Nutritional value of commercial and traditional lettuce (Lactuca sativa L.) and wild relatives: Vitamin C and anthocyanin content

Public perception of folate-biofortified genetically modified lettuce varieties in Brazil

Lettuce is one of the most widely consumed vegetables in the world, commonly eaten fresh in salads, sandwiches, wraps, and as a garnish in various dishes. Consequently, it is a very promising vehicle to deliver vitamins, such as folate (vitamin B9), to a specific population using biofortified varieties generated by conventional or molecular breeding. A new genetically modified lettuce was generated with increased folate content. However, some issues related to public perception regarding this technology should still be evaluated. The aim of this study was to analyze whether consumers are willing to accept a folate-biofortified GM lettuce that could become available to the Brazilian market. A questionnaire involving several issues regarding lettuce consumption was answered by 2,391 people from almost all Brazilian states. When informed that the folic acid biofortified lettuce is a transgenic plant, 46.1% of respondents stated that they would eat it and 30.5% stated that it would be a possibility. This study demonstrated that if there is any explanation regarding the advantage in relation to the use of biotechnology, like enrichment with folic acid, the number of people who accept it increases.

Augmentation of physiology and productivity, and reduction of lead accumulation in lettuce grown in lead contaminated soil by rhizobacteria-assisted rhizoengineeing

Microbial-assisted rhizoengineering is a promising biotechnology for improving crop productivity. In this study, lettuce roots were bacterized with two lead (Pb) tolerant rhizobacteria including Pseudomonas azotoformans ESR4 and P. poae ESR6, and a consortium consisted of ESR4 and ESR6 to increase productivity, physiology and antioxidants, and reduce Pb accumulation grown in Pb-contaminated soil i.e., 80 (Pb in native soil), 400 and 800 mg kg-1 Pb. In vitro studies showed that these strains and the consortium produced biofilms, synthesized indole-3-acetic acid and NH3, and solubilized phosphate challenging to 0, 100, 200 and 400 mg L-1 of Pb. In static conditions and 400 mg L-1 Pb, ESR4, ESR6 and the consortium adsorbed 317.0, 339.5 and 357.4 mg L-1 Pb, respectively, while 384.7, 380.7 and 373.2 mg L-1 Pb, respectively, in shaking conditions. Fourier transform infrared spectroscopy results revealed that several functional groups [Pb-S, M - O, O-M-O (M = metal ions), S-S, PO, CO, -NH, -NH2, C-C-O, and C-H] were involved in Pb adsorption. ESR4, ESR6 and the consortium-assisted rhizoengineering (i) increased leaf numbers and biomass production, (ii) reduced H2O2 production, malondialdehyde, electrolyte leakages, and transpiration rate, (iii) augmented photosynthetic pigments, photosynthetic rate, water use efficiency, total antioxidant capacity, total flavonoid content, total phenolic content, and minerals like Ca2+ and Mg2+ in comparison to non-rhizoengineering plants grown in Pb-contaminated soil. Principal component analysis revealed that higher pigment production and photosynthetic rate, improved water use efficiency and increased uptake of Ca2+ were interlinked to increased productivity by bacterial rhizoengineering of lettuce grown in different levels of Pb exposures. Surprisingly, Pb accumulation in lettuce roots and shoots was remarkably decreased by rhizoengineering than in non-rhizoengineering. Thus, these bacterial strains and this consortium could be utilized to improve productivity and reduce Pb accumulation in lettuce.

Regulation of anthocyanin synthesis in red lettuce in plant factory conditions: A review

Anthocyanins, natural pigments known for their vibrant hues and beneficial properties, undergo intricate genetic control. However, red vegetables grown in plant factories frequently exhibit reduced anthocyanin synthesis compared to those in open fields due to factors like inadequate light, temperature, humidity, and nutrient availability. Comprehending these factors is essential for optimizing plant factory environments to enhance anthocyanin synthesis. This review insights the impact of physiological and genetic factors on the production of anthocyanins in red lettuce grown under controlled conditions. Further, we aim to gain a better understanding of the mechanisms involved in both synthesis and degradation of anthocyanins. Moreover, this review summarizes the identified regulators of anthocyanin synthesis in lettuce, addressing the gap in knowledge on controlling anthocyanin production in plant factories, with potential implications for various crops beyond red lettuce.

Dietary Sources, Stabilization, Health Benefits, and Industrial Application of Anthocyanins-A Review

Natural phytochemicals are well known to protect against numerous metabolic disorders. Anthocyanins are vacuolar pigments belonging to the parent class of flavonoids. They are well known for their potent antioxidant and gut microbiome-modulating properties, primarily responsible for minimizing the risk of cardiovascular diseases, diabetes, obesity, neurodegenerative diseases, cancer, and several other diseases associated with metabolic syndromes. Berries are the primary source of anthocyanin in the diet. The color and stability of anthocyanins are substantially influenced by external environmental conditions, constraining their applications in foods. Furthermore, the significantly low bioavailability of anthocyanins greatly diminishes the extent of the actual health benefits linked to these bioactive compounds. Multiple strategies have been successfully developed and utilized to enhance the stability and bioavailability of anthocyanins. This review provides a comprehensive view of the recent advancements in chemistry, biosynthesis, dietary sources, stabilization, bioavailability, industrial applications, and health benefits of anthocyanins. Finally, we summarize the prospects and challenges of applications of anthocyanin in foods.

Impact of drought stress on vitamin C and anthocyanin content in cultivated lettuces (Lactuca sativa L.) and wild relatives (Lactuca spp.)

Introduction

Lettuce production and quality could be seriously affected by the increasingly limited water resources.

Methods

The effect of drought on the content of two antioxidant compounds, vitamin C and anthocyanins, in five cultivated lettuces and two wild relatives was assessed for 2 years.

Results and discusion

In leaf samples, Lactuca wild species generally had a higher content of total vitamin C than the cultivated lettuces. In contrast, the commercial varieties usually contained more total anthocyanins than the wild species. Total vitamin C decreased with the drought stress in all accessions, commercial varieties, and lettuce wild relatives, with this tendency being consistent and reproducible across the 2 years. These differences were significant in the case of the green commercial varieties 'Winter Crop' (in 2020/2021) and 'Dolomiti G12' (in 2021/2022) and very significant in the red commercial variety 'Red Sails' (in 2020/2021). However, the only group in which the effect of drought was either significant or very significant in both years was the wild species, Lactuca homblei and Lactuca dregeana, and in the latter also in both tissues (leaf and stem) analyzed. Water stress resulted in an increase of the total anthocyanin content in the leaves from all the accessions, both red commercial varieties and wild relatives, in both years. The most significant enrichment and the only one being either significant or very significant in both years was observed in one of the wild relatives assayed (L. homblei). Stems (L. dregeana) contained more anthocyanins than leaves under control conditions, and it was exactly the opposite under drought. Changes in anthocyanins in the two tissues in response to drought stress were in opposite directions, increasing in leaves and decreasing in stems. This could suggest a translocation of anthocyanins as a first quick mechanism to cope with a severe lack of water. In conclusion, anthocyanins (unlike vitamin C) could play a role in the mechanisms deployed by the plant to tolerate drought stress. The wild species with a robust significant enrichment in anthocyanins as a response to drought (L. homblei) is a promising plant material to breed more resilient lettuces.

Impact of Sclerotinia sclerotiorum Infection on Lettuce (Lactuca sativa L.) Survival and Phenolics Content-A Case Study in a Horticulture Farm in Poland

Sclerotinia sclerotiorum is a cause of a prevalent and destructive disease that attacks many horticultural food crops, such as lettuce. This soil-borne necrotrophic fungal pathogen causes significant economic losses in worldwide lettuce production annually. Furthermore, current methods utilized for management and combatting the disease, such as biocontrol, are insufficient. In this study, three cultivars of lettuce (one Crispy and two Leafy cultivars of red and green lettuce) were grown in central Poland (Lodz Voivodeship), a widely known Polish horticultural region. In the summer and early autumn, lettuce cultivars were grown in control and S. sclerotiorum-infected fields. The lettuce cultivars (Templin, Lollo Rossa, and Lollo Bionda) differed phenotypically and in terms of the survival of the fungal infection. The Crispy iceberg Templin was the most susceptible to S. sclerotiorum infection compared to the other cultivars during both vegetation seasons. The total content of phenolic compounds, flavonoids, and anthocyanins varied among cultivars and fluctuated during infection. Moreover, phenolic content was affected by vegetation season with alterable environmental factors such as air temperature, humidity, soil temperature, and pH. The most increased levels of phenolics, both flavonoids and anthocyanins in infected plants, were observed in the Leafy red Lollo Rossa cultivar in both crops. However, the highest survival/resistance to the fungus was noticed for Lollo Rossa in the summer crop and Lollo Bionda in the autumn crop.

Heukharang lettuce (Lactuca sativa L.) leaf extract displays sleep-promoting effects through GABAA receptor

ETHNOPHARMACOLOGICAL RELEVANCE

Although lettuce is traditionally known to have hypnotic and sedative effects, to date, only a few studies have documented its sleep-promoting effects and elucidated the related mechanisms.

AIM OF THE STUDY

We aimed to investigate the sleep-promoting activity of Heukharang lettuce leaf extract (HLE) with increased lactucin content, known as a sleep-promoting substance in lettuce, in animal models.

MATERIALS AND METHODS

To evaluate the effect of HLE on sleep behavior, analysis of electroencephalogram (EEG), gene expression of brain receptors, and activation mechanisms using antagonists were investigated in rodent models.

RESULTS

High-performance liquid chromatography analysis showed that HLE contained lactucin (0.78 mg/g of extract) and quercetin-3-glucuronide (1.3 mg/g of extract). In the pentobarbital-induced sleep model, the group administered 150 mg/kg of HLE showed a 47.3% increase in sleep duration time as compared to the normal group (NOR). The EEG analysis showed that the HLE significantly increased non-rapid eye movement (NREM), where delta waves were improved by 59.5% when compared to the NOR, resulting in increased sleep time. In the caffeine-induced arousal model, HLE significantly decreased the awake time increased by caffeine administration (35.5%) and showed a similar level to NOR. In addition, HLE increased the gene and protein expression of gamma-aminobutyric acid receptor type A (GABAA), GABA type B, and 5-hydroxytryptamine (serotonin) receptor 1A. In particular, in comparison to the NOR, the group administered 150 mg/kg HLE showed an increase in expression levels of GABAA and protein by 2.3 and 2.5 times, respectively. When the expression levels were checked using GABAA receptor antagonists, HLE showed similar levels to NOR, as the sleep duration was reduced by flumazenil (45.1%), a benzodiazepine antagonist.

CONCLUSIONS

HLE increased NREM sleep and significantly improved sleep behavior due to its action on the GABAA receptors. The collective findings suggest that HLE can be used as a novel sleep-enhancing agent in the pharmaceutical and food industries.

Phytochemical and Agronomic Characterization of High-Flavonoid Lettuce Lines Grown under Field Conditions

Flavonoids are antioxidant phytochemicals that confer a beneficial effect on human health. We have previously developed and characterized eight lettuce (Latuca sativa L.) lines that accumulated high levels of diverse flavonoids and their precursors in controlled environment conditions. Three Rutgers Scarlet lettuce (RSL) lines selected in tissue culture for deep-red color (RSL-NAR, RSL-NBR, RSL-NFR) accumulate anthocyanins and quercetin, three lines identified in a chemically mutagenized red lettuce population accumulate kaempferol (KfoA and KfoB) or naringenin chalcone (Nco), and two lines that were spontaneous green mutants derived from the red line RSL-NAR (GSL, GSL-DG) accumulate quercetin. These eight lines were field-grown in the Salinas Valley of California for four years together with seven control accessions of varying colors (light green, dark green, red, and dark red). At market maturity, a substantial variation in plant composition was observed, but the three RSL lines consistently accumulated high levels of cyanidin, GSL and GSL-DG accumulated the highest levels of quercetin, KfoA and KfoB accumulated kaempferol, and Nco amassed naringenin chalcone, confirming that these mutant lines produce high levels of beneficial phytochemicals under field conditions. Mutant lines and control accessions were also assessed for their biomass production (plant weight, height, and width), overall content of pigments (leaf chlorophyll and anthocyanins), resistance to diseases (downy mildew, lettuce drop, and Impatiens necrotic spot virus), postharvest quality of processed tissue (deterioration and enzymatic discoloration), and composition of 23 mineral elements. All but one mutant line had a fresh plant weight at harvest comparable to commercial leaf cultivars; only Nco plants were significantly (p < 0.05) smaller. Therefore, except for Nco, the new, flavonoid hyperaccumulating lines can be considered for field cultivation.

Effect of Dopamine on Growth, Some Biochemical Attributes, and the Yield of Crisphead Lettuce under Nitrogen Deficiency

Nitrogen (N) represents the most important nutrient for plant growth and productivity, but extreme and ineffective usage of N fertilizer results in boosted plant production expenditures and environmental contamination. For the world’s sustainable food production and environmental profits, there has been increased research interest in reducing the use of N fertilization along with improving plant N deficiency (ND) tolerance. Dopamine (DA), a potential antioxidant, mediates several physio-biochemical processes in plants under normal or stressful conditions. However, their roles in increasing ND tolerance in crisphead lettuce are not well-documented. We investigate the role of DA concentration (0.50 and 100 µM) on the growth and yield of crisphead lettuce plants under ND. Under normal conditions (100% recommended N fertilizer dose), DA (50 and 100 μM) application significantly enhanced growth, chlorophyll concentration, N%, antioxidant enzymes activity, as well as yield and its components, decreased nitrate accumulation and oxidative biomarkers compared to untreated plants (0 μM DA). ND significantly decreased plant growth and yield attributes as well as evoked oxidative impairment and nitrate accumulation as compared to 100% recommended N fertilizer dose in the absence of DA. However, within ND conditions, the application of DA concentrations significantly mitigated ND-induced oxidative burst and improved plant growth, chlorophyll concentration, N%, nitrate concentration, peroxidase, catalase, superoxide dismutase, total soluble solid, vitamin C, dry matter %, and total sugars, over 0 μM DA treated plants. Current findings highlighted that exogenous application of 100 μM DA could reinforce the crisphead lettuce plant’s resilience to ND by minimizing reactive oxygen species accumulation and promoting enzymatic antioxidants alongside growth, yield, and quality improvement. The beneficial effects of DA in lessening ND’s drastic impacts on crisphead lettuce resulted from upregulating antioxidant enzyme activity, impairment of oxidative biomarkers, and maintaining chlorophyll levels. The current findings open pioneering prospects to reduce nitrogen fertilization by DA application without any drastic effect on plant productivity. But further research is needed to fully understand DA effects and their mechanisms in inducing ND tolerance in different plant species, including crisphead lettuce.

Discovering and Mapping Colloquial Terminologies Describing Underutilized and Neglected Food Crops-A Comprehensive Review

Global levels of biodiversity and dietary diversity are decreasing, leading to food and nutrition insecurity. This is partially due to the homogenization of the global food supply with commodity crops. The reintroduction or introduction of neglected and underutilized species, minor, forgotten, and indigenous crops and landrace varieties to the wider food systems and further diversification have been outlined as the future strategies for tackling the above by the United Nations and the Food and Agriculture Organization in their policy frameworks. Most of the above species/crops are marginalized and only used across local food systems and in research. With over 15,000 different seed banks and repositories worldwide, information transparency and communication are crucial for database searching and their effective utilization. Much confusion persists around the true nature of those plants, and this prohibits the efficient utilization of their economic potential. A linguistic corpus search and a systematic literature review were conducted using the six most popular collocates to the above terms, which were as follows: ancient, heirloom, heritage, traditional, orphan, and the more distinct term 'landrace'. The results were interpreted using the Critical Discourse Analysis method. The definitions' findings show that heirloom, heritage, and ancient are mainly used in the United Kingdom and USA, where they are used to describe 'naturalized' and 'indigenized' or 'indigenous' food crops with a strong affiliation to 'family' and the 'act of passing seeds down from generation to generation'. Orphan crops, on the other hand, are often described as being 'overlooked' by growers and 'underfunded' by researchers. Landrace is most strongly affiliated with 'locality', 'biocultural diversity', and 'indigenous', and with genomics literature, where the characteristics are often discussed in the context of genetics and population biology. Contextualizing, most of the terms were found to be 'arbitrary' and 'undefinable' due to their continuing evolution in the socially accepted form of language, perhaps apart from landrace. The review has retrieved 58 definitions for the mentioned 6 terms, together with the primary key terms creating a tool to facilitate a better inter-sector communication and aid in policy.

Chemical Characterization and In Vitro Gas Production Kinetics of Alternative Feed Resources for Small Ruminants in the Maltese Islands

The ever-increasing human population, the problem associated with climate change and recent crises-COVID-19 disease and trade conflicts-all impacted on the availability and cost of animal feed raw materials. This is clearly visible in realities which heavily rely on importation such as islands and small states, where producers involved in the agricultural sector were strongly affected by the sharp increase in prices. To deal with these global issues, alternative resources are perceived to replace conventional ingredients. This work aimed at assessing the nutritive value of different resources (sheep feed, mature carob, Maltese bread, wild asparagus, prickly lettuce, and loquat) for small ruminants present in the Maltese Islands, analyzing their chemical composition, gas production kinetics and antioxidant properties. In general, the variation in chemical composition resulted in different rumen fermentation kinetics (p < 0.007). The ratio between GP-24 h and GP-48 h was higher in Maltese bread than other substrates; loquat, prickly lettuce and wild asparagus showed lower fermentation kinetics in accordance with their high NDF and ADF contents. The antioxidant activity may be partially related to the polyphenolic content that was higher in wild asparagus, prickly lettuce and loquat. All feed characteristic confirmed their potential to be included as ingredients in ruminant diets and as a source of fiber.

Development of 2D and 3D front face fluorescence spectroscopy for monitoring ultrasound treatment in the removal of pesticides residues from fresh lettuces at the laboratory and pilot scales

Pesticide residues in vegetables are potentially toxic components to humans and can cause serious health problems. To remove pesticide residues from fresh agricultural products and improve consumer food safety, various pesticide removal methods have been investigated over the past decades. In this study, the effectiveness of laboratory and pilot scale ultrasonic cleaning on the removal of boscalid and pyraclostrobin residues from lettuce was examined. 2D fluorescence spectroscopy, 3D fluorescence spectroscopy represented by excitation-emission matrix (EEM), and parallel factor analysis (PARAFAC) were used to characterize and discriminate the fluorescence signatures of these pesticides in the cleaning water to determine the effectiveness of the ultrasonic cleaning method as a function of the level of pesticide removal. The 2D fluorescence results showed that the rate of removal of boscalid by ultrasonics at the laboratory scale increased with the cleaning time. The ultrasonic treatment showed a higher cleaning efficiency compared to only soaking in distilled water for 10 min. The same trends were observed at the pilot scale. The EEM also showed differences in the concentration of pesticides removed by ultrasonication between the different parts of the lettuce, the concentration was higher in the upper part than the lower part. This study showed that ultrasonication is an effective technique for the removal of pesticide residues on lettuce, and it also showed the significant potential of fluorescence spectroscopy coupled with PARAFAC for the discrimination and characterization of pesticides.

Selection of Novel Reference Genes by RNA-Seq and Their Evaluation for Normalising Real-Time qPCR Expression Data of Anthocyanin-Related Genes in Lettuce and Wild Relatives

Lettuce is a popular vegetable source of bioactive compounds, like anthocyanins, powerful antioxidants present in red and semi-red varieties. Selection of reliable reference genes (RGs) for the normalization of real-time quantitative PCR (qPCR) data is crucial to obtain accurate gene expression results. Among the genes with totally unrelated biological functions, six candidate RGs (ADF2, CYB5, iPGAM, SCL13, TRXL3-3, and VHA-H) with low variation in expression according to RNA-seq analyses, were selected for future expression studies of anthocyanin-related genes in three different experiments: leaf colour comparison (green vs. red) in commercial varieties; tissue comparison (leaf vs. stem) in a wild relative; and drought stress experiment in commercial and traditional varieties, and a wild relative. Expression profiles of the candidate RGs were obtained by qPCR and their stability was assessed by four different analytical tools, geNorm, NormFinder, BestKeeper, and Delta Ct method, all integrated in RefFinder. All results considered, we recommend CYB5 to be used as RG for the leaf colour experiment and TRXL3-3 for the tissue and drought stress ones, as they were the most stable genes in each case. RNA-seq is useful to preselect novel RGs although validation by qPCR is still advisable. These results provide helpful information for gene expression studies in Lactuca spp. under the described conditions.

Combined analysis of the transcriptome and metabolome provides insights into the fleshy stem expansion mechanism in stem lettuce

As a stem variety of lettuce, the fleshy stem is the main product organ of stem lettuce. The molecular mechanism of fleshy stem expansion in stem lettuce is a complex biological process. In the study, the material accumulation, gene expression, and morphogenesis during fleshy stem expansion process were analyzed by the comparative analysis of metabolome, transcriptome and the anatomical studies. The anatomical studies showed that the occurrence and activity of vascular cambium mainly led to the development of fleshy stems; and the volume of pith cells gradually increased and arranged tightly during the expansion process. A total of 822 differential metabolites and 9,383 differentially expressed genes (DEGs) were identified by the metabolomics and transcriptomics analyses, respectively. These changes significantly enriched in sugar synthesis, glycolysis, and plant hormone anabolism. The expression profiles of genes in the sugar metabolic pathway gradually increased in fleshy stem expansion process. But the sucrose content was the highest in the early stage of fleshy stem expansion, other sugars such as fructose and glucose content increased during fleshy stem expansion process. Plant hormones, including IAA, GA, CTK, and JA, depicted important roles at different stem expansion stages. A total of 1,805 DEGs were identified as transcription factors, such as MYB, bHLH, and bZIP, indicating that these transcription factor families might regulate the fleshy stems expansion in lettuce. In addition, the expression patterns identified by qRT-PCR were consistent with the expression abundance identified by the transcriptome data. The important genes and metabolites identified in the lettuce fleshy stem expansion process will provide important information for the further molecular mechanism study of lettuce fleshy stem growth and development.

Arbuscular Mycorrhizal Fungi Increase Nutritional Quality of Soilless Grown Lettuce while Overcoming Low Phosphorus Supply

Lettuce is widely used for its healthy properties, and it is of interest to increase them with minimal environmental impact. The purpose of this work was to evaluate the effect of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae in lettuce plants (Lactuca sativa L. cv. Salinas) cultivated in a soilless system with sub-optimal phosphorus (P) compared with non-inoculated controls at two different P concentrations. Results show that lettuce inoculation with the selected AMF can improve the growth and the nutritional quality of lettuce even at sub-optimal P. Leaf content of chlorophylls, carotenoids, and phenols, known as important bioactive compounds for human health, was higher in mycorrhizal lettuce plants compared with non-mycorrhizal plants. The antioxidant capacity in AMF plants showed higher values compared with control plants grown at optimal P nutrition level. Moreover, leaf gas exchanges were higher in inoculated plants than in non-inoculated ones. Nitrogen, P, and magnesium leaf content was significantly higher in mycorrhizal plants compared with non-mycorrhizal plants grown with the same P level. These findings suggest that F. mosseae can stimulate plants growth, improving the nutritional quality of lettuce leaves even when grown with sub-optimal P concentration.

Secondary Metabolite Profile and Pharmacological Opportunities of Lettuce Plants following Selenium and Sulfur Enhancement

Selenium (Se) is an essential trace nutrient for humans and animals owing to its role in redox regulation, thyroid hormone control factors, immunity, inflammatory reactions, brain activities, and carbohydrate regulation. It is also important to support muscle development, as well as for reproductive and cardiovascular well-being. Furthermore, sulfur is known to be a healing element, due to the remarkable function of specialized and secondary S-containing compounds. The scope of the current study was to determine the impact of Se and S enrichment on the secondary metabolite accumulation and antibacterial and NO inhibition activities in green and red leaf lettuce (V1 and V2, respectively). The plants were grown in a hydroponic system supplied with different S concentrations (S0: 0, S1: 1 mM and S2: 1.5 mM K₂SO₄) via the nutrient solution and foliar-applied varying levels of Se (0, 0.2 and 2.6 µM). Electrospray ionization-quadrupole time-of-flight mass spectrometry (ESI-QTOF/MS) combined with ultra-performance liquid chromatography (UPLC) was used to identify the secondary metabolites in green and red lettuce. The results indicated that extracts of the biofortified lettuce were not cytotoxic to Vero kidney cells at the highest concentration tested of 1 mg/mL. The ESI/MS of the tentatively identified metabolites showed that the response values of 5-O-caffeoylquinic acid, cyanidin 3-O-galactoside, quercetin 3-O-(6''-acetyl-glucoside) and quercetin 3-O-malonylglucoside were induced synergistically under higher Se and S levels in red lettuce plants. The acetone extract of red lettuce had antibacterial activity against Pseudomonas aeruginosa, with a minimum inhibitory concentration (MIC) of 0.156 and 0.625 μg/mL under S2/Se1 and S2/Se2 treatments, respectively. As with antibacterial activity, the acetone extract of green (V1) lettuce treated with adequate (S1) and higher S (S2) under Se-limiting conditions showed the ability to inhibit nitric oxide (NO) release from macrophages. NO production by macrophages was inhibited by 50% at respective concentrations of 106.1 ± 2.4 and 101.0 ± 0.6 μg/mL with no toxic effect on the cells, in response to S1 and S2, respectively, under Se-deficient conditions (Se0). Furthermore, the red cultivar (V2) exhibited the same effect as the green cultivar (V1) regarding NO inhibition, with IC₅₀ = 113.0 ± 4.2 μg/mL, in response to S1/Se2 treatments. Collectively, the promising NO inhibitory effect and antibacterial activity of red lettuce under the above-mentioned conditions might be attributed to the production of flavonoid glycosides and phenylpropanoic acid esters under the same condition. To the best of our knowledge, this is the first report to show the novel approach of the NO inhibitory effect of Se and S enrichment in food crops, as an indicator for the potential of Se and S as natural anti-inflammatory agents.

Improving the Tolerance to Salinity Stress in Lettuce Plants (Lactuca sativa L.) Using Exogenous Application of Salicylic Acid, Yeast, and Zeolite

Salinity is among the most limiting factors of crop production worldwide. This study aims to investigate the influence of the exogenous application of zeolite, yeast, and salicylic acid in alleviating the negative effect of salt stress under field conditions. Lettuce plants (Lactuca sativa L. cv. Batavia) were tested in a split-plot arrangement replicated three times. The salt stress was applied as a whole-plot factor in the concentrations (0 mM, 50 mM, 100 mM, and 150 mM NaCl). After 28 days of sowing, the plants were sprayed twice during the foliage growth with (control, salicylic acid 0.02%, yeast extract 3%, and zeolite 0.5%) as a split-plot factor. The length of roots and shoots, the number and area of leaves, and the biomass accumulation (dry and fresh weights) were measured 50 days after sowing. The concentrations of total soluble sugars, proline, Chlorophylls a and b in leaves have also been quantified. Salt stress significantly reduced the growth and the total chlorophyll of the lettuce plants (p < 0.05) and increased their proline and sugar contents’. Zeolite application improved the growth of lettuce at 0 and 50 mM NaCl, but at the highest salinity level only the number of leaves was improved by 15%. At a mild salinity stress, the application of salicylic acid has significantly (p < 0.05) increased the root length, height of plant, chlorophyll, and proline contents. Regarding the high stress levels (100 and 150 mM NaCl), yeast application showed the best tolerance to salinity stress by improving significantly most of the growth parameters (p < 0.05) but with lower proline, sugar, and chlorophyll contents. In general, foliar spray of yeast extract may offer a good alternative source of nutrients through leaves, leading to a better tolerance of the high salt stress exerted on roots.

Phytochemicals, Nutrition, Metabolism, Bioavailability, and Health Benefits in Lettuce-A Comprehensive Review

Lettuce is one of the most famous leafy vegetables worldwide with lots of applications from food to other specific uses. There are different types in the lettuce group for consumers to choose from. Additionally, lettuce is an excellent source of bioactive compounds such as polyphenols, carotenoids, and chlorophyll with related health benefits. At the same time, nutrient composition and antioxidant compounds are different between lettuce varieties, especially for green and red lettuce types. The benefit of lettuce consumption depends on its composition, particularly antioxidants, which can function as nutrients. The health benefits rely on their biochemical effect when reaching the bloodstream. Some components can be released from the food matrix and altered in the digestive system. Indeed, the bioaccessibility of lettuce is measuring the quantity of these compounds released from the food matrix during digestion, which is important for health-promoting features. Extraction of bioactive compounds is one of the new trends observed in lettuce and is necessarily used for several application fields. Therefore, this review aims to demonstrate the nutritional value of lettuce and its pharmacological properties. Due to their bioaccessibility and bioavailability, the consumer will be able to comprehensively understand choosing a healthier lettuce diet. The common utilization pattern of lettuce extracted nutrients will also be summarized for further direction.

Applications of Genomic Tools in Plant Breeding: Crop Biofortification

Crop breeding has mainly been focused on increasing productivity, either directly or by decreasing the losses caused by biotic and abiotic stresses (that is, incorporating resistance to diseases and enhancing tolerance to adverse conditions, respectively). Quite the opposite, little attention has been paid to improve the nutritional value of crops. It has not been until recently that crop biofortification has become an objective within breeding programs, through either conventional methods or genetic engineering. There are many steps along this long path, from the initial evaluation of germplasm for the content of nutrients and health-promoting compounds to the development of biofortified varieties, with the available and future genomic tools assisting scientists and breeders in reaching their objectives as well as speeding up the process. This review offers a compendium of the genomic technologies used to explore and create biodiversity, to associate the traits of interest to the genome, and to transfer the genomic regions responsible for the desirable characteristics into potential new varieties. Finally, a glimpse of future perspectives and challenges in this emerging area is offered by taking the present scenario and the slow progress of the regulatory framework as the starting point.

The Nutritional Quality Potential of Microgreens, Baby Leaves, and Adult Lettuce: An Underexploited Nutraceutical Source

Interest in the cultivation of lettuce landraces is increasing because native varieties, as high-quality products, are particularly attractive to consumers. Lettuce is a popular leafy vegetable worldwide, and interest in the consumption of first leaves (microgreens) and seedlings (baby leaves) has grown due to the general belief that young plants offer higher nutritional value. The content of some bioactive compounds and antioxidants (chlorophylls, carotenoids, anthocyanins, ascorbic acid, phenols, antioxidant activity) was monitored in six lettuce landraces and five commercial varieties, and compared across three development stages: microgreen, baby, and adult. Ascorbic acid and phenolic contents were 42% and 79% higher, respectively, in the early stages than in adult lettuces, and red-leaf varieties (CL4 and L11) stood out. This finding agrees with lettuce’s marked antioxidant capacity and correlates with its pigment contents, especially anthocyanins. The nutritional value of adult lettuce is conditioned by its size, shape, and head structure as phytochemical concentrations are regulated by light. The low content of ascorbic acid, phenolics, and anthocyanins in crisphead lettuce (CL5) is a clear example (49, 67%, and 27% lower, respectively, than the adult mean). Our results indicate the wide variability of lettuces’ nutritional characteristics and emphasize that traditional varieties are a helpful source of agricultural biodiversity.

Bioactive compounds in lettuce: Highlighting the benefits to human health and impacts of preharvest and postharvest practices

Lettuce is one of the most commonly consumed leafy vegetables worldwide and is available throughout the entire year. Lettuce is also a significant source of natural phytochemicals. These compounds, including glycosylated flavonoids, phenolic acids, carotenoids, the vitamin B groups, ascorbic acid, tocopherols, and sesquiterpene lactones, are essential nutritional bioactive compounds. This review aims to provide a comprehensive understanding of the composition of health-promoting compounds in different types of lettuce, the potential health benefits of lettuce in reducing the risks of chronic diseases, and the effect of preharvest and postharvest practices on the biosynthesis and accumulation of health-promoting compounds in lettuce.

Alternative splicing triggered by the insertion of a CACTA transposon attenuates LsGLK and leads to the development of pale-green leaves in lettuce

Lettuce (Lactuca sativa) is one of the most important vegetable crops in the world. As a leafy vegetable, the polymorphism of lettuce leaves from dark to pale green is an important trait. However, the genetic and molecular mechanisms underlying such variations remain poorly understood. In this study, one major locus controlling the polymorphism of dark- and pale-green leaves in lettuce was identified using genome-wide association studies (GWAS). This locus was then fine mapped to an interval of 5375 bp on chromosome 4 using a segregating population containing 2480 progeny. Only one gene, homologous to the GLK genes in Arabidopsis and other plants, is present in the candidate region. A complementation test confirmed that the candidate gene, LsGLK, contributes to the variation of dark- and pale-green leaves. Sequence analysis showed that a CACTA transposon of 7434 bp was inserted 10 bp downstream of the stop codon of LsGLK, followed by a duplication of a 1826-bp fragment covering exons 3-6 of the LsGLK gene. The transposon insertion did not change the expression level of the LsGLK gene. However, because of alternative splicing, only 6% of the transcripts produced from the transposon insertion were wild-type transcripts, which led to the production of pale-green leaves. An evolutionary analysis revealed that the insertion of the CACTA transposon occurred in cultivated lettuce and might have been selected in particular cultivars to satisfy the diverse demands of consumers. In this study, we demonstrated that a transposon insertion near a gene may affect its splicing and consequently generate phenotypic variations.

Determination of Specific Parameters for Early Detection of Botrytis cinerea in Lettuce

In horticulture, the demand for efficient farming processes and food industries increases rapidly. Plant diseases cause severe crop production and economic losses. Therefore, early detection and identification of the diseases in plants are critical. This study aimed to determine the specific parameters for early detection of Botrytis cinerea in lettuce. The lettuce “Little Gem” was inoculated with B. cinerea isolate spore suspension and disc to evaluate the plant response to inner and outer infection, respectively. The non-destructive measurements of leaf spectral reflectance indices and biochemical compounds (phenols, proteins, DPPH, FRAP, chlorophyll, and carotenoids) were used to evaluate the plant physiological response to inoculation with B. cinerea after 12, 18, 36, 60, and 84 h. Our data showed that lettuce responded differently to inner and outer inoculation with B. cinerea. Therefore, the findings of this study allow for the inoculation method to be chosen to determine the early plant response to infection with B. cinerea according to specific leaf spectral reflectance indexes and phytochemicals in further research.

Plant Response to Mechanically-Induced Stress: A Case Study on Specialized Metabolites of Leafy Vegetables

Plants have evolved various adaptive mechanisms to environmental stresses, such as sensory mechanisms to detect mechanical stimuli. This plant adaptation has been successfully used in the production practice of leafy vegetables, called mechanical conditioning, for many years, but there is still a lack of research on the effects of mechanically-induced stress on the content of specialized metabolites, or phytochemicals with significant antioxidant activity. Therefore, the aim of this study was to determine the content of specialized metabolites and antioxidant capacity of lettuce and green chicory under the influence of mechanical stimulation by brushing. Mechanically-induced stress had a positive effect on the content of major antioxidants in plant cells, specifically vitamin C, total phenols, and flavonoids. In contrast, no effect of mechanical stimulation was found on the content of pigments, total chlorophylls, and carotenoids. Based on the obtained results, it can be concluded that induced mechanical stress is a good practice in the cultivation of leafy vegetables, the application of which provides high quality plant material with high nutritional potential and significantly higher content of antioxidants and phytochemicals important for human health.