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To improve several agronomic traits in crisphead lettuce (Lactuca sativa L.) under high-temperature growth conditions, we investigated the correlation among those traits in multiple cultivars and performed genetic mapping of their causal genes. In a field cultivation test of Empire type (serrated leaf) and Salinas type (wavy leaf) cultivars, Empire type cultivars showed increased tipburn susceptibility and late bolting compared with Salinas type cultivars. We attempted genetic mapping of leaf shape and bolting time by ddRAD-seq using the F2 population derived from a cross between 'VI185' (Empire type) and 'ShinanoGreen' (Salinas type). These analyses suggested that both traits are controlled by a single locus in LG5. Genotyping of 51 commercial lettuce cultivars with a tightly linked marker (LG5_v8_252.743Mbp) at this locus showed an association between its genotype and the serrated leaf phenotype. By further fine mapping and transcriptome analysis, a gene encoding putative CIN-like TCP transcription factor was determined to be a candidate gene at this locus and was designated as LsTCP4. An insertion of retrotransposable element was found in the allele of 'VI185', and its transcript level in the leaves was lower than that in 'ShinanoGreen'. Because shapes of leaf epidermal cells in 'VI185' were similar to those in the TCP family mutant of Arabidopsis thaliana, the leaf shape phenotype was likely caused by reduced expression of LsTCP4. Furthermore, because it is known that the TCP family protein also controls flowering time via interaction with FT in A. thaliana, it was highly possible that LsTCP4 gave pleiotropic effects on both leaf shape and bolting time in lettuce. [ABSTRACT FROM AUTHOR]

Abstract Lettuce (Lactuca sativa L.) is known to have high cadmium (Cd) concentrations in its shoots, which makes it necessary to protect against Cd toxicity. Understanding Cd-induced physiological responses in lettuce plants can contribute to the definition of useful strategies to decrease Cd uptake. This study aimed to gain new insights into Cd-induced stress by measuring Cd bioaccumulation, nutrient composition, anatomical and ultrastructural changes, and antioxidative metabolism in three lettuce genotypes characterized as having different degrees of Cd tolerance (Vanda = low, Lidia = medium and Stela = high). Plants were grown hydroponically with Cd concentrations of 0.0 and 0.1 or 0.5 μmol L−1, for 30 days. Cadmium uptake in the lettuce genotypes assayed is controlled by the root/shoot ratio, higher root/shoot ratios allowing greater Cd uptake. The Fe and Ni content increased in shoots of the genotype Lidia, which could be associated with a decrease in oxidative stress in chloroplasts due to superoxide dismutase (SOD) isozyme activity. Cadmium-induced oxidative stress is associated with de-structuring of the phloem and xylem in roots, and starch grain and plastoglobule accumulation in chloroplasts. Lettuce genotypes that presented higher SOD and ascorbate peroxidase (APX) activity presented better preserved anatomical structures. These results suggest that genotypes with less efficient antioxidant defence in the roots tend to take up more Cd, increasing root-to-shoot Cd translocation. Graphical abstract fx1 Highlights • Cd uptake by lettuce genotypes is linked with biomass partitioning. • Nutrient accumulation decreased in all genotypes, in response of Cd exposure, except for Fe and Ni in the genotype Lidia. • Plastoglobule accumulation is associated with Fe-SOD activity in the genotype Lidia. • Better-preserved xylem–phloem anatomy may be the result of increased APX and SOD activity in roots. [ABSTRACT FROM AUTHOR]

Abstract Land application of coal ash is considered an environmentally friendly option to improve soil quality, but limited information exists on metal bioavailability and phytotoxicity of coal ash to sensitive plant species such as lettuce (Lactuca sativa L.). Germination and pot bioassay experiments were conducted at six coal application rates (0% (control), 5%, 15%, 25%, 50% and 75% v/v) to investigate the hypothesis that, coal ash will have a hormetic effect on germination, growth, metal uptake and biomass yield of lettuce, characterized by stimulatory and phytotoxicity effects at low and high application rates, respectively. Total concentrations (mg/kg) of metals in coal ash spanned several orders of magnitude, and decreased in the order: Fe (5150.5), Mn (326.0), Zn (102.6), Cu (94.7), Ni (74.7) and Pb (11.6). Bioavailable concentrations of metals were very low (0.0–14.1 mg/kg), accounting for less than 2% of the total concentrations. Coal ash had no significant effect on germination indices, but had hormetic effects on radicle elongation, evidenced by stimulatory and phytotoxicity effects at low (5–25%) and high (50–75%) application rates, respectively. Coal ash application at 50% and 75% significantly (p < 0.05) reduced lettuce growth and edible biomass yield, but lower application rates (5–25%) were similar to the unamended soil (control). Fe, Mn, Zn, Cu and Ni bioavailability and plant uptake generally decreased with increasing coal ash application rates particularly at 50% and 75%. Soil pH significantly increased (p < 0.05) from 6.5 for the control to about 8 for 75% coal ash, while electrical conductivity (EC) increased by 2–7 times to about 0.9 and 1.5 dS/m at 50% and 75% coal ash, respectively. Significant inverse linear relationship (p < 0.05; r2 = 0.80) were observed between edible and total biomass yields and EC, suggesting that increased salinity at high coal ash application rates could account for reduced growth and biomass. Partial elemental balances showed that plant uptake of metals was very low, accounting for just less than 2% of the bioavailable concentrations, while the bulk of the metals (98–99%) remained in the soil. In conclusion, the current findings show that coal ash may have hormetic and phytotoxic effects on sensitive plant species, an observation contrary to the bulk of earlier literature documenting beneficial effects of coal ash application to soils. Long-term field studies are required to confirm the current findings based on laboratory and pot bioassay experiments. Highlights • The phytotoxicity of coal ash (CA) used as a soil amendment on lettuce was studied. • CA had no effect on germination, but had a hormetic effect on radicle elongation. • CA reduced the bioavailability of metals, but increased soil pH and salinity. • CA significantly (p < 0.05) reduced metal uptake, growth and biomass of lettuce. • Biomass yield and electrical conductivity were inversely related (p < 0.05; r2 = 0.8). [ABSTRACT FROM AUTHOR]

The present study was carried out to determine the effect of ozonated water (2 mg L−1) at different temperatures (4 °C and 15 °C) on the microbiological, color and sensory properties of lettuce. Cold ozone treatment (4 °C) significantly reduced the natural background microflora of lettuce. Salmonella Typhimurium and Escherichia coli inoculated on lettuce samples were insignificantly influenced by the temperature of water. During storage period at +4 °C for 14 days, the highest quality was observed from the samples treated with cold ozonated water. Ozone treatments did not affect the color properties and sensory quality of lettuce samples. [ABSTRACT FROM AUTHOR]

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Key message : Micropropagation protocol of transgenic lettuce bearing S-, M- and L-HBsAg was developed for increased production of uniformised material for oral vaccine preparation. Abstract: Effective manufacturing of plant-based biopharmaceuticals, including oral vaccines, depends on sufficient content of a protein of interest in the initial material and its efficient conversion into an administrable formulation. However, stable production of plants with a uniformised antigen content is equally important for reproducible processing. This can be provided by micropropagation techniques. Here, we present a protocol for micropropagation of transgenic lettuce lines bearing HBV surface antigens: S-, M- and L-HBsAg. These were multiplied through axillary buds to avoid the risk of somaclonal variation. Micropropagation effectiveness reached 3.5-5.7 per passage, which implies potential production of up to 6600 plant clones within a maximum 5 months. Multiplication and rooting rates were statistically homogenous for most transgenic and control plants. For most lines, more than 90 % of clones obtained via in vitro micropropagation had HBsAg content as high as reference plants directly developed from seeds. Clones were also several times more uniform in HBsAg expression. Variation coefficients of HBsAg content did not exceed 10 % for approximately 40-85 % of clones, or reached a maximum 20 % for 90 % of all clones. Tissue culture did not affect total and leaf biomass yields. Seed production for clones was decreased insignificantly and did not impact progeny condition. Micropropagation facilitates a substantial increase in the production of lettuce plants with high and considerably equalised HBsAg contents. This, together with the previously reported optimisation of plant tissue processing and its long-term stability, constitutes a successive step in manufacturing of a standardised anti-HBV oral vaccine of reliable efficacy. [ABSTRACT FROM AUTHOR]

Rapid development of plants is important for the production of 'baby-leaf' lettuce that is harvested when plants reach the four- to eight-leaf stage of growth. However, environmental factors, such as high or low temperature, or elevated concentrations of salt, inhibit lettuce growth. Therefore, non-destructive evaluations of plants can provide valuable information to breeders and growers. The objective of the present study was to test the feasibility of using non-destructive phenotyping with optical sensors for the evaluations of lettuce plants in early stages of development. We performed the series of experiments to determine if hyperspectral imaging and chlorophyll fluorescence imaging can determine phenotypic changes manifested on lettuce plants subjected to the extreme temperature and salinity stress treatments. Our results indicate that top view optical sensors alone can accurately determine plant size to approximately 7 g fresh weight. Hyperspectral imaging analysis was able to detect changes in the total chlorophyll (RCC) and anthocyanin (RAC) content, while chlorophyll fluorescence imaging revealed photoinhibition and reduction of plant growth caused by the extreme growing temperatures (3 and 39°C) and salinity (100 mM NaCl). Though no significant correlation was found between Fv/Fm and decrease in plant growth due to stress when comparisons were made across multiple accessions, our results indicate that lettuce plants have a high adaptability to both low (3°C) and high (39°C) temperatures, with no permanent damage to photosynthetic apparatus and fast recovery of plants after moving them to the optimal (21°C) temperature. We have also detected a strong relationship between visual rating of the green- and red-leaf color intensity and RCC and RAC, respectively. Differences in RAC among accessions suggest that the selection for intense red color may be easier to perform at somewhat lower than the optimal temperature. This study serves as a proof of concept that optical sensors can be successfully used as tools for breeders when evaluating young lettuce plants. Moreover, we were able to identify the locus for light green leaf color (qLG4), and position this locus on the molecular linkage map of lettuce, which shows that these techniques have sufficient resolution to be used in a genetic context in lettuce. [ABSTRACT FROM AUTHOR]

Lettuce is an important edible crop which possesses various medicinal properties. In this study Lactuca sativa L. (cv Grand Rapids) was transformed by Agrobacterium-mediated transformation with rol C gene. Transgene integration and expression was confirmed through PCR and semiquantitative RT-PCR. The transformed extracts were evaluated for their in vitro antioxidant and in vivo analgesic, anti-inflammatory and antidepressant activities in rats. The transformed plants showed 53-98 % increase in total phenolic and 45-58 % increase in total flavonoid contents compared with untransformed plants. Results of total reducing power and total antioxidant capacity exhibited 90-118 and 61-75 % increase in transformed plants, respectively. In contrast to control, DPPH, lipid peroxidation and DNA protection assay showed up to 37, 20 and 50 % enhancement in transformed plants, respectively. The extracts showed similar but significant enhancement behavior in hot plate analgesic and carrageenan-induced hind paw edema test. The transformed extracts showed 72.1 and 78.5 % increase for analgesic and anti-inflammatory activities, respectively. The transformants of rol C gene exhibited prominent antidepressant activity with 64-73 % increase compared with untransformed plants. In conclusion, the present work suggests that transformation with rol C gene can be used to generate lettuce with enhanced medicinally important properties, such as antioxidant, analgesic, anti-inflammatory and antidepressant potential. [ABSTRACT FROM AUTHOR]

This study aimed to verify the economic viability of a project involving hydroponic lettuce production in Tijucas, Santa Catarina. For data collection, ten interviews were done with the representatives of supermarkets and restaurants located in the metropolitan area of Florianópolis and, based on this information, the volume of sales of that product in those companies was determined. A greenhouse project was developed that could produce enough to meet the identified demand of hydroponic lettuce, which is around 3.840 heads of lettuce/month. The initial investment for the implementation of the project was estimated at R$54.352,42, the annual costs of the system are around R$33.091,57 and the annual gross revenue is R$62.208,00. The economic viability was analyzed using the Net Present Value (NPV), Internal Rate of Return (IRR) and discounted Payback economic indicators. The risk analysis of the investment using the sensitivity analysis was also performed. It was concluded that the project to produce hydroponic lettuce in Tijucas is economically viable, because the the NPV obtained was R$156.765,06, the IRR was 53,45% and the recovery time of the investment was 2 years and 2 months. [ABSTRACT FROM AUTHOR]

In the present study, tannin extracts (rinsed or not) were compared to the use of sodium hypochlorite and tap water on fresh cut crisp leaf lettuce stored under modified atmosphere packaging. Effects of these sanitizers on total color difference and microbial levels of the product after sanitization and storage for 9 days at 3°C were evaluated. Performance of rinsed SM® tannin extract was comparable to the results of chlorine solution for all the analyzed parameters and; furthermore, that extract presented a high reduction in the initial bacterial count of minimally processed lettuce. However, storage of tannin extracts, did not impart better outcomes than the use of tap water. Therefore, the tannin extract storage SM® could be used in washing water to reduce the initial microbiological load, avoiding cross contamination in vegetables minimally processed. [ABSTRACT FROM AUTHOR]

Previous research showed that the use of plant growth promoting rhizobacteria helped to increase nutrient use efficiency. The individual and combined effects of combined action of humic fertilizer and rhizobacteriaBacillus subtilisNo. 2 on the lettuce yield, chlorophyll, total nitrogen and nitrate-(N) contents in lettuce leaves was studied. Traditional biochemical analysis and crop reflectance method were compared. Vegetation Indices and key spectrum characteristics - a median of frequency spectrum and bandwidth of frequency spectrum were used to estimate chlorophyll content in plant leaves. The synergistic effect of bacteria and humic fertilizer was evidenced by increase in N and chlorophyll contents and in decreased nitrates content in lettuce leaves. Humic fertilizer resulted in decreased nitrates concentration in plants, whereasbacillus(B).subtilisNo. 2 increased total N and chlorophyll contents. Results indicated that the application rate of humic fertilizer may be reduced whenB. subtilisNo. 2 is also applied. [ABSTRACT FROM AUTHOR]

Although, the circadian clock is a universal biological system in plants and it orchestrates important role of plant production such as photosynthesis, floral induction and growth, there are few such studies on cultivated species. Lettuce is one major cultivated species for both open culture and plant factories and there is little information concerning its circadian clock system. In addition, most of the relevant genes have not been identified. In this study, we detected circadian oscillation in the lettuce transcriptome using time-course RNA sequencing (RNA-Seq) data. Constant light (LL) and light-dark (LD) conditions were used to detect circadian oscillation because the circadian clock has some basic properties: one is self-sustaining oscillation under constant light and another is entrainment to environmental cycles such as light and temperature. In the results, 215 contigs were detected as common oscillating contigs under both LL and LD conditions. The 215 common oscillating contigs included clock gene-like contigs CCA1 (CIRCADIAN CLOCK ASSOCIATED 1)-like, TOC1 (TIMING OF CAB EXPRESSION 1)- like and LHY (LATE ELONGATED HYPOCOTYL)-like, and their expression patterns were similar to those of Arabidopsis. Functional enrichment analysis by GO (gene ontology) Slim and GO Fat showed that the GO terms of response to light stimulus, response to stress, photosynthesis and circadian rhythms were enriched in the 215 common oscillating contigs and these terms were actually regulated by circadian clocks in plants. The 215 common oscillating contigs can be used to evaluate whether the gene expression pattern related to photosynthesis and optical response performs normally in lettuce. [ABSTRACT FROM AUTHOR]

Twenty seven newly introduced genotypes of lettuce collected from different indigenous and exotic sources were characterized with respect to economically important traits by using principle component and regression analyses. Significant differences were observed among the genotypes for all the characters under study. CGN-10944 performed best among all the genotypes for most of the traits under study. Principal component analysis indicated that the first five factors had variances of 3.88, 2.78, 1.47, 1.42 and 1.24 with 25.87%, 18.57%, 9.81%, 9.49% and 8.26% of total variation, respectively and aggregating to 72.01% of totalvariation. The highest positive values of different traits in different components indicated that main emphasis should be given onthe gross head weight (X2), polar (X6) & equatorial diameter (X7) and seed vigour index-I (X12) & II (X13) to have higher yieldsin lettuce. To quantify the importance of each variable in predicting yield, multiple linear regression model was developed. Thecoefficient of determination (R2) in linear regression model revealed that 94% of total variation in yield per plot (X15) wasinfluenced by days to marketable maturity (X1), gross head weight (X2), heading percentage (X4), seed germination (X11), seedvigour index-II (X13) and severity of bacterial soft rot (X14). Therefore, main emphasis should be given on days to marketablematurity, gross head weight, polar & equatorial diameter, heading percentage, seed germination, seed vigour index-I & II andseverity of bacterial soft rot during selection and hybridization programmes for yield improvement in lettuce. [ABSTRACT FROM AUTHOR]

The putrefactive activity of organisms such as diplopods in the edaphic macrof auna can be leveraged to promote the transformation of agricultural and urban waste into a lowcost substrate for the production of vegetable seedlings. This research aimed to evaluate: (1) the quantity of Gervais millipedes (Trigoniulus corallinus) needed to produce an acceptable quantity of organic compost; (2) the main physical and chemical characteristics of different compost types; and (3) compost efficiency in the production of lettuce seedlings. The first experiment lasted 90 days and was conducted using 6.5L of Gliricidia, 6.5L of Flemingia, 13.5L of grass cuttings, 4.5L of cardboard, 4.5L of coconut husk, and 4.5L of corncob. Treatments consisting of 0, 0.10, 0.30, 0.50, and 0.90L of millipedes were applied. This experiment compared millicompost and vermicompost, using four repetitions. After 23 days, the heights of grown lettuce plants and the weights of the fresh and dry mass of above ground lettuce and of the roots were assessed. A millipede volume of 0.1L proved to be sufficient for the production of an acceptable volume of organic compost. However, the addition of greater volumes leads to increased calcium, magnesium, and phosphorous content. Millicompost has similar physicochemical characteristics those of vermicompost, and both are equally efficient as a substrate for the production of lettuce seedlings. [ABSTRACT FROM AUTHOR]

Lettuce is one of the major crops of the United States and can provide a large portion of income for small to medium size growers. Growing lettuce in adverse environmental conditions can have negative effects on quality. Elevated levels of potassium (K) have been shown to positively influence quality in various fruits and vegetables, such as tomato, pepper, and strawberry. However, research is lacking on the effects of elevated levels of K on leafy vegetables such as lettuce. Therefore, seeds of 'Cimmaron' lettuce were sown into a soilless medium and grown in greenhouse conditions at 25/20 °C (day/night). At 27 days after seeding, the plantlets were transferred to 3.8-L plastic nursery pots. Plants were grown under increasing K treatments of 98 (control), 185 (2?), 370 (3?), and 740 (8?) kg·ha-1. Plants were harvested 56 days after seeding. Application of elevated levels of K fertilizer treatments in red romaine lettuce had a positive quadratic effect on plant height increasing 7.0% from the control. Fresh weight (FW) increased 13.0% from the control and dry weight (DW) increased 15.5%. There was linear increase of 30.0% in sucrose concentrations in lettuce leaf tissue. In addition, the increase in K treatments caused an increase of 43.3% in K concentrations in the leaf tissue. In other nutrients, such as Calcium (Ca), Magnesium (Mg), and Sulfur (S), there was a decrease in the leaf tissue of 61%, 52%, and 46% when compared with the control treatment, respectively. The results of the current study suggest that increasing K fertilizer to 185 kg·ha-1 has the best results for plant height, FW and DW, and mineral nutrient concentrations. This study may initiate research that could examine the effects of increasing K fertilizer levels in lettuce or other leafy green vegetables on antioxidant levels and postharvest storability. [ABSTRACT FROM AUTHOR]

Despite reports that food-borne parasitic infections have been increasing worldwide, the methodologies employed to detect food contamination by helminths are still largely based on methodologies used to detect these pathogens in feces and water. This study sought to improve the diagnosis of parasitic contaminants in lettuce by standardizing a method for detecting helminth eggs and larvae and estimating their percentage of recovery. Sanitized lettuces were artificially contaminated with different amounts of Ascaris suum and hookworm eggs and larvae. To standardize the method, we tested liquid extractors, vegetable washing steps, and spontaneous sedimentation times. Higher percentages of egg and larvae recovery were obtained using 1 M glycine as the liquid extractor, manual shaking for 3 min and 2 h of sedimentation. Five different levels of artificial contamination (ten replicates each; n = 50) were tested using these standardized conditions, yielding an average recovery of 62.6 % (±20.2), 51.9 % (±20.0), and 50.0 % (±27.3) for A. suum eggs, hookworm eggs, and larvae, respectively. Tests were performed with a different matrix to evaluate the performance of the method. Furthermore, collaborative analytical studies performed by different laboratories produced satisfactory results. The method for the identification of helminth eggs and larvae proposed in this study proved to be simpler and more efficient than previously published procedures, thereby demonstrating its potential contribution to health surveillance and epidemiological studies. [ABSTRACT FROM AUTHOR]

Seed germination and flowering, two critical developmental transitions in plant life cycles, are coordinately regulated by genetic and environmental factors to match plant establishment and reproduction to seasonal cues. The DELAY OF GERMINATION1 (DOG1) gene is involved in regulating seed dormancy in response to temperature and has also been associated genetically with pleiotropic flowering phenotypes across diverse Arabidopsis thaliana accessions and locations. Here we show that DOG1 can regulate seed dormancy and flowering times in lettuce (Lactuca sativa, Ls) and Arabidopsis through an influence on levels of microRNAs (miRNAs) miR156 and miR172. In lettuce, suppression of LsDOG1 expression enabled seed germination at high temperature and promoted early flowering in association with reduced miR156 and increased miR172 levels. In Arabidopsis, higher miR156 levels resulting from overexpression of the MIR156 gene enhanced seed dormancy and delayed flowering. These phenotypic effects, as well as conversion of MIR156 transcripts to miR156, were compromised in DOG1 loss-of-function mutant plants, especially in seeds. Overexpression of MIR172 reduced seed dormancy and promoted early flowering in Arabidopsis, and the effect on flowering required functional DOG1. Transcript levels of several genes associated with miRNA processing were consistently lower in dry seeds of Arabidopsis and lettuce when DOG1 was mutated or its expression was reduced; in contrast, transcript levels of these genes were elevated in a DOG1 gain-of-function mutant. Our results reveal a previously unknown linkage between two critical developmental phase transitions in the plant life cycle through a DOG1-miR156-miR172 interaction. [ABSTRACT FROM AUTHOR]

Haploidisation is a biotechnological method used to obtain plants with improved traits that are of use to humans. Lettuce ( Lactuca sativa L.), a well-known and popular leafy vegetable, is consumed worldwide. Its haploid form would provide a good basis for producing a pure line of plants (doubled haploids) allowing new varieties to be regenerated. The main aim of this work was to develop an effective haploidisation method for this economically important species. In order to stimulate the development of haploid embryos of lettuce based on our previous experience, we conducted in vivo distant pollination with fresh pollen grains of Helianthus annuus L. or H. tuberosus L. Because the haploid proembryos obtained after pollination did not develop further (despite the presence of cellular endosperm), we implemented the technique of in vitro culture of an isolated embryo sacs (surrounded by endothelium) with parthenogenetic embryos on various, modified Murashige and Skoog media. During the in vitro culture, we observed the formation of callus tissue and, after subsequent cultures of calluses, 23 haploid L. sativa plants were regenerated. The haploid status of the regenerated plantlets was confirmed by estimation of the genome size by flow cytometry, chromosome counting in root tips, stomata cell size and by disturbances in pollen formation resulting from abnormal microsporogenesis. This paper contains the complete protocol for obtaining haploid plants of L. sativa. [ABSTRACT FROM AUTHOR]

Shiga toxin-producing Escherichia coli (STEC) strains produce extracellular cellulose and colanic acid, which may influence stress tolerance. This study investigates the role of these extracellular polymers on the tolerance of STEC to chlorine treatment after attachment to lettuce and spinach. Four STEC strains, two wild-type cellulose-producing and their cellulosedeficient derivatives, were used. One strain pair produced colanic acid in addition to cellulose. Spinach and lettuce with attached cells were treated with chlorinated water (50 and 150 ppm of free chlorine). The production of the extracellular polymers by the planktonic cells had small, but significant, effects on the survival of the attached pathogen when subjected to chlorine treatment. On the lettuce surface, the colanic acid-producing, cellulose-negative mutant (49d) was most susceptible to the treatment, declining significantly (P < 0.05) in population by 0.9 and 1.4 log units after treatment with 50 and 150 ppm of chlorine, respectively. Chlorine treatment reduced populations of cellulose-deficient cells on the intact spinach surface 1.2 log units more than the wild type when treated with 150 ppm of chlorine (P < 0.05). However, populations of cellulose-producing cells were reduced by 1.5 log units more than their mutant counterparts when the cells also produced colanic acid (P < 0.05). A greater proportion of cells attached to the spinach leaf edge were injured by chlorine treatment compared with attached to the leaf surface. These results indicate that extracellular polymers do not generally increase the ability of STEC to survive chlorine treatment and that any effects on survival are influenced by location of attachment, type of leafy green, and concentration of chlorine. [ABSTRACT FROM AUTHOR]

Since the salinity of irrigation water is a critical constraint to the production of certain vegetable crops, salinity has been considered as one of the most important factors of irrigation water. The objective of this study was to investigate the response of lettuce and Chinese cabbage to various salinity levels of irrigation water in greenhouse cultivation. A pot experiment was conducted with different salinities under a glasshouse condition in Korea. A completely randomized experimental design was used with three replications. The analysis results of crop growth and yield of lettuce and Chinese cabbage indicated that the factors that were more significantly affected by saline irrigation water were crop yields rather than crop components such as number of leaves, leaf length, and leaf width. In this study, the point of salt concentration during an increase in salinity levels of irrigation water (ECw) at which yield starts to decline was determined to be 0.9 and 1.5 dS/m for lettuce and Chinese cabbage, respectively. Furthermore, the present study demonstrated that the continuous irrigation of saline water under greenhouse conditions could lead to a significant increase in electric conductivity (ECe) level and Na+ concentration in soil, as well as Na+ concentration in leaves of crops. [ABSTRACT FROM AUTHOR]

The uptake of polybrominated diphenyl ethers (PBDEs) by carrot and lettuce was investigated. Degradation of PBDEs in soil in the absence of the plants was discarded. Different carrot ( Nantesa and Chantenay) and lettuce ( Batavia Golden Spring and Summer Queen) varieties were grown in fortified or contaminated compost-amended soil mixtures under greenhouse conditions. After plant harvesting, roots (core and peel) and leaves were analyzed separately for carrot, while for lettuce, leaves and hearts were analyzed together. The corresponding bioconcentration factors (BCFs) were calculated. In carrots, a concentration gradient of 2,2′,3,4,4′,5′-hexabromodiphenyl ether (BDE-138) became evident that decreased from the root peel via root core to the leaves. For decabromodiphenyl ether (BDE-209) at the low concentration level (7 and 20 ng g), the leaves incorporated the highest concentration of the target substance. For lettuce, a decrease in the BCF value (from 0.24 to 0.02) was observed the higher the octanol-water partition coefficient, except in the case of BDE-183 (BCF = 0.51) and BDE-209 (BCF values from 0.41 to 0.74). Significant influence of the soils and crop varieties on the uptake could not be supported. Metabolic debromination, hydroxylation or methylation of the target PBDEs in the soil-plant system was not observed. [ABSTRACT FROM AUTHOR]

The application of biosolids to agricultural fields is becoming increasingly common. The effect of biosolids on the behavior of metals in different plants has been reported to be variable and ambiguous. A greenhouse experiment was conducted on a soil spiked with four rates of copper (Cu) (0, 50, 100, and 150 mg kg−1) and zinc (Zn) (0, 150, 300, and 450 mg kg−1) in lettuce culture. When Cu and Zn were spiked to anaerobically-digested biosolids, their availability in lettuce increased. Root and shoot fresh weight decreased due to a decrease in photosynthetic rate. superoxide dismutase (SOD) and peroxidases (POD) activity increased after the application of Cu and Zn. The bioavailability of Zn in lettuce was greater than that of Cu because of a higher transfer factor in plants and due to a higher endogenous Zn concentration.These results will allow for better fertilization management when biosolids are applied to tomato culture. [ABSTRACT FROM AUTHOR]

Genome-wide motif searches identified 1134 genes in the lettuce reference genome of cv. Salinas that are potentially involved in pathogen recognition, of which 385 were predicted to encode nucleotide binding-leucine rich repeat receptor (NLR) proteins. Using a maximum-likelihood approach, we grouped the NLRs into 25 multigene families and 17 singletons. Forty-one percent of these NLR-encoding genes belong to three families, the largest being RGC16 with 62 genes in cv. Salinas. The majority of NLRencoding genes are located in five major resistance clusters (MRCs) on chromosomes 1, 2, 3, 4, and 8 and cosegregate with multiple disease resistance phenotypes. Most MRCs contain primarily members of a single NLR gene family but a few are more complex. MRC2 spans 73 Mb and contains 61 NLRs of six different gene families that cosegregate with nine disease resistance phenotypes. MRC3, which is 25 Mb, contains 22 RGC21 genes and colocates with Dm13. A library of 33 transgenic RNA interference tester stocks was generated for functional analysis of NLR-encoding genes that cosegregated with disease resistance phenotypes in each of the MRCs. Members of four NLR-encoding families, RGC1, RGC2, RGC21, and RGC12 were shown to be required for 16 disease resistance phenotypes in lettuce. The general composition of MRCs is conserved across different genotypes; however, the specific repertoire of NLRencoding genes varied particularly of the rapidly evolving Type I genes. These tester stocks are valuable resources for future analyses of additional resistance phenotypes. [ABSTRACT FROM AUTHOR]

The imazethapyr herbicide (formulation Verosil) was evaluated for phytotoxicity and genotoxicity using a battery of bioassays: (1) the growth inhibition of the green alga Pseudokirchneriella subcapitata, (2) the root growth and germination of the higher plant Lactuca sativa, (3) the genetic damage using the Salmonella/microsome test, and (4) the aneugenic and clastogenic effects on Allium cepa. The Verosil formulation was highly toxic to the non-target green alga (median effective concentration (EC50) = 1.05 ± 0.05 mg active ingredient (a.i.) L), and concentrations above 10 mg a.i. L inhibited root elongation in lettuce: relative growth index (RGI) between 0.28 ± 0.01 and 0.66 ± 0.10. No genotoxic effect was observed in S almonella typhimurium at 100 mg a.i. L, either with or without the microsomal fraction. However, significant differences in the frequency of chromosomal aberrations in anaphases and telophases (bridges, chromosome fragments, and vagrants) were observed in A. cepa at concentrations between 0.01 and 1 mg a.i. L with respect to the control. The frequencies of micronuclei showed significant differences with respect to the control at concentrations between 0.001 and 0.1 mg a.i. L. A very high mitotic index (MI = 93.8 ± 5.8) was observed associated with a high number of cells in the prophase stage at 100 mg a.i. L, indicating cytotoxicity. These results showed that imazethapyr is toxic to the non-target populations in both aquatic and terrestrial ecosystems. This herbicide might also exert clastogenic and aneugenic mitotic damage in higher plants. Therefore, the imazethapyr formulation may constitute an environmental risk to plants. [ABSTRACT FROM AUTHOR]

The garden symphylan, Scutigerella immaculata Newport, is a serious soil pest whose root feeding affects yield and survival of several high valued crops in the California's central coast. Because or- ganophosphate insecticides, widely used for S. immaculata control, are rigorously regulated and little is known about the efficacy of alternate insecticides, laboratory bioassays were conducted to determine insecticide efficacy through repellency and lethality. To determine indirect repellency (noncontact) of insecticides, choice assays were conducted where five S. immaculata were introduced into the arena to choose between insecticide-treated and untreated wells whereas, in direct repellency (contact) assays, three insecticide-treated 1-cm-diameter discs were pasted into the arena and the number of visits, time spent per visitation, and number of long-duration (>10 s) stays of five S. immaculata were quantified. To determine efficacy through direct mortality, number of S. immaculata died after 72 h were determined by introducing 10 S. immaculata to insecticide-treated soil assays. In indirect exposure bioassays, seven (clothianidin, oxamyl, zeta-cypermethrin, chlorpyrifos, ethoprop, azadirachtin, and a combination of beta-cyfluthrin and imidacloprid) out of 14 insecticides tested elicited repellency to S. immaculata. Of six insecticides tested in the direct exposure assays, only tolfenpyrad elicited contact repellency. In soil assays, after 72 h of introduction, bifenthrin, oxamyl, clothianidin, zeta-cypermethrin, and tolfenpyrad caused 100, 95, 80, 44, and 44% S. immaculata mortality, respectively, which was significantly greater than distilled water and four other insecticides. The implications of these results on S. immaculatamanagement in the California's central coast are discussed. [ABSTRACT FROM AUTHOR]

The goal of the present paper was to present microbial aspects in rhizosphere of four horticultural plants grown on various substrates based on use of perlite and its combinations with peat, as easily biodegradable material and to reveal the interrelations between natural antagonists and potential plant pathogenic species. A better control of pathogens developed in greenhouse, due to the ease of perlite substrate disinfection and its recycling was signaled as beneficial for yields and its quality, with cost benefits and important advantages for the health of consumers. Samples from rhizosphere of tomato, pepper, cucumber and lettuce plants cultivated in soilless systems on substrates from perlite or perlite-peat mixture were analyzed from a microbiological point of view comparatively with non-cultivated substrates for assessing the bacterial and fungal density and taxonomic composition of community. Peat-perlite substrate was more favorable to bacterial microflora than perlite alone, with highest values in the rhizosphere of pepper plants. Cucumber roots found good aeration conditions in the perlite from nutritive mattresses and its exudates stimulated the increase of microbial community number and diversity more than in pepper or tomato rhizosphere. Microbial counts and global physiological activity were determined in lettuce rhizosphere cultivated on perlite-peat mixt substrate and showed doubled values comparatively with samples from extra-radicular substrate in mattress. Dominant rhizosphere fungal species belonged to genera Penicillium, Trichoderma, Fusarium, Aspergillus and bacteria to genera Psedomonas, Bacillus, Arthrobacter, both accompanied sometimes by actinomycetes. The existence of antagonistic species (e.g. Trichoderma viride strains D2, D6 and D11 with proved in vitro effect on the pathogenic isolates of Fusarium and Penicillium) indicated a good relationship antagonist-pathogen in rhizosphere of horticultural plants. The possibilities of biological control of pathogens by natural antagonists, beneficial influence of plant root exudates and rhizosphere effect similar to soil conditions recommend perlite-based substrates as environmental friendly for using in greenhouse soilless systems for horticultural plants. [ABSTRACT FROM AUTHOR]

Low temperatures can slow down emergence, decrease weed competitiveness, and lead to uneven crop maturity in direct-seeded crops such as baby leaf lettuce (Lactuca sativa L.). In this study, seeds of 103 single-parent lineage, homozygous lettuce accessions (53 cos and 50 leaf type) from the USDA National Plant Germplasm System (NPGS) and six commercial standard lettuce cultivars (three cos and three leaf type) were evaluated in replications for percent germination after 7 and 10 days at 5 °C in a germination chamber. Cos and leaf types were selected for this study as they are most commonly used for baby leaf lettuce production. Differences were observed among entries in percent seeds germinated after both 7 and 10 days. Overall, an average of 68% of seeds germinated after 7 days and 94% germinated after 10 days. Although several NPGS accessions had higher percent germination than the commercial cultivars, the average percent germination was not statistically different between the two seed sources at 7 or 10 days. Percent germination also did not differ between entries of cos and leaf type after 7 or 10 days. Similarly, no difference in percent germination between entries of dark and white seed color was observed after 7 or 10 days. No relationship between 100 seed weight and percent germination was observed after 7 days (r² = 0.07) or 10 days (r² = 0.13). Thus, lettuce seed type, color, and 100 seed weight do not appear to be good predictors of germination under cold conditions in lettuce. The accessions with the highest percent germination after 7 days at 5 °C have the potential to be used for the development of new lettuce cultivars suitable for an extended, early season production in temperate climates when soil temperature is lower than optimal for lettuce germination. Further studies are needed to assess the ability of these accessions to germinate rapidly under cold field soil conditions. [ABSTRACT FROM AUTHOR]

Six types of light sources [0G, 20G, 40G, cool-white light-emitting diode (LED CW), cool-white fluorescent lamp (FLCW), and plant light fluorescent lamp (TLRA)| were used as the sole light sources to cultivate boston lettuce (Lactuca sativa L. cv. Ostinata). The photosynthetically active radiation (PAR) range was separated into five sections and the contributions of each spectral section on fresh weight (FW) were quantified. The results indicate that the conventional method of separating PAR into red, green, and blue at 100 nm apart was not accurate enough to clarify the contribution of different spectral sections to FW of boston lettuce. Green light (525-575 nm) at less than 30% of PAR is even more important than red (625-700 nm) and blue (400-475 nm) to plant growth. Yellow light (575-625 nm) has very little effect on plant growth. [ABSTRACT FROM AUTHOR]

Germination and thermoinhibition in lettuce (Lactuca sativa 'Jianyexianfeng No. 1') seeds were investigated by a proteomic comparison among dry seeds, germinated seeds at 15°C, at 15°C after imbibition at 25°C for 48 h, or at 25°C in KNO3 (all sampled individually at germination), and ungerminated seeds at 25°C, a thermoinhibitory temperature. Before two-dimensional gel electrophoresis analysis, storage proteins (greater than 50% of total extractable protein) were removed by polyethylene glycol precipitation, which significantly improved the detection of less abundant proteins on two-dimensional gels. A total of 108 protein spots were identified to change more than 2-fold (P, 0.05) in abundance in at least one germination treatment. Nineteen proteins increasing and one protein decreasing in abundance during germination had higher abundance in germinated 15°C, 15°C after imbibition at 25°C for 48 h, and 25°C in KNO3 seeds than in ungerminated 25°C seeds. Gene expression of 12 of those proteins correlated well with the protein accumulation. Methionine metabolism, ethylene production, lipid mobilization, cell elongation, and detoxification of aldehydes were revealed to be potentially related to lettuce seed germination and thermoinhibition. Accumulation of three proteins and expression of five genes participating in the mevalonate (MVA) pathway of isoprenoid biosynthesis correlated positively with seed germinability. Inhibition of this pathway by lovastatin delayed seed germination and increased the sensitivity of germination to abscisic acid. MVA pathway-derived products, cytokinins, partially reversed the lovastatin inhibition of germination and released seed thermoinhibition at 25°C. We conclude that the MVA pathway for isoprenoid biosynthesis is involved in lettuce seed germination and thermoinhibition. [ABSTRACT FROM AUTHOR]

The influence of soil properties on the phytoavailability of metal(loid)s in a soil–plant system was evaluated. The content of extractable metal(loid)s obtained by using different extraction methods was also compared. To perform this study, a test plant ( Lactuca sativa ) and rhizosphere soil were sampled at 5 different time points (2, 4, 6, 8 and 10 weeks of plant growth). Four extraction methods (Mehlich 3, DTPA, NH4 NO3 and CaCl2) were used. Significant positive correlations between the soil extractable content and lettuce shoot content were obtained for several metal(loid)s. The extraction with NH4 NO3 showed the higher number of strong positive correlations indicating the suitability of this method to estimate metal(loid)s phytoavailability. The soil CEC, OM, pH, texture and oxides content significantly influenced the distribution of metal(loid)s between the phytoavailable and non-phytoavailable fractions. A reliable prediction model for Cr, V, Ni, As, Pb, Co, Cd, and Sb phytoavailability was obtained considering the amount of metal(loid) extracted by the NH4 NO3 method and the main soil properties. This work shows that the analysis of rhizosphere soil by single extractions methods is a reliable approach to estimate metal(loid)s phytoavailability. [ABSTRACT FROM AUTHOR]

Human pharmaceuticals have been detected in the terrestrial environment at µg to mg kg−1 concentrations. Repeated application of sewage sludge (biosolids) and increasing reclaimed wastewater use for irrigation could lead to accumulation of these novel contaminants in soil systems. Despite this, potential phytotoxicological effects on higher plants have rarely been evaluated. These studies aimed to test effects upon germination, development, growth and physiology of two crop plants, namely radish ( Raphanus sativus Spakler 3) and lettuce ( Lactuca sativa All Year Around), after exposure to different, but structurally related non-steroidal anti-inflammatory drugs (NSAIDs) at environmentally relevant concentrations. A range of biological endpoints comprising biomass, length, water content, specific root and shoot length, root to shoot ratio, daily progress of stages of cell elongation and organ emergence (primary root, hypocotyl elongation, cotyledon emergence, cotyledon opening, and no change), as well as photosynthetic measurements were evaluated. Compounds from the fenamic acid class were found to affect R. sativus root endpoints (root length and water content), while ibuprofen affected early root development of L. sativa . In general, phytotoxicological effects on root endpoints demonstrated that impacts upon higher plants are not only compound specific, but also differ between plant species. It was found that the usage of a wide range of biological endpoints (all simple, cost-effective and ecologically relevant) were beneficial in detecting differences in plant responses to NSAID exposure. Due to paucity and discrepancy within the few previously available phytotoxicological studies with pharmaceuticals, it is now essential to allocate time and resources to consider development of suitable chronic toxicity tests, and some suggestions regarding this are presented. [ABSTRACT FROM AUTHOR]

Natural rubber (cis-1,4-polyisoprene) is an indispensable biopolymer used to manufacture diverse consumer products. Although a major source of natural rubber is the rubber tree (Hevea brasiliensis), lettuce (Lactuca sativa) is also known to synthesize natural rubber. Here, we report that an unusual cis-prenyltransferase-like 2 (CPTL2) that lacks the conserved motifs of conventional cis-prenyltransferase is required for natural rubber biosynthesis in lettuce. CPTL2, identified from the lettuce rubber particle proteome, displays homology to a human NogoB receptor and is predominantly expressed in latex. Multiple transgenic lettuces expressing CPTL2-RNAi constructs showed that a decrease of CPTL2 transcripts (3-15% CPTL2 expression relative to controls) coincided with the reduction of natural rubber as low as 5%. We also identified a conventional cis-prenyltransferase 3 (CPT3), exclusively expressed in latex. In subcellular localization studies using fluorescent proteins, cytosolic CPT3 was relocalized to endoplasmic reticulum by co-occurrence of CPTL2 in tobacco and yeast at the log phase. Furthermore, yeast two-hybrid data showed that CPTL2 and CPT3 interact. Yeast microsomes containing CPTL2/CPT3 showed enhanced synthesis of short cis-polyisoprenes, but natural rubber could not be synthesized in vitro. Intriguingly, a homologous pair CPTL1/CPT1, which displays ubiquitous expressions in lettuce, showed a potent dolichol biosynthetic activity in vitro. Taken together, our data suggest that CPTL2 is a scaffolding protein that tethers CPT3 on endoplasmic reticulum and is necessary for natural rubber biosynthesis in planta, but yeast-expressed CPTL2 and CPT3 alone could not synthesize high molecular weight natural rubber in vitro. [ABSTRACT FROM AUTHOR]

Measuring the nitrogen content of plants is useful for nitrogen fertilizer management. The aim of this work is to explore the use of spectroscopy for estimating lettuce leaf nitrogen content. Leaf reflectance spectra were measured using a spectroradiometer with a range of 350-2500 nm, and 160 fresh lettuce leaves given five different nitrogen treatments were used for spectra acquisition and total nitrogen determination. Interval partial least squares (iPLS), synergy interval partial least squares (siPLS), and siPLS combined with genetic algorithms (GA-siPLS) were used to select the optimal intervals or variables. Partial least squares (PLS) and extreme learning machine (ELM) methods were used to develop calibration models. One characteristic wavelength region (470-590 nm) using 120 variables was selected by iPLS; four characteristic wavelength regions (440-530, 530-620, 620-710 and 890-980 nm) using 362 variables were selected by siPLS, and 56 wavelength variables were selected by GA-siPLS. Six different regression models were established for nitrogen content by PLS and ELM based on optimal intervals or variables. The results imply that GA-siPLS is an efficient variable selection algorithm and ELM is a successful nonlinear regression tool. Furthermore, GA-siPLS combined with ELM is a feasible method for measuring nitrogen content in lettuce, as it performed better than other models. The optimal results achieved a root mean square error of prediction (RMSEP) = 0.2890% and correlation coefficient Rp = 0.9218. [ABSTRACT FROM AUTHOR]

Leafy vegetables are the source of many valuable components like vitamins, minerals and phenolic compounds as antioxidants. Chlorophyll derivatives have antioxidant and anticarcinogenic activity, or may even act as signalling molecules in organisms. However, during the storage of the leafy vegetables in the cold and darkness, numerous biochemical changes usually occurs, demonstrated as the breakdown of chlorophyll. Storage ability of plants depends to some extent on the conditions under which plants grew. Lamb's lettuce plants were grown in the greenhouse in different light regimes -- emitted with sodium (HPS-control) and LED lamps (100% red, 90% red + 10% blue, 70% red + 30% blue and 50% red + 50% blue light). The intensity of radiation at the height of the leaves of the plants was the same in every treatment. After harvesting, the plants were stored at the temperature of 5 °C and high humidity in plastic bags. The analyses of the material were done four times: after harvest and three times during storage at weekly intervals. Fresh weight lost, dry matter, phenolics and chlorophyll content were analysed. Additionally, the fluorescence of chlorophyll a was carried out. Changes in plant fresh weight and dry matter content during storage did not depend on the lighting used during cultivation. After 3 weeks of storage, higher value of indicator of the vitality of PSII (PIABS -- Performance Index) was noticed in leaves treated with higher red light intensity during cultivation (100%, 90% and 70% red). LED lamps, which emitted 100% and 90% red light, enhanced concentration of total phenolics in lamb's lettuce leaves. Light of HPS lamps decreased radical scavenging activity in leaves. Quality and usefulness of plants produced under LED lamps was just as good as those grown under HPS lamps. [ABSTRACT FROM AUTHOR]

According to the physical properties of leaf lettuce and its heat and mass transfer mechanism in vacuum pre-cooling process, the pre-cooling temperature, pressure and volume of spray-applied water were verified throughout the experiment. The key factors affecting the water removal and storage quality of leaf lettuce during vacuum pre-cooling were the water volume and pre-cooling pressure. The quantities of water tested were equal to 4.21-5.98% of the total sample mass and the mass loss of the sample was 1.99-2.87%. Under pre-cooling pressure of 600, 1000 and 1500 Pa, the mass loss was 2.76, 2.70 and 1.93%, respectively. The optimum quantity of the spray-applied water was 5% of the total sample mass. [ABSTRACT FROM AUTHOR]

Aims: Metal chemical forms and subcellular partitioning model (SPM) in organisms can provide valuable insights into metal toxicity. Methods: Two cultivars of lettuce ( Lactuca sativa L.) were grown in Cd and Cu contaminated soils and chemical forms and subcellular distribution of Cd and Cu within the lettuce shoots were determined. Results: Examination of the inhibition of superoxide dismutase (SOD) and catalase (CAT) activities, as well as the production of HO showed that Lactuca sativa L. var. longifolia is more sensitive to metal-stress than is Lactuca sativa L. var. crispa. In L. crispa, the majority of accumulated Cd was in the pectate- and protein-integrated forms (53.7-62.9 %), while in L. longifolia, a higher proportion of the Cd was in the water soluble forms (33.0-39.2 %) and in the organelles fraction - these forms being potentially associated with toxicity. The chemically-based chemical form approach agreed closely with independent biologically-based SPM, as demonstrated by their significant linear relationships. Conclusions: This study provides a first step towards the integration of chemical form approach and SPM into a common mechanistic framework, which is important for predicting the likelihood of toxic effects of metals in the environment of interest. [ABSTRACT FROM AUTHOR]

Postharvest processes for fresh produce commonly include washing in water containing antimicrobial chemicals, such as chlorine; however, if the antimicrobials are not present in sufficient levels, washing can promote the spread of contamination that might be present. To understand cross-contamination risk during washing, we tested a collection of Shiga toxigenic Escherichia coli (STEC), including 0157:H7 and other non-0157 strains, for certain traits during washing of fresh-cut lettuce, i.e., sensitivity to sublethal chlorine levels and ability to cross-contaminate (detach from and attach to) lettuce in the presence of sublethal chlorine levels. Nonpathogenic E. coli Nissle 1917 (EcN) and Pediococcus pentosaceus lactic acid bacterial species (LAB) were included as potential washing process validation surrogates. As measured by extension of the lag phase of growth in media containing 0.15 ppm of chlorine, chlorine sensitivity varied among the STECs. Cross-contamination was assessed by evaluating transfer of bacteria from inoculated to uninoculated leaves during washing. Without chlorine, similar transfer to wash water and uninoculated leaves was shown. In 1 ppm of chlorine, cross-contamination was not detected with most strains, except for the substantial transfer by a STEC 0111 strain and EcN in some replicates. Strain 0111 and EcN showed less inactivation in 0.25 ppm of chlorine water compared with 0157 (P < 0.05). LAB showed similar transfer and similar chlorine inactivation to 0157. Considering together the sublethal chlorine sensitivity and detachment/attachment traits, neither EcN nor LAB displayed optimal characteristics as washing process surrogates for the STEC strains, although further evaluation is needed. This work demonstrated a range of behaviors of STEC strains during lettuce washing and may be helpful in hazard characterization, identifying factors to consider for evaluating washing process efficacy, and identifying phenotypic traits to select surrogates to validate washing processes. [ABSTRACT FROM AUTHOR]

Angiostrongylus cantonensis, the causative agent of human rat lungworm disease, is the most common cause of eosinophilic meningitis worldwide and is endemic throughout Asia Pacific. It is acquired through the consumption of infected freshwater mollusks or contaminated produce. Human angiostrongyliasis is usually a self-limited disease presenting with headache and various neurologic sequelae varying from cranial nerve palsies to radiculitis and/or paresthesias. Fatal cases are rare, and manifest as fulminant meningomyeloencephalitis. The diagnosis is made through the use of clinical history, exam, and laboratory data including peripheral blood counts, cerebrospinal fluid (CSF) examinations, and serologic or molecular diagnostic techniques. Medical therapy is largely focused on symptomatic relief, and includes analgesics, lumbar puncture, and corticosteroids. In resource-limited settings, prevention is key, and the use of analgesics can provide symptomatic relief after infection. Efforts to increase disease awareness have been made in endemic areas, as evidenced by the recent Rat Lungworm Disease Scientific Workshop which was held in Honolulu in 2011. The proceedings of the workshop were published in a supplement to this journal (Hawaii J Med Public Health. Jun 2013;72(6):Supp 2). However, wilderness medicine and travel medicine specialists must also be aware of the disease, how it is contracted, its presentation, and treatment options should they encounter a patient who is in or has returned from an endemic area. This brief review highlights eosinophilic meningitis caused by A. cantonensis, including an example case, an overview of its clinical presentation, treatment options, and prevention. [ABSTRACT FROM AUTHOR]

The worldwide demand for pro-insulin increases continuously as new medical applications are developed. Lettuce (Lactuca sativa L.) has the potential to help supply this rising demand as a "green bio-reactor". A DNA construct containing the immunoglobulin G-binding protein A gene of Staphylococcus aureus (ProA) genetically fused to a nucleotide sequence encoding pro-insulin (Pins) was produced and transformed into lettuce. Integration of the ProA-Pins fusion gene into the chromosomes of transgenic lettuce, and copy numbers were verified by PCR amplification of genomic DNA and Southern blotting, respectively. Expression of the ProA-Pins fusion protein gene in transgenic lettuce was confirmed by reverse transcription-PCR analysis. Western immunobloting analysis of the proteins extracted from the leaves of transgenic lettuce plants revealed the presence of an immuno-reactive band with a molecular weight of approx. 20 kDa using rabbit polyclonal antibody against insulin. The plant-produced ProA-Pins fusion protein gave significant readings for indirect enzyme-linked immunosorbent assays (ELISA) using rabbit polyclonal antibody against insulin. The highest level of ProA-Pins expression in transgenic lettuce plants was 0.13% (w/w) of total soluble protein. This work demonstrated that plant-based systems expressing pro-insulin may provide an effective, low-cost approach to produce insulin for the treatment of Types I and II diabetes. [ABSTRACT FROM AUTHOR]

Agriculture in Japan is approaching a crisis for two reasons: a declining self-sufficiency rate and a decreasing number of agriculture workers. To solve these problems, plant factories have been attracting attention recently. Plant factories are facilities that aid the steady production of high-quality vegetables year round by artificially controlling the cultivation environment, allowing growers to drastically decrease production time. Despite the many advantages of plant factories, a main impediment is the reduction of initial and running costs. This paper utilizes leaf lettuce (Early impulse), which is a typical item cultivated in plant factories, as a target to improve productive efficiency of plant factories due to its relatively high price. Various pulsed electric fields (PEFs) were applied to roots of the lettuce to increase lettuce growth rate. The experimental results show PEF intensity from 0.2 to 1.0 kV/cm is positive for growth stimulation. Conversely, those over 1.0 kV/cm resulted in growth inhibition. Furthermore, roots of the samples which exhibited increased leaf weight grew more robustly than those of decreased leaf weight. In addition, analysis results showed that there was no significant difference when liquid fertilizer was applied prior to or after application of PEF. The results suggest that PEF does not affect the composition change of liquid fertilizer but directly influences the growth of leaf lettuce. [ABSTRACT FROM PUBLISHER]

Oil spill in the Central Patagonian zone was studied to evaluate if any relationship exists between the parameters used to characterize weathering spilled oil and soil toxicity for two plant species and to evaluate if the phytotoxicity to local species would be a good index for the soil contamination. Nuclear magnetic resonance (NMR) structural indexes and column chromatography compositional indexes were determined to characterize the oil spill in the soil samples. Bioassays were also carried out usingLactuca sativaL (reference) andAtriplex lampa(native species) as test organisms. Measurements of the total petroleum hydrocarbon (TPH) and the electrical conductivity (EC) of the soil were carried out to evaluate the effect on the bioassays. The principal components analysis of the parameters determined by NMR, compositional indexes, EC, TPH, and toxicology data shows that the first three principal components accounted for the 78% of the total variance (40%, 25%, and 13% for the first, second, and third PC, respectively). A good agreement was found between information obtained by compositional indexes and NMR structural indexes. Soil toxicity increases with the increase of EC and TPH. Other factors, such as, the presence of branched and aromatic hydrocarbons is also significant. The statistical evaluation showed that the Euclidean distances (3D) between the background and each one of the samples might be a better indicator of the soil contamination, compared with chemical criterion of TPH. [ABSTRACT FROM PUBLISHER]

Cross-contamination of fresh-cut leafy greens with residual Escherichia coli 0157:H7-contaminated product during commercial processing was likely a contributing factor in several recent multistate outbreaks. Consequently, radicchio was used as a visual marker to track the spread of the contaminated product to iceberg lettuce in a pilot-scale processing line that included a commercial shredder, step conveyor, flume tank, shaker table, and centrifugal dryer. Uninoculated iceberg lettuce (45 kg) was processed, followed by 9.1 kg of radicchio (dip inoculated to contain a four-strain, green fluorescent protein-labeled nontoxigenic E. coli O157:H7 cocktail at 106 CFU/g) and 907 kg (2,000 lb) of uninoculated iceberg lettuce. After collecting the lettuce and radicchio in about 40 bags (~22.7 kg per bag) along with water and equipment surface samples, all visible shreds of radicchio were retrieved from the bags of shredded product, the equipment, and the floor. E. coli O157:H7 populations were quantified in the lettuce, water, and equipment samples by direct plating with or without prior membrane filtration on Trypticase soy agar containing 0.6% yeast extract and 100 ppm of ampicillin. Based on triplicate experiments, the weight of radicchio in the shredded lettuce averaged 614.9 g (93.6%), 6.9 g (1.3%), 5.0 g (0.8%), and 2.8 g (0.5%) for bags 1 to 10, 11 to 20, 21 to 30, and 31 to 40, respectively, with mean E. coli 0157:H7 populations of 1.7, 1.2, 1.1, and 1.1 log CFU/g in radicchio-free lettuce. After processing, more radicchio remained on the conveyor (9.8 g; P < 0.05), compared with the shredder (8.3 g), flume tank (3.5 g), and shaker table (0.1 g), with similar E. coli O157:H7 populations (P > 0.05) recovered from all equipment surfaces after processing. These findings clearly demonstrate both the potential for the continuous spread of contaminated lettuce to multiple batches of product during processing and the need for improved equipment designs that minimize the buildup of residual product during processing. [ABSTRACT FROM AUTHOR]

The research aimed to evaluate melissa's biomass production and its essential oil output, both single cultivation and linked cultivation to yarrow and lettuce. The treatments were consisted in single cultivantion melissa, melissa linked to yarrow, melissa linked to lettuce, yarrow and lettuce in single cultivation. The experimental design used was a totally randomized design with five treatment and six repetitions. Was evaluated the content and the yield of essential oil of melissa, the fresh matter and the dry matter of the aerial part of all species. It was seen from the average valuations that the melissa linked cultivation to the lettuce obtained the greatest output, fresh matter and diy matter. The smaller values of all variables was observed in melissa in single cultivation. To the the Effective Land Use (ELU), the yarrow and lettuce linking cultivated to the melissa generated good species biomass output, because the calculated results to the plants were higher than 1,0. The species linking cultivation did not interfere significantly in melissa .V essential oil content. [ABSTRACT FROM AUTHOR]

Enterobacter asburiae L1 is a quorum sensing bacterium isolated from lettuce leaves. In this study, for the first time, the complete genome of E. asburiae L1 was sequenced using the single molecule real time sequencer (PacBio RSII) and the whole genome sequence was verified by using optical genome mapping (OpGen) technology. In our previous study, E. asburiae L1 has been reported to produce AHLs, suggesting the possibility of virulence factor regulation which is quorum sensing dependent. This evoked our interest to study the genome of this bacterium and here we present the complete genome of E. asburiae L1, which carries the virulence factor gene virK, the N-acyl homoserine lactone-based QS transcriptional regulator gene luxR and the N-acyl homoserine lactone synthase gene which we firstly named easI. The availability of the whole genome sequence of E. asburiae L1 will pave the way for the study of the QS-mediated gene expression in this bacterium. Hence, the importance and functions of these signaling molecules can be further studied in the hope of elucidating the mechanisms of QS-regulation in E. asburiae. To the best of our knowledge, this is the first documentation of both a complete genome sequence and the establishment of the molecular basis of QS properties of E. asburiae. [ABSTRACT FROM AUTHOR]

It is necessary and urgent the search by sources of organic fertilizer and decrease the consumption of water for irrigation. In the conte×t, the aim of this study was to evaluate the nutritional effects of the use of bovine biofertilizers incorporated into the soil and of the irrigation in the development of lettuce. The research was developed, using an e×perimental design in randomized blocks, factorial scheme 6×2, with si× levels of fertilization (4 doses of bovine biofertilizer and two witnesses: without fertilizer and mineral fertilizer) and two irrigation layers (80 and 100% of reference evapotranspiration) with four replications, in the field. The variables analyzed were: height, head diameter, chlorophyll, leaf number, fresh matter and dry matter of plant tops. It was performed by analysis of variance of F test, comparison of means by Tukey test (p <0.05) and polynomial regression. The results showed that the levels of biofertilizer were similar to the mineral control, pointing the possibility to replace them with the dose of 90m3ha-1 more recommendable, and the best water layer, of 80% of the evapotranspiration. [ABSTRACT FROM AUTHOR]

Two pathogenic races of Verticillium dahliae have been described on lettuce and tomato. Host resistance to race 1 is governed by plant immune receptors that recognize the race 1-specific fungal effector Ave1. Only partial resistance to race 2 exists in lettuce. Although polymerase chain reaction (PCR) assays are available to identify race 1, no complementary test exists to positively identify race 2, except for lengthy pathogenicity assays on host differentials. Using the genome sequences of two isolates of V. dahliae, one each from races 1 and 2, we identified potential markers and PCR primers to distinguish the two races. Several primer pairs based on polymorphisms between the races were designed and tested on reference isolates of known race. One primer pair, VdR2F-VdR2R, consistently yielded a 256-bp amplicon in all race 2 isolates exclusively. We screened DNA from 677 V. dahliae isolates, including 340 from spinach seedlots, with the above primer pair and a previously published race 1-specific primer pair. DNA from isolates that did not amplify with race 1-specific PCRs amplified with the race 2-specific primers. To validate this, two differential lines of lettuce were inoculated with 53 arbitrarily selected isolates from spinach seed and their pathogenicity and virulence were assessed in a greenhouse. The reactions of the differential cultivars strongly supported the PCR data. V. dahliae race structure was investigated in crops in coastal California and elsewhere using primers specific to the two races. All artichoke isolates from California were race 1, whereas nearly all tomato isolates were race 2. Isolates from lettuce, pepper, and strawberry from California as well as isolates from spinach seed from two of four countries comprised both races, whereas only race 2 was observed in cotton, mint, olive, and potato. This highlights the importance of identifying resistance against race 2 in different hosts. The technique developed in this study will benefit studies in ecology, population biology, disease surveillance, and epidemiology at local and global scales, and resistance breeding against race 2 in lettuce and other crops. [ABSTRACT FROM AUTHOR]

Lettuce (Lactuca sativa) is a nutritious leafy vegetable, rich in minerals and vitamins. It is considered as one of the most important salad crops, grown around the world, which is used particularly as the base for salad. Salad has short vegetation period, so several production cycles can be achieved during the year. It has sedative, diuretic and expectorant features and is beneficial for functioning of the cardiovascular and digestive systems. Among the other valuable compounds, lettuce contains vitamin C, one of the essential nutrients for humans. It is very important to store lettuce after harvest in the environment in which its nutritional value does not deteriorate. Therefore, the aim of this study was to assess the effect of different cold storage conditions on concentration of vitamin C in lettuce. Four cultivars of lettuce (Murai, Kitare, Carmesi and Levistro) were included in the experiment. Plants were grown under controlled conditions ofa greenhouse to technological maturity, in growing cubes. After harvest, lettuce heads were stored in the refrigerator in two ways: 1) together with growing cube or 2) without growing cube. Every three days after the beginning of the storage period, at three time points in total, concentration of vitamin C was determined. These results were also compared to concentration of vitamin C in lettuce which was not harvested and continued growth in a greenhouse, in growing cubes, during the entire period. Storage conditions effected concentration of vitamin C to varying extent in different cultivars. In cultivar Murai concentration of vitamin C declined the least over time, regardless of storage conditions (the lowest recorded value was 60% since the beginning of storage period). In the other three cultivars concentrations of vitamin C were very similar in cold storage. However, the differences between cultivars were observed in lettuce stored with growing cubes in a greenhouse where Kitare and Murai had 98-80% of vitamin C in comparison with respective controls. In Carmesi and Levistro concentration of vitamin C declined much more (in Levistro to about 25%, and this cultivar had the highest initial concentration of vitamin C). Generally, the results showed that there was a decrease in the concentration of vitamin C in lettuce over time, but less when lettuce was stored in the refrigerator without a growing cube. [ABSTRACT FROM AUTHOR]

In the past decade, leafy greens have been implicated in several outbreaks of foodborne illness, and research has focused on contamination during preharvest operations. Concerns have been raised that internalization of pathogens into the edible tissue occurs where postharvest chemical interventions would be ineffective. This study was initiated to measure the degree and fate of Escherichia coli O157:H7 internalized in the phyllosphere tissue of leafy greens when spray conditions, inoculum level, and type of leafy green were varied. Two spraying treatments were applied: (i) spraying individual spinach or lettuce leaves on plants once with a high dose (7 to 8 log CFU/ml) of E. coli O157:H7 and (ii) spraying spinach, lettuce, or parsley plants repeatedly (once per minute) with a low dose (2.7 to 4.2 log CFU/ml) of E. coli O157:H7 over a 10- to 20-min period. With the high-dose spray protocol, no significant differences in the prevalence of internalization occurred between Shiga toxin-negative E. coli O157:H7 isolates and virulent isolates (P > 0.05), implying that the Shiga toxin virulence factors did not influence internalization or the subsequent fate of those populations under these test conditions. Significantly greater internalization of E. coli O157:H7 occurred in spinach leaves compared with lettuce leaves when leaves were sprayed once with the high-dose inoculum (P < 0.05), whereas internalization was not observed in lettuce leaves but continued to be observed in spinach and parsley leaves following repeated spraying of the low-dose inoculum. Based on these results, it is surmised that a moisture film was generated when spraying was repeated and this film assisted in the mobilization of pathogen cells to plant apertures, such as stomata. E. coli O157:H7 cells that were internalized into spinach tissue using a low-dose repeat-spray protocol were temporary residents because they were not detected 2 days later, suggesting that plant-microbe interactions may be responsible. [ABSTRACT FROM AUTHOR]