Lettuce Cultivars Research Articles

Diagrammatic scale for evaluation of Bremia lactucae sporulation in lettuce seedlings

In disease assessment, the use of diagrammatic scales provides a standard reference point for comparison. There is still no precise and accurate scale for the evaluation of sporulation intensity of downy mildew in lettuce seedlings. The objective of this study was to propose a diagrammatic scale for the evaluation of downy mildew severity in lettuce seedlings. Thirty lettuce seedlings with different sporulation intensities were used to develop the proposed diagrammatic scale. Solaris lettuce cultivar was sown, and fifteen days after sowing, inoculations occurred using distilled water, the pathogen sporangia, and Tween 20. The monitoring of disease development was performed daily.When the first sporulation appeared on the cotyledonaryleaves,the proposed scale was verified to meet the minimum and maximum levels of disease severity. Two evaluators verified the accuracy, precision and performed the estimation of the sporulation and reproducibility using a scale. The images obtained are important in the standardization of a scale to identify resistant, tolerant and susceptible plants to downy mildew. Furthermore, it allows validating a diagrammatic scale of sporulation intensity of B. lactucae in lettuce seedlings. Thus, it is the diagrammatic scale developed in the work will guide future research to accelerate the detection of mildew severity in lettuce seedlings.

Assessment of romaine lettuce cultivars grown in a vertical hydroponic system at two levels of LED light intensity

Romaine lettuce (Lactuca sativa var. longifolia) was cultivated in a hydroponic system, in the free-standing container equipped with two-shelf racks. The luminous intensity of the upper shelves was 200 µmol m−2 s−1, and that of the bottom was 160 µmol m−2 s−1. The plants were exposed to light for 16 h each day. Seven cultivars from two groups were cultivated in this study. There were four cultivars from the midi subtype (‘Casual,’ ‘Pivotal,’ ‘Delcaso,’ and ‘Airton’) and three from the mini subtype (‘Xiomara,’ ‘Coventry,’ and ‘Elizium’). The growth period of lettuce in the hydroponic chamber was 30 days. Immediately after harvest, lettuce was evaluated for plant morphological parameters and for the content of macro- and microelements and metabolites with health-promoting properties. Additionally, sensory evaluation was performed and leaf color parameters were measured.The genotype of romaine lettuce had a major impact on its extrinsic and intrinsic properties. The mini cultivars produced lower fresh mass but contained higher amounts of nitrogen, phosphorus, potassium, copper, and boron than varieties from the midi group. The contents of bioactive compounds were higher for midi romaine lettuce than for the mini type. In terms of nitrate, there were significant differences, and lower nitrate levels occurred in the mini group, except in ‘Coventry.’ The results obtained in this study did not allow us to single out any cultivar from the midi group as the best or the worst in terms of chemical composition. Among the mini cultivars, ‘Elizium’ shown the tendency to accumulate a relatively small amount of nitrate and a relatively large amount of chlorophyll, carotenoid, polyphenol and flavonoid. ‘Coventry’ with the lowest chlorophyll, carotenoid, and flavonoid contents was found to be the poorest in bioactive compounds. The sensory evaluation indicated the good quality of all mini and two midi cultivars, while ‘Delcaso’ (midi cultivar) received the worst marks, because of poor smell and crispness and a bitter aftertaste. The higher light intensity (200 µmol m−2 s−1) used for plant illumination did not unequivocally increase the content of health-promoting components or improve other characteristics of romaine lettuce compared to the light 160 µmol m−2 s−1.

Agronomic biofortification with zinc in hydroponically cultivated lettuce

Lettuce is the most cultivated leafy vegetable in hydroponic systems. The biofortification of lettuce with zinc (Zn) can contribute to relieving nutritional deficiencies in socially vulnerable populations. Biofortification is affordable, easy and fast, even in urban areas. Our objective was to evaluate the effect of Zn concentration in nutrient solutions on the production and agronomic biofortification of lettuce cultivars. The experimental design was completely randomized, in a split-plot design, with four replicates. We tested Zn concentrations of 0.3, 1.0, 1.7 and 2.4 mg L-1 in the hydroponic solution and the cultivars 'Vanda' and 'Saladela'. We evaluated plant diameter, number of leaves, fresh and dry mass of the aerial part and root, a chlorophyll index, Zn content and the accumulation of Zn in leaves and roots. 'Vanda' lettuce had the largest diameter, and 'Saladela' lettuce had the most leaves. The fresh mass of the aerial part was higher in 'Vanda' lettuce. For a Zn concentration of 2.4 mg L-1, the Zn contents of the leaves and roots were 733.3 and 2441 mg kg-1 and the accumulations of Zn in the leaves and roots were 931.66 and 4890 mg plant-1, respectively. Zn content and accumulation were higher in 'Saladela' lettuce. FM, DM did not decrease with increasing Zn concentration in the nutrient solution. Agronomically biofortifying the lettuce produced hydroponically using the nutrient film technique was thus possible

Maximização de benefícios agro-bioeconômicos em sistemas consorciados de rabanete e alface em ambiente semiárido

ABSTRACT Radish and lettuce are two crop vegetables that can be intercropped because they are companion cultures that complement each other. Thus, this study aimed to evaluate agro-bioeconomic returns arising from radish-lettuce intercropping in different equitable amounts of hairy woodrose (Merremia aegyptia) and roostertree (Calotropis procera) biomass at different population densities of lettuce, in the semi-arid environment. The experimental design was in randomized blocks, with treatments arranged in a 4 × 4 factorial scheme with four replicates. The first factor consisted of equitable amounts of M. aegyptia and C. procera biomass at doses of 20, 35, 50, and 65 Mg ha-1 on a dry basis. The second factor comprised four lettuce population densities of 150, 200, 250, and 300 thousand plants ha-1. The lettuce and radish cultivars planted were ‘Tainá’ and ‘Crimson Gigante’, respectively. Expressive agro-bioeconomic returns from this radish-lettuce intercropping were obtained in the land equivalent ratio (LER) of 2.25, a score of the canonical variable Z of 3.00, net income (NI) of 52,270.48 R$ ha-1, respectively, in the biomass amount of 65 Mg ha-1 of the green manures and lettuce population density of 300 thousand plants ha-1. Also, there was a productive efficiency index (PEI) of 0.96 and a competitive ratio (CR) of 2.61 in the biomass amount of green manure of 65 Mg ha-1 and lettuce density of 150 thousand plants ha-1. Using M. aegyptia and C. procera biomass from the Caatinga biome proved to be a viable technology for producers who practice the cultivation of radish and lettuce in intercropping in the semi-arid environment.

Lettuce Soil Microbiome Modulated by an L-α-Amino Acid-Based Biostimulant

Maintenance of soil health is of foremost importance to sustain and increase crop productivity, while meeting the demand of a rising global population. Soil microbiome is gaining increasing attention as a modulator of soil health. Microbial communities confer traits to the soil as a living organism, which functions holistically and conforms part of the plant holobiont, reassembling the human-gut axis. Novel strategies in biostimulant development advocate for modulation of the native soil microbiome and the reinforcement of microbial networking to outpace pathogen inclusion. Consequently, we hypothesize that Terramin® Pro may promotes beneficial microorganisms, depending on the native microbiota of soil, which would lead to an improvement of crop performance indicators. We proposed a soil microbiome-based approach to characterize the effect of an L-α-amino acid based biostimulant (Terramin® Pro) on resulting plant phenotypes in lettuce cultivars (Lactuca sativa L.) to address our hypothesis. First, product application promoted Actinobacteria group in assorted soils with different track of agronomic practices. Secondly, biostimulant application improved chlorophyll content in particular soils deviating from standard conditions, i.e., sick or uncultivated ones. Specially, we observed that product application at 30 L ha−1 improved lettuce phenotype, while potentially promoted entomopathogenic fungi (Beauveria and Metarhizium spp.) and suppressed other lettuce disease-related fungi (Olpidium spp.) in nematode-infested soils. Further investigations could deepen into Terramin® Pro as a sustainable prebiotic strategy of soil indigenous microbiota, through in-house microbiome modulation, even in additional crops.

Períodos de interferência de plantas daninhas na cultura da alface

ABSTRACT The knowledge of the adequate period for the beginning of weed management in lettuce crop can increase the efficiency of production, reducing the costs with management. The aim of this study was to determine the pre-interference period (PIP), the critical time for weed removal (CTWR) and the critical period of weed control (CPWC) in three lettuce cultivars, Elisa, Lucy Brown and Solaris. Coexistence and the absence of weeds were evaluated for each cultivar. The design was in randomized blocks with seven treatments (0, 7, 14, 21, 28, 35 and 42 days after transplanting - DAT) of coexistence and the same seven periods of weed absence with four replicates in each experiment. The highest infestation densities were with the species Oxalis latifolia, Coronopus didymus and Amaranthus hybridus. The leaf area and number of leaves per plant were reduced by up to 50% and 66%, respectively, in relation to the longest period of coexistence with weeds and yield reduced by 48% (Elisa), 40% (Lucy Brown) and 33% (Solaris). The cultivar Solaris showed greater tolerance to weed interference. Based on yield, PIP was 1, 3 and 3 DAT and CTWR was 37, 37 and 35 DAT, and CPWC was 2 to 37, 3 to 37 and 3 to 35 for the cultivars Elisa, Lucy Brown and Solaris, respectively.

Effect of inoculation methods of Azospirillum brasilense on growth and yield of lettuce in the hydroponic system

Lettuce (Lactuca sativa L.) is one of the most popular and economically critically leafy vegetable crops in the world. Nevertheless, the existing studies offered information limited on the Azospirillum brasilense effects in this research system makes it necessary to verify the best method of inoculation for these bacteria. Currently, a variety of techniques for producing Lettuce have been investigated, including soilless aeroponic, hydroponic, and deep-water culture systems. Therefore, this study aimed to verify the beneficial effects of inoculation methods of A. brasilense on plant growth and nutrition of two lettuce cultivars grown in the hydroponic system. The study was conducted in a greenhouse with 30% shading at Vietnam National University of Forestry – Dong Nai campus, Trang Bom district, Dong Nai province. A randomized block design with three replicates in a 4 × 2 factorial scheme was used. Four A. brasilense inoculation methods (non-inoculated, foliar application, nutrient solution, and nutrient solution + foliar application) and two lettuce cultivars were evaluated. All inoculation methods improved plant height, shoot fresh and dry mass, fresh leaf yield, and accumulation of potassium, calcium, phosphorus, iron, manganese, and copper. Inoculation via nutrient solution + foliar application of A. brasilense is the most suitable for hydroponic lettuce GR-607 cultivation because it provides greater fresh leaf yield. All inoculation methods increased leaf yield in hydroponic lettuce.

Evaluation of Three Nutrient Compositions for Lettuce Cultivers in two Hydroponic Systems

A greenhouse field experiment was conducted at Plasticulture Farm in MPUAT, Udaipur Rajasthan in 2021 to examine the effects of different EC levels on the growth and weight of two lettuce cultivars grown in two hydroponic systems. Two lettuce cultivars, Ice Berg (V1) and Green Rapid (V2), were subjected to three levels of EC i.e. 0.75 dS/m, 1.0 dS/m and 1.25 dS/m and two hydroponic systems (DWC and NFT). The Green Rapid cultivar with 1.0 dS/m and NFT treatment combination proved significantly more productive than the other cultivar/treatment combinations. Based on the results, for all parameters, i.e. plant height, number of leaves, fresh weight, plant spread and dry matter were found more effective in Green rapid with 1.0 dS/m EC and NFT treatment combination. It is expected that the development of a good and easy-touse hydroponic system will help growers produce high-quality vegetables including lettuce.

Autumn Production of Romaine Lettuce on an Extensive Green Roof

Extensive green roofs provide a significant amount of potential available space to expand urban agriculture. Successful crop production in this type of growing system requires growers to overcome temperature extremes, as well as drought conditions and low fertility associated with a shallow and porous rooting substrate. Four cultivars of Romaine lettuce (Lactuca sativa) that included ‘Outredgeous’, 'Parris Island Cos', 'Rouge d'Hiver', and 'Rubens Baby', were grown to maturity in an 8 cm deep expanded lightweight clay substrate on an extensive green roof during the autumn production seasons of 2012 and 2013. Fast and slow release fertilizer regimes popular with growers and a no fertilizer control were provided along with supplemental water via drip irrigation as needed. Chlorophyll content, as measured by a SPAD meter, provided a useful indicator of crop plant vigor and overall plant productivity. Abnormally cold growing conditions during the critical maturation period in autumn 2013 resulted in lower yields compared to 2012. Results indicated that lettuce productivity was improved by the addition of fertilizers, with the fast release providing the greatest growth and productivity. These results demonstrate the feasibility of producing a nutritious and popular autumn crop on an extensive green roof suitable for local urban food systems. However, this research also highlights the vulnerabilities of this system to weather. Utility of green infrastructure for teaching urban agriculture and plant biology is also discussed.

Compostagem de resíduos vegetais frescos e sua aplicação no cultivo de alface

ABSTRACT A considerable part of fresh plant-based food has been discarded as waste, although it could be used to make organic compost for growing plants, retaining nutrient that would be discarded without any control in the environment. The aim of this study was to produce an organic compost using fresh vegetable food discarded from restaurants and mowed grass and to evaluate it for production of lettuce. The compost was produced and mixed with the commercial substrate Tropstrato HT Hortaliças® to occupy 0, 5, 10, 15, 20 or 25% of the volume of the mixture, which was used to grow Imperial and Imperial Roxa cultivars in the first experiment, and Camila and Red Star lettuce cultivars in the second one. The experiments were conducted under protected environment, organized in a 6x2 factorial scheme, following completely randomized design with three replicates. Chemical analyses of the substrate and compost and measurements of plant size and mass were carried out. The addition of compost caused an increase in all measurements of the plant traits, with the maximum estimated increase ranging from 1.7 to 9.0 times that estimated for the absence of compost in the plant growth substrate. Maximum estimated values for size and mass were observed with compost concentrations ranging from 20.1 to 26.7% of the mixture volume. The production of organic compost and its mixture with a commercial substrate proved to be an alternative for lettuce production, giving a better destination to the organic residues and promoting a reduction in the use of industrial inputs.

Artificial neural networks discriminate lettuce seeds with different levels of thermoinhibition

Abstract: The thermoinhibition of lettuce seed germination causes important losses for producers, who do not have thermotolerant commercial cultivars. One of the obstacles has been the scarcity of optimizing techniques capable of efficiently discriminating thermotolerant and thermosensitive cultivars. The aim of this work was to evaluate the use of neural networks to discriminate different levels of thermoinhibition in lettuce seeds. Seeds of 18 cultivars were evaluated for thermoinhibition considering the characteristics of the first and last germination count and germination speed index, in seeds subjected to temperatures of 20, 25, 30 and 35 °C. The remaining seeds, which did not germinate, were subjected to the tetrazolium test. Analyses were performed immediately after seed harvesting and repeated after six months of storage. Discriminant analysis was performed and the Kohonen’s Self-Organizing Map (SOM) was created using Artificial Neural Networks (ANNs). Neural networks discriminate lettuce cultivars and organizes them in terms of seed thermoinhibition tolerance through Kohonen’s Self-Organizing Map. Discriminant analysis consistently identifies the Everglades and Luiza genotypes as tolerant to thermoinhibition.

Pre-harvest biocontrol of Listeria and Escherichia coli O157 on lettuce and spinach by lactic acid bacteria

Recent outbreaks linked to contaminated leafy greens underline the need for identifying effective natural approaches to improve produce safety at pre-harvest level. Lactic acid bacteria (LAB) have been evaluated as biocontrol agents in food products. In this study, the efficacy of a cocktail of LAB including Lactococcus lactis, Lactiplantibacillus plantarum, Lactobacillus johnsonii, and Lactobacillus acidophilus as pre-harvest biocontrol agents against Listeria and Escherichia coli O157 on lettuce and spinach was investigated. Bacterial pathogens L. monocytogenes and E. coli O157:H7 and the non-pathogenic surrogates L. innocua and E. coli O157:H12 were used to spray-inoculate cultivars of lettuce and spinach grown in growth chamber and in field, respectively. Inoculated plants were spray-treated with water or a cocktail of LAB. On day 0, 3, and 5 post-inoculation, four samples from each group were collected and bacterial populations were determined by serial dilution and spiral plating on selective agars. LAB treatment exhibited an immediate antimicrobial efficacy against L. monocytogenes and E. coli O157:H7 on “Green Star” lettuce by ~2 and ~ 1 log reductions under growth chamber conditions, respectively (P < 0.05). The effect of LAB against E. coli O157:H7 on “New Red Fire” lettuce remained effective during the 5-day period in growth chamber (P < 0.05). Treatment of LAB delivered an effective bactericidal effect against E. coli O157:H12 immediately after application on the field-grown lettuce plants (P < 0.05). Approximately 1 log L. innocua reduction was observed on “Matador” and “Palco” spinach on day 5 (P < 0.05). Results of this study support that LAB could potentially be applied as biocontrol agents for controlling Listeria and E. coli O157 contamination on leafy greens at the pre-harvest level.

Untargeted metabolites and chemometric approach to elucidate the response of growth and yield attributes on different concentrations of an amino acid based biostimulant in two lettuce cultivars

• Application of Phytostim® biostimulant at 3% dose improved growth and yield components in lettuce cv ‘Lara’ and ‘Elisa’. • Application of Phytostim® biostimulant at 6% dose retarded growth and yield components in lettuce cv ‘Lara’ and ‘Elisa’. • There was major heterogeneity on untargeted metabolites profile in control (untreated) samples of both cv ‘Lara’ and ‘Elisa’ using the LC-MS data and chemometrics techniques. • Targeted metabolites including total phenols, flavonoids, carotenoids and chlorophyll elucidated the antioxidant activity in studied treatments. • Obtained results is practically beneficial on sustainable strategies to improve productivity. The study aims to underpin biochemical mechanisms induced by the application of different concentrations of an amino-acid based Phytostim® biostimulant on growth and yield attributes. Different concentrations of Phytostim® biostimulant: 0 (untreated), 1, 3, and 6% were foliar applied on lettuce cultivars (‘Lara’ and ‘Elisa’). After 45 days of transplanting, analysis growth and yield attributes, biochemical analysis and LC-MS untargeted metabolites profile were performed. Application of 3% dose improved both growth and yield parameters in both cultivars in comparison to the 6% dose which inhibited growth. Similar trend was observed for biochemical and antioxidant analysis (phenolic, flavonoids, carotenoids, chloroplyll a and b and scavenging activity). The PCA and OPLS-DA score-plot clustered the metabolome profile of biostimulant treated vs untreated samples with major heterogeneity distinction observed in the untreated samples. Obtained results validate the use of biostimulants in agriculture while giving information on the effects of the treatments towards changes in the chemical composition within the studied cultivars.

Growth Analysis of Plant Factory-Grown Lettuce by Deep Neural Networks Based on Automated Feature Extraction

The mechanisms of lettuce growth in plant factories under artificial light (PFALs) are well known, whereby the crop is generally used as a model in horticultural science. Deep learning has also been tested several times using PFALs. Despite their numerous advantages, the performance of deep learning models is commonly evaluated based only on their accuracy. Therefore, the objective of this study was to train deep neural networks and analyze the deeper abstraction of the trained models. In total, 443 images of three lettuce cultivars were used for model training, and several deep learning algorithms were compared using multivariate linear regression. Except for linear regression, all models showed adequate accuracies for the given task, and the convolutional neural network (ConvNet) model showed the highest accuracy. Based on color mapping and the distribution of the two-dimensional t-distributed stochastic neighbor embedding (t-SNE) results, ConvNet effectively perceived the differences among the lettuce cultivars under analysis. The extension of the target domain knowledge with complex models and sufficient data, similar to ConvNet with multitask learning, is possible. Therefore, deep learning algorithms should be investigated from the perspective of feature extraction.

Effects of Air Anions on Growth and Economic Feasibility of Lettuce: A Plant Factory Experiment Approach

Anions are molecules that have gained one or more extra electrons, and oxygen anions are the anions most commonly present in the atmosphere. Several studies have reported an improvement in plant respiration and growth through the application of air anions in several plants. In this study, the effect of air anions on the growth of lettuce was explored, and further, the economic feasibility of this technique was analyzed in a plant factory. Two cultivars of lettuce were cultivated for 4 weeks with the application of negatively ionized air in a commercial plant factory. The exposure to air anions improved the growth of the lettuce plants in the plant factory. A profitability analysis of applying air anions revealed that the annual net profit per 1500 m2 cultivation area was about USD 60,000 and USD 70,000 for red leaf lettuce and Lollo bionda lettuce, respectively. Therefore, the application of air anions to lettuce in plant factories or greenhouses could increase crop production and has high economic feasibility.

Using leaf spectroscopy and pigment estimation to monitor indoor grown lettuce dynamic response to spectral light intensity.

Rising urban food demand is being addressed by plant factories, which aim at producing quality food in closed environment with optimised use of resources. The efficiency of these new plant production systems could be further increased by automated control of plant health and nutritious composition during cultivation, allowing for increased produce value and closer match between plant needs and treatment application with potential energy savings. We hypothesise that certain leaf pigments, including chlorophylls, carotenoids and anthocyanins, which are responsive to light, may be good indicator of plant performance and related healthy compounds composition and, that the combination of leaf spectroscopy and mathematical modelling will allow monitoring of plant cultivation through noninvasive estimation of leaf pigments. Plants of two lettuce cultivars (a green- and a red-leaf) were cultivated in hydroponic conditions for 18 days under white light spectrum in climate controlled growth chamber. After that period, plant responses to white light spectrum ('W') with differing blue wavelengths ('B', 420 - 450 nm) percentage (15% 'B15', and 40% 'B40') were investigated for a 14 days period. The two light spectral treatments were applied at photon flux densities (PFDs) of 160 and 240 µmol m-2 s-1, resulting in a total of four light treatments (160WB15, 160WB40, 240WB15, 240WB40). Chlorophyll a fluorescence measurements and assessment of foliar pigments, through destructive (in vitro) and non-destructive (in vivo) spectrophotometry, were performed at 1, 7 and 14 days after treatment initiation. Increase in measured and estimated pigments in response to WB40 and decrease in chlorophyll:carotenoid ratio in response to higher PFD were found in both cultivars. Cultivar specific behavior in terms of specific pigment content stimulation in response to time was observed. Content ranges of modelled and measured pigments were comparable, though the correlation between both needs to be improved. In conclusion, leaf pigment estimation may represent a potential noninvasive and real-time technique to monitor, and control, plant growth and nutritious quality in controlled environment agriculture.

Effects of exogenous melatonin on the growth and cadmium accumulation of lettuce under cadmium‐stress conditions

AbstractMelatonin (MT) is a signaling molecule that is widely present in plants and can help them resist abiotic stresses. In this study, the effects of different concentrations of exogenous MT on the growth and development of lettuce (Lactuca sativa) under cadmium stress (50 μmol/L) were investigated. Based on their Cd accumulation differences, the “Hong Feng” and “Luo Ma” lettuce cultivars were selected as research materials. The results showed that different concentrations of MT could promote the growth of lettuce under 50 μmol/L cadmium stress. The application of exogenous melatonin can significantly increase the plant height, biomass, chlorophyll, soluble protein and soluble sugar content of lettuce, and increase the net photosynthetic rate. MT could also reduce the malondialdehyde content in lettuce under cadmium stress and increase the activities of superoxide dismutase, peroxidase, and catalase activities. After treatment with different concentrations of MT, the Cd content in the shoots of both cultivars significantly decreased; in contrast, the Cd content in the roots was significantly increased, which limited the transport of Cd from underground to the shoots. In addition, both Cd stress and exogenous MT induced the synthesis of endogenous MT, and 50 μmol/L MT treatment most effectively induced this response. In conclusion, this study demonstrated that MT could alleviate the negative effects of Cd stress on lettuce with different Cd accumulation differences in terms of physiological indicators. Therefore, it provides a certain reference for the potential of MT to be applied to crops threatened by heavy metals.

Performance of Different Lettuce Cultivars Grown Hydroponically under Fluorescent and Light-emitting Diode Light Growth Conditions

Lettuce (Lactuca sativa L.) is one of the most consumed fresh vegetables in the United States. However, lettuce production is heavily limited to California and Arizona, posing a high risk to the supply chain. Hydroponic production is a soilless cultivation method and provides a sustainable alternative to growing lettuce in the field. Light is a critical factor in plant development, and light quality highly affects plant morphogenesis. The goals of this study were 2-fold, with the first to investigate the growth of 26 lettuce cultivars under a hydroponic system supplemented with fluorescent light to determine adaptability. Subsequently, the second goal was to determine how light-emitting diodes (LEDs) affect lettuce plant morphology and photosynthesis compared with fluorescent light for four lettuce cultivars. Results showed that 23 of 26 lettuce cultivars were grown successfully using a hydroponic system. However, lettuce grown under fluorescent light experienced stem elongation—a morphological response to low-light conditions known as shade avoidance syndrome. Stem elongation decreased significantly under LED light, whereas other morphological characteristics remained relatively the same between the two light treatments. Although there were no differences in dry weight and leaf area, the carbon assimilation rate increased significantly in lettuce cultivars Coastal Star, Muir, Green Butter, and Rouge d’Hiver when treated with LED light. Correspondingly, intercellular carbon dioxide (CO2) decreased in these four lettuce cultivars under the LED light treatment. Our study results indicate that LED light increased photosynthetic activity and reduced stem elongation to enhanced lettuce quality.

Natural variation and drought-induced differences in metabolite profiles of red oak-leaf and Romaine lettuce play a role in modulating the interaction with Salmonella enterica

Nutrients on produce surfaces are vital for successful enteric pathogen colonisation. In this study, we investigated natural variation in metabolite profiles of Romaine ‘Parris Island Cos’ and red oak-leaf lettuce ‘Mascara’ under regular and restricted watering conditions. We also investigated the impact of plant drought stress on the Salmonella – lettuce association. Salmonella Newport and Typhimurium were able to persist at higher levels on regularly watered Romaine than red oak-leaf lettuce. Drought treatment to lettuce impaired epiphytic Salmonella association, with S. Newport and Typhimurium being differentially affected. A higher log reduction of both serotypes was measured on drought-subjected red oak-leaf lettuce plants than controls, but S. Typhimurium was unaffected on water deficit-treated Romaine lettuce (p < 0.05). To assess Salmonella interaction with leaf surface metabolites, leaf washes collected from both cultivars were inoculated and found to be able to support S. Newport growth, with higher levels of Salmonella retrieved from Romaine washes (p < 0.05). The lag phase of S. Newport in washes from water restricted red oak-leaf lettuce was prolonged in relation to regularly-watered controls (p < 0.05). Untargeted plant metabolite profiling using electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) revealed natural variation between Romaine and red oak-leaf lettuce profiles for leaf tissue and leaf washes. Metabolite profile shifts were detected in both lettuce types in response to drought stress, but more unique peaks were detected in red oak-leaf than Romaine lettuce after drought treatment. Variation between the two cultivars was in part attributed to naturally higher levels of flavonoids and anthocyanins in red oak-leaf lettuce compared to Romaine. Moreover, red oak-leaf, but not Romaine lettuce, responded to drought by inducing the accumulation of proline, phenolics, flavonoids and anthocyanins. Drought stress, therefore, enhanced the functional food properties of red oak-leaf lettuce. Salmonella growth dynamics in lettuce leaf washes suggested that natural variation and drought-induced changes in metabolite profiles in lettuce could partly explain the differential susceptibility of various lettuce types to Salmonella, although the primary or secondary metabolites mediating this effect remain unknown. Regulated mild water stress should be investigated as an approach to lower Salmonella contamination risk in suitable lettuce cultivars, while simultaneously boosting the health beneficial quality of lettuce.

Coupled aquaponics (CAS) 및 Decoupled aquaponics (DAS) 생산 방식에 따른 비단잉어 및 엽채류의 성장 비교

Aquaponics is an fusion production practice which combines aquaculture, the raising of fish, and hydroponics, a soil-less crop production method, to create a system that symbiotically produces both. Many of today’s coupled aquaponic systems (CAS) circulate water and nutrients from fish to plants and vice versa, but It is not always guaranteed that the fish preferences are completely aligned with the optimum requirements of the plants. This solution, which is referred to as decoupled aquaponic systems (DAS) would better secure optimal environmental conditions for both the plant and fish production units. The study examined the growth difference of leafy vegetables and Fancy carp between CAS and DAS method applying hybrid biofloc technology-aquaponics (HBFT-AP) water quality management for 14 weeks. Eight cultivars of european lettuce (fairly, decarte, gauguin, ezabel, ovired, volare, xaroma and skelton) were employed in the two experiment (EXP1 and EXP2) for 7~14 weeks. After planting leafy vegetables in two system, leafy vegetable productivity was compared at the end of growth period (25 days). Productivity (CAS vs DAS) was somewhat higher (total leaf weight; CAS 28,293 g vs DAS 26,087 g) in CAS for EXP1 period, but in EXP2, the total leafy weight was higher in DAS (71,247 g) than in CAS (67,749 g). Also, weight gain (%) value of fish was higher in fish group of DAS (33.09) than CAS (23.40) due to the higher feed supply in fish tank of DAS.