Head Lettuce Research Articles

Enhancing Head Lettuce Growth and Quality under Water Stress with Proline, Melatonin and Vermicompost Applications

Enhancing Head Lettuce Growth and Quality under Water Stress with Proline, Melatonin and Vermicompost Applications

Impact of Ultraviolet radiation and 1-methylcyclopropane treatments on maintain quality and storability of Iceberg lettuce head during cold storage.

Impact of Ultraviolet radiation and 1-methylcyclopropane treatments on maintain quality and storability of Iceberg lettuce head during cold storage.

Lettuce Genotype-Dependent Effects of Temperature on Escherichia coli O157:H7 Persistence and Plant Head Growth

Lettuce has been commonly associated with the contamination of human pathogens, such as Escherichia coli O157:H7 (hereafter O157:H7), which has resulted in serious foodborne illnesses. Contamination events may happen throughout the farm-to-fork chain, when O157:H7 colonizes edible tissues and closely interacts with the plant. Environmental conditions have a significant impact on many plant–microbe interactions; however, it is currently unknown whether temperature affects O157:H7 colonization of the lettuce phyllosphere. In this study, we investigated the relationship between elevated growth temperatures, O157:H7 persistence, and lettuce head growth using 25 lettuce genotypes. Plants were grown under optimal or elevated temperatures for 3.5 weeks before being inoculated with O157:H7. The bacterial population size in the phyllosphere and lettuce head area was estimated at 0- and 10-days postinoculation (DPI) to assess bacterial persistence and head growth during contamination. We found that growing temperature can have a positive, negative, or no effect on O157:H7 persistence depending on the lettuce genotype. Furthermore, temperature had a greater effect on head area size than the presence of O157:H7. The results suggested that the combination of plant genotype and temperature level is an important factor for O157:H7 colonization of lettuce and the possibility to combine desirable food safety traits with heat tolerance into the lettuce germplasm.

Evaluation of Growth, Yield and Quality of Head Lettuce in Response to Salicylic Acid Foliar Spraying

Evaluation of Growth, Yield and Quality of Head Lettuce in Response to Salicylic Acid Foliar Spraying

Screening Subtropical Lettuce Accessions for Heat Tolerance by Incorporating Accelerated Shelf Life Testing

Lettuce (Lactuca sativa L.) is grown worldwide, from temperate to subtropical climates. Spring season production in humid, subtropical regions, such as southern Florida, is characterized by rising ambient temperatures that can stress lettuce to prematurely bolt and lose shelf life. The objectives of this research were 1) to identify genetic variability in heat tolerance and shelf life among lettuce types and accessions grown under humid, subtropical conditions, and 2) to understand the genotype × environment (G × E) interaction to estimate shelf life of these lettuce accessions. Five lettuce types (romaine, crisphead, butterhead, leaf, and Latin) were grown under commercial conditions in the Everglades Agricultural Area near Belle Glade, FL, USA, for five field experiments over two seasons. Lettuce heads were evaluated at harvest, and subsets were transported to a local commercial grower/shipper for vacuum-cooling and storage at 15 °C according to previously determined protocols for accelerated shelf life testing. Visual appearance ratings were made across harvests and storage time points to segregate lettuce accessions with an estimated marketable shelf life >14 days. The breeding lines tested in this research had head weight and marketability comparable to commercial cultivars. Notably, the crisphead accessions 50113, 60157, 60159, and H1098 had the highest estimated and actual shelf life of more than 21 days, with no presence of bolting or tipburn. Meanwhile, romaine, butterhead, leaf, and Latin types had accessions with estimated and actual shelf life ranging from 14 to 28 days and no presence of bolting or tipburn. A G × E analysis indicated that this interaction is significant; therefore, breeders should consider analyzing G × E when developing new cultivars with good horticultural characteristics, longer shelf life, and most importantly, adaptation to warmer humid, subtropical conditions.

Soil Type and Associated Microbiome Influence Chitin's Growth Promotion Effect in Lettuce

Chitin amendment of peat substrate has been proven effective in promoting lettuce growth and increasing phenolic compounds in lettuce seedlings. However, the effect of chitin soil amendment on lettuce growth in mineral soil remains unexplored. The effect of chitin amendment of mineral soil on lettuce growth and metabolite changes was investigated for the first time in the present study in comparison with chitin-amended peat substrate. Our findings showed that chitin addition in peat substrate increased lettuce head weight by approximately 50% at harvest, whereas this increase was 30% when chitin was added to mineral soil. Targeted metabolomics analysis indicated that chitin addition affected the phenolic compounds in lettuce seedlings, but this effect varied between soil types. Moreover, untargeted metabolomics analysis suggested that using peat substrate or mineral soil had a greater influence on produced lettuce metabolites than chitin addition. Rhizobiome analysis showed that specifically Mortierellaceae family members, known for chitin degradation and plant growth promotion, significantly increased in peat substrate upon chitin treatment. In mineral soil, three bacterial genera and five fungi, including known plant-growth-promoting genera, were significantly more abundant upon chitin treatment but Mortierellaceae family members were not. We assume that the observed effects primarily stem from soil characteristics and from chitin-induced alterations in rhizobiome composition, particularly the presence of Mortierellaceae members, leading to promoted lettuce growth. Despite the variability, chitin remains an environmentally friendly alternative to synthetic fertilizers in lettuce production, but its beneficial effects are dependent on rhizobiome composition, which should be considered before chitin application. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

The Influence of Salicylic Acid and Chitosan on Lettuce Head Quality and Productivity Grown in Two Different Locations in Egypt

The Influence of Salicylic Acid and Chitosan on Lettuce Head Quality and Productivity Grown in Two Different Locations in Egypt

Effect of Maturity Stages on the Quality of Cold Storage Iceberg Lettuce (Lactuca sativa var. capitate) for Export

Iceberg lettuce is one of the most important vegetables economically and nutritionally, but its perishable nature poses challenges for storage and long-distance transportation. This study investigated the effect of maturity stages on the quality of iceberg lettuce for export under cold storage conditions. A completely randomized design with three replications was used to evaluate four maturity stages based on days after planting (DAP): 52, 55, 58, and 61 DAP. The lettuce heads were stored at 3±2oC and a 95% relative humidity, and quality parameters were analyzed every three days until the end of storage. Sensory properties, weight loss, color change, total soluble solids, total phenolics, and decay rates were evaluated. The results showed that maturity stages significantly (P <0.05) affected the quality attributes of iceberg lettuce and that harvesting at the optimal stage is very important. Findings from this study confirmed that the quality parameters were preserved for the 58 DAP samples throughout the storage time. They indicated that at three weeks of storage time, the lowest weight loss (5.9%), color change (14.1), and decay rate (8.3%), and the highest sensory analysis (5 scores) and appearance were shown by the 58 DAP maturity stage lettuce. Therefore, harvesting iceberg lettuce at 58 DAP is recommended for long-distance exportation.

Faecal contamination on lettuce irrigated with different water sources in Maputo, Mozambique

ABSTRACT Faecal contamination across the lettuce value chain was assessed in Maputo, Mozambique. Escherichia coli was used as an indicator of faecal contamination, with concentrations ranging from 3.4 to 5.7 log units/100 ml in groundwater, river water and partially treated wastewater. Municipal tap water used to wash lettuce heads in the markets had lower than 1 log unit/100 ml. Irrespective of the source of irrigation water, the lettuce heads were contaminated throughout the value chain, with concentrations ranging between 6.5 and 7.8 log units/100 g. Interventions and awareness raising should be applied at every stage of the value chain.

Antioxidant Potential, Phenolic Content, and Nitrate/Nitrite Content in Various Lettuce Varieties

<p>Ten lettuce varieties are analyzed for antioxidant activity, total phenolic, nitrate, and nitrite contents, and the effects of harvest maturity and cold storage in selected varieties are determined. Antioxidant activity and total phenolic content (TPC) are the highest in Red Oak, Red Coral, Red Rapids, and Grand Rapids; intermediate in Green Oak, Green Cos, and Frillice Iceberg; and the lowest in Butterhead, Mini Green Cos, and Head lettuce. Nitrate content is the highest in Red Coral, while the other 9 varieties have comparably lower contents. Nitrite content is inadequate and does not differ with variety. Harvest maturity of 45 days after transplanting (DAT) produced the highest antioxidant activity and TPC, much higher in Red Bowl and Red Butterhead varieties than in Mini Green Cos, Butterhead, Frillice Iceberg, and Green Big Bowl varieties. Storage at 8<sup>o</sup>C for 21 days has no remarkable effects on antioxidant activity, TPC, nitrate, and nitrite contents. Stored Red Bowl lettuce has higher antioxidant activity and TPC than Butter-head and Green Big Bowl varieties. Nitrate content decreases at the end of storage, while nitrite content is below 1 mg/kg FW during the entire storage period, regardless of variety.</p>

UIO-66-NH2 encapsulated polyoxometalate loaded on graphene oxide accommodated on mixed cellulose esters (MCE) paper for thin film microextraction of pesticides besides their quantification via high-performance liquid chromatography-ultraviolet detection

A POM@UIO-66-NH2/GO composite was designed and prepared via a facile in-situ synthesis method for microextraction purposes. The proper sizes (window size and pore size) of UIO-66-NH2 can effectively seal POM as a monomolecular active component and prevent POM leaching during the extraction. After that, a membrane containing POM@UIO-66-NH2/GO nanocomposite was synthesized and utilized in thin film microextraction (TFME) of various pesticides such as imidacloprid, tebuconazole, and propiconazole as the model analytes in different real samples such as cucumber, tomato, potato, head lettuce, and strawberry. It is worth mentioning that the introduction of GO can improve the electron transfer of the sorbent. The extracted model analytes were desorbed by a suitable organic solvent. The extracted analytes were quantified via high-performance liquid chromatography-ultraviolet detection (HPLC-UV). Under the optimized condition, the method's linear dynamic range (LDR) was obtained in the range of 1.0–200.0 μg L−1 for testing analytes. The obtained correlation coefficients (r2) were higher than 0.9918. The limits of detection (LODs) were also calculated to be between 0.31 and 0.34 μg L−1. The relative standard deviations (%RSDs) were obtained in the range of 2.06 to 4.11. The enrichment factor (EF) values for the studied analytes were also obtained in the range of 89–102. The obtained recoveries indicated that the presented method is useful for analyzing pesticides in various real samples.

Comparison the Effect of an Organic Nutrient (Nektafol) Under Production and Open Field Condition on the Growth and Yield of Lettuce

The Horticulture Department & Landscape Design/College of Agriculture at the University of Mosul conducted the study in two cultivation systems (unheated plastic house and open field) connected to the fields to examine the effects of using the liquid nutrient (Nektafol) at concentrations (0,2,4,6 mlL-1) on the vegetative growth characteristics, quantitative and qualitative yield of plants of lettuce (Quantum variety). Three replications of the experiment were used, and the averages were compared using Duncan’s multiple range test at the 5% level of probability. The experiment was conducted utilizing split. Plot. System. with R.C.B.D. Design. The characteristics of vegetative development and the quantitative and qualitative yield can be summed up as follows: When compared to plants grown under plastic house, plants that were grown in a field in the open. were significantly better in most of the studied characteristics. It was found that using the liquid nutrient Nektafol at two concentrations of 4 and 6ml L-1 significantly improved the qualities of vegetative growth and the total yield of heads of lettuce, as well as the qualities under open field and plastic house.

Effect of Different Substrates and Nutrient Solutions on Growth and Productivity of Soilless Cultured Head Lettuce with using Solar Energy for Operating Fertigation System

Effect of Different Substrates and Nutrient Solutions on Growth and Productivity of Soilless Cultured Head Lettuce with using Solar Energy for Operating Fertigation System

Moringa leaf extract increases tolerance to salt stress, promotes growth, increases yield, and reduces nitrate concentration in lettuce plants

The use of large amounts of synthetic chemicals in plant cultivation harms the environment and reduces food quality. Therefore, natural alternatives should be used to protect the environment, increase food quality, and decrease food contamination. This study investigated the effect of moringa leaf extract (MLE) as a plant stimulator to enhance growth, yield, and quality of lettuce grown in a saline environment. To examine the effect of application method and extract concentration, this experiment included three levels of seed priming (0, 5 %, and 10 % MLE) and three levels of foliar spray (0, 5 %, and 10 % MLE). MLE application, either by seed priming or foliar spraying, reduced the adverse effects of salt stress and increased lettuce growth, yield, and quality. However, the combined treatment of 5 % seed soaking and 10 % foliar spray showed the best results in increasing antioxidant levels (catalase (CAT), ascorbate peroxidase (APX), and ascorbic acid), relative water content (RWC %), nutrient concentration (N, P, and K), and chlorophyll content, and maintaining membrane integrity by reducing electrolyte leakage (EL %) and sodium accumulation, leading to improved yield parameters (head diameter, head weight, and total yield), and increasing lettuce head quality by reducing nitrate concentration. The results suggest that MLE (5 % seed soaking and 10 % foliar spray) is a practical, effective, and inexpensive approach to alleviate salt stress and improve lettuce yield and quality under saline conditions. However, despite the observed positive effects, further studies are needed to understand the factors determining the response of plants to MLE application.

Reusing Coir-Based Substrates for Lettuce Growth: Nutrient Content and Phytonutrients Accumulation

This research aimed to assess the influence of reusing coir-based substrates on growth, nutrient content, and phytonutrients accumulation in lettuce. The experiment included a new coir pith and four coir-based mixes (1) coir, biochar, and perlite; (2) coir, compost, and perlite; (3) coir, biochar, and pine bark; and (4) coir, compost, and pine bark. All mixes had been previously utilized to grow transplanted spinach and possessed identical ratios of 78:12:10% (v/v) among their components. Lettuce (Lactuca sativa L. cv. ‘Godzilla’) seedlings were transplanted into Styrofoam plant boxes. Each day, the planting boxes received a nutrient solution via drip irrigation. Plants grown in reused mixes had similar macronutrient concentrations as those grown in coir for the first time, except for N and K in the third mix. Plants grown in reused mixtures had similar yields as those in new coir. Lettuce heads yielded 4.6–4.9 kg/m2, while plants grown in reused mixtures had equal or higher total phenols than those in new coir. Ascorbic acid content was higher in plants cultivated in reused mixes. Coir-based growing media can be reused for another short-cycle crop, like lettuce, without yield loss or phytonutrients decrease.

Yield and quality of lettuce (Lactuca sativa L.) depending on variety and type of nitrogen fertilizer

The aim of this research was to determine the effect of the application of different types of nitrogen fertilizer in five different varieties of lettuce on yield. The experiment was performed in the open field, in the spring cycle of growing during 2018 and 2019. The size of the base plot was 3 m2, and the trial was set up in a random block system. The trial covered the application of various forms of nitrogen fertilizers: ammonium sulphate, ammonium nitrate and urea. The applied nitrogen dose is 100 kg/ha (May 10th 2018 and May 8th 2019). Samples for the analysis of vitamin C and nitrate content, as well as yield determination, were carried out at the stage of the technological maturity of lettuce (60-62 days after seedling). The average weight of lettuce, depending on the variety, varied in the range of 211.3 g to 258.7 g. The use of ammonium nitrate resulted in the highest average weight of lettuce head (246.7 g), followed by the use of urea (238.9 g) and the lowest by the use of ammonium sulphate (221.0 g). The nutritional value of lettuce (vitamin C content) shows that depending on the applied form of nitrogen in the fertilizer, the highest content of vitamin C was determined by urea (10.86 mg/100 g), then ammonium sulphate (9.61 mg/100 g), and the lowest by ammonium nitrate (7.38mg/100g). The lower content of vitamin C was found in varieties of lettuce with red leaves compared to varieties with green leaves. The accumulation of nitrate in lettuce leaves directly depends on the variety and the applied fertilizer. The highest nitrate content was with ammonium nitrate (2355.6 mg/kg). The accumulation of nitrate in lettuce varieties with red leaves was higher compared to varieties with green leaves. Keywords: Lettuce, Nitrate, Vitamin C, Yield, Open field

Growth and Quality of Leaf and Romaine Lettuce Grown on a Vertical Farm in an Aquaponics System: Results of Farm Research

The integration of indoor vertical cultivation with a recirculating aquaculture system into an aquaponic system has the potential to become one of the most effective sustainable production systems for fish and leafy vegetables. In this study, lettuce was produced on rafts in a coupled recirculation aquaponic system in the plant factory under controlled environmental conditions. The aims of this study were to evaluate the yield, mineral status, and health-promoting bioactive compounds of leaf and romaine lettuce cultivars grown in a recirculating aquaponic system. The yield and biometric parameters and quality parameters of lettuce leaves (nitrate, mineral, L-ascorbic acid, carotenoid, phenolic compound, and total polyphenolic contents) were examined. Monitoring of the water in the aquaponic system showed a low concentration of nitrates, phosphorus (P), potassium (K), and magnesium (Mg), but the proportion of mineral nutrients as well as pH were stable throughout the lettuce cultivation period. The heads of romaine lettuce ‘Yakina’, ‘Pivotal’, and ‘Waygo’ reached a fresh weight of 86 g, on average, 23% higher than the leaf lettuce ‘Nordice’ over a three-week cultivation period. Despite the low nutrient concentration in the aquaponic solution, the nutrient status of the romaine lettuces ‘Yakina’ and ‘Pivotal’ was within the optimal range. The concentrations of chlorophyll a and carotenoids in ‘Yakina’ and ‘Pivotal’ were higher than those in ‘Nordice’ and ‘Waygo’. The nitrate, phosphorus, and potassium contents in the leaves of ‘Nordice’ and ‘Waygo’ were below the optimal range; however, their polyphenol concentrations were the highest. Our results indicate that the effectiveness of aquaponic cultivation of lettuce in terms of biomass production and the nutritional and health-promoting value of lettuce depends on the plant genotype.

Endophytic Biostimulants for Smart Agriculture: Burkholderia seminalis 869T2 Benefits Heading Leafy Vegetables In-Field Management in Taiwan

Heading leafy vegetables (HLVs) are essential horticultural crops that feed many people worldwide. An increasing global population demands more cropping systems, leading to stresses such as fertilizer overuse and soil salination, decreasing in crop productivity and agricultural sustainability. Hence, developing those eco-friendly farming strategies that could simultaneously reduce fertilizer usage and increase crop harvest is urgent for agriculture. An endophytic bacterium Burkholderia seminalis 869T2 with pyrroloquinoline quinone (PQQ) producing ability were applied as biostimulant for vegetable seedlings under greenhouse or field conditions. Two globally important HLVs, cabbage and head lettuce, were preliminarily tested, and further examinations under in-field farming during two different seasons were carried out to develop an endophytic biostimulants (EBs)-assisted lettuce production system. In this study, we confirmed that B. seminalis 869T2 is versatile EBs for HLVs, which significantly promote plant growth and enhance the qualities of crops by increasing the harvested head weight, size and nutrient composition. Nevertheless, the harvest was accelerated by two weeks, together with higher product qualities and 50% fertilizing cost savings per hectare. Our study provides an in-field EBs-assisted management for lettuce production that could decrease costs and increase the product’s value. The results highlight the importance of endophytic bacteria that deserve further investigation due to their enigmatic symbiotic relationships with their hosts and potential usage in the agro-industry.

Melatonin reduces pink rib discoloration in wounded lettuce midribs

Pink rib discoloration is a physiological disorder resulting in loss of quality and marketability of minimally processed and whole head lettuce (Lactuca sativa L.). Although the biochemistry of pink rib is complex and a comprehensive understanding is lacking, multiple research efforts have focused on inhibiting or reducing pink rib through exogenous application of small molecules such as L-cysteine. In this study, the effects of naturally occurring phytochemicals [serotonin (0.5 or 1 g L−1), naringenin (0.5 g L−1), L-cysteine (0.5 g L−1), and melatonin (1 g L−1)] on pink rib expression were examined in iceberg and Romaine lettuce. The exogenous application of these natural compounds was investigated for reduced pink rib discoloration in lettuce during simulated commercial storage and examined for metabolite and enzymatic activity changes. Immersing wounded midribs for 30 s in serotonin, naringenin, or L-cysteine solutions had no or only a slight inhibitory effect to inhibit pink rib discoloration while those immersed in a melatonin solution had reduced development of pink rib in both iceberg and Romaine lettuces after 5 d at 5 °C. Phenylalanine ammonia lyase (PAL) activity and chlorogenic acid concentration increased upon pink rib discoloration, consistent with previous reports. However, melatonin-treated samples did not result in reduced PAL activity, chlorogenic acid content, or polyphenol oxidase (PPO) activity. Untargeted metabolite analysis showed that melatonin treatment resulted in a global effect on metabolite changes in the wounded lettuce midrib tissue. To compare the severity of pink rib among treatments, pink rib was quantified throughout storage visually and by converting digital images of the lettuce midribs to the L*a*b* color space. The a* component of L*a*b* represents redness versus greenness, thus its values were used to objectively measure pink rib severity. Melatonin was shown to be a promising compound to minimize development of pink rib discoloration at cut surfaces of iceberg and Romaine lettuce during commercial handling and storage.

GREENBOX Technology II - Comparison of Environmental Conditions, Productivity, and Water Consumption With Greenhouse Operation

Highlights Increasing population, demand, and urbanization have increased food security pressures. We compared GREENBOX with a greenhouse for urban crop production. GREENBOX and greenhouse provided the required environmental conditions and comparable biomass output year-round. GREENBOX performance is comparable to a greenhouse for urban crop production but with more advantages. Abstract. The Yang Laboratory at the University of Connecticut has developed the GREENBOX technology for growing fresh produce in urban areas to meet the increasing demand for sustainable and local food production. Previous studies have shown that GREENBOX units can provide the desired environmental conditions to sustain crop production in midlatitude urban warehouse environments. This study was conducted to compare the environmental conditions, productivity, and water consumption for growing lettuce between GREENBOX and a conventional greenhouse that has been widely applied for crop production. Two modular GREENBOX units, equipped with LED lighting, hydroponic growing platform, and climate controls, were located in a high ceiling headhouse of a greenhouse complex to mimic warehouse conditions. We used bays in a nearby greenhouse that was glass glazed, equipped with supplemental lighting, and fully controlled by an Argus Titan control system for comparison purposes. Forty-eight (48) heads of Butterhead Rex lettuce (Lactuca sativa) were grown over four 30-day cycles in spring, summer, fall, and winter in the GREENBOX units and the greenhouse bays, respectively, at the University of Connecticut, Storrs, Connecticut, United States. Environmental variables, including light, temperature, relative humidity, and carbon dioxide concentration, were measured at a frequency of every minute. Biomass data of wet weight, dry weight, total leaf area, and lettuce head area were collected using destructive and non-destructive methods every three days. The water consumption rate was logged using a lysimeter. We derived the Daily Light Integral (DLI), Leaf Area Index (LAI), Specific Leaf Area (SLA), productivity, and water consumed per lettuce head, per unit wet weight, and per unit dry weight from the measurements. Results were analyzed using descriptive statistics and ANOVA. The DLI values in the GREENBOX units were significantly higher than the recommended minimum DLI by over 20 mol/m2.d in the GREENBOX units and over 10 mol/m2.d in the greenhouse bays. The range of the daily temperature variation is only a few degrees in the GREENBOX units, while in the greenhouse bays was over 20°C. The average daily temperature in both growing locations fell within the optimal range of 17-29°C for lettuce. The relative humidity inside both growing locations fell primarily within the optimal range of 40%-60%. The mean CO2 concentrations inside both growing locations were slightly lower than the ambient concentration of 350 ppm. Measured parameters such as LAI, SLA, and productivity followed similar patterns, slightly different amongst seasons and higher in warmer seasons. ANOVA revealed a slightly (statistically insignificant) higher level of productivity in the GREENBOX units over the greenhouse bays (p=0.16), with higher values during the warmer seasons (p=0.72 in spring and summer). GREENBOX used 1.83-2.69 L of water per lettuce head, while the greenhouse bays used 1.69-3.84 L of water per lettuce head year-round. The water use was consistently lower in the GREENBOX units. We found that the GREENBOX units and greenhouse bays provided comparable environmental conditions, biomass output, and water consumption. Those variables, however, were more consistent in the GREENBOX units. GREENBOX environment was less affected by outside weather and, therefore, exhibited reduced fluctuations. The GREENBOX is advantageous over the greenhouse as it does not require arable or open land for intercepting sunlight and can be operated in available urban buildings such as warehouses. Keywords: GREENBOX, Greenhouse, Lettuce, Productivity, Water use.