growth.

Glucosinolate variation among organs, growth stages and seasons suggests its dominant accumulation in sexual over asexual-reproductive organs in white radish

Radish (Raphanus sativus L.), a root vegetable crop, contains a large amount of glucosinolate but information on its changes in field condition among different organs, growth stages and seasons is very limited. The glucosinolate composition, concentration (mmol∙kilogram−1) and content (μmol∙organ−1) of radish were analyzed among shoots, roots, inflorescences and siliques in vegetative and/or reproductive growth stages during autumn and spring to estimate sink/source relation and proper harvest time for high glucosinolate. Glucosinolates were measured weekly during autumn and spring using two autumn and one spring cultivars. All cultivars did not flower in autumn while only autumn cultivars had inflorescences in spring. Among three glucosinolates detected, glucoraphasatin was predominant, and glucobrassicin and gluconasturtiin varied in ratio among organs, growth stages and seasons. Root and shoot glucosinolate concentrations decreased as plants grow during autumn. Glucosinolate concentration in roots tended to decrease but that in shoots continuously increased during spring. Glucosinolate concentration was higher in roots than shoots during autumn and early spring but higher in shoots during late spring. Total glucosinolate content was also significantly higher in roots than shoots during autumn. However, it was higher in shoots at vegetative stage but in roots shortly at flower initiation, and then sharply increased in shoots at developmental stage during spring. The sharp increase in shoot glucosinolate content never happened in a spring cultivar without inflorescences. Glucosinolate concentration in the tenth week was significantly higher in inflorescences than other organs. These results suggest that when they co-exist, glucosinolate accumulates more in inflorescences than roots, which act as organs for sexual and asexual reproduction, respectively. Proper harvest time for leaves and roots were suggested based on the glucosinolate content and growth of radish plants.

Structural Studies of Aliphatic Glucosinolate Chain-Elongation Enzymes.

Plants evolved specialized metabolic pathways through gene duplication and functional divergence of enzymes involved in primary metabolism. The results of this process are varied pathways that produce an array of natural products useful to both plants and humans. In plants, glucosinolates are a diverse class of natural products. Glucosinolate function stems from their hydrolysis products, which are responsible for the strong flavors of Brassicales plants, such as mustard, and serve as plant defense molecules by repelling insects, fighting fungal infections, and discouraging herbivory. Additionally, certain hydrolysis products such as isothiocyanates can potentially serve as cancer prevention agents in humans. The breadth of glucosinolate function is a result of its great structural diversity, which comes from the use of aliphatic, aromatic and indole amino acids as precursors and elongation of some side chains by up to nine carbons, which, after the formation of the core glucosinolate structure, can undergo further chemical modifications. Aliphatic methionine-derived glucosinolates are the most abundant form of these compounds. Although both elongation and chemical modification of amino acid side chains are important for aliphatic glucosinolate diversity, its elongation process has not been well described at the molecular level. Here, we summarize new insights on the iterative chain-elongation enzymes methylthioalkylmalate synthase (MAMS) and isopropylmalate dehydrogenase (IPMDH).

Genomic Origin and Diversification of the Glucosinolate MAM Locus

Glucosinolates are a diverse group of plant metabolites that characterize the order Brassicales. The MAM locus is one of the most significant QTLs for glucosinolate diversity. However, most of what we understand about evolution at the locus is focused on only a few species and not within a phylogenetic context. In this study, we utilize a micro-synteny network and phylogenetic inference to investigate the origin and diversification of the MAM/IPMS gene family. We uncover unique MAM-like genes found at the orthologous locus in the Cleomaceae that shed light on the transition from IPMS to MAM. In the Brassicaceae, we identify six distinct MAM clades across Lineages I, II, and III. We characterize the evolutionary impact and consequences of local duplications, transpositions, whole genome duplications, and gene fusion events, generating several new hypothesizes on the function and diversity of the MAM locus.

Natural Variation of Glucosinolates and Their Breakdown Products in Broccoli (Brassica oleracea var. italica) Seeds.

Seeds of 32 pure lines and 6 commercial broccoli cultivars were used to investigate variation in glucosinolates and their breakdown products. The aliphatic glucosinolate content was 54.5-218.7 μmol/g fresh weight, accounting for >90% of the total glucosinolates. The major glucosinolates found were glucoraphanin and glucoerucin in 27 samples and progoitrin in 7 samples. A gas chromatography-flame ionization detector (GC-FID) method was used to identify glucosinolate breakdown products; nine products were directly determined using standards. Using Arabidopsis thaliana lines myb28myb29 and Landsberg erecta to hydrolyze each reference glucosinolate, seven products were tentatively identified. 4-(Methylsulfinyl)butyl isothiocyanate and 5-(methylsulfinyl)pentanenitrile contents were 2.6-91.1 μmol/g fresh weight and 0-35.4 μmol/g fresh weight, respectively, with epithionitriles being more common than nitriles in accessions rich in alkenyl glucosinolate. Additionally, (S)-5-vinyl-1,3-oxazolidine-2-thione was detected in accessions rich in progoitrin. Specific lines with altered glucosinolate profiles and breakdown products were obtained and discussed according to the putative glucosinolate metabolism pathway.

Genetic architecture of glucosinolate variation in Brassica napus

The diverse biological activities of glucosinolate (GSL) hydrolysis products play significant biological and economical roles in the defense system and nutritional qualities of Brassica napus (oilseed rape). Yet, genomic-based study of the B. napus GSL regulatory mechanisms are scarce due to the complexity of working with polyploid species. To address these challenges, we used transcriptome-based GWAS approach, Associative Transcriptomics (AT), across a diversity panel of 288 B. napus genotypes to uncover the underlying genetic basis controlling quantitative variation of GSLs in B. napus vegetative tissues. Single nucleotide polymorphism (SNP) markers and gene expression markers (GEMs) associations identify orthologues of MYB28/HAG1 (AT5G61420), specifically the copies on chromosome A9 and C2, to be the key regulators of aliphatic GSL variation in leaves. We show that the positive correlation observed between aliphatic GSLs in seed and leaf is due to the amount synthesized, as controlled by Bna.HAG1.A9 and Bna.HAG1.C2, rather than by variation in the transport processes. In addition, AT and differential expression analysis in root tissues implicate an orthologue of MYB29/HAG3 (AT5G07690), Bna.HAG3.A3, as controlling root aromatic GSL variation. Based on the root expression data we also propose Bna.MAM3.A3 to have a role in controlling phenylalanine chain elongation for aromatic GSL biosynthesis. This work uncovers a regulator of homophenylalanine-derived aromatic GSLs and implicates the shared biosynthetic pathways between aliphatic and aromatic GSLs.

Evolution of Glucosinolate Diversity via Whole-Genome Duplications, Gene Rearrangements, and Substrate Promiscuity.

Over several decades, glucosinolates have become a model system for the study of specialized metabolic diversity in plants. The near-complete identification of biosynthetic enzymes, regulators, and transporters has provided support for the role of gene duplication and subsequent changes in gene expression, protein function, and substrate specificity as the evolutionary bases of glucosinolate diversity. Here, we provide examples of how whole-genome duplications, gene rearrangements, and substrate promiscuity potentiated the evolution of glucosinolate biosynthetic enzymes, regulators, and transporters by natural selection. This in turn may have led to the repeated evolution of glucosinolate metabolism and diversity in higher plants.

Intracontinental plant invader shows matching genetic and chemical profiles and might benefit from high defence variation within populations

Abstract Whereas many studies have revealed mechanisms driving plant invasions between continents, research on intracontinental range expanders is scarce. Therefore, we studied genetic, chemical and ecological traits of a range‐expanding Brassicaceae, assuming that high genetic diversity should maintain chemical variation, which potentially benefits the invasion success. Moreover, we expected that within‐individual defence diversity plays an essential role in biotic interactions. We compared Bunias orientalis L. plants from 16 populations of native, invasive or exotic non‐invasive origin. The genetic structure was investigated by analysing the plastid DNA and amplified fragment length polymorphisms. For characterisation of the leaf chemistry, metabolic fingerprinting and profiling of glucosinolates as defence compounds were performed. The plant defence potential was tested using the generalist herbivore Mamestra brassicae. We found two major genetic lineages, which were mirrored in distinct chemical fingerprints of the plants. Genetic differentiation patterns point to a multiple introduction history of B. orientalis underlying the range expansion. Moreover, the genetic distance between individuals was correlated with the distance in chemical features. Genetic diversity tended to be reduced in potential leading edge (exotic) populations and was positively associated with quantitative metabolic diversity. Concentrations of indole glucosinolates were elevated in non‐native populations, and high glucosinolate diversity was associated with low herbivore survival. Synthesis. This study suggests that the invasion success of this species may be facilitated by high chemical variation within populations. Moreover, high defence diversity within individuals of a population might be the main factor reducing herbivory and can be more important than the total concentration of defences. The combination of genetic and chemical analyses combined with bioassays revealed to be a powerful tool to study the differentiation between native and non‐native populations and should be applied more often to explore intraspecific divergence.

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.

Flowering Locus C (FLC) Is a Potential Major Regulator of Glucosinolate Content across Developmental Stages of Aethionema arabicum (Brassicaceae).

The biochemical defense of plants can change during their life-cycle and impact herbivore feeding and plant fitness. The annual species Aethionema arabicum is part of the sister clade to all other Brassicaceae. Hence, it holds a phylogenetically important position for studying crucifer trait evolution. Glucosinolates (GS) are essentially Brassicales-specific metabolites involved in plant defense. Using two Ae. arabicum accessions (TUR and CYP) we identify substantial differences in glucosinolate profiles and quantities between lines, tissues and developmental stages. We find tissue specific side-chain modifications in aliphatic GS: methylthioalkyl in leaves, methylsulfinylalkyl in fruits, and methylsulfonylalkyl in seeds. We also find large differences in absolute glucosinolate content between the two accessions (up to 10-fold in fruits) that suggest a regulatory factor is involved that is not part of the quintessential glucosinolate biosynthetic pathway. Consistent with this hypothesis, we identified a single major multi-trait quantitative trait locus controlling total GS concentration across tissues in a recombinant inbred line population derived from TUR and CYP. With fine-mapping, we narrowed the interval to a 58 kb region containing 15 genes, but lacking any known GS biosynthetic genes. The interval contains homologs of both the sulfate transporter SULTR2;1 and FLOWERING LOCUS C. Both loci have diverse functions controlling plant physiological and developmental processes and thus are potential candidates regulating glucosinolate variation across the life-cycle of Aethionema. Future work will investigate changes in gene expression of the candidates genes, the effects of GS variation on insect herbivores and the trade-offs between defense and reproduction.

The genome sequence of Barbarea vulgaris facilitates the study of ecological biochemistry

The genus Barbarea has emerged as a model for evolution and ecology of plant defense compounds, due to its unusual glucosinolate profile and production of saponins, unique to the Brassicaceae. One species, B. vulgaris, includes two ‘types’, G-type and P-type that differ in trichome density, and their glucosinolate and saponin profiles. A key difference is the stereochemistry of hydroxylation of their common phenethylglucosinolate backbone, leading to epimeric glucobarbarins. Here we report a draft genome sequence of the G-type, and re-sequencing of the P-type for comparison. This enables us to identify candidate genes underlying glucosinolate diversity, trichome density, and study the genetics of biochemical variation for glucosinolate and saponins. B. vulgaris is resistant to the diamondback moth, and may be exploited for “dead-end” trap cropping where glucosinolates stimulate oviposition and saponins deter larvae to the extent that they die. The B. vulgaris genome will promote the study of mechanisms in ecological biochemistry to benefit crop resistance breeding.

Macroevolutionary patterns of glucosinolate defense and tests of defense-escalation and resource availability hypotheses.

We explored macroevolutionary patterns of plant chemical defense in Streptanthus (Brassicaceae), tested for evolutionary escalation of defense, as predicted by Ehrlich and Raven's plant-herbivore coevolutionary arms-race hypothesis, and tested whether species inhabiting low-resource or harsh environments invest more in defense, as predicted by the resource availability hypothesis (RAH). We conducted phylogenetically explicit analyses using glucosinolate profiles, soil nutrient analyses, and microhabitat bareness estimates across 30 species of Streptanthus inhabiting varied environments and soils. We found weak to moderate phylogenetic signal in glucosinolate classes and no signal in total glucosinolate production; a trend toward evolutionary de-escalation in the numbers and diversity of glucosinolates, accompanied by an evolutionary increase in the proportion of aliphatic glucosinolates; some support for the RAH relative to soil macronutrients, but not relative to serpentine soil use; and that the number of glucosinolates increases with microhabitat bareness, which is associated with increased herbivory and drought. Weak phylogenetic signal in chemical defense has been observed in other plant systems. A more holistic approach incorporating other forms of defense might be necessary to confidently reject escalation of defense. That defense increases with microhabitat bareness supports the hypothesis that habitat bareness is an underappreciated selective force on plants in harsh environments.

Genetic analysis of glucosinolate variability in broccoli florets using genome-anchored single nucleotide polymorphisms.

The identification of genetic factors influencing the accumulation of individual glucosinolates in broccoli florets provides novel insight into the regulation of glucosinolate levels in Brassica vegetables and will accelerate the development of vegetables with glucosinolate profiles tailored to promote human health. Quantitative trait loci analysis of glucosinolate (GSL) variability was conducted with a B. oleracea (broccoli) mapping population, saturated with single nucleotide polymorphism markers from a high-density array designed for rapeseed (Brassica napus). In 4 years of analysis, 14 QTLs were associated with the accumulation of aliphatic, indolic, or aromatic GSLs in floret tissue. The accumulation of 3-carbon aliphatic GSLs (2-propenyl and 3-methylsulfinylpropyl) was primarily associated with a single QTL on C05, but common regulation of 4-carbon aliphatic GSLs was not observed. A single locus on C09, associated with up to 40 % of the phenotypic variability of 2-hydroxy-3-butenyl GSL over multiple years, was not associated with the variability of precursor compounds. Similarly, QTLs on C02, C04, and C09 were associated with 4-methylsulfinylbutyl GSL concentration over multiple years but were not significantly associated with downstream compounds. Genome-specific SNP markers were used to identify candidate genes that co-localized to marker intervals and previously sequenced Brassica oleracea BAC clones containing known GSL genes (GSL-ALK, GSL-PRO, and GSL-ELONG) were aligned to the genomic sequence, providing support that at least three of our 14 QTLs likely correspond to previously identified GSL loci. The results demonstrate that previously identified loci do not fully explain GSL variation in broccoli. The identification of additional genetic factors influencing the accumulation of GSL in broccoli florets provides novel insight into the regulation of GSL levels in Brassicaceae and will accelerate development of vegetables with modified or enhanced GSL profiles.

Fundamental Differences between Perennial Wall Rocket and Annual Garden Rocket Influence the Commercial Year-Round Supply of These Crops

Perennial wall rocket (Diplotaxis tenuifolia [L.] DC.) and annual garden rocket (Eruca sativa Mill.) are cultivated around the world as salad crops and as an ingredient of condiments. From a botanical perspective these species are classified in the Rapa/Oleracea linage, which is consistent with their similar morphological characteristics, chromosomal number and the diversity of glucosinolates. It is understandable that these species have been informally grouped together for convenience. However, the evaluation of a wide range of factors over a typical production cycle has clearly illustrated that these species should be considered distinct crops from a commercial perspective. We will demonstrate with examples why these species should be managed differently and considered commercially distinct crops.