This study aimed to investigate the impact of virus and viroid infections on tree growth and fruit quality attributes in apple, pear, peach, and grape. Trials were conducted in 2019 at the National Institute of Horticultural and Herbal Science in Korea, utilizing virus-infected, viroid-infected, combined virus/viroid-infected, and uninfected trees in an experimental fruit-tree orchard. Additionally, the experimental orchard served as an exhibition package for farmers and agricultural workers. Annual measurements of tree growth were compared between virus-free and virus/viroid-infected trees. Fruit quality attributes, including yield, weight, firmness, titratable acidity, and anthocyanin content, were assessed during 2021-2023. The results revealed significant differences between virus-free trees and those infected with virus, viroid, or both. Viral and viroid infections led to reduced tree height, trunk area, fruit yield, fruit weight, and anthocyanin content, while increasing fruit firmness and titratable acidity, respectively. These findings are expected to contribute to fruit tree virus and viroid disease control and fruit cultivation management. Furthermore, we anticipate that this research will enhance the understanding of agricultural stakeholders through scientific and comprehensive evidence on the damages caused by fruit tree viruses and viroid infections, thereby stimulating the adoption of virus-free stocks and promoting their widespread distribution.
In recent years, controlled environment agriculture (CEA) has gained popularity as a sustainable and efficient method of cultivation, offering solutions to challenges posed by traditional farming practices and meeting the growing demand for high-quality produce. However, advancements in CEA have raised concerns about food safety, requiring new approaches to minimize the risk of produce contamination. This research explores the effectiveness of a bacteriophage cocktail as a biocontrol agent against Salmonella contamination in lettuce grown in water-recirculating systems. Salmonella Newport and Salmonella Typhimurium (103 CFU/mL) were inoculated into aquaponic and hydroponic nutrient solutions into a water-recirculating system to mimic sporadic contamination, followed by treatment with a bacteriophage cocktail (S7, S10, and S13) at different multiplicities of infection (MOI 0.01 and MOI 1). The results demonstrated a significant reduction in Salmonella Newport and Salmonella Typhimurium populations at both MOI 0.01 and MOI 1 in aquaponic and hydroponic nutrient solutions, with levels reaching below the limit of detection (LOD) after 3 to 4 days of bacteriophage cocktail inoculation. From the plant parts, there was a significant reduction in the microbial population of Salmonella serovars in media plugs and roots from the hydroponic nutrient solution, reaching levels below the LOD in both phage cocktail treatments after a 2-day inoculation period. Contrarily, significant reductions were not observed in Salmonella serovar levels in plant roots and media plugs from the aquaponic nutrient solution treatment. These findings highlight the potential of utilizing bacteriophages to improve food safety in indoor-grown lettuce by controlling Salmonella populations while also indicating the necessity for further research to understand the microbial dynamics within each type of system.
In the southeast US, tomatoes (Solanum lycopersicum) and bell pepper (Capsicum annuum) are typically staked and trellised and grown using plastic mulch for weed control. The Produce Safety Rule that is part of the Food Safety Modernization Act requires that fruit from tomato and pepper be declared non-harvestable if they fall to the ground or contact the ground through drooping while attached to the plant before harvest. The objective of this study was to quantify percent transfer from plastic mulch inoculated with Escherichia coli with green fluorescent protein (GFP) to pepper and tomato fruit making ground contact in spring and fall growing seasons. E. coli GFP was spot inoculated on plastic mulch in the field using ten - 10 µL drops (100 uL total) at approximately 7 log CFU/mL and allowed to dry for at least 1 h before fruit contact. In the spring season, white and black colored plastic mulch were compared and in the fall season, reused (second crop) plastic mulch and new white plastic mulch were compared. Fruit contacted the ground by drooping (remained attached to the plant) with a contact time of 1 h or 24 h as well as contact through dropping fruit at heights of 30 cm, 60 cm, and 120 cm (n=9 per treatment). After inoculum was allowed to dry on the plastic mulch, the E. coli population was reduced an average of 2.8 and 4.8 log CFU/mL, in the spring and fall seasons, respectively. In both seasons all dropped peppers had significantly different percent transfer than dropped tomatoes, while drooping fruit were not significantly different between the two commodities. In the fall, dropped fruit on new plastic had significantly greater bacterial transfer than fruit which was dropped on reused plastic for both tomato and pepper. No significant differences were obtained between drooping duration treatments or between the different height of dropping in either season. There was relatively low transfer overall from both drooping and dropping of fruit on inoculated plastic mulch, regardless of crop or season. Further, in this inoculated study, results suggest that there was a significant reduction in E. coli populations in a field setting after a short period of exposure to the natural environment.
The shift towards sustainable food production has forced farmers to explore alternative practices, such as the use of Biological Soil Amendments of Animal Origin (BSAAOs). However, concerns due to food safety regulations restrict the use of BSAAOs on crops consumed raw. This study assessed the microbial safety of bell peppers, the impact of BSAAOs on soil properties, and on quality. The field experiment was established with 36 plots (88 ft2) planted with bell pepper seedlings on 12-inch centers for a total of 20 plants/plot. BSAAO treatments consisted of either raw CM, PL, or non-BSAAO (NB) application, with each treatment being either tilled or top dressed. E. coli/Total Coliforms were determined from soil samples collected during weeks 1, 3, 6, and 12 and from harvested bell peppers during weeks 13 and 14. Nalidixic acid resistant E. coli was inoculated on bell peppers for a 5-day die-off determination (40 inoculated on the upper portion and 40 on the side). Ammonium and nitrate content in soil was determined before and after the establishment of the experiment, while SOM content was determined from soil samples collected after the experiment. Higher levels of E. coli (1.1–2.6 log CFU/g) and total coliforms (4.1–4.7 log CFU/g) were reported in plots with BSAAO application as compared to NB plots (1.00–1.17 log CFU/g; 3.89–4.14 respectively), although levels decreased significantly after one week. E. coli levels on bell peppers previously inoculated declined by over 2 logs within four days, with a die-off rate of 0.57 and 0.51 log CFU/cm2/day for bell peppers inoculated on top and on the side, respectively. CM tilled plots had slightly higher E. coli levels (0.02 log CFU/ cm2). The quality of bell peppers was unaffected by BSAAOs. NB top dressed and CM tilled plots had higher soil organic matter (SOM) content (2.18 and 2.08%, respectively) while both CM and PL increased soil nitrate and ammonium content significantly by the end of the experiment. CM and PL can enrich soil with inorganic nitrogen without compromising produce quality. However, the use of untreated BSAAOs poses a risk of cross-contamination, which highlights the importance of minimizing potential contamination events. Overall, this study highlighted the potential of CM and PL as BSAAOs to enhance soil fertility while maintaining food safety. It emphasized the need for appropriate management practices to mitigate risks associated with microbial contamination, ensuring the safety and sustainability of food production systems.
The proliferation of foodborne pathogens and the formation of biofilms poses a major threat to the food industry, particularly in fresh produce. Raw and minimally processed fruits and vegetables are often sold to consumers in ready-to-use or ready-to-eat forms and are at the forefront of this risk. These products lack preservatives and rarely undergo any heat processing prior to consumption, making them more susceptible to contamination. To address this, we synthesized an oil/water emulsion encapsulating eugenol, using exopolysaccharide extracted from Lactobacillus as a natural emulsifier, and investigated its effectiveness against pathogenic cell populations within biofilm matrices. Different strains of Listeria monocytogenes, Salmonella, and E. coli were studied; results reveal substantial variations in biofilm-forming abilities among different E. coli, Salmonella, and L. monocytogenes strains. Specifically, L. monocytogenes V7 and Scott A strains displayed resistance to the emulsion, resulting in a minimal reduction of 2.8 log CFU/cm2 on the stainless-steel surface within the biofilm. Conversely, other strains exhibited reductions ranging from 3 to 4.5 log CFU/cm2. Most strains’ biofilm inhibition was 85% on plastic surfaces, whereas L. monocytogenes V7, Scott A, and Salmonella enterica ATCC 35664 showed less inhibition. The emulsion was applied to fresh produce (tomatoes, blueberries, and lettuce), where the reduction in E. coli and Salmonella biofilms, along with planktonic cells, varied from 0.53 to 5.1 log CFU/cm2, indicating that the emulsion significantly inhibited the growth of the tested pathogens. In conclusion, the results indicate that biofilm inhibition depends on the microbial species due to the observed individual variation in strains. However, combining eugenol and exopolysaccharide as emulsions is a promising natural alternative and sustainable technology for removing pathogenic biofilms. This research has the potential to advance food safety and hygiene standards, with practical applications in preserving fresh produce and disinfecting surfaces. This work was supported by USDA-NIFA- SCRI- 2017-51181-26834 through the National Center of Excellence for Melon at the Vegetable and Fruit Improvement Center of Texas A
Light quality is known to affect the growth and phytochemical content of numerous crops, including lettuce (Lactuca sativa L.). High tunnel production of lettuce provides many benefits to growers including increased yield due to higher soil temperatures and protection from abiotic stressors, such as strong wind and heavy rains. However, the use of UV-blocking polyethylene films can also result in lower antioxidant capacity and phenolic content, leading to a decrease in nutritional quality compared to lettuce grown in the open-field. Movable tunnels provide the ability to expose the crop to full-spectrum light once the crop has grown to full size. Our objective was to identify management strategies to optimize yield, phytochemical production, color, safety, and consumer acceptability of red-leaf cultivar (‘New Red Fire’). Lettuce was planted in a movable high tunnel April 2022 and exposed to 0, 2, 7, or 14 days of full sun prior to harvest. Total marketable yield, leaf color (L*a*b* color space), total phenolic content (TPC) and anthocyanin content were measured at harvest. Lettuce consumers (N=100) were asked to rate overall liking and various sensory attributes using continuous intensity scales, CATA, and open-ended comments. Total marketable yield and TPC were not affected. Leaf redness (a*) and anthocyanin content were significantly higher after 14, 7, and 2 days of full-sun exposure compared to 0 days. Significant differences were found in consumer liking for overall liking, color intensity, and ruffleness. The crop that was exposed to 14 days of full-spectrum light had a higher liking and more red color intensity. Using a movable tunnel system provides lettuce growers the ability to affect the color, phytochemical content, and consumer liking of their crop to varying degrees. This level of flexibility provides local, small-scale growers a crucial advantage in marketing their produce.
