romaine lettuce
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Sensors ◽  
2022 ◽  
Vol 22 (2) ◽  
pp. 475
Author(s):  
Devendra Bhandari ◽  
Fur-Chi Chen ◽  
Roger C. Bridgman

Salmonella is one of the major foodborne pathogens responsible for many cases of illnesses, hospitalizations and deaths worldwide. Although different methods are available to timely detect Salmonella in foods, surface plasmon resonance (SPR) has the benefit of real-time detection with a high sensitivity and specificity. The purpose of this study was to develop an SPR method in conjunction with magnetic nanoparticles (MNPs) for the rapid detection of Salmonella Typhimurium. The assay utilizes a pair of well-characterized, flagellin-specific monoclonal antibodies; one is immobilized on the sensor surface and the other is coupled to the MNPs. Samples of romaine lettuce contaminated with Salmonella Typhimurium were washed with deionized water, and bacterial cells were captured on a filter membrane by vacuum filtration. SPR assays were compared in three different formats—direct assay, sequential two-step sandwich assay, and preincubation one-step sandwich assay. The interaction of flagellin and MNPs with the antibody-immobilized sensor surface were analyzed. SPR signals from a sequential two-step sandwich assay and preincubation one-step sandwich assay were 7.5 times and 14.0 times higher than the direct assay. The detection limits of the assay were 4.7 log cfu/mL in the buffer and 5.2 log cfu/g in romaine lettuce samples.


2022 ◽  
Vol 147 (1) ◽  
pp. 45-52
Author(s):  
Camila M.L. Alves ◽  
Hsueh-Yuan Chang ◽  
Cindy B.S. Tong ◽  
Charlie L. Rohwer ◽  
Loren Avalos ◽  
...  

Shading has been used to produce high-quality lettuce (Lactuca sativa) in locations where production conditions are not optimal for this cool-season crop. To learn what additional benefits shading provides if heat-tolerant cultivars are used and to understand the effects of shading on growth, sensory quality, chemical content, and transcriptome profile on heat-tolerant lettuce, we grew two romaine lettuce cultivars with and without shading using 50% black shadecloth in 2018 and 2019. Shading reduced plant leaf temperatures, lettuce head fresh weights, glucose and total sugars content, and sweetness, but not bitterness, whereas it increased lettuce chlorophyll b content compared with unshaded controls. Transcriptome analyses identified genes predominantly involved in chlorophyll biosynthesis, photosynthesis, and carbohydrate metabolism as upregulated in unshaded controls compared with shaded treatments. For the tested cultivars, which were bred to withstand high growing temperatures, it may be preferable to grow them under unshaded conditions to avoid increased infrastructure costs and obtain lettuce deemed sweeter than if shaded.


2022 ◽  
Vol 32 (1) ◽  
pp. 39-46
Author(s):  
Jenny C. Moore ◽  
Brian Leib ◽  
Zachariah R. Hansen ◽  
Annette L. Wszelaki

Growers seeking alternatives to traditional polyethylene plastic mulch may use biodegradable plastic mulches (BDMs). However, plasticulture systems typically also use plastic drip tape underneath the mulch, which must be removed from the field and disposed of at the end of the season, making tilling the BDM into the soil more difficult and expensive. A potential solution to this dilemma may be to use other irrigation methods, such as overhead sprinklers, that could be more easily removed from the field and reused from year to year. At Knoxville, TN, in 2019 and 2020, we grew three cultivars of romaine lettuce (Lactuca sativa) on BDM with two irrigation systems (overhead sprinklers above the mulch and drip irrigation tape under the mulch) to compare water use, disease, and yield in these two irrigation systems. Water use was higher in overhead vs. drip irrigation in both years; however, the difference in water use was much smaller in 2019 due to higher rainfall amounts during the time period the lettuce was growing in the field (March to May). Disease incidence and severity were very low both years for both irrigation systems. There were no differences in marketable yield (number of heads) between irrigation treatment in 2019. In 2020, marketable yield by number was greater in the drip vs. overhead irrigation treatment. Unmarketable yield in 2019 was due to heads that were too small; in 2020, unmarketability was predominantly due to tipburn in overhead irrigated ‘Jericho’. Overall, marketable lettuce yield did not differ between irrigation treatments in 2019 and was similar for ‘Parris Island Cos’ in 2020. Although quantitative weed counts were not made, observations of weed pressure between rows showed that weed pressure was higher in overhead irrigated compared with drip irrigated subplots. This highlights the need to have a between-row weed management program in place. The results of this study suggest that with attention to cultivar and weed management, overhead irrigation could be a viable alternative to drip irrigation for lettuce production on BDM, especially for early spring lettuce when rainfall is historically more plentiful.


2021 ◽  
pp. 1-22
Author(s):  
Michelle A. Waltenburg ◽  
Colin Schwensohn ◽  
Asma Madad ◽  
Sharon L. Seelman ◽  
Vi Peralta ◽  
...  

2021 ◽  
Author(s):  
Joshua Schafer ◽  
Troy Puga ◽  
Pearce Harris ◽  
Nora Strasser ◽  
Gary Branum ◽  
...  

The concept of bioremediation is quickly becoming the norm in the resolution of environmental issues. The steady increase in carbon dioxide levels, as documented by NASA, inspired scientists to engineer plants to absorb excess carbon dioxide from the atmosphere. Here, we have explored the consequences of the uptake of excess carbon dioxide by select plants. Carbon dioxide dissolves in water to produce carbonic acid, which dissociates to yield H+ ions. We hypothesized that increased carbon dioxide absorption results in decrease in pH of plant sap. Three plants (Byophyllum pinnatum, Romaine Lettuce and Nevada Lettuce), exposed to increased carbon dioxide concentrations (15%), demonstrated a consistent increase in pH towards alkalinity compared to control plants. Based on the outcome being opposite of what we have hypothesized, our results suggest Byophyllum pinnatum, Romaine lettuce and Nevada lettuce, all have a unique homeostatic system to prevent over-absorption of carbon dioxide in a carbon dioxide-rich environment.


Agriculture ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1133
Author(s):  
Bożena Matysiak ◽  
Stanisław Kaniszewski ◽  
Jacek Dyśko ◽  
Waldemar Kowalczyk ◽  
Artur Kowalski ◽  
...  

The study examined the influence of light quality on the growth and nutritional status of romaine lettuce grown in deep water culture with a floating raft system using two different nutrient solutions. Four spectra of LED light were used with different ratios of R, G, and B lights (80:10:10, 70:10:20, 60:10:30, and 70:18:12). Two nutrient solutions with a low (A) and moderately high (B) nutrient content were used. Regardless of the nutrient solution, the RGB 70:18:12 light promoted the production of leaf biomass as well as inhibited the accumulation of K and Mg in the leaves. Moreover, those plants were characterized by a low Nitrogen Balance Index (NBI) and a high flavonol index. In the last week of cultivation, there was a strong decrease in K, P, and nitrates in the nutrient solution, and an increase in Ca. In the final stage of growth, symptoms of withering of the tips of young leaves (tipburn) were observed on the plants. The most damage was observed on the plants growing under 70:10:20, 70:18:12, and with the higher concentration of minerals in the solution (B).


Horticulturae ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 461
Author(s):  
In-Lee Choi ◽  
Joo-Hwan Lee ◽  
Dam-Hee Choi ◽  
Li-Xia Wang ◽  
Ho-Min Kang

This study aimed to examine the effect of modified atmosphere (MA) storage on the quality and storability of romaine lettuce. Whole and fresh-cut romaine lettuce were packaged with 1300; 10,000; 50,000; 100,000 cc m−2·day−1·atm−1 O2 transmission rate (OTR) films and stored at 2 or 8 °C for 15 days. The respiration and ethylene production rates before pre-cooling were higher in fresh-cut lettuce than in whole romaine lettuce. The reduction in fresh weight for whole and fresh-cut romaine lettuce during storage was less than 0.5%. The CO2 concentration was less than 2%, except for the 1300 cc treatment (at 8 °C for whole and fresh-cut lettuce) and 10,000 cc (in fresh-cut lettuce). At the end date of storage, the overall quality of the whole lettuce was good, the off-odor was lower in the 10,000 cc treatment, and the 50,000 cc treatment at 8 °C led to good overall quality in the fresh-cut lettuce. The chlorophyll content of the whole lettuce was maintained at a higher level in the treatment of 10,000 cc at 8 °C, while it was higher in the 50,000 cc treatments at 2 and 8 °C in the fresh-cut lettuce. Correlation and PCA confirmed that the main factors affecting the storability and quality of romaine lettuce were fresh weight loss rate, off-odor, and the concentration of CO2. In addition, the storage characteristics of whole and fresh-cut lettuce were opposite to 0 in PC1 and PC2, indicating that the storage characteristics were different depending on the processing type.


2021 ◽  
Vol 181 ◽  
pp. 111653
Author(s):  
Hui Peng ◽  
Yaguang Luo ◽  
Zi Teng ◽  
Bin Zhou ◽  
Ellen R. Bornhorst ◽  
...  

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Anirudha R. Dixit ◽  
Christina L. M. Khodadad ◽  
Mary E. Hummerick ◽  
Cory J. Spern ◽  
LaShelle E. Spencer ◽  
...  

Abstract Background Seed sanitization via chemical processes removes/reduces microbes from the external surfaces of the seed and thereby could have an impact on the plants’ health or productivity. To determine the impact of seed sanitization on the plants’ microbiome and pathogen persistence, sanitized and unsanitized seeds from two leafy green crops, red Romaine lettuce (Lactuca sativa cv. ‘Outredgeous’) and mizuna mustard (Brassica rapa var. japonica) were exposed to Escherichia coli and grown in controlled environment growth chambers simulating environmental conditions aboard the International Space Station. Plants were harvested at four intervals from 7 days post-germination to maturity. The bacterial communities of leaf and root were investigated using the 16S rRNA sequencing while quantitative polymerase chain reaction (qPCR) and heterotrophic plate counts were used to reveal the persistence of E. coli. Result E. coli was detectable for longer periods of time in plants from sanitized versus unsanitized seeds and was identified in root tissue more frequently than in leaf tissue. 16S rRNA sequencing showed dynamic changes in the abundance of members of the phylum Proteobacteria, Firmicutes, and Bacteroidetes in leaf and root samples of both leafy crops. We observed minimal changes in the microbial diversity of lettuce or mizuna leaf tissue with time or between sanitized and unsanitized seeds. Beta-diversity showed that time had more of an influence on all samples versus the E. coli treatment. Conclusion Our results indicated that the seed surface sanitization, a current requirement for sending seeds to space, could influence the microbiome. Insight into the changes in the crop microbiomes could lead to healthier plants and safer food supplementation.


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