Lettuce Varieties Research Articles

Identification and Preliminary Functional Analysis of Responsive Genes to Short-term Heat Stress in Lettuce

Lettuce is a commonly consumed vegetable worldwide, due to its crisp edible organs and rich nutrition. Heat stress is known to seriously threaten its growth and development. However, research on lettuce response to heat stress focusing on molecular aspects is limited. Therefore, we aimed to understand the complex molecular mechanisms underlying the regulation of lettuce plant response to heat stress (37 °C), by transcriptomic analysis of a heat-resistant lettuce variety (K482) following heat stress treatment for 1.5 and 3 days. A total of 3798 and 4121 differentially expressed genes (DEGs) were identified at 1.5 and 3 days vs. the control after heat treatment, respectively; they were mostly enriched in protein processing in the systemic lupus erythematosus, alcoholism, neurotrophin signaling pathways, and the cell cycle. Most DEGs were NACs, HSPs, MYBs, bHLHs, and WRKYs. Transcriptome analysis showed that the NAC domain transcription factor LsNAC28, which is associated with heat response, is up-regulated during heat stress and LsNAC28 inhibited yeast growth under heat stress (37 °C). These findings provide a basis to comprehensively understand the complex molecular mechanism of lettuce response to heat stress.

Variety of Lettuce (Lactuca sativa L.) Growth and Yield in Response to Various Organic Fertilizers in Makurdi, Nigeria

This study was conducted in 2023 at the nursery of the Teaching and Research farm of the Department of Crop production of Joseph Sarwuan Tarka University Makurdi, Benue State, Nigeria. The experimental treatments were two (2) varieties of lettuce (ice berg and Butter head) and three (3) organic manure sources (Poultry dropping, cow dung, goat manure) and a control. An experiment was set up as a 2 x 4 factorial design using a randomized complete block design (RCBD) with three replications. Data were collected from the following parameters, plant height, plant diameter, number of leaves, leaf area index (LAI), crop growth rate (CGR), roof weight, and fresh weight. All the study parameters of lettuce were significantly (P<0.05) different, on both organic manure, and variety. The iceberg variety surpassed the butter head variety, with statistically significant (P<0.05) differences observed in several parameters: plant height (20.32 cm), number of leaves (23.85), leaf area index (15.19 cm³), сrop growth rate (1.54 g m³ per day), chlorophyll content (23.32 mg/g), fresh weight (83.86 g), root weight (20.23 g), and yield (3.19 t/ha) Similarty, poutry droppings obtained significantly (P<0.05) better results in terms of plant height (21.73 cm), number of leaves (23 92), leaf area Index (16.75 cm²), crop growth rate (3.70 g m³ per day), chlorophyll content (25.73 mg/g), fresh weight (632.02 g), root weight (22.13 g) and yield (3.75 t/ha) as compared to other organic manure sources such as cow dung, goat manure and control. In addition, a significant difference (P<0.05) was observed in the interaction between lettuce varieties selection and organic fertilizers at various levels, particularly with the high level of iceberg x poultry manure

Genome-wide association study of salt tolerance at the seed germination stage in lettuce.

Developing lettuce varieties with salt tolerance at the seed germination stage is essential since lettuce seeds are planted half an inch deep in soil where salt levels are often highest in the salinity-affected growing regions. Greater knowledge of genetics and genomics of salt tolerance in lettuce will facilitate breeding of improved lettuce varieties with salt tolerance. Accordingly, we conducted a genome-wide association study (GWAS) in lettuce to identify marker-trait association for salt tolerance at the seed germination stage. The study involved 445 diverse lettuce accessions and 56,820 single nucleotide polymorphism (SNP) markers obtained through genotype-by-sequencing technology using lettuce reference genome version v8. GWAS using two single-locus and three multi-locus models for germination rate (GR) under salinity stress, 5 days post seeding (GR5d_S) and a salinity susceptibility index (SSI) based on GR under salinity stress and control conditions, 5 days post seeding (SSI_GR5d) revealed 10 significant SNPs on lettuce chromosomes 2, 4, and 7. The 10 SNPs were associated with five novel QTLs for salt tolerance in lettuce, explaining phenotyping variations of 5.85%, 4.38%, 4.26%, 3.77%, and 1.80%, indicating the quantitative nature of these two salt tolerance-related traits. Using the basic local alignment search tool (BLAST) within 100 Kb upstream and downstream of each of the 10 SNPs, we identified 25 salt tolerance-related putative candidate genes including four genes encoding for major transcription factors. The 10 significant salt tolerance-related SNPs and the 25 candidate genes identified in the current study will be a valuable resource for molecular marker development and marker-assisted selection for breeding lettuce varieties with improved salt tolerance at the seed germination stage.

Hydroponic lettuce in-situ water circulation evaluation via nondestructive mass measurement in controlled environment.

This study proposed a hydroponic system with the capacity to acquire high-resolution in situ mass data for non-destructive evaluation of water circulation in lettuce. The system customizes the watering profile, enables high-frequency in situ weight measurement, and monitors multidimensional environment changes. Key air, water, and light parameters were collected to evaluate the plant response, susceptibility, and adaptability to environmental conditions. Multiple physiological indices were defined to characterize the properties of two lettuce varieties in response to different environmental factors.

Antimicrobial activities of polyphenol-based metabolites present in lettuce and recent methods for their estimation

The tissue structure of fresh-cut lettuce is easy to be damaged during processing and transportation, which leads to the reduction of its edible quality and safety. Ultra-high-performance liquid chromatography (UHPLC) combined with time-of-flight tandem mass spectrometry (TMS) metabolomics was used to identify the differential metabolites related to the antibacterial activity in lettuce and explore their bacteriostatic mechanism. The experimental results revealed that the growth of Escherichia coli was quite different when different varieties of lettuce were used as the nutrient substrate. Between the varieties Beizisheng No. 3 (BZ3) and Shooter 101 (SS), 204 differential metabolites showed significant changes (P < 0.05), 86 metabolites showed changes between the varieties BZ3 and Beisansheng No. 1 (BS1). Among the metabolites, isoquercitrin was the upregulated differential metabolite in BZ3 compared to SS and BS1. The content of isoquercitrin in lettuce juice positively correlated with the antibacterial activity of polyphenol extract, but negatively correlated with the growth of E. coli. The bacteriostatic property of polyphenol extract destroys the morphological structure of E. coli. The higher the isoquercitrin content, the stronger the resistance of fresh-cut lettuce to E. coli.

Optimizing Lettuce Growth in Nutrient Film Technique Hydroponics: Evaluating the Impact of Elevated Oxygen Concentrations in the Root Zone under LED Illumination

Evaluating different concentrations of oxygen on lettuce physiology, growth, and biochemical assays is pivotal for optimizing the nutrient film technique (NFT), boosting yields, and enhancing resource efficiency in sustainable greenhouse cultivation. Two lettuce varieties Lactuca sativa var. Lolo Bionta (Lugano) and Lolo Rosa (Carmesi), were grown using NFT in a greenhouse for two consecutive years during the months of December and January. A comparative methodology was adopted under a randomized complete block design (RCBD) to study plant growth under three different oxygen concentration levels: natural oxygen concentrations (NOC); elevated oxygen concentrations (EOC); and elevated oxygen concentrations under LED light (380–840 nm) (LED + EOC). The plants were exposed to EOC levels of 8.1–8.7 mg L−1 in December and 8.7–9.0 mg L−1 in January. Under LED + EOC conditions, the levels were 8.2–8.3 mg L−1 in December and 8.8–9.0 mg L−1 in January. The NOC levels were 6.8–7.1 mg L−1 in December and 7.2–7.8 mg L−1 in January for Lugano and Carmesi, respectively. The applied light intensity, measured as photosynthetic photon flux density (PPFD), ranged from 463 to 495 µmol m−2 s−1 for the Lugano and from 465 to 490 µmol m−2 s−1 for the Carmesi. The dissolved oxygen concentration and LED light exposure under greenhouse conditions had significant effects (p < 0.05) on the plant growth parameters. The biochemical and physiological attributes, including transpiration rate, stomatal conductance, nitrate, chlorophyll, sugar contents, net photosynthesis, and respiration rates, varied significantly across different oxygen concentrations. Data were analyzed using a two-way ANOVA with post hoc Tukey’s HSD tests for significance (p < 0.05) using IBM SPSS Statistics (version 29.0.2.0). Both EOC and LED + EOC treatments significantly improved growth attributes compared to NOC in Lugano, with increases in plant height (16.04%, 0.85%), fresh mass (110.91%, 29.55%), root length (27.35%, 29.55%), and root mass (77.69%, 34.77%). For Carmesi, similar trends were observed with increases in plant height (5.64%, 13.27%), fresh mass (10.45%, 21.57%), root length (37.14%, 47.33%), and root mass (20.70%, 41.72%) under EOC and LED + EOC. In the intertreatment analysis, the effect of LED + EOC was more pronounced compared to EOC. In view of the intertreatment response, Lolo Bionta (Lugano) appeared to have a high overall horticultural performance (growth and yield in both EOC and LED + EOC compared to Lolo Rosa (Carmesi). The practical significance of these results lies in their potential to inform strategies for optimizing greenhouse environments, particularly through the manipulation of oxygen levels and light exposure. The significant increases in growth metrics, especially under the LED + EOC conditions, suggest that targeted environmental adjustments can lead to substantial improvements in lettuce yield and quality. The findings also contribute to the advancement of sustainable agricultural technologies aiming to enhance food security and sustainability.

Global identification of LIM genes in response to different heat stress regimes in Lactuca sativa

BackgroundLIM (Lineage-11 (LIN-11), Insulin-1 (ISL-1), and Mechanotransduction-3 (MEC-3)) genes belong to a family that hold ubiquitous properties contributing to organ, seed, and pollen development as well as developmental and cellular responses to biotic and abiotic stresses. Lettuce (Lactuca sativa) is a highly consumed vegetable crop susceptible heat stress. High temperatures limit lettuce’s overall yield, quality and marketability. Lettuce LIM genes have not been identified and their role in response to high temperatures is not known. Aiming to identify potential new targets for thermoresilience, we searched for LIM genes in lettuce and compared them with orthologous of several dicotyledons and monocotyledons plant species.ResultsWe identified fourteen lettuce LIM genes distributed into eight different subgroups using a genome-wide analysis strategy. Three belonging to DAR (DA means “large” in Chinese) class I, two DAR class II, one in the WLIM1, two in the WLIM2, one in the PLIM1, two in the PLIM2 class, one ßLIM and two δLIMs. No DAR-like were identified in any of the species analyzed including lettuce. Interestingly, unlike other gene families in lettuce which underwent large genome tandem duplications, LIM genes did not increase in number compared to other plant species. The response to heat stress induced a dynamic transcriptional response on LsLIM genes. All heat stress regimes, including night stress, day stress and day and night stress were largely responsible for changes in LIM transcriptional expression.ConclusionsOur global analysis at the genome level provides a detailed identification of LIM genes in lettuce and other dicotyledonous and monocotyledonous plant species. Gene structure, physical and chemical properties as well as chromosomal location and Cis-regulatory element analysis together with our gene expression analysis under different temperature regimes identified LsWLIM1, LsWLIM2b, LsDAR3 and LsDAR5 as candidate genes that could be used by breeding programs aiming to produce lettuce varieties able to withstand high temperatures.

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.

Manure-based composts influence soil quality after lettuce (Lactuca sativa L.) production

Declining soil fertility is a major constraint for vegetable crops like lettuce in sub-Saharan Africa. With the purpose of contributing to enhancing crop yields and soil productivity, while safeguarding the environment, this study aims to assess the effect of composts made from chicken droppings (CCD) and horse dung (CHD) on soil quality after lettuce growing. The phytotoxicity of the composts was assessed by testing the germination of two varieties of lettuce (V1: Eden and V2: Blonde de Paris) with aqueous extracts of the composts at different concentrations (0, 25, 50, 75 and 100 %). For the field evaluation, treatments (C0: control without fertilizer, C1: 15 t.ha−1 of chicken droppings, C2: 15 t.ha−1 of horse dung, C3: chemical fertilizers) and varieties were distributed in a completely randomized block design with three replications. Physico-chemical soil analysis was carried out before (Ct) and after lettuce production depending on the treatments. Soil’s parameters determined included: pH, organic matter, carbon, C/N ratio, granulometry, cation exchange capacity, exchangeable bases, nitrogen, phosphorus, calcium, magnesium, sodium and potassium contents. The results of the phytotoxicity test showed that the lowest germination percentages were obtained at V1C2100%Ster+ (48.33 ± 6.01 %) and V2C2100%Ster+ (53.33 ± 6.01 %). These values were around the standard (50 %), showing that these composts were non-toxic. The results showed that overall, the composts improved soil properties, with significant increases in P and Ca content. So, soil Ca contents of C0, C1, C2 and C3 were respectively 2, 3, 2 and 2 times that of Ct. CCD and CHD can be therefore recommended for growing lettuce and maintaining soil quality.

Macam Varietas Tanaman Selada Perlakuan Media Organik

This research seeks to assess how organic and varietal planting media impact the growth and yield of lettuce plants (Lactuca sativa. L). The study was conducted using the Complete Group Random Design (CGRD) method with two treatment factors. The first factor involved three types of organic planting media: (M1) a blend of soil, manure, and burnt husks; (M2) a blend of soil, manure, and cocopeat; (M3) a blend of soil, manure, burnt husks, and cocopeat. The second factor comprised three varieties: (V1) Grand Rapid green lettuce, (V2) Red Rapid red lettuce, and (V3) Lollo Rossa red lettuce. The findings indicate that treatment (M3), consisting of soil, manure, burnt husks, and cocopeat, influences leaf width, plant weight, and dry stash weight. The best yield was observed in treatment (V1) with the Grand Rapid green lettuce variety showing significant effects across all parameters. The conclusions are as follows: 1. Organic growing media does not affect all observation parameters related to the growth and yield of lettuce plants. 2. Varietal differences have a noticeable impact on all observation parameters related to lettuce growth and yield. 3. The interaction between organic growing media and plant varieties significantly affects the observation parameters of plant height and plant weight, while it does not affect leaf width and dry stash weight.

Analysis of diseases, pests and qualitative parameters of various varieties of lettuce grown under hydroponic conditions

Analysis of diseases, pests and qualitative parameters of various varieties of lettuce grown under hydroponic conditions

Evaluating temperature variation of nutrient solution in Nutrient Film Technique (NFT) cooling system for temperate vegetable

The production of leafy green vegetables in hydroponic systems within greenhouses has gained global prominence in the fresh vegetable production industry. Hydroponic systems, particularly Nutrient Film Technique (NFT), are highly effective due to their soilless nature and efficient nutrient and water circulation. However, maintaining ideal greenhouse temperatures can be challenging. One strategy to reduce energy costs is to heat or cool the nutrient solution instead of the entire greenhouse environment. By regulating the root zone temperature through nutrient solution management, growers can provide more favourable conditions for temperate leafy greens. These conditions are critical because temperatures above 23°C can inhibit plant growth, while temperatures exceeding 35°C can significantly reduce plant metabolism efficiency. This study investigates how lettuce responds to nutrient solution cooling. Importantly, this research focuses on Malaysia, an equatorial country with a consistently warm and humid climate. In such environments, controlling nutrient solution or air temperature to match the crops' optimal growth requirements is crucial. The study employed Butterhead and Romaine lettuce varieties in a hydroponic NFT system. The EC (Environmental Cooling) treatment involved cooling the nutrient solution, while the RZC (Root Zone Cooling) treatment utilized environmental cooling. The results demonstrated that maintaining a consistent nutrient solution temperature within the range of 14°C to 18°C (as observed in the EC treatment) led to superior plant growth and quality, particularly in the early growth stages. In contrast, the RZC treatment showed temperature fluctuations, causing plant stress and inhibiting growth.

The Use of Imaging to Quantify the Impact of Seed Aging on Lettuce Seed Germination and Seedling Vigor.

The decline in seed quality over time due to natural aging or mishandling requires assessing seed vigor for resilience in adverse conditions. Accelerated aging (AA) methods simulate seed deterioration by subjecting seeds to high temperatures and humidity. Saturated salt accelerated aging (SSAA) is an AA method adopted for small seeds like lettuce (Lactuca sativa). In this study, we subjected seeds of two lettuce cultivars ('Muir' and 'Bauer') to SSAA by sealing them in a box containing 40 g/100 mL of a sodium chloride (NaCl) solution in a dark growth chamber at 41 °C for 24, 48, and 72 h with a control. We monitored their vigor using embedded computer cameras, tracking the projected canopy size (PCS) daily from sowing to harvest. The cultivar 'Muir' exhibited consistent PCS values across the treatments, while 'Bauer' showed PCS variations, with notable declines after prolonged aging. The germination rates dropped significantly after 48 and 72 h of SSAA. A nonlinear regression model revealed a strong relationship between PCS and shoot dry weight across harvests and cultivars (R2 = 0.93, RMSE = 0.15, p < 0.001). The research found that the projected canopy size and shoot dry weight increased over time with significant differences in treatments for the cultivar 'Bauer' but not for 'Muir,' with the canopy size being a strong predictor of dry weight and no significant impact from the SSAA treatments. This study highlights cultivar-specific responses to aging and demonstrates the efficacy of our imaging tool in predicting lettuce dry weight despite treatment variations. Understanding how aging affects different lettuce varieties is crucial for seed management and crop sustainability.

Stability Evaluation for Heat Tolerance in Lettuce: Implications and Recommendations.

Lettuce is an important cool-temperature crop, and its principal abiotic stress is low heat tolerance. Lettuce production has become more challenging in the context of global warming changes. Hence, the main objective of this research was to investigate the relationship between stability and lettuce heat tolerance. Field and greenhouse trials were run in 2015 (summer) and 2016 (fall and spring). The environments were composed of a combination of season and place (field, glass, and plastic greenhouse), and the assessed genotypes were BRS Leila and Mediterrânea, Elisa, Everglades, Simpson, and Vanda. Statistical analysis showed a significant effect (p < 0.05) of environments (E), genotypes (G), and the GEI. BRS Leila, Elisa, and BRS Mediterrânea showed the greatest means to the first anthesis in suitable environments (milder temperatures). Among these cultivars, BRS Mediterrânea was the most stable and adapted to hot environments. The environmental conditions studied in this research, mainly high temperatures, could become a reality in many lettuce-producing areas. Therefore, the results can help indicate and develop lettuce varieties with greater heat tolerance.

Production of Flathead Grey Mullet (Mugil cephalus) and Lettuce (Lactuca sativa) in a Coupled Aquaponic System under Suboptimal Water Temperatures

The combined production of three varieties of lettuce (romaine, iceberg, and red leaf) with flathead grey mullet (Mugil cephalus) was tested in triplicate in three independent coupled aquaponic units with no thermal control. For this purpose, a total of 114 fish (2.5 kg/m3) were stocked in each fish tank (2 m3), and 92 lettuces were planted in the hydroponic unit (6 m2). As no thermal control was included in the design of the aquaponic system, water temperatures declined from maximum values of 20.4 °C to minimum values of 5.0 °C, which directly affected fish growth. However, the conditions imposed by the aquaponic system were suitable for promoting lettuce’s growth and external appearance, as no pests or leaf discoloration were noticed. Lettuce survival was similar among the three tested varieties (98.5 ± 1.7%). The yields for the romaine and iceberg varieties were 384 ± 100 g/lettuce and 316 ± 70 g/lettuce, respectively, and that for the red leaf variety was lower, at 176 ± 75 g/lettuce. Yield values ranged between 3.6 and 4.4 kg/m2 depending on the replicate considered (4.0 ± 0.4 kg/m2). According to present results, each aquaponic unit required ca. 2.6–2.7 L of water per unit of lettuce produced.

Low frequency of the wild-type freezing-tolerance LsCBF7 allele among lettuce population suggests a negative selection during domestication and breeding

Key messageSustainable winter production in lettuce requires freezing tolerant varieties. This study identified a wild-type allele of LsCBF7 that could contribute to freezing tolerance improvement in lettuce.Lettuce is one of the most consumed vegetables globally. While ideally grown in 13–21 °C, its cultivation extends into winter in milder climates. However, occasional freezing temperatures can significantly reduce yields. Therefore, the development of freezing-tolerant lettuce varieties has become a long-term goal of lettuce breeding programs. Despite its significance, our understanding of freezing tolerance in lettuce remains limited. Plants have evolved a coping mechanism against freezing, known as cold acclimation, whereby they can increase freezing tolerance when pre-exposed to low nonfreezing temperatures. The CBF pathway is well-known for its central role in cold acclimation. Previously, we identified 14 CBF genes in lettuce and discovered that one of them, LsCBF7, had a loss-of-function mutation. In this study, we uncovered that accessions from colder regions carried the wild-type allele of LsCBF7 and this allele likely contributed to increased freezing tolerance, with 14% of the lettuce population carrying this allele. Interestingly, in wild lettuce (L. serriola) that is considered a progenitor of cultivated lettuce, this wild-type allele was much more common, with a frequency of 90%. This finding suggests that this wild-type allele may have undergone negative selection during the domestication or breeding of lettuce. Our data strongly indicate that this allele could be linked to early bolting, an undesirable trait in lettuce, which may have driven the negative selection. While this wild-type allele shows promise for improving freezing tolerance in lettuce, it is crucial to decouple it from the early bolting trait to fully harness its potential in lettuce breeding.

Does This Look Infected? Hidden Host Plant Infection by the Pathogen Botrytis cinerea Alters Interactions between Plants, Aphids and Their Natural Enemies in the Field.

Few studies have considered whether hidden (asymptomatic) plant pathogen infection alters ecological interactions at the higher trophic levels, even though such infection still affects plant physiology. We explored this question in two field experiments, where two varieties of lettuce (Little Gem, Tom Thumb) infected with Botrytis cinerea were either (1) naturally colonised by aphids or (2) placed in the field with an established aphid colony. We then recorded plant traits and the numbers and species of aphids, their predators, parasitoids and hyperparasitoids. Infection significantly affected plant quality. In the first experiment, symptomatically infected plants had the fewest aphids and natural enemies of aphids. The diversity and abundance of aphids did not differ between asymptomatically infected and uninfected Little Gem plants, but infection affected the aphid assemblage for Tom Thumb plants. Aphids on asymptomatically infected plants were less attractive to predators and parasitoids than those on uninfected plants, while hyperparasitoids were not affected. In the second experiment, when we excluded natural enemies, aphid numbers were lower on asymptomatically and symptomatically infected plants, but when aphid natural enemies were present, this difference was removed, most likely because aphids on uninfected plants attracted more insect natural enemies. This suggests that hidden pathogen infection may have important consequences for multitrophic interactions.

Optimum flow rate enhances the performance of lettuce (Lactuca sativa L.) in hydroponic culture

Poor substate flow rate affects the production of crops under hydroponic systems as contact and collision times of ions (nutrients) with roots is affected deciding nutrients uptake rate and quantity required for crop growth. Keeping in view, a study was conducted under hydroponic culture to obtain optimal flow rate for higher production of lettuce, which is an important leafy vegetable. Two lettuce varieties (Boston and Lollo Bionda) were subjected to 4 different flow rates (0.5, 1.0, 1.5, 2.0 L min-1) under completely randomized design (CRD) with factorial arrangement and replicated four times. The outcomes of the study suggest that performance of Lollo Bionda variety was better than Boston regarding root and shoot fresh and dry biomass, leaf number, area, length and width and head diameter and plant height. The same parameters kept on increasing with increase of flow rate and achieved maximum values at 1.5 L min-1. Beyond that flow rate the values for these parameters declined which indicated that the optimal flow rate for these 2 lettuce verities is 1.5 L min-1. Hence, it was concluded that for higher production of lettuce, the flow rate should be kept at 1.5 L min-1 in Nutrient Film Technique (NFT) using hydroponic system with environmental and substrate conditions mentioned in materials and method portion of this article.

Use of dynamic simulation and Forrester diagrams to describe the growth of lettuce (Lactuca sativa L.) under field conditions

The use of computational tools to describe some processes of crop growth has evolved in recent decades and remains an area of active research, where more and more applications are incorporated with the integration of a greater number of mathematical tools, statistics, and computational calculation efficiency, simplifying the tasks of modeling and visualizing the components of the system used. Current research proposes a dynamic growth model for lettuce cultivation using Forrester diagrams to evaluate different scenarios involving five growth functions and five lettuce cultivars in field conditions of the Bailadores region (Venezuelan Andes, 2550 m a.s.l.). The lettuce variety Coastal Star achieved the greatest accumulation of dry matter used as a response in each model. The logistics of growth function was properly adjusted to the experimental data compared to the other models. The proposed diagram model can be used as a basis for the construction of more complex models that incorporate other physiological variables of the crop and the growth environment.

The Stimulation of Chemical Male Sterility for F1 Hybrid Lettuce (Lactuca Sativa Var. Longifolia) Production

Male sterility is a unique application in the production of F1 hybrid seeds of some important species. Today, while F1 hybrid lettuce varieties of abroad origin take their place in the Türkiye seed market, unfortunately, we do not have a native F1 hybrid variety. Besides, F1 hybrid seed production has become a prestige for multi-national companies regardless of the type of vegetable. Within this perspective, the effects of some chemical hybridizing agents (CHAs) such as E4FO, Ethrel and GA3 on male sterilizing activity in lettuce cultivars (Maylight352 F1, Presidential and Yedikule) were evaluated. Therefore, pollen presence in the early bud stage, seed formation and seed viability (germination) were examined. The applications had different effects on pollen presence, seed formation and seed germination, and thus male sterility. Ethrel was not effective at low doses, but at high doses, it caused flower bud deformation and growth retardation. E4FO is partially effective, but the application doses are low. Therefore, E4FO should be used at higher than 1500 ppm and 2000 ppm. GA3 applications produced the best results in stimulating male sterility, and full sterility (% 100) was achieved from 200, 250 and 300 ppm in all cultivars. As a result, 200 ppm GA3 was determined as the recommendable dose in the production of Fı hybrid lettuce.