Trichoderma hamatum Increases Productivity, Glucosinolate Content and Antioxidant Potential of Different Leafy Brassica Vegetables

Brassica crops include important vegetables known as “superfoods” due to the content of phytochemicals of great interest to human health, such as glucosinolates (GSLs) and antioxidant compounds. On the other hand, Trichoderma is a genus of filamentous fungi that includes several species described as biostimulants and/or biological control agents in agriculture. In a previous work, an endophytic strain of Trichoderma hamatum was isolated from kale roots (Brassica oleracea var. acephala), describing its ability to induce systemic resistance in its host plant. In the present work, some of the main leafy Brassica crops (kale, cabbage, leaf rape and turnip greens) have been root-inoculated with T. hamatum, having the aim to verify the possible capacity of the fungus as a biostimulant in productivity as well as the foliar content of GSLs and its antioxidant potential, in order to improve these “superfoods”. The results reported, for the first time, an increase in the productivity of kale (55%), cabbage (36%) and turnip greens (46%) by T. hamatum root inoculation. Furthermore, fungal inoculation reported a significant increase in the content of total GSLs in cabbage and turnip greens, mainly of the GSLs sinigrin and gluconapin, respectively, along with an increase in their antioxidant capacity. Therefore, T. hamatum could be a good agricultural biostimulant in leafy Brassica crops, increasing the content of GSLs and antioxidant potential of great food and health interest.

Effects of Different Light Spectra on Final Biomass Production and Nutritional Quality of Two Microgreens

To improve microgreen yield and nutritional quality, suitable light spectra can be used. Two species—amaranth (Amaranthus tricolor L.) and turnip greens (Brassica rapa L. subsp. oleifera (DC.) Metzg)—were studied. The experiment was performed in a controlled LED environment growth chamber (day/night temperatures of 24 ± 2 °C, 16 h photoperiod, and 50/60% relative humidity). Three emission wavelengths of a light-emitting diode (LED) were adopted for microgreen lighting: (1) white LED (W); (2) blue LED (B), and (3) red LED (R); the photosynthetic photon flux densities were 200 ± 5 µmol for all light spectra. The response to light spectra was often species-specific, and the interaction effects were significant. Morphobiometric parameters were influenced by species, light, and their interaction; at harvest, in both species, the fresh weight was significantly greater under B. In amaranth, Chl a was maximized in B, whereas it did not change with light in turnip greens. Sugar content varied with the species but not with the light spectra. Nitrate content of shoots greatly varied with the species; in amaranth, more nitrates were measured in R, while no difference in turnip greens was registered for the light spectrum effect. Polyphenols were maximized under B in both species, while R depressed the polyphenol content in amaranth.

Phytochemical characterization of turnip greens (Brassica rapa ssp. rapa): A systematic review

Objective The Turnip (Brassica rapa L. ssp. rapa) is a leaf and root vegetable grown and consumed worldwide. The consumption of Turnip has been associated with beneficial effects on human health due to their phytochemicals that may control a variety of physiological functions, including antioxidant activity, enzyme regulation, and apoptotic control and the cell cycle. The current systematic review of the literature aims to evaluate both the profile and quantity of phytochemicals commonly found in Turnip greens and to provide perspectives for further investigation. Methods This review was conducted following the PRISMA guidelines. Four bibliographic databases (PubMed, Embase, Web-of-Science and Cochrane Central Register of Controlled Trials) were searched to identify published studies until April 8th, 2020 (date last searched) without data and language restriction. Studies were included if they used samples of Turnip greens (the leaves), and evaluated its phytochemical content. Two reviewers independently evaluated the titles and abstracts according to the selection criteria. For each potentially eligible study, two reviewers assessed the full-texts and independently extracted the data using a predesigned data extraction form. Results Based on the search strategy 5,077 potentially relevant citations were identified and full texts of 37 studies were evaluated, among which 18 studies were eligible to be included in the current review. The majority of included studies were focused on identification of glucosinolates and isothiocyanates (n = 14, 82%), four studies focused on organic acids, and five studies reported phenolic component profile in Turnip greens. Among included studies nine studies (50%) provided information on phytochemical’s content. We found 129 phytochemicals (19 glucosinolates, 33 glucosinolate-breakdown products, 10 organic acids and 59 polyphenolic compounds) reported in Turnip greens. Flavonoids were mainly present as quercetin, kaempferol and isorhamnetin derivatives; while aliphatic forms were the predominant glucosinolate (gluconapin was the most common across five studies, followed by glucobrassicanapin). In general, the phytochemical content varied among the leaves, tops and Turnip roots. Conclusions Emerging evidence suggests the Turnip as a substantial source of diverse bioactive compounds. However, detailed investigation on the pure compounds derived from Turnip green, their bioavailability, transport and metabolism after consumption is further needed. Additional studies on their biological activity are crucial to develop dietary recommendations on the effective dosage and dietary recommendation of Turnip greens for nutrition and health.

Evaluation of Italian and Spanish Accessions of Brassica rapa L.: Effect of Flowering Earliness on Fresh Yield and Biological Value

A comparative study for evaluating Italian and Spanish accessions of Brassica rapa var. rapa L., including turnip greens and turnip tops, was carried out at different locations with a view to determine the effect of earliness on crop production, antioxidant activity, glucosinolates amount, and profile (GLSs) and total phenolics content. The accessions evaluated were represented by two turnip top local varieties (one Italian variety and a Galician one), four new synthetic varieties established by Misión Biológica de Galicia (MBG-CSIC), and three commercial varieties widely used by growers in Galicia and in Italy. The results showed a great variability regarding flowering time, fresh and dry weight of the leaves and flower buds, and the branch number per plant. The highest turnip greens production was found in two synthetic varieties (“SIN07” and “SIN01”) for both countries. Local varieties “BRS550” and “CM39” were also suitable for turnip greens production in Spain and Italy, respectively. For turnip tops, the highest production was found for “SIN07” in Spain, for “CM39” in Italy and for “BRS550” in both countries. We found a high diversity in the total and individual glucosinolate, phenolic content, and antioxidant activity among genotypes, geographical origins, and the different parts of the plant (leaf and flower). Varieties “SIN01” and “SIN07” showed the highest values in total GLSs, total aliphatic and gluconapin contents in turnip greens followed by the two commercial varieties. For turnip tops, the highest values in gluconapin, aliphatic, and total GLSs contents were found in “SIN01” and “BRS550”. Even though different varieties stand out over the rest depending on the location, “SIN01”, “SIN07”, “CM39”, and “BRS550” could be recommended for turnip greens production because of its high antioxidant activity. The study showed that the latest varieties are more productive and show higher bioactive compounds than the earlier ones and that it is possible to improve genotypes for different growing cycles. Therefore, these varieties could be proposed for further breeding programs for B. rapa production.

Analysis of the Acid Detergent Fibre Content in Turnip Greens and Turnip Tops (Brassica rapa L. Subsp. rapa) by Means of Near-Infrared Reflectance

Standard wet chemistry analytical techniques currently used to determine plant fibre constituents are costly, time-consuming and destructive. In this paper the potential of near-infrared reflectance spectroscopy (NIRS) to analyse the contents of acid detergent fibre (ADF) in turnip greens and turnip tops has been assessed. Three calibration equations were developed: in the equation without mathematical treatment the coefficient of determination (R2) was 0.91, in the first-derivative treatment equation R2 = 0.95 and in the second-derivative treatment R2 = 0.96. The estimation accuracy was based on RPD (the ratio between the standard deviation and the standard error of validation) and RER (the ratio between the range of ADF of the validation as a whole and the standard error of prediction) of the external validation. RPD and RER values were of 2.75 and 9.00 for the treatment without derivative, 3.41 and 11.79 with first-derivative, and 3.10 and 11.03 with second-derivative. With the acid detergent residue spectrum the wavelengths were identified and associated with the ADF contained in the sample. The results showed a great potential of NIRS for predicting ADF content in turnip greens and turnip tops.

First Report of Bacterial Leaf Blight on Mustard Greens (Brassica juncea) Caused by Pseudomonas cannabina pv. alisalensis in Mississippi

In 2010, a brassica leafy greens grower in Sunflower County, MS, observed scattered outbreaks of a leaf blight on mustard greens (Brassica juncea) in a 180-ha field. A severe outbreak of leaf blight occurred on mustard greens and turnip greens (B. rapa) in the same field in 2011 with more than 80 ha affected. The affected field, established in 2010, had no prior history of being cropped to brassica leafy greens. Symptoms appeared on the 6-week-old transplants as brown to tan necrotic spots with faint chlorotic borders and associated water-soaking. Lesions varied from 4 mm to 3 cm in diameter and often coalesced to cover >90% of older leaves. Whole plants of the mustard greens cv. Florida Broadleaf were collected in 2011 from the symptomatic field. Leaves were surface-disinfested with 0.5% NaOCl for 5 min, rinsed twice in sterilized distilled water [(sd)H2O], macerated in sdH2O, then streaked onto nutrient agar (NA), pseudomonas agar F (PAF), and potato dextrose agar (PDA). Little or no bacterial growth was observed on PDA, while on NA and PAF the majority of bacterial growth appeared to be a single colony type. All strains collected (25 total, one per plant) were gram-negative and fluoresced blue-green under UV light after 48 h at 28°C on PAF. All 25 strains were identified as belonging to Pseudomonas group 1a using Lelliot's determinative assay (2). Ten of the 25 strains were tested for pathogenicity on Florida Broadleaf, and turnip greens cv. Alamo. Bacteria were grown on PAF for 48 h, and a bacterial suspension was prepared and adjusted to an optical density of 0.1 at 600 nm. Three-week-old plants (three plants per cultivar) were sprayed with the appropriate bacterial suspension to runoff, placed at 100% relative humidity for 48 h, and then put in a growth chamber at 28°C with a 16-h diurnal light cycle for 14 days. Additionally, three plants each of Florida Broadleaf and Alamo were either sprayed with H2O or inoculated with Pseudomonas cannabina pv. alisalensis (Pca) pathotype strain BS91 (1). All 10 strains, as well as the Pca pathotype strain, were pathogenic on both cultivars and caused symptoms similar to those observed in the field. Symptoms were not observed on H2O-sprayed plants. Comparative rep-PCR analysis using the BOXA1R primer showed the 10 strains had identical DNA-banding profiles and were identical to that of Pca BS91 (5). Five strains tested using a Pca-specific, ‘light-tagged’ reporter bacteriophage gave a strong positive reaction, while a negative control strain, P. syringae pv. maculicola, gave no signal (3). From these tests, the isolated bacteria were determined to be Pca. Bacteria re-isolated on PAF from the inoculated Florida Broadleaf plants had identical rep-PCR profiles with those of the strains used for inoculations. Over the past 10 years, Pca has been found in numerous states in the United States, as well as in Europe, Australia, and Japan (4). As brassica leafy greens production expands to new fields and new states, leaf blight caused by Pca appears to become a problem rapidly. Since resistant cultivars and highly effective bactericides are lacking, growers are extremely concerned about the rapid spread of this disease into existing and new brassica leafy greens regions. References: (1) N. A. Cintas et al. Plant Dis. 86:992, 2002. (2) R. Lelliott. J. Appl. Bacteriol. 29:470, 1066. (3) D. Schofield et al. Appl. Environ. Microbiol. 78:3592, 2012. (4) F. Takahashi et al. J. Gen. Plant Pathol. 79:260, 2013. (5) J. Versalovic et al. Methods Mol. Cell Biol 5:25, 1994.