Leaf Lettuce Research Articles

Inactivation of Salmonella enterica on post-harvest cantaloupe and lettuce by a lytic bacteriophage cocktail

Salmonella enterica (S. enterica) is a causative agent of multiple outbreaks of foodborne illness associated with fresh produce, including pre-cut melon and leafy vegetables. Current industrial antimicrobial interventions have been shown to reduce microbial populations by <90%. Consequently, bacteriophages have been suggested as an alternative to chemical sanitizers. Seven S. enterica strains from four serovars (105 CFU/mL) were separately inoculated onto excised pieces of Romaine lettuce leaf and cantaloupe flesh treated with a five-strain bacteriophage cocktail 24 h before S. enterica inoculation. S. enterica, total aerobic populations and water activity were measured immediately after inoculation and after 1 and 2 days of incubation at 8 °C. The efficacy of the bacteriophage cocktail varied between strains. Populations of S. enterica Enteritidis strain S3, S. Javiana S203, S. Javiana S200 were reduced by > 3 log CFU/g and S. Newport S2 by 1 log CFU/g on both lettuce and cantaloupe tissues at all sampling times. In contrast, populations of strains S. Thompson S193 and S194 were reduced by 2 log CFU/g on day 0 on lettuce, but were not significantly different (P > 0.05) from the controls thereafter, S. Newport S195 populations were reduced on lettuce by 1 log CFU/g on day 0 and no reductions were found on cantaloupe tissue. Both aerobic populations and water activity were higher on cantaloupe than on lettuce. The water activity of lettuce decreased significantly (P < 0.05) from 0.845 ± 0.027 on day 0–0.494 ± 0.022 on day 1, but that of cantaloupe remained between 0.977 and 0.993 from day 0–2. The results of this study showed that bacteriophages can reduce S. enterica populations on lettuce and cantaloupe tissues but that the magnitude of the effect was strain-dependent.

Visual quality and waste of leafy vegetable and fresh herbs in a typical retail market

Because of their high perishability, leafy vegetables and fresh herbs are transported to the market soon after harvest. It is very likely that most of the damage caused in the farm and during transport will result in food discard only later in the retail market or in the household. Inadequate handling and marketing strategies in the store are expected to further contribute to waste. The study was designed to address the following questions: (1) what is the visual quality of leafy vegetables and fresh herbs received in the retail market; (2) what is the volume of discard of these produce in the retail market (3) what are the main causes of discard and (4) how these variables are influenced by the vegetable species, the suppliers and the stores evaluated. The study was conducted in 4 stores of a regional supermarket chain in Distrito Federal – Brazil, for a period of 6 months. It was evaluated: (1) number of produce items received and discarded; (2) visual quality of produce at reception; (3) cause of discard. The operations in each shop were described based on observations and discussion with the store staff. When considering the sum of all produce, the discard (expressed as units per day and corrected for quantity purchased) was influenced by all the factors studied, namely store, supplier and day of the week. Delivery of produce with any signs of wilting and yellowing was negligible but produce with bruised and old leaves which should have been trimmed in the farm were frequent. Visual quality was important to determine shelf life and preference by the consumer but how important it was depended on other factors such as the produce considered and the workflow in the store. The percentage of discard varied from 8.7 % to 97.0 % of the number of units purchased. Smaller waste volume was observed for spring onion, parsley, coriander, collard, leak and green leaf lettuce. Waste volume equal to or above 50 % was observed for vegetables baby romaine lettuce, broad leaved endive, wild chicory and mustard greens and fresh herbs sage and thyme. The vegetable and fresh herbs discard in the Brazilian retail market is in great measure the result of technological constraints and are not intentional. The implications of this situation in the definitions of food waste and food loss are discussed.

Influence of lighting spectral characteristics on the lettuce leaf optical properties

The paper concerns the efficiency of light absorption with different spectral composition by lettuce leaves, and the optimal conditions of light environment and mineral nutrition to increase the productivity and quality of plant products grown under artificial lighting. The greatest positive effect has been achieved on the productivity and quality of the lettuce plants Typhoon variety when been grown on the 1N Knop nutrient solution and illuminated with quasi-continuous spectrum in a limited wavelength range in the yellow area with addition of ∼ 10-20% of the total photosynthetically active radiation (PAR) in the near infrared. The most efficient conditions results in the increase on amount of absorbed photon energy by ∼ 40% per gram of plant leaf surface over 10 days when rapid biomass growth and plant development take place. It is proposed to use the index of light absorption, describing the absorption increment with biomass growth, as an indicator for the intensity of light energy processing into biomass.

Development of deep learning method for lead content prediction of lettuce leaf using hyperspectral images

ABSTRACTThe validity and reliability of visible–near infrared (Vis–NIR) hyperspectral imaging were investigated for the determination of lead concentration in lettuce leaves. Besides, a method involving wavelet transform and stacked auto-encoders (WT-SAE) is proposed to decompose the spectral data in the multi-scale transform and obtain the deep spectral features. The Vis–NIR hyperspectral images of 1120 lettuce leaf samples were obtained and the whole region of lettuce leaf sample spectral data was collected and preprocessed. In addition, WT-SAE the deep spectral features using db5 as wavelet basis function, and support vector machine regression (SVR) was used for regression modelling. Furthermore, the best prediction performances for detecting lead (Pb) concentration in lettuce leaves was obtained from raw data set, with coefficient of determination for calibration (Rc2) of 0.9911, root mean square error for calibration (RMSEC) of 0.05187, coefficient of determination for prediction (Rp2) of 0.9590, root mean square error for prediction (RMSEP) of 0.05587 and residual predictive deviation (RPD) of 3.251 using db5 as wavelet basis function with wavelet fifth layer decomposition. The results of this study indicated that WT-SAE can effectively select the optimal deep spectral features and Vis–NIR hyperspectral imaging has great potential for detecting lead content in lettuce leaves.

The distinct impact of multi-color LED light on nitrate, amino acid, soluble sugar and organic acid contents in red and green leaf lettuce cultivated in controlled environment

In this study we explore the effects of multi-colour LED lighting spectrum on nutritive primary metabolites in green (‘Lobjoits green cos’) and red (‘Red cos’) leaf lettuce (Lactuca sativa L.), cultivated in controlled environment. The basal lighting, consisting of blue 455 nm, red 627 and 660 nm and far red 735 nm LEDs, was supplemented with UV-A 380 nm, green 510 nm, yellow 595 nm or orange 622 nm LED wavelengths at total photosynthetic photon flux density of 300 μmol m−2 s−1. Supplemental lighting colours did not affect lettuce growth; however had distinct impact on nitrite, amino acid, organic acid, and soluble sugar contents. Orange, green and UV-A light had differential effects on red and green leaf lettuce metabolism and interplay with nutritional value and safety of lettuce production. The metabolic response was cultivar specific; however green light had reasonable impact on the contents of nutritive primary metabolites in red and green leaf lettuce.

Influence of photoluminophore-modified agro textile spunbond on growth and photosynthesis of cabbage and lettuce plants.

Light-converting polypropylene spunbond was first used in the study of the key physiological parameters of plants. A comparative study of the functioning of the photosynthetic apparatus and the dynamics of growth in late cabbage plants (Olga variety) and leaf lettuce (Emerald variety) was conducted using the ordinary nonwoven polypropylene fabric (spunbond) (density 30 g·m-2) and the spunbond containing a photoluminophore (PL) (1.6% yttrium oxysulfide doped with europium). The plants were grown in a glass greenhouse without spunbond and under the spunbond containing and not containing the PL that transforms a part of UV-radiation into red light radiation. The use of the spunbond led to a decrease in the rate of photosynthesis, activity of the photosystem 2, and the accumulation of plant biomass and to an increase in the stomatal conductance. By contrast to unmodified spunbond, the application of the spunbond containing the PL led to an increase in the rate of photosynthesis, the water-use efficiency (WUE), and the accumulation of the total biomass of plants by 30-50% but to a decrease in the transpiration rate and the stomatal conductance. It is assumed that the positive effect of the PL is associated with an increase in the fraction of fluorescent red light, which enhances photosynthetic activity and accelerates plant growth.

Comparison of romaine, loose leaf and iceberg lettuces grown in saline

Comparison of romaine, loose leaf and iceberg lettuces grown in saline

Effect of Vegetal- and Seaweed Extract-Based Biostimulants on Agronomical and Leaf Quality Traits of Plastic Tunnel-Grown Baby Lettuce under Four Regimes of Nitrogen Fertilization

Nitrogen (N) fertilizers play a crucial role in agriculture, representing a powerful tool for farmers for increasing yields throughout the seasons under both optimal and suboptimal conditions. At the same time, their synthetic/chemical nature could have several influences on ecosystems and human health. For this reason, there is an urgent need to find new and more sustainable means of production to increase plant productivity and optimize nitrogen use. An experiment was conducted in a plastic tunnel to assess the response of baby lettuce crop to the foliar application of three plant biostimulants (PBs): Legume-derived protein hydrolysate (LDPH) ‘Trainer®’, tropical plant extract (TPE) ‘Auxym®’ and seaweed extract (SwE) from Ecklonia maxima ‘Kelpak®’ under different N rates of 0, 10, 20 and 30 kg N·ha−1. The responses of baby lettuce plants were assessed in terms of yield, growth parameters and physicochemical composition of the leaves. The fresh yield of baby lettuce in both biostimulant-treated and untreated plants was positively affected by increasing N rates from 0 to 20 kg N·ha−1, reaching a plateau thereafter indicating luxury N conditions at 30 kg N·ha−1. However, high N fertilizer application (20 and especially 30 kg N·ha−1) resulted in undesirable decreases in antioxidant activities and total ascorbic acid (TAA). Under non-fertilized regimens, foliar PBs application boost growth and yield of baby lettuce in comparison to non-treated plants. Foliar spray with LDPH and especially SwE elicited significant increases in marketable fresh yield (averaging 14%, 6% and 7% at 10, 20 and 30 kg N·ha−1, respectively) compared to TPE and untreated plants. Improved agronomical performance of baby lettuce under optimal (10 kg N ha−1) and especially suboptimal N regimens (0 kg N ha−1) was associated with increasing photochemical efficiency and a better activity of photosystem II (higher Soil Plant Analysis Development-SPAD index and chlorophyllous pigments biosynthesis). The application of LDPH enhanced antioxidant capacity and TAA in baby lettuce leaf and did not increased nitrate content as recorded in SwE and TPE treatments. Overall, plant biostimulants may be considered as a sustainable tool of production to increase leafy vegetable productivity in low fertility soils.

Leaf cuticular waxes of lettuce are associated with reduced attachment of the foodborne pathogen Salmonella spp. at harvest and after postharvest storage

The amount and composition of cuticular wax on bolting lettuce leaves of different maturity was shown to be associated with Salmonella attachment and survival. The amount of cuticular wax on leaves from the top (40.9 ± 4.7 μg cm−2) and middle stem (44.7 ± 2.9 μg cm−2) locations was significantly greater than that observed on those from the bottom area (17.5 ± 11.9 μg cm−2). Salmonella attachment was compared between leaves from the middle of the lettuce stem (a visible waxy layer) and mature leaves from the lettuce rosette (lacking with a visible waxy layer) to assess the impact of these crystals. Mature rosette leaves on bolting lettuce showed significantly higher Salmonella attachment (5.72 ± 0.16 CFU g−1) than immature leaves (5.18 ± 0.30 CFU g−1) at harvest. After 7 days of storage at 4 °C, the Salmonella survival rate on mature leaves (5.16 ± 0.23 CFU g−1) was significantly higher (P = 0.01) than that observed on immature leaves (4.38 ± 0.33 CFU g−1). Hexacosanol was identified as the major component of platelet-shaped crystals in the recrystallized wax, which were similar to the wax structures on the lettuce leaf surface. These results suggest that the presence of wax crystals may affect Salmonella attachment on lettuce and that their primary component is hexacosanol.

Influence of Preharvest Gibberellic Acid Treatments on Postharvest Quality of Minimally Processed Leaf Lettuce and Rocket

Plant growth regulators are used in high-value vegetable crops during cultivation and after harvest to increase yield, enhance crop management, and improve or retain the produce quality. The aim of this work was to evaluate the quality characteristics during cold storage of minimally processed leaf lettuce and rocket, obtained from plants grown in a hydroponic floating system with mineral nutrient solutions (MNS) containing different levels of gibberellic acid (GA3). Plants were grown in greenhouse conditions on nutrient solutions containing 0, 10−8, and 10−6 M GA3. At harvest, lettuce and rocket were immediately processed as fresh-cut vegetables and stored for 21 d at 4 °C. After processing, weight loss, total soluble solids, titratable acidity, ascorbic acid and nitrate content, leaf color characteristics, and overall quality were evaluated. Adding 10−6 M GA3 to the MNS of a floating system significantly increased the yield of leaf lettuce and rocket plants and of minimally-processed leaves. In addition, preharvest GA3 treatments had positive effects on delaying senescence and enhancing shelf-life of minimally processed lettuce and rocket. The slowed senescence of GA3-treated samples maintained an overall quality over the threshold of marketability in both lettuce and rocket for up to 21 d of cold storage.

Lighting intensity and photoperiod serves tailoring nitrate assimilation indices in red and green baby leaf lettuce.

Understanding plant responses to light quantity in indoor horticultural systems is important for optimising lettuce growth and metabolism as well as energy utilisation efficiency. Light intensity and photoperiod sufficient for normal plant growth parameters might be not efficient for nitrate assimilation. Therefore, this study explored and compared the effects of different light intensities (100-500 μmol m-2 s-1 ) and photoperiods (12-24 h) on the growth and nitrate assimilation in red and green leaf lettuce (Lactuca sativa L.). For efficient nitrate assimilation, 300-400 μmol m-2 s-1 photosynthetic photon flux density (PPFD) and 16-18 h photoperiod is necessary for red and green lettuces. The insufficient light quantity resulted in reduced growth and remarkable increase in nitrate and nitrite contents in both cultivars. Short photoperiods, similarly to low PPFD, growth parameters, chlorophyll indices and nitrate assimilation indices showed the shortage of photosynthetic products for normal plant physiological processes. Short photoperiods had the least pronounced effect on nitrate and nitrite contents in lettuce leaves. Light intensity was superior compared to photoperiods for efficient nitrate assimilation in both lettuce cultivars. Under short photoperiods, similarly to low intensity, growth parameters, chlorophyll index and nitrate assimilation indices showed a shortage of photosynthetic products for normal physiological processes. The free amino acid concentration increased, but it was not efficiently incorporated in proteins, as their level in lettuce was lower compared to those for moderate photoperiods. © 2019 Society of Chemical Industry.

Genetic variation and relationship among content of vitamins, pigments, and sugars in baby leaf lettuce.

Baby leaf lettuce harvested approximately 30 days after planting is the primary component of spring mix salads, a popular type of packaged salads. Very little is known, however, about the content of vitamins, sugars, and pigments in young lettuce plants. Therefore, plants of 42 accessions harvested at baby leaf stage were analyzed for the contents of vitamin C, ß‐carotene, anthocyanins, chlorophylls, glucose, fructose, and sucrose. Significant differences among accessions were found for content of all seven compounds plus sucrose sweetness equivalency (SSE) and average vitamin load (AVLAC). “Floricos” was highest in all sugars, SSE and vitamin C; “Taiwan” was highest in ß‐carotene and AVLAC, and “Annapolis” and “Darkland” were highest for anthocyanins and chlorophyll contents, respectively. The lowest content of glucose and sucrose was found in iceberg “Salinas,” fructose in L. serriola accession UC96US23, vitamin C in PI 257288, and β‐carotene in “Solar.” The lowest relative sweetness (SSE) was calculated for UC96US23, followed by “Salinas,” while the lowest AVLAC was estimated for PI 257288. There were very strong, positive correlations among contents of the three sugars, and between β‐carotene and vitamin C, and β‐carotene and anthocyanins. Composition profiles of accessions presented in this study, together with identified associations between compounds, can be used by breeders, growers, and producers to select lettuces with desirable combinations of sugars, pigments, and vitamins. This information can help in development of new cultivars and breeding lines with desirable combination of traits, pleasing taste, and higher vitamin content.

Measured cup weights of ten raw leafy vegetables are lower than weights previously reported

Raw dark-green leafy vegetables (LVs) are excellent sources of vitamins A, C, K, folate and manganese. LV intake is reported in cups in the United States (US) and inaccurate cup weights could impact calculated nutrient composition. This project measured the cup weight of ten raw LVs purchased in Coralville, Iowa, compared them to weights reported in two US databases and the Nutrition Facts Label, and assessed changes in nutrient levels for a two-cup serving (one cup-equivalent, c-eq). Six individuals measured one package/head/bunch of each LV. Loosely/moderately packed pieces were weighed in a measuring cup to the nearest 0.1 g. Ready-to-eat produce was measured as purchased; heads/bunches were cut/torn into 2.5-cm pieces. All cup weights were significantly lower than weights previously reported (p < 0.05). Cup weights for seven LVs were <20 g. Highest weights were for Dole® Garden Salad and bok choy. Coefficients of variation between and within measurers were <16% except chopped parsley (35.3% between). LVs except leaf lettuce had one to three fewer nutrients (A, C, folate, manganese) at ≥20% Daily Value for one c-eq at the Iowa cup weight. New Iowa measured cup weights are lower than previously reported, which impacts the calculated nutrient composition.

Characterization of four polymorphic genes controlling red leaf colour in lettuce that have undergone disruptive selection since domestication.

SummaryAnthocyanins protect plants from biotic and abiotic stressors and provide great health benefits to consumers. In this study, we cloned four genes (Red Lettuce Leaves 1 to 4: RLL1 to RLL4) that contribute to colour variations in lettuce. The RLL1 gene encodes a bHLH transcription factor, and a 5‐bp deletion in some cultivars abolishes its function to activate the anthocyanin biosynthesis pathway. The RLL2 gene encodes an R2R3‐MYB transcription factor, which was derived from a duplication followed by mutations in its promoter region. The RLL3 gene encodes an R2‐MYB transcription factor, which down‐regulates anthocyanin biosynthesis through competing with RLL2 for interaction with RLL1; a mis‐sense mutation compromises the capacity of RLL3 to bind RLL1. The RLL4 gene encodes a WD‐40 transcription factor, homologous to the RUP genes suppressing the UV‐B signal transduction pathway in Arabidopsis; a mis‐sense mutation in rll4 attenuates its suppressing function, leading to a high concentration of anthocyanins. Sequence analysis of the RLL1‐RLL4 genes from wild and cultivated lettuce showed that their function‐changing mutations occurred after domestication. The mutations in rll1 disrupt anthocyanin biosynthesis, while the mutations in RLL2, rll3 and rll4 activate anthocyanin biosynthesis, showing disruptive selection for leaf colour during domestication of lettuce. The characterization of multiple polymorphic genes in this study provides the necessary molecular resources for the rational breeding of lettuce cultivars with distinct levels of red pigments and green cultivars with high levels of health‐promoting flavonoids.

Effect of Gibberellic Acid on Growth, Yield, and Quality of Leaf Lettuce and Rocket Grown in a Floating System

Gibberellins (GAs) are growth hormones strongly involved in a wide variety of physiological activities. Currently, gibberellins are commercially used to enhance phenotypic characteristics, earliness, and productivity of many vegetable and ornamental crops. In this work, the efficacy of supplementation of low levels of gibberellic acid (0, 10−8, 10−6, and 10−4 M GA3) through the mineral nutrient solution of a floating system on yield and quality of leaf lettuce and rocket plants was tested. The marketability of plants was lost when 10−4 M GA3 was added to the mineral nutrient solution. This study demonstrated that the addition of 10−4 M GA3 exceeded the acceptable threshold for use in hydroponics production systems. Below the concentration of 10−4 M, the presence of GA3 in the mineral nutrient solutions (MNS), especially at 10−6 M GA3, stimulated plant growth and enhanced the yield. Various morphological and physiological traits were enhanced by GA3 treatments (biomass accumulation, leaf expansion, stomatal conductance, water use efficiency (WUE), Nitrogen use efficiency (NUE), etc.), with superimposable trends in both lettuce and rocket. The addition of 10−6 M GA3 to the nutrient solution of a hydroponic floating system can promote growth and quality of lettuce and rocket plants.

Effects of exogenous putrescine on the ultrastructure of and calcium ion flow rate in lettuce leaf epidermal cells under drought stress

The alleviation effects of exogenous putrescine treatment on the ultrastructure of and calcium ion flow rate in lettuce (Lactuca sativa L.) leaf cells under drought stress were studied. Lettuce seedlings were treated with foliar sprays of 0.1 mM putrescine for 8 days, after which drought stress was simulated by using 10% polyethylene glycol 6000. The morphological characteristics of the seedlings and the calcium ion flow rate across stomatal guard cells were subsequently determined, and the leaf cell ultrastructure was observed via transmission electron microscopy. Under drought stress, the morphological characteristics of the seedlings decreased, and calcium ion influx was predominant in the guard cells. In addition, compared to that under control conditions, the stomatal density under drought stress conditions increased significantly, the open/closed stoma ratio was lower, and the degree of stomatal opening was smaller. Exogenous putrescine sprays effectively reduced the stomatal density, increased the degree of stomatal opening, and increased the proportion of open stomata. In addition, the chloroplasts became round in shape, the thylakoid structure became blurry in appearance, the number of starch grains decreased, many osmium granules were produced, and plasmolysis occurred in the mesophyll cells. However, the chloroplasts were elongated, the thylakoid structure was clear, the starch grains were abundant, few osmium granules were produced, and plasmolysis did not occur. The above results show that, by altering the leaf cell ultrastructure as well as the flow rate and direction of calcium ions in guard cells, exogenous putrescine effectively improves the drought tolerance of lettuce.

The Kinetics and Mechanisms for Photodegradation of Nitrated Polycyclic Aromatic Hydrocarbons on Lettuce Leaf Surfaces: An In Vivo Study.

Insights into the environmental fates of nitrated polycyclic aromatic hydrocarbons (NPAHs) in edible vegetables are of great significance for better evaluating human exposure to NPAHs through the dietary pathway. In this work, a fluorescence quenching method using graphene quantum dots as a fluorescent probe was first applied for the in vivo determination of 9-nitroanthracene (9-NAnt) and 1-nitropyrene (1-NPyr) adsorbed on the leaf surfaces of living lettuce (Lactuca sativa L.) seedlings. Moreover, the photolysis kinetics and mechanisms of the two adsorbed NPAHs were discussed. The photodegradation kinetics followed the pseudo-first-order equation, and the photodegradation half-life of 1-NPyr (7.4 ± 0.2 h) was greater than that of 9-NAnt (2.3 ± 0.1 h). Anthraquinone and pyrenediones were identified to be the main photolytic products of 9-NAnt and 1-NPyr, respectively. Intramolecular rearrangement was the most reasonable mechanism for the NPAH photolysis. The photolysis-driven degradation exhibited a key role in scavenging NPAHs from the vegetable leaf, indicating the reduction of NPAH transportation in the food chain.

P-Phenylenediamine-modified graphene oxide as a sorbent for solid-phase extraction of phenylurea herbicides, nitroimidazoles, chlorophenols, phenylurea insecticides and phthalates.

Graphene oxide was covalently modified with p-phenylenediamine via a diazonium reaction. The resulting material was employed as a sorbent for the solid-phase extraction of six phenylurea herbicides (metoxuron, monuron, chlortoluron, isoproturon, monolinuron, and buturon) from environmental water and lettuce leafs. Some key factors that influence the extraction efficiency were studied, including sample loading rate, sample pH, and desorption conditions. Following desorption with acetonitrile, the analytes were quantified by HPLC with UV detection. Under optimized conditions, response to phenylurea herbicides is linear in the 2.0-100ngmL-1 concentration range for water samples, and 5.0-100ngg-1 for leaf lettuces. The limits of detection are 0.10-0.25ngmL-1 for water samples, and 1.5-2.5ngg-1 for leaf lettuces. The sorbent was also applied to the preconcentration of organic compounds including nitroimidazoles, chlorophenols, phenylurea insecticides and phthalates. This shows that this sorbent has a large potential for the enrichment of organic pollutants. Graphical abstract A graphene oxide/p-phenylenediamine (GO@PA) composite was prepared via a simple and environmentally-friendly diazonium reaction between p-phenylenediamine diazonium salt and graphene oxide. It was used as the solid phase extraction (SPE) adsorbent to extract phenylurea herbicides with the extraction efficiency higher than that of commercial C18, multi-walled carbon nanotube and polystyrene polymer. The SPE method was combined with HPLC for simultaneous determination of six phenylurea herbicides in environment water and vegetable samples.

Lettuce-derived secretory IgA specifically neutralizes the Shiga toxin 1 activity.

An edible plant was tested as a host for the production of secretory monoclonal IgA against Shiga toxin 1 (Stx1). The lettuce-derived IgA completely protected Vero cells from Stx1. Secretory immunoglobulin A (SIgA) is thought to control mucosal infections and thus it may be applicable to oral passive immunotherapy. Edible plants are candidate hosts for producing oral formulations with SIgA against pathogenic agents. We previously established a recombinant IgA specific for the B subunit of Shiga toxin 1 (Stx1B) consisting of the Fab fragment of Stx1B-specific monoclonal IgG and the Fc region of IgA (hyIgA). Here, we developed transgenic lettuce (Lactuca sativa) that produces hyIgA in a secretory form (S-hyIgA). An Arabidopsis-derived light-harvesting complex II (LHCB) promoter was used for the expression of all four transgenes (hyIgA heavy, light and j chains, and secretory component). Agrobacterium-mediated transformation was carried out to introduce genes into lettuce leaf discs by means of a single vector harboring all four transgenes. Consistent with the tissue specificity of the LHCB promoter, the expression of hyIgA transgenes was observed in leaf and stem tissues, which contain chloroplasts, at the mRNA and protein levels. The leaves produced hyIgA in a more than tenfold higher yield as compared with stems. The lettuce-derived S-hyIgA was found to bind to Stx1B in a dose-dependent manner by means of ELISA. A leaf extract of the transgenic lettuce completely neutralized the cytotoxicity of Stx1 against Vero cells, which are highly susceptible to Stx1. In conclusion, we established a transgenic lettuce producing a secretory form of hyIgA that can bind bacterial toxin. The results indicate that edible practical plants containing S-hyIgA will provide a possible means for immunotherapy for food poisoning.

Use of black soldier fly (Hermetia illucens (L.), Diptera: Stratiomyidae) larvae processing residue in peat-based growing media

The Black Soldier Fly (Hermetia illucens (L.), Diptera: Stratiomyidae) is an insect whose larvae thrive on agro-industrial by-products. This study reports the first use of black soldier fly larvae processing residue (BSPR) as an innovative ingredient for growing media. BSPR was characterized and evaluated to partially replace commercial peat (CP) in the production of potted plants. Chemical and microbiological analysis showed the suitability of BSPR for soilless production. Hence, six growing media mixtures (CP 100% + slow acting synthetic solid fertilizer, CP 90% + BSPR 10%, CP 80% + BSPR 20%, CP 70% + BSPR 30%, CP 60% + BSPR 40% and CP 100% without fertilizer) were assessed for the production of baby leaf lettuce, basil and tomato potted plants. Using BSPR in a proportion up to 20%, all investigated crops showed values significantly greater than or comparable to those obtained using CP 100% + slow acting synthetic solid fertilizer. In general, BSPR used in a proportion up to 20% increased the crop growth of baby leaf lettuce, basil and tomato, recording a high total dry weight (+31%, compared to the total average) and the measured leaf parameters (+39% of leaf area, +14% of leaf number), without showing abiotic stresses. This study indicates that BSPR used in a proportion up to 20% might be a valid approach for soilless production of potted baby leaf lettuce, basil and tomato plants.