Diplotaxis Tenuifolia Research Articles

Variations in the most abundant types of glucosinolates found in the leaves of baby leaf rocket under typical commercial conditions

Changes in the concentration of the three most abundant glucosinolates were measured in the leaves of perennial wall rocket [Diplotaxis tenuifolia (L.) DC.], and annual garden rocket (Eruca sativa Mill.). HPLC-MS was used to identify glucoraphanin, 4-hydroxyglucobrassin and glucoerucin from perennial wall rocket, and glucoraphanin, glucobrassicin and 4-methoxyglucobrassicin from annual garden rocket. In separate experiments the responses of glucosinolates to harvest number, seasonal conditions, nitrogen supply and post-harvest storage conditions were measured. For perennial wall rocket, season influenced the concentration of glucoraphanin, which were highest for the spring [379 µg kg(-1) fresh weight (FW)] and summer (317 µg kg(-1) FW) plantings. The concentration of 4-hydroxyglucobrassin was higher in the leaves of first harvest crops. This response was due to this glucosinolate not being detected in the leaves of second harvest crops. Thus, the parent glucosinolate was altered between the first and second harvests in response to the abiotic stresses caused by harvesting. For annual garden rocket, there was an interaction between the harvest number and season for all glucosinolates measured. However, no clear response was observed between these factors. Higher concentrations of glucobrassicin and 4-methoxyglucobrassicin were measured for first harvest leaves when compared to the second harvest. This was due to the absence of detection of these glucosinolates in the leaves of second harvested plants; consequently higher total glucosinolate concentrations were measured for the first harvest winter (1224 µg kg(-1) FW) and summer (864 µg kg(-1) FW) crops. The concentrations of individual glucosinolates vary greatly over typical pre- and post-harvest commercial conditions. The absence of 4-hydroxyglucobrassin for perennial wall rocket, and glucobrassicin and 4-methoxyglucobrassicin for annual garden rocket between harvests, illustrates that abiotic stress from harvesting has the capacity to alter the types of glucosinolates in leaves. Concentrations do not generally decline during a typical storage period, indicating that the potential benefits of these compounds are not lost during post-harvest storage.

First Report of Necrotic Leaf Spot Caused by Plectosphaerella cucumerina on Lamb's Lettuce in Southern Italy

During spring 2013, lamb's lettuce plants (Valerianella locusta) cv. Calarasi (Rijk Zwaan) in a commercial greenhouse in Sele Valley (Salerno Province, southern Italy) exhibited small, black-brown, irregular spots (1 mm2) that became necrotic, enlarged, and coalesced. The spots were mostly on the tips of leaves, and were surrounded by a yellow halo. The disease was severe under greenhouse conditions of 60 to 90% RH and maximum air temperature of 26°C, and affected up to 70% of the plants. The greenhouses covered an area of ~3,000 ha where many salad species are grown. Tissue fragments were excised from symptomatic leaves, sterilized by sequential dipping in 70% ethanol for 30 s and in 1% NaOCl for 30 s, rinsed in sterilized distilled water, and placed in 9-cm-diameter petri dishes containing potato dextrose agar (PDA) medium amended with streptomycin sulfate (0.1 g/liter). The plates were incubated at 24°C in the dark. A fungus was isolated consistently from infected leaf tissue after 4 days. Each colony was whitish to orange. Mycelium was hyaline, branched, septate, 3 to 4 μm wide, with numerous anastomosis-forming hyphal coils. Conidiophores were solitary, hyaline, smooth, thin-walled, unbranched or rarely irregularly branched. Conidiogenous cells were phialidic, determinate, discrete, smooth, solitary, and formed on hyphal coils. Phialides were aseptate or occasionally 1-septate near the base. Conidia (n = 100) were ellipsoidal, hyaline, smooth, septate or aseptate, and 6.6 ± 0.9 × 2.8 ± 0.4 μm. On the basis of morphological criteria (3), the fungus was ascribed to Plectosphaerella cucumerina (L.) Laterr. (anamorph Plectosporium tabacinum). An aliquot (50 ng) of genomic DNA extracted from mycelium of five cultures obtained by monosporic isolation on PDA was used as template for a PCR reaction with primers ITS5/ITS4, specific for the ITS 5.8S rDNA region of fungi (3). The 500-bp sequences amplified from the five isolates were identical, and the sequence of isolate Val-2 was submitted to GenBank (KF753234). Sequence analysis with BLASTn showed 100% identity of this sequence to the ITS-5.8S rDNA sequences of 11 isolates of P. cucumerina in GenBank. Three isolates were selected for pathogenicity tests on the lamb's lettuce cv. Calarasi. Before planting, seeds were surface-disinfected in 1% NaOCl and rinsed with sterilized distilled water. Plants (35 days old, 30 plants tested/isolate) were grown in 0.7-liter pots filled with a sterilized (autoclaved at 112°C for 1 h on each of two consecutive days) mixture of soil:sand:perlite (2:1:1), and inoculated by spraying the leaves with a spore suspension (106 CFU/ml, ~3 ml applied/plant) of each isolate prepared from 7-day-old cultures on PDA. As a control, five plants were sprayed with sterilized water. All plants were incubated in a growth chamber at 90% RH with a 12-h photoperiod at 24°C. Leaf spots typical of those on the original symptomatic plants appeared 7 to 10 days after inoculation on all inoculated plants. No symptoms were observed on control plants. P. cucumerina was re-isolated only from symptomatic leaves, as described for the original isolations. P. cucumerina has been associated with root and collar roots of some horticultural crops (1), and a leaf spot on Diplotaxis tenuifolia (2), often grown in rotation with lamb's lettuce in southern Italy. To our knowledge, this is the first report of P. cucumerina as a pathogen of V. locusta in Italy or elsewhere. The disease caused economic loss to lamb's lettuce, primarily used in Italy in fresh-cut, mixed salads.

Effect of flat covers on macronutrient concentrations in arugula leaves

Arugula is a common name for several leafy vegetable species of the family Brassicaceae, characterized by a strong aroma and pungent peppery flavor. The perennial wall rocket Diplotaxis tenuifolia (L.) D.C. and the annual salad rocket Eruca sativa Mill. are grown commercially for human consumption. The objective of this study was to determine the effect of two types of flat covers, perforated PE film and non-woven PP fabric, on macroelement concentrations in arugula leaves. A two-factorial experiment was conducted in 2006 2008 in the Experimental Garden of the University of Warmia and Mazury in Olsztyn. The experimental factors were: (1) plant species Diplotaxis tenuifolia (L.) D.C. and Eruca sativa Mill., (2) the type of plant cover perforated PE film with 100 openings per m2 and non-woven PP fabric with surface density of 17 g m-2; plants grown without protective covers served as control. Arugula was grown on proper black earth soil of quality class IIIb and cereal-fodder strong complex. Each year, seeds were sown in the middle of April. After planting out in the field, the seedlings were covered with PE film or non-woven PP fabric. The covers were removed after approximately five weeks. Leaves were harvested gradually over the growing season, one to three times from each treatment. The concentrations of mineral compounds were determined in dried plant material from the first harvest, as follows: total nitrogen – by the Kjeldahl method, phosphorus – by the vanadium molybdate method, potassium and calcium – by emission flame photometry (EFP), magnesium – by atomic absorption spectrometry (AAS). The concentrations of all analyzed macroelements in arugula leaves were significantly affected by both plant species and the type of cover. Leaves of Diplotaxis tenuifolia (L.) D.C. had a higher content of phosphorus, potassium and calcium, whereas leaves of Eruca sativa Mill. accumulated more total nitrogen and magnesium. Leaves of arugula plants covered with non-woven PP fabric contained the highest concentrations of phosphorus, potassium, calcium and magnesium, while plants covered with PE film had the highest total nitrogen content. The Ca:P, Ca:Mg and K:Mg ratios were wide in all treatments. The K:(Ca+Mg) and K:Ca ratios were relatively narrow, but they remained within the normal range.

Wild rocket – effect of water deficit on growth, flowering, and attractiveness to pollinators

Wild rocket, Diplotaxis tenuifolia (L.) DC. (Brassicaceae), is one of the three cultivated rocket species, the demand and production of which have recently increased in Mediterranean countries where irrigation water is scarce. Besides its use as a crop, D. tenuifolia has been observed to flower for a long period and to be attractive to pollinators. In this study we assessed the effect of drought stress and moderate- and severe-deficit irrigation on growth, flower development, and attractiveness to pollinators in D. tenuifolia. The results showed that in greenhouse conditions, potted D. tenuifolia could be without irrigation for 4 days without affecting its growth, flowering, and attractiveness to pollinators. However, lack of irrigation for 8 days or longer significantly reduced the vegetative growth, number of open flowers, total floral area, flower diameter, corolla tube diameter, and corolla tube length of D. tenuifolia. This study shows that regulated-deficit irrigation can improve water use efficiency, and depending on the purpose of growing D. tenuifolia, as a crop or as a beneficial plant to attract pollinators, it can reduce water consumption from 40% to 70% without affecting its vegetative and floral development and without reducing its attractiveness to pollinators.

Tenualexin, Other Phytoalexins and Indole Glucosinolates from Wild Cruciferous Species

In general, the chemodiversity of phytoalexins, elicited metabolites involved in plant defense mechanisms against microbial pathogens, correlates with the biodiversity of their sources. In this work, the phytoalexins produced by four wild cruciferous species (Brassica tournefortii, Crambe abyssinica (crambe), Diplotaxis tenuifolia (sand rocket), and Diplotaxis tenuisiliqua (wall rocket)) were identified and quantified by HPLC with photodioarray and electrospray mass detectors. In addition, the production of indole glucosinolates, biosynthetic precursors of cruciferous phytoalexins, was evaluated. Tenualexin, (=2-(1,4-dimethoxy-1H-indol-3-yl)acetonitrile), the first cruciferous phytoalexin containing two MeO substituents in the indole ring, was isolated from D. tenuisiliqua, synthesized, and evaluated for antifungal activity. The phytoalexins cyclobrassinin and spirobrassinin were detected in B. tournefortii and C. abyssinica, whereas rutalexin and 4-methoxybrassinin were only found in B. tournefortii. D. tenuifolia, and D. tenuisiliqua produced 2-(1H-indol-3-yl)acetonitriles as phytoalexins. Because tenualexin appears to be one of the broad-range antifungals occurring in crucifers, it is suggested that D. tenuisiliqua may have disease resistance traits important to be incorporated in commercial breeding programs.

“Rock-Ad”, a new wild rocket (Diplotaxis tenuifolia) mutant with late flowering and delayed postharvest senescence

Wild rocket (Diplotaxis tenuifolia) is a leafy herb in salads and cooked dishes originating in the Mediterranean basin. The leaves contain many nutrients, plus beneficial phytochemicals such as flavonoids and glucosinolates. Rocket suffers from two major limitations: early bolting during growth and leaf yellowing after harvest, both of which affect both yield and market quality. We have used ethyl methanesulfonate (EMS) to induce mutation in wild rocket, and selected a mutant line (registered as cv. “Rock-Ad”), which has a two week delay in flowering time compared to current commercial cultivars. “Rock-Ad” plants began to flower when more than 50% of commercial plants had flowered. Storage properties of the mutant were also better than the commercial cultivar. In storage, after simulation of shipment by sea, there was no yellowing in young “Rock-Ad” leaves, chlorophyll levels were higher, fewer flower buds developed, and hydrophilic antioxidant levels decreased less than the commercial cultivar. Holding leaves in 5kPa CO2 in air decreased yellowing and decay significantly in both cultivars compared to air storage, while exposure to 2.23μmolL−1 ethylene increased yellowing and decay. When ethylene and CO2 were applied together (5kPa and 2.23μmolL−1, respectively), yellowing and decay decreased in both cultivars compared to air storage. 1-MCP treatment reduced yellowing and decay in leaves of the commercial variety, but had no effect on leaves of “Rock-Ad”. The respiration rate of the leaves increased after 7 days of storage in both cultivars, but was significantly higher in leaves of the commercial cultivar, and 1-MCP significantly moderated this increased respiration. Although treatment with 1-MCP led to increased ethylene levels on the first day after harvest, during storage, ethylene levels decreased in all treatments and cultivars.

Notas sobre algunas plantas ruderal-arvenses de Lanzarote (islas Canarias)

In this paper we comment 11 angiosperm taxa collected in Lanzarote Island. Two of them, Centaurea bimorpha and Diplotaxis tenuifolia, are recorded for the first time for the Canaries. Ammi majus, Centaurea diluta, Euphorbia cyatophora, Lathyrus cicera, and Tanacetum parthenium are new records for Lanzarote, while Amaranthus retroflexus, Anisantha rubens subsp. rubens, Polygonum aviculare and Vicia hirsuta are revived for the checklist of the vascular flora of the Island.

Phenolic profile evolution of different ready-to-eat baby-leaf vegetables during storage

Ready-to-eat baby-leaf vegetables market has been growing and offering to consumers convenient, healthy and appealing products, which may contain interesting bioactive compounds. In this work, the composition and the evolution of the phenolic compounds from different baby-leaf vegetables during refrigerated storage was studied. The phenolic compounds were extracted using pressurized liquid extraction (PLE) and the phenolic profile of each sample was analyzed and quantified by using LC–MS and LC–DAD methods, respectively, at the beginning and at the end of a 10-day storage period. The baby-leaf vegetables studied included green lettuce, ruby red lettuce, swiss chard, spinach, pea shoots, watercress, garden cress, mizuna, red mustard, wild rocket and spearmint samples and a total of 203 phenolic compounds were tentatively identified and quantified. The main naturally phenolic compounds identified correspond to glycosylated flavonoids, with exception of green lettuce and spearmint leaves which had a higher content of hydroxycinnamic acids. Quantification of the main compounds showed a 10-fold higher content of total phenolic content of ruby red lettuce (483mgg−1) in relation to the other samples, being the lowest values found in the garden cress (12.8mgg−1) and wild rocket leaves (8.1mgg−1). The total phenolic content only showed a significant change (p<0.05) after storage in the green lettuce (+17.5%), mizuna (+7.8%), red mustard (−23.7%) and spearmint (−13.8%) leaves. Within the different classes of phenolic compounds monitored, the flavonols showed more stable contents than the hydroxycinnamic and hydroxybenzoic acids, although the behavior of each compound varied strongly among samples.

Germination and electrical conductivity tests on artificially aged seed lots of 2 wall-rocket species

The aim of this study was to determine whether the loss of germinability and vigour in wall-rocket seed lots was related to electrolyte leakage. Ten seed lots of 2 wall-rocket species (9 of Diplotaxis tenuifolia and one of D. erucoides (Brassicaceae)) were stored at 45 °C and 70% relative humidity and electrolyte leakage was measured using the conductivity test. Small differences in longevity were found among species or seed lots, suggesting that a similar relative longevity might be expected within the genus Diplotaxis after artificial ageing, and that it will be above the average of that found in other species of the same family at similar storage conditions. Electrolyte loss was strongly related to loss of seed viability. There was a negative linear relationship between conductivity and seed germination (R2 = 0.85), and a positive relationship with T50 (R2 = 0.77). Small differences were found among species or seed lots regarding the correlation between electrolyte leakage and seed germination and vigour. Our results indicate that the conductivity method is able to predict the viability of wall-rocket seeds stored at 45 °C and 70% RH, with the same regression equation of conductivity and germination (–33.97x + 135.59) being able to predict the viability of different seed lots and species. A conductivity level ranging from 1.4 to 2.2 mS g–1 DW would indicate that the potential of a Diplotaxis seed lot to germinate has decreased to 80%. The correlation between electrolyte leakage and seed germination provides a valuable means for early detection of seed viability in wall-rocket seeds.

Antioxidant assays - consistent findings from FRAP and ORAC reveal a negative impact of organic cultivation on antioxidant potential in spinach but not watercress or rocket leaves.

Watercress (Rorippa nasturtium-aquaticum), wild rocket (Diplotaxis tenuifolia), and spinach (Spinacia oleracea) are commercial crops reported to have high concentrations of antioxidants, possibly contributing to disease prevention following human consumption. Following analysis of supermarket-purchased salad leaves, we report the antioxidant content potential of these species using two comparable techniques assessing the consistency between the assays – by the ferric reducing antioxidant power (FRAP) assay and the oxygen radical absorbance capacity (ORAC) assay. The leaves were harvested from both conventionally and organically managed crops, to investigate whether organic agriculture results in improved crop quality. Watercress had the highest FRAP and ability to scavenge free radicals, followed by spinach and rocket. For watercress and rocket, there was no significant effect of organic agriculture on FRAP and ORAC, but for spinach, the antioxidant potential was reduced and this was significant at the 5% level of probability for FRAP but not ORAC, although the trend was clear in both tests. We conclude that there is variation in salad crop antioxidant potential and that FRAP and ORAC are useful techniques for measuring antioxidants in these salad crops with similar ranking for each salad crop studied.

NEW DISEASES OF WILD AND CULTIVATED ROCKET IN ITALY

During the past ten years several diseases caused by soil-borne and foliar pathogens were observed for the first time in Italy on wild (Diplotaxis tenuifolia) and cultivated (Eruca sativa) rocket grown in intensive cropping systems for fresh cut production. This sector is particularly exposed to the risk of the emergence of new diseases as a consequence of its dynamism, specialization and use of intensive cultivation techniques. Two Fusarium wilts have been observed in Italy on wild and cultivated rocket. Among soil-borne pathogens, attacks of Rhizoctonia solani, and Pythium spp. were increasingly observed. Among foliar diseases, downy mildew of wild rocket and a leaf spot of wild and cultivated rocket caused by Alternaria japonica were recently observed. A new leaf spots caused by Fusarium equiseti, was observed for the first time in the world on Eruca sativa. During spring 2012, symptoms of an unusual leaf spot caused by Plectosphaerella cucumerina were observed in several commercial greenhouses near Salerno (southern Italy) on plants of D. tenuifolia. The biology, epidemiology, physiological characteristics of the causal agents are reported.

New sources of resistance to Sclerotinia sclerotiorum for crucifer crops

Current management of Sclerotinia rot (Sclerotinia sclerotiorum) relies heavily upon cultural and chemical control options that provide, at best, only partial, sometimes sporadic control and can be cost prohibitive. Effective host resistance to S. sclerotiorum is urgently needed if Sclerotinia rot is to be successfully managed across diverse oilseed, forage and vegetable crucifer crops worldwide. Differences in resistance across 127 diverse cruciferous genotypes to S. sclerotiorum in one experiment, and a set of 55 Brassica napus lines carrying one or more B. carinata B genome introgressions in a second experiment, were assessed by field-inoculation of stems and natural ascospore infection. Reactions on B. fruticulosa, B. oxyrrhina, B. parachinensis, B. tournefortii, Camelina sativa, Carrichtera annua, Diplotaxis tenuifolia, Eruca vesicaria, Hirschfeldia incana, Raphanus raphanistrum, Raphanus sativus, Rapistrum rugosum, Sinapis arvensis and Sisymbrium irio to this pathogen are reported for the first time. Among these, and across other species previously explored, including B. carinata, B. napus, B. juncea, B. rapa, B. cretica, B. incana, B. insularis, B. nigra, and B. montana, responses ranged from highly resistant (stem lesion length 2mm) to highly susceptible (155mm). Against a highly virulent and prevailing pathogen pathotype, R. raphanistrum RRA 41, B. napus Mystic, B. carinata BRA 926/78, B. carinata 054113, R. sativus Krasnodar. Market B, B. carinata PI 193459 and R. raphanistrum WARR 20 all showed very high-level resistance, with stem lesion length <5mm; with a further 29 genotypes across these species and/or B. incana, B. rapa var. rosularis, B. oleracea vars acephala and italica, and S. arvensis, that showed slightly less but still high resistance (lesions 5–10mm). Natural air-borne ascospore leaf infection occurred in 89% of plots, yet some forage and/or vegetable crucifers, such as B. rapa var. chinensis Ivory and R. sativus Oriental radish, showed high-level resistance to such infections. B. napus with introgression(s) from B. carinata, ranged from highly resistant (lesions <2mm) to very susceptible (>67mm). There appeared to be separate genetic control for stem vs. leaf resistance, crucial to the understanding needed in developing resistant cultivars across different cruciferous crop types. While this study highlighted individual genotypes that offer great potential for improving resistance to Sclerotinia rot in commercial cruciferous crops, it also demonstrated that assessment of the overall value of a species is only possible when a significant number of genotypes within the species are tested. Overall, while genotypes with high-level stem or leaf resistance identified are of particularly significant value for developing new disease-resistant cultivars of oilseed, forage and vegetable crucifers, even genotypes with moderate levels of resistance, if deployed commercially, offer prospects of improving current integrated disease management strategies compared with current reliance upon cultural and/or chemical controls utilized in conjunction with cultivars lacking any effective resistance. As resistance was identified for the first time across many of these diverse cruciferous species, it is likely that some resistances identified constitute new sources and/or types of host resistance not previously identified.

Preparative mass-spectrometry profiling of genotoxic pyrrolizidine alkaloids in Jacobaea vulgaris (syn. Senecio jacobaea) by spiral-coil countercurrent chromatography and ESI-MS/MS off-line continuous injection

Pyrrolizidine alkaloids (PAs) are genotoxic natural products. Almost 350 PAs are known with respective N-oxides. Legal regulations of PAs in food, and feed are discussed. There is a lack of available reference substances for targeted quantification [1]. PA-contamination was reported for honey, and bee products [2,3]. PA-contamination of retail ready-to-use lettuce was demonstrated. Morphological similarities of rocket salad (Diplotaxis tenuifolia, syn.: rucola), and the PA-plant Senecio vulgaris resulted in unintentional co-harvesting. In our study, PA-extract of J. vulgaris flower heads (Asteraceae) was fractionated by prep. spiral-coil countercurrent chromatography (spCCC, 5.7 L coil). The system n-hexane – EtOAc – MeOH – H2O (3:7:5:5) was used to separate 5 g of crude alkaloid extract. Obtained fractions were sequentially off-line injected to ESI-MS/MS. This target-guided isolation procedure [4] made use of selected ion traces of PAs. Elution of major (2, 5, 7), and minor (1, 3, 4, 6) PAs were monitored (altern. mode MS2, m/z 100 – 1500). The spCCC elution resulted in the fractionation of PAs, and one non-PA (8) in the extrusion-mode (8 not presented) [5]. Almost pure compounds were obtained for PAs 1, 2, 5, 7, and the non-PA 8 could be used as reference materials. Minor PAs were enriched and will be further purified with other separation techniques.

Noxious or nutritious? Progress in controlling nitrate as a contaminant in leafy crop species

AbstractHigh levels of nitrate in forage are a danger to the health of ruminant livestock consuming leafy crop species. Nitrate is also classed by food safety authorities as a contaminant in fresh produce. Since limits on nitrate levels in fresh produce marketed within the European Union were set, research has aimed to reduce nitrate, and to limit its variation. Progress is reported which focuses on the agronomy of a range of leafy salad crop species including lettuce (Lactuca sativa), spinach (Spinacea oleracea) and wild rocket (Diplotaxis tenuifolia). Genetic studies aiming to understand the sources of genetic variation in nitrate accumulation in lettuce are reviewed and considered in the context of research aiming to improve the nitrogen use efficiency of crop plants. Recent evidence is reported which suggests that nitrate could have significant health benefits that may contribute to the positive effects of eating a diet rich in fresh fruit and vegetables. Therefore, with the exception of babies and very young children, the risks from excess nitrate consumption are much greater for farm animals than they are for humans. Nevertheless, producers still need to carefully control nitrogen supply to leafy salad crops, to ensure that the risks of diffuse pollution from overuse of nitrogen fertilizer are minimized.

Italian Wild Rocket [Diplotaxis Tenuifolia (L.) DC.]: Influence of Agricultural Practices on Antioxidant Molecules and on Cytotoxicity and Antiproliferative Effects

Wild rocket [Diplotaxis tenuifolia (L.) DC.] belongs to the Brassicaceae family and has its origin in the Mediterranean region. The effect of conventional and integrated cultivation practices on the nutritional properties and benefits of wild rocket [Diplotaxis tenuifolia (L.) DC.] were studied. Bioactive molecules content (vitamin C, quercetin, lutein), antioxidant properties and bioactivity of polyphenolic extracts from the edible part of rocket in Caco-2 cells were determined. Regarding antioxidant properties, FRAP (Ferric Reducing Antioxidant Power) values ranged from 4.44 ± 0.11 mmol/kg fw to 9.92 ± 0.46 mmol/kg fw for conventional rocket and from 4.13 ± 0.17 fw mmol/kg to 11.02 ± 0.45 mmol/kg fw for integrated rocket. The characteristics of wild rocket as a dietary source of antioxidants have been pointed out. Significant differences in the quality of conventional and integrated rocket have been shown, while no influence of agronomic practice on biological activity was reported. A significant accumulation of cells in G1 phase and a consequent reduction in the S and G2 + M phases were observed in Caco-2 cells treated with rocket polyphenol extract.

Seed transmission of Plectosphaerella cucumerina, causal agent of leaf spot of Diplotaxis tenuifolia in Italy

Plectosphaerella cucumerina has been described recently as the causal agent of a leaf spot on wild rocket (Diplotaxis tenuifolia). Eight seed samples of wild rocket obtained from commercial seed lots used for sowing by farms severely affected by P. cucumerina, were assayed for the presence of the pathogen. Isolations were carried out on subsamples of seeds (400) unwashed or disinfected in 1% sodium hypochloride. The pathogenicity of the isolates of P. cucumerina obtained was tested in two trials carried out on wild rocket; four out of eight samples of rocket seeds were contaminated by P. cucumerina. Eleven isolates of P. cucumerina were obtained from 7,200 not disinfected seeds tested, while none was isolated from an equal number of disinfected seeds. All isolates were pathogenic on wild rocket. The results obtained indicate that rocket seeds are a potential source of inoculum for P. cucumerina. The possibility of isolating the pathogen from seeds, albeit from a low percentage of them, supports the hypothesis that the rapid spread of this new disease of rocket recently observed in Italy is due to the use of infected propagation material. Measures for prevention and control of the disease are discussed.

Nutritive Potentials of Allium Cepa and Diplotaxis Tenufolia Vegetable Leaf Protein Concentrates

Leaf protein concentrates were derived from two vegetable species; Allium ceppa and Diplotaxis Tenuifolia. The two samples were evaluated for their nutritional values using standard analytical techniques for proximate, amino acid and functional properties. In proximate analysis, ash, carbohydrates, proteins, fibre, fats and moisture were assayed, while amino acid was determined using method of Sparkman et al. and functional properties determined using method of coffman Gargia and Beuchat. The highest value of crude protein was recorded in Allium ceppa while Diplotaxis Tenuifolia has highest value of Nitrogen free extract. Other values of proximate analysis were present in significant proportion. The amino acid profile of the leaf protein concentrates indicated favourable nutritional balance except that tryptophan which is the limiting amino acid.The water absorption capacity, fat emulsion capacity foaming and foaming stability reveal good functional properties.

Electrical resistivity tomography to delineate greenhouse soil variability

Abstract Appropriate management of soil spatial variability is an important tool for optimizing farming inputs, with the result of yield increase and reduction of the environmental impact in field crops. Under greenhouses, several factors such as non-uniform irrigation and localized soil compaction can severely affect yield and quality. Additionally, if soil spatial variability is not taken into account, yield deficiencies are often compensated by extra-volumes of crop inputs; as a result, over-irrigation and overfertilization in some parts of the field may occur. Technology for spatially sound management of greenhouse crops is therefore needed to increase yield and quality and to address sustainability. In this experiment, 2D-electrical resistivity tomography was used as an exploratory tool to characterize greenhouse soil variability and its relations to wild rocket yield. Soil resistivity well matched biomass variation (R2=0.70), and was linked to differences in soil bulk density (R2=0.90), and clay content (R2=0.77). Electrical resistivity tomography shows a great potential in horticulture where there is a growing demand of sustainability coupled with the necessity of stabilizing yield and product quality.

Influence of Storage Temperature on the Seasonal Shelf Life of Perennial Wall Rocket and Annual Garden Rocket

Baby leaf crops, particularly leaves from plants commonly known as rocket, account for an increasing proportion of the global salad market due to their distinctive taste and texture. It is important to determine the effect of preharvest abiotic factors on the shelf life of these crops in order to improve the supply of quality produce with an appropriately long shelf life. The visual shelf life of minimally processed leaves of perennial wall rocket (Diplotaxis tenuifolia [L.] DC.) and annual garden rocket (Eruca sativa Mill.) were assessed across different harvest number, season, and storage temperature conditions. A separate experiment examined the effect of fertilizer rate on the shelf life of rocket crops. The shelf life of leaves from three growing seasons were determined at 0, 4, and 7°C, and leaves grown with various nitrogen rates were stored at 0°C. There was an interaction between harvest number, season, and storage temperature for both rocket crops, with storage at lower temperatures consistently resulting in longer shelf life. Under these conditions, the shelf life of perennial wall rocket was longest for the second harvest of the summer planting; for annual garden rocket the second harvest of the winter planting had the longest shelf life. The reasons for the response maybe related to differences in the carbon fixation and reproductive cycles of these plants. Substantial differences in shelf life across harvest number and season occurred for perennial wall rocket, where there was a variation in shelf life of 12 to 26 days when stored at 4°C. For annual garden rocket, an interaction among cultivar, harvest number, and season occurred, with the cv. Highway [ES5] having a shorter shelf life than the other cultivars for the first harvest of the winter planting. Nitrogen rate did not affect the shelf life of either crop. To achieve maximum shelf life, leaves should be stored at about 0°C.

Soil Suppressiveness to Fusarium Disease: Shifts in Root Microbiome Associated with Reduction of Pathogen Root Colonization

Soil suppressiveness to Fusarium disease was induced by incubating sandy soil with debris of wild rocket (WR; Diplotaxis tenuifolia) under field conditions. We studied microbial dynamics in the roots of cucumber seedlings following transplantation into WR-amended or nonamended soil, as influenced by inoculation with Fusarium oxysporum f. sp. radicis-cucumerinum. Disease symptoms initiated in nonamended soil 6 days after inoculation, compared with 14 days in WR-amended soil. Root infection by F. oxysporum f. sp. radicis-cucumerinum was quantified using real-time polymerase chain reaction (PCR). Target numbers were similar 3 days after inoculation for both WR-amended and nonamended soils, and were significantly lower (66%) 6 days after inoculation and transplanting into the suppressive (WR-amended) soil. This decrease in root colonization was correlated with a reduction in disease (60%) 21 days after inoculation and transplanting into the suppressive soil. Fungal community composition on cucumber roots was assessed using mass sequencing of fungal internal transcribed spacer gene fragments. Sequences related to F. oxysporum, Fusarium sp. 14005, Chaetomium sp. 15003, and an unclassified Ascomycota composed 96% of the total fungal sequences in all samples. The relative abundances of these major groups were highly affected by root inoculation with F. oxysporum f. sp. radicis-cucumerinum, with a 10-fold increase in F. oxysporum sequences, but were not affected by the WR amendment. Quantitative analysis and mass-sequencing methods indicated a qualitative shift in the root's bacterial community composition in suppressive soil, rather than a change in bacterial numbers. A sharp reduction in the size and root dominance of the Massilia population in suppressive soil was accompanied by a significant increase in the relative abundance of specific populations; namely, Rhizobium, Bacillus, Paenibacillus, and Streptomyces spp. Composition of the Streptomyces community shifted significantly, as determined by PCR denaturing gradient gel electrophoresis, resulting in an increase in the dominance of a specific population in suppressive soils after only 3 days. This shift was related mainly to the increase in Streptomyces humidus, a group previously described as antagonistic to phytopathogenic fungi. Thus, suitable soil amendment resulted in a shift in the root's bacterial communities, and infection by a virulent pathogen was contained by the root microbiome, leading to a reduced disease rate.