Search

The involvement of stress ethylene in early chilling injury (CI) symptom development of mature-green (MG) banana fruit was examined using the ethylene action inhibitor, 1-methyclopropene (1-MCP). MG banana fruit pretreated with 0 or 50 μg L−1 1-MCP were stored at two chilling temperatures, 5 °C or 10 °C, for 0, 1, 12, or 72 h (different CI stresses), then transferred to 20 °C (rewarming) for 2 d. Irreversible CI symptoms that developed during 72 h storage at 5 or 10 °C included vascular browning and epidermal color parameters (L*, chroma, and hue angle). Some CI symptoms drastically intensified during exposure to 5 or 10 °C for 72 h, even being exacerbated after rewarming. Fruit in the other treatments suffered milder CI, and the recovery response progressed from slight and reversible to severe and irreversible with longer durations of exposure to lower temperatures. The effect of 1-MCP pretreatment was to attenuate the effect of chilling in terms of the CI symptom development (i.e., the browning of sub-epidermal tissues and the increasing of electrolyte efflux) and to promote recovery after rewarming, especially for the fruit stored at 5 °C, indicating the potential involvement of ethylene in membrane structural alterations under CI stress. [ABSTRACT FROM AUTHOR]

The application of seaweed extract and microbial biostimulants has been suggested as a promising approach to overcome yield-limiting factors in organic farming. Yet, information regarding their impact on organic strawberry production is limited. This 2-year field study evaluated the effect of seaweed extract and microbial biostimulants and their synergistic effects on strawberry plant growth, nutrient uptake, fruit yield, and quality under organic production. The biostimulant effects were compared on two strawberry cultivars: Sweet SensationVR Florida127 and Florida Brilliance. Over two seasons, the combination of seaweed extract plus microbial biostimulants applied biweekly consistently resulted in a significant increase of whole-season marketable and total strawberry fruit yields by 23% and 20% on average, respectively, compared with the no-biostimulant control. Application of either biostimulant alone did not consistently show positive effects on strawberry productivity. Modified strawberry root system architecture, enhanced N uptake, increased number of crowns, and higher soil respiration were observed in the biostimulant combination treatment in contrast to the no-biostimulant control. The biostimulant impact was not influenced by strawberry cultivar, but genotypic difference in yield performance under organic production was observed. 'Florida Brilliance' produced significantly higher total fruit number and yield than 'Florida127' by 26% and 12%, respectively, in the first season, and by 34% and 11%, respectively, in the second season. Marketable fruit number (by 18%) and yield (by 9%) of 'Florida Brilliance' were also higher in the first season, along with greater marketable fruit number (by 31%) in the second season. In addition, 'Florida Brilliance' showed significantly higher values of SPAD index, photosynthetic rate (early harvest), and fruit mineral contents based on dry weight (late harvest) than 'Florida127' in both seasons. Although the biostimulant treatments exhibited little influence on the fruit quality attributes including soluble solids content (SSC), titratable acidity (TA), SSC/TA, and total anthocyanin content, varietal differences were observed with significantly higher levels of SSC and lower contents of total anthocyanins in 'Florida 127' vs. 'Florida Brilliance' during each season. The benefits of combined application of seaweed extract and microbial biostimulants demonstrated in this study suggest the need to further elucidate their synergistic functions in promoting nutrient uptake and fruit yield in organic strawberry production systems under different soil and environmental conditions. [ABSTRACT FROM AUTHOR]

The use of high tunnels, which allows growers to extend their season and improve yields, is increasing in the Southeastern U.S., yet growers face challenges related to weed and disease management, particularly in organic systems. On-station experiments were conducted during fall 2021 and spring 2022 in a split-plot design to assess the efficacy of anaerobic soil disinfestation (ASD) in high tunnels for the organic production of direct-seeded baby leaf lettuce. Soil treatments (ASD, Compost, and Control) and lettuce types (romaine and oakleaf cultivars) were included in whole plots and subplots, respectively. The ASD-treated soils received molasses and granular organic fertilizer as carbon and nitrogen sources. The Compost treatment involved the application of yard waste-based compost and the same organic fertilizer, while the Control soils received organic fertilizer only. The ASD treatment period lasted 8 days rather than the typical 21-day period evaluated in Florida. Crop yield, biometrics (leafy dry matter content, specific leaf area, specific leaf weight), and lettuce quality attributes (leaf color, soluble solids content, total titratable acidity, ferric reducing antioxidant power, ascorbic acid content, total phenolics) were assessed following harvest. In both trials, numerical differences in lettuce fresh weight yield between soil treatments were evident, though not statistically significant. Differences in leaf quality attributes were driven by lettuce cultivar rather than soil treatments. Bottom rot incidence caused by Rhizoctonia solani was reduced by 93% and 87% in the ASD-treated plots compared with the Compost- and Control-treated soils during the spring 2022 trial. The ASD-treated soils had a reduced population density of broadleaf weeds in both baby leaf lettuce production trials. The current study presents novel evidence of the potential of integrating ASD into HT organic production systems without reducing the yield and quality attributes of direct-seeded baby leafy greens compared with common grower practices. [ABSTRACT FROM AUTHOR]

Despite the growing interest in high tunnel organic vegetable production, limited information is available regarding optimizing nutrient management for organic leafy greens. This 3-year study examined the impacts of cowpea cover crop as well as different organic fertilizers and composts on yield, leaf mineral nutrient content, and phytochemical properties of organic leafy greens produced in high tunnels under Florida sandy soil conditions. The experiment was arranged in a split-split-plot design with three replications. The whole plots consisted of a cowpea (Vigna unguiculata 'Iron & Clay') cover crop and a weedy fallow control, with fertilization treatments in the subplots, including preplant application of granular fertilizer vs. weekly injection of liquid fish fertilizer at the same seasonal rates of nitrogen (112 kg/ha), phosphorus (9.8 kg/ha), and potassium (74.4 kg/ha). The sub-subplots included yard waste-based compost (22.4 Mt/ha), cow manure-based compost (22.4 Mt/ha), vermicompost (5.6 Mt/ha), and no compost control. Cowpea was broadcasted (112 kg/ha) in early July or mid-August and terminated 51 to 53 days after seeding. Pac choi (Brassica rapa var. chinensis 'Mei Qing Choi') was transplanted inmid-Sep. ormid-Oct. and harvested after 33 to 36 days. Baby spinach (Spinacia oleracea 'Corvair') or baby leaf lettuce (Lactuca sativa 'Outredgeous') was direct seeded subsequently as a catch crop. Each experimental unit remained in the same location across the 3 years of the study. Cover cropping had little influence on yields, leafmineral nutrients, ascorbic acid content, total phenolics, and total antioxidant capacity of pac choi and baby spinach/lettuce. Compared with preplant application of the granular organic fertilizer, weekly liquid organic fertigation improved pac choimarketable yield and dryweight by 16.8%and 5.4%on average, respectively, and enhanced leaf nitrogen and phosphorus contents on a dry weight basis. Relative to the no compost control, yard waste compost consistently improved marketable yields of pac choi by 11.6%on average and led to higher yields of the baby spinach/lettuce catch crop in years 1 and 3, suggesting that compost applications may enhance seasonal nutrient availability to better meet crop demand. However, compost application exhibited inconsistent effects on crop mineral nutrient and phytochemical contents across the years, which could be attributed to the different nutrient compositions of the composts applied in each season, as well as the legacy effects from the previous season. Furthermore, the compost benefits may be influenced by the fertilization programas indicated by their interaction effects observed in this study. [ABSTRACT FROM AUTHOR]

Sunn hemp (Crotalaria juncea L.), a warm season leguminous cover crop, is commonly used in rotation with organic strawberry production in Florida's subtropical environment. This study was conducted to explore the impacts of sunn hemp on growth and yield performance of the subsequent organic strawberry crop in sandy soils, taking into consideration the nutrient contribution from soil incorporation of sunn hemp biomass. Sunn hemp was seeded during the summer off-season and terminated before flowering, three weeks prior to the fall planting of two strawberry cultivars ('Strawberry Festival' and 'Camino Real'). With sunn hemp residues incorporated into the soil, two application rates of nitrogen (N) through pre-plant organic fertilization for the strawberry season were used, including N at a rate of 84 kg/ha, without consideration of the N credit from sunn hemp, and N at a rate of 19.8 kg/ha, with consideration of the estimated N credit from sunn hemp. A summer fallow without cover crop and with a pre-plant organic fertilizer application at the N rate of 84 kg/ha was included as the control. Overall, the sunn hemp incorporation at three weeks after termination did not benefit the strawberry plant growth or fruit yield in this study, with rather low levels of soilborne pathogen and nematode infestations. Both sunn hemp treatments exhibited a significantly lower level of total soil N compared to the summer fallow plots at the end of the strawberry season. The reduction in the pre-plant N fertilization resulted in lower above-ground plant dry weight and accumulation of N, phosphorus (P), and potassium (K) at the end of the strawberry season, along with fewer leaves and smaller crowns of the strawberry plants during the early season. Both sunn hemp treatments decreased early fruit yields, while the sunn hemp treatment with the reduced N fertilization also led to a significant reduction in the total fruit number and weight, although no significant differences in the whole-season marketable fruit yield were observed among the nutrient management treatments. Overall, 'Strawberry Festival' yielded higher than 'Camino Real', but the effects of nutrient management did not vary with the strawberry cultivars. Further studies are needed to enhance organic strawberry nutrient management involving rotational cover crops. [ABSTRACT FROM AUTHOR]

Previous studies of tomato rootstock effects on fruit quality have yielded mixed results, and few attempts have been made to systematically examine the association between rootstock characteristics and tomato fruit quality. In this study, grape tomato (‘BHN 1022’) and beefsteak tomato (‘Skyway’) were grafted onto four rootstocks [‘Estamino’ (vigorous and “generative”), ‘DR0141TX’ (vigorous and “vegetative”), ‘RST-04-106-T’ (uncharacterized), and ‘SHIELD RZ F1 (61–802)’ (mid-vigor, uncharacterized)] and compared to non-grafted scion controls for two growing seasons (Spring and Fall in Florida) in organically managed high tunnels. In both seasons and for both scions, the two vigorous rootstocks, regardless of their designation as “vegetative” (‘DR0141TX’) or “generative” (‘Estamino’), exhibited negative impacts on dry matter content, soluble solids content (SSC), SSC/titratable acidity (TA), lycopene, and ascorbic acid contents. Similar effects on fruit dry matter content and SSC were also observed with the ‘RST-04-106-T’ rootstock, although little to no change was seen with grafting onto ‘SHIELD RZ F1 (61– 802)’. Further studies are needed to elucidate the impact of rootstock vigor on tomato volatile profiles and consumer sensory acceptability in order to better determine whether any of the documented effects are of practical importance. On the other hand, the evident effects of scion cultivar and planting season on fruit quality were observed in most of the measurements. The scion by rootstock interaction affected fruit length, firmness, pH, and total phenolic content, while the planting season by rootstock interaction impacted fruit firmness, pH, total antioxidant capacity, and ascorbic acid and lycopene contents. The multivariate separation pattern of planting season, scion, and rootstock treatments as revealed by the canonical discriminant analysis further indicated that the influence of scion cultivar and planting season on tomato fruit quality could be much more pronounced than the rootstock effects. The fruit color (C∗ and H◦), length and width, SSC, pH, total antioxidant capacity, ascorbic acid, and lycopene contents were the main attributes distinguishing different scion-planting season groups. [ABSTRACT FROM AUTHOR]

Storage at the putative chilling threshold temperature (CTT) to avoid chilling injury still limits postharvest handling of tropical fruit like banana in that ripening may occur at the CTT. To determine whether chilling injury (CI) symptoms would develop in mature green (MG) banana fruit if the CTT exposure was extended by inhibiting ethylene action and thus ripening, 1-methylcyclopropene (1-MCP) was applied. Individual 'fingers' from multiple 'clusters' of MG bananas were either immersed in water or 50 µg L-1 1-MCP (a.i.) solution and each treatment was divided into three subgroups for storage at 5.0°C (severe CI), 13.0°C (mild CI), or 14.0°C (CTT) ± 0.1°C. 1-MCP delayed ripening in terms of color change for 10 days for fruit stored at the CTT. Ethylene production by fruit at 5.0°C remained around 0.04 ng kg-1 s-1 with no obvious increase during 31-day storage. Ethylene production at 14.0°C (-1-MCP/+1-MCP) increased on Day 33 while increasing on Day 38 for 13.0°C fruit without 1-MCP and on Day 39 for fruit with 1-MCP. Peak climacteric ethylene occurred on Days 44 and 39 for 13.0 and 14.0°C fruit without 1-MCP, respectively, and on Days 59 and 51 for 13.0°C and 14.0°C 1-MCP-treated fruit, respectively. As hypothesized, longer exposure of MG banana fruit to the CTT of 14.0°C without onset of ripening as was allowed by prior 1-MCP treatment allowed CI to develop at that normally non-chilling temperature. Vascular browning was the first visual and most sensitive CI symptom in the experiment and was observed on Day 4 at 5.0°C, Day 10 at 13.0°C, Day 19 at 14.0°C without 1-MCP, and on Day 28 at 14.0°C with 1-MCP. Using a 1-MCP pre-treatment to remove the influence of ethylene from bananas stored at 13°C or 14°C also resulted in slight reduction in vascular browning severity. In conclusion, a putative safe temperature may become a CI temperature if the shelf-life-limiting factor is removed, allowing longer exposure. Chilling at the CTT caused relatively mild injury on fruit, and vascular browning is a sensitive indicator of CI status, while the light-adapted quantum yield of photosystem II [Y(II)] could be a non-destructive indicator of early CI stress in MG banana. Fruit at 13.0/14.0°C developed CI symptoms slightly later with 1-MCP than without 1-MCP. This suggests that ethylene might be involved in early CI symptom development. [ABSTRACT FROM AUTHOR]

The subtropical peach cultivar UFSun grafted on five different rootstocks ('Flordaguard', 'Barton', 'MP‐29', 'P‐22', and 'Okinawa') was investigated in terms of the pomological and biochemical parameters of the fruit. Significant differences in fruit weight and size, soluble solids content, titratable acidity, and firmness were found among some rootstocks. The fruit length and diameter were different between the 'MP‐29' and other rootstocks. It was also found that firmness of 'UFSun' fruit was affected by the rootstock. The highest firmness value was found when 'UFSun' was grafted on 'Flordaguard'.' 'MP‐29' fruit had the highest soluble solids content, but there were no differences among the other rootstocks. 'UFSun' fruit from trees grafted on 'MP‐29' were smaller and had the most intense color compared to 'UFSun' fruit from other rootstocks. Rootstock had a significant influence on total fruit phenolic compounds, anthocyanin content, and total antioxidant activity, with fruit from 'UFSun' on 'MP‐29' having the highest values in all of them. A high correlation between fruit total antioxidant activity and total phenolic content was found. Overall, the results showed that 'MP‐29' seems to induce the highest fruit quality, showing higher contents of total soluble solids, total titratable acidity, total phenolic compounds, total antioxidant activity, and total anthocyanin content. Selecting the right combination of the rootstock and cultivar is important for optimizing fruit quality parameters. [ABSTRACT FROM AUTHOR]

Bruising of strawberry (Fragaria 3ananassa Duch.) fruit is a common mechanical injury that reduces product value. Wound-induced ethylene may accelerate deterioration or decay, affecting strawberry quality and shelf life. However, bruising susceptibility varies among strawberry cultivars. In this study, cultivars Monterey, Sweet Sensation, Radiance, and two proprietary cultivars (Cultivar A and Cultivar B) from a private breeding program were investigated to evaluate their bruising susceptibility and wound response. Bruising consisted of dropping a 28-g steel ball from 27 cm onto individual fruit; unbruised fruit were the primary control, while fruit exposed to 1 mL·LL1 ethylene were used as a check for ethylene response. All fruit were stored at 20 8C, 90% relative humidity (RH), with respiration and ethylene production measured at 2-hour intervals for 24 hours. Appearance observations were recorded daily until decay onset. Peak respiration rates of 30-40 mL CO2·kgL1·hL1 mostly occurred within 4 hours ('Cultivar B') to 6 hours ('Cultivar A' and 'Sweet Sensation') after bruising, except 'Monterey', which peaked at 60 mL CO2·kgL1·hL1 in 2 hours, and 'Radiance', which reached 70 mL CO2·kgL1·hL1 in 6 hours. Maximum ethylene production rates after bruising were 0.05 to 0.06 mL·kgL1·hL1 for 'Monterey', 'Cultivar A', and 'Cultivar B', 0.10 mL·kgL1·hL1 for 'Sweet Sensation', and 0.20 to 0.37 mL·kgL1·hL1 for 'Radiance'. 'Cultivar B', with the lowest ethylene production, exhibited the lowest overall bruising severity, whereas 'Radiance', with the highest ethylene production, exhibited the most severe bruising-induced water soaking, and the other cultivars were intermediate, although 'Monterey' bruises were more discolored than those of the other cultivars. 'Monterey', 'Radiance', and 'Sweet Sensation' showed more yellowing and browning of the calyx in response to both bruising and ethylene exposure than 'Cultivar A' and 'Cultivar B'. Except for 'Cultivar B', bruising and ethylene exposure increased decay severity. [ABSTRACT FROM AUTHOR]