Fruit Mineral Research Articles

Seaweed Extract and Microbial Biostimulants Show Synergistic Effects on Improving Organic Strawberry Production

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 Sensation® 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.

Global analysis of spatio-temporal variation in mineral nutritional quality of pepper (Capsicum spp.) fruit and its regulatory variables: A meta-analysis

Pepper (Capsicum spp.) is an important fruit vegetable worldwide, and it is a rich dietary source of minerals for human being. Yet, the spatio-temporal distribution of pepper fruit mineral composition and the factors influencing such variations at global scale remain unknown. A global meta-analysis of 140 publications providing 649, 562, 690, 811 datapoints was conducted to quantify and evaluate the nutritional quality, comprising potassium (K), magnesium (Mg), iron (Fe) and zinc (Zn), of pepper fruits and its influencing variables. The analysis showed that the global average of K, Mg, Fe and Zn content in pepper fruits was 20–25 g kg−1, 1–1.5 g kg−1, 80–100 mg kg−1, and 20–40 mg kg−1, respectively. There had been a downward trend in pepper fruit nutritional quality over the last decade, especially for Fe and Zn. And, the concentration of all these four nutrients were at lower levels in less developed regions, especially in Africa. Our results showed that the vegetable “green pepper” contains more K, Mg, Fe and Zn than the “hot pepper” used as spice. The concentration of K, Mg, Fe and Zn were increased with fruit yield but that of Fe and Zn were decreased with increase in single fruit weight. Nutritional quality was optimal at mean annual temperature of 10 ℃ − 20 ℃, and was adversely affected when mean annual precipitation was < 500 mm. Pepper fruits produced at pH 6.5–7.5 had higher fruit K concentration while acidic soils (pH<6.5) favored higher Fe and Zn concentrations. The higher soil organic matter (SOM) generally improved the nutritional quality of the pepper. Our results suggest that systematic selection of superior varieties and soil amelioration (adjusting pH and SOM) of the soil-crop system are needed to achieve higher nutritional quality of pepper fruit.

Internal Fruit Quality Is Maintained in Eggplant under Mild Long-Term Salt Treatment

Modern Solanum melongena varieties have been developed to improve the content of phenolics, sugars, and nutritionally relevant minerals in fruit. However, fruit composition might be altered due to abiotic stresses like salinity. Physiological and fruit quality traits were evaluated in four eggplant landraces under usual irrigation and moderately salty irrigation conditions (80 mM NaCl). Growing parameters measured included root length, leaf surface, and fresh weight, while fruit composition traits included sugars, phenolics, and mineral content determinations. Few differences were observed for agronomic traits, probably due to the mild tolerance of eggplant to salinity. Some varieties showed signs of salt tolerance like an increase in primary root length to overcome salt stress. Glucose was the metabolite more affected by the salt treatment in the fruit, while phenolic compounds and other metabolites studied were not altered. Significant differences were observed in the main minerals Na, K, Ca, P, and Mg, both between genotypes and treatments. Although salinity produced changes in some physiological and developmental traits, the composition of the fruit was not significantly modified for the accessions tested. Mineral, sugar, and phenolic contents were not particularly altered in unripe fruits, indicating tolerance of eggplant varieties to salinity in terms of fruit quality.

Improving mangoes' productivity and crop water productivity by 24-epibrassinosteroids and hydrogen peroxide under deficit irrigation

In nature, plants are frequently subjected to a wide range of abiotic stresses that drastically reduce crop productivity. Deficit in irrigation is one of the main factors of abiotic stresses that affect agricultural productivity. Nevertheless, not much research has been done on how to use water with brassinosteroids (Br) and hydrogen peroxide (H2O2)in deficit water conditions in order to reach comparatively good values of mango tree growth, productivity, and fruit quality as well as crop water productivity (WPC). A split-plot experiment in a complete randomized block system design study with 3 regulated deficit irrigation levels i.e. 100% IR (Irrigation requirement), 80% IR, and 60% IR was implemented in 2022 and 2023, each irrigation regime was combined with the foliar application of distilled water (control), 1 mg/L Br, 10 mM H2O2, 1 mg/L Br + 10 mM H2O2. Foliar treatments were applied at 3 different phenological stages: flower bud induction and differentiation, full bloom, and beginning of fruit set. The results showed that fruit shape index and acidity significantly improved as irrigation volume increased, however, the proportion of fruit mineral content and fruit chemical characteristics was inversely correlated with the volume of water. Meanwhile, moderate regular deficit irrigation (80% IR) achieved marked increases in leaf minerals and total chlorophyll content, fruit quality, yield, and water use efficiency. Drought stress (60% IR) significantly decreased fruit set, fruit retention, yield traits, and fruit physical and chemical properties, at the same time, significant improvements in the content of stress indicators (proline, total phenols, and carotenoids) were observed compared with control. All treatments with Br and H2O2 alone or in combination under drought stress had a pronounced effect in this regard. Overall, foliar spray of 1 mg/L Br+10 mM H2O2 was the most powerful treatment that emended the unpropitious effect of water stress.

Cornelian cherry (Cornus mas L.) as a promising source of antioxidant phenolic substances and minerals

This study aimed to evaluate the mineral content, and content of bioactive compounds in fruits of Cornelian cherry (Cornus mas L.). Neochlorogenic acid, chlorogenic acid, caffeic acid, and rutin were determined in the samples. Vitamin C content ranged from 610.36 to 1344 mg kg−1 FW. Content of K, Ca, P, Mg, and Na in samples ranged from 1750.8 to 2645.7 mg kg−1 FW, from 281.14 to 561.62 mg kg−1 FW, from 180.38 to 294.95 mg kg−1 FW, from 68.19 to 115.43 mg kg−1 FW, and from 2.48 to 71.33 mg kg−1 FW respectively. Content of Fe, Zn, Cu, Mn, Ni, Cr, and Co in samples ranged from 2.77 to 4.88 mg kg−1 FW, from 0.49 to 0.99 mg kg−1 FW, from 0.25 to 0.53 mg kg−1 FW, from 0.07 to 0.17 mg kg−1 FW, from 0.02 to 0.13 mg kg−1 FW, from 0.01 to 0.02 mg kg−1 FW, and from 0.01 to 0.08 mg kg−1 FW respectively. Variations across cultivars were found to be statistically significant, indicating that genetics is a key factor influencing the concentration of bioactive compounds and minerals in Cornelian cherry fruits. Understanding the genetic factors influencing mineral and bioactive compound content in cornelian cherry cultivars is essential for targeted breeding programs, crop improvement, and the development of cultivars with enhanced nutritional and health-promoting attributes. This knowledge contributes to sustainable agriculture and supports the production of crops that align with consumer preferences and health trends.

Diversity of phenolic compounds, antioxidant capacity, and mineral element content in four fig cultivars (Ficus carica L.) and their correlation with the rooting of hardwood cuttings

We investigated the phenolic compound profile, antioxidant capacity, rooting of cutting and fruit mineral concentration on 15-year-old trees of four Iranian figs (Ficus carica cvs. “Siyah”, “Kashki”, “Shahanjir” and “Sabz”) planted under rain-fed conditions with different fruit skin color, as well as the correlation between these traits. The range of TSS and antioxidant capacity of fruit (without significant differences) was 75.3–76.7°Brix and 87.9–90.3 DPPHsc %, respectively. “Kashki” had the highest total phenolic (TP) (mg GAE/100 g dw) in both the fruit (1964) and the stem bark (1702) and “Sabz” had the lowest flavonoid content (µg CE mg−1 dw) in the fruit (652.3), leaf (1274.5), and stem bark (1501.9). Although the rooting percentage of cuttings was similar in “Siyah”, “Shahanjir”, and “Sabz”, the lowest rooting percentage (62.7%) and the lowest polyphenol oxidase enzyme (PPO) activity (42.5 U.mL−1) were in “Kashki”. Rooting of the cuttings had a direct correlation with PPO activity and catechin and a negative correlation with the TP, vanillin and trans-ferulic acid concentration in cutting bark. These results showed that the fresh cultivar such as “Shahanjir” with outstanding characteristics, such as high potassium and antioxidant content of fruits and good rooting of the cuttings (97.2%) can be recommended for the development programs of light-colored fresh figs. On the other hand, there were two cultivars, “Siyah” and “Kashki” with dark fruit color; due to their content of TP, total flavonoid, quercetin, trans-ferulic acid and high calcium content in the fruit, these should also be considered.

Fruit quality assessment based on mineral elements and juice properties in nine citrus cultivars

IntroductionCitrus fruit is considered a superfood due to its multiple nutritional functions and health benefits. Quantitative analysis of the numerous quality characteristics of citrus fruit is required to promote its sustainable production and industrial utilization. However, little information is available on the comprehensive quality assessment of various fruit quality indicators in different citrus cultivars.MethodsA total of nine different fresh citrus fruits containing seeds were collected as the experimental materials. The objectives of this study were: (i) to determine the morphological and juice properties of citrus fruits, (ii) to measure the mineral elements in the peel, pulp, and seeds, and (iii) to evaluate the fruit quality index (FQI) using the integrated quality index (IQI) and the Nemoro quality index (NQI) methods.ResultsThere were significant differences in fruit quality characteristics, including morphological, mineral, and juice quality, among the investigated citrus cultivars. The proportion of pulp biomass was the highest, followed by that of peel and seeds. N and Cu had the highest and lowest concentrations, respectively, among the measured elements across all citrus fruits, and the amounts of N, P, Mg, Cu, and Zn in seeds, K and Al in pulp, and Ca, Fe, and Mn in peel were the highest, dramatically affecting the accumulation of minerals in the whole fruit and their distribution in various fruit parts. Additionally, Ningmeng fruits had the highest vitamin C and titratable acidity (TA) but the lowest total soluble solids (TSS) and total phenolic (TP) contents, resulting in the lowest TSS/TA and pH values. In contrast, Jinju fruits had the highest TSS and TP contents. Based on the mineral element and juice quality parameters, principal component analysis showed that the citrus fruits were well separated into four groups, and the dendrogram also showed four clusters with different distances. The FQI range based on the IQI method (FQIIQI) and NQI method (FQINQI) was 0.382-0.590 and 0.106-0.245, respectively, and a positive relationship between FQIIQI and FQINQI was observed.ConclusionOur results highlight the great differences in mineral and juice characteristics among fruit parts, which mediated fruit quality. The strategy of fruit quality assessment using the FQI can be expanded for targeted utilization in the citrus industry.

Fruit Mineral Content and Postharvest Quality of Quince (Cydonia oblonga Mill.) as Affected by Soil Lime Stress

Fruit Mineral Content and Postharvest Quality of Quince (Cydonia oblonga Mill.) as Affected by Soil Lime Stress

Ammonium nitrogen combined with partial root-zone drying enhanced fruit quality of tomato under elevated atmospheric CO2

Increasing nitrogen fertilization and reduced irrigation regimes can alleviate the negative effect of elevated CO2 (e[CO2]) on fruit quality of tomatoes, yet little is known about the effects of N forms combined with partial root-zone drying irrigation (PRI) on tomato growth and fruit quality under e[CO2]. This study aimed to investigate the response of tomato plants to N forms, PRI and their interactions under e[CO2]. Tomato plants (Solanum lycopersicum L.) were grown in split-root pots in climate-controlled growth chambers with CO2 concentration of 400 ppm and 800 ppm, respectively, supplied with two N forms i.e. nitrate nitrogen (NN) and ammonium nitrogen (AN). Three irrigation regimes, i.e. full irrigation (FI), deficit irrigation (DI) and PRI were applied from anthesis to fruit maturity. The results showed that e[CO2] decreased plant water use (WU) while increased biomass accumulation (ΔDW), water use efficiency (WUE) and fruit number (FN). Under e[CO2], AN plants had less ΔDW, leaf area and WU while similar yield, as compared with NN plants. Additionally, under e[CO2] with PRI treatment, AN fruits had greater [N], [K], [N/P], and soluble solid (Brix) to acid ratio, but lower [C/N], [P/K] and acid concentration, and similar fruit [C], [P], [Ca], [Mg] and [S], in comparison with the NN fruits. Collectively, AN treatment combined with PRI under e[CO2] improved fruit mineral nutrition and the flavor of tomato fruits without reduction in yield and WUE. Therefore, AN combined with PRI could be an alternative strategy to improve tomato fruit quality in future drier and CO2-enriched environment.

Factors affecting development of disorders expressed after storage of ‘Gala’ apple fruit

This study investigated factors influencing susceptibility and development of physiological disorders and decay expressed after long-term storage in ‘Gala’ apple fruit (Malus domestica Borkh.). Five experiments were performed over ten production years with fruit from two environmentally different orchard locations in a humid subtropical climate at 990 m (warmer) and 1415 m above sea level. Fruit were harvested at two maturity stages (early and advanced), treated or not treated with 1-methylcyclopropene (1-MCP) and stored at 0.5 °C or 2 °C in a controlled atmosphere (CA, 1.5 kPa O2 and 2.5 kPa CO2), for 240 d plus 7 d shelf life. In one experiment, fruit were stored in CA with CO2 concentrations of 1.5 or 3 kPa. The relationship between fruit mineral composition and physiological disorders was assessed in one production year. Flesh browning (FB) was the predominant disorder, followed by decay, cracking, and lenticel breakdown-wet (LB-wet). The average severity index of lenticel breakdown-dry (LB-dry), leather blotch and bitter pit were low and variable across production years. The FB index was lowest in fruit produced at the colder orchard location, early harvest, treatment with 1-MCP, and storage at 2 °C. These factors also influenced fruit softening after storage. The major source of variance of the FB index in order of decreasing contribution were harvest maturity, production year, orchard location, 1-MCP and storage temperature. Production year variability of FB index correlated positively with early summer rain and negatively with early spring temperature. A weak positive correlation was also found between FB index and fruit K+Mg/Ca ratio. Higher CA CO2 concentration increased FB in fruit stored at 0.5 °C but not at 2 °C. The same factors affected decay, cracking and LB-wet disorder similarly as for FB, except that decay and cracking were not consistently affected by storage temperature, and decay and LB-wet were not impacted by 1-MCP. Storage temperature had the most influence on the variance of LB-wet. LB-dry was highest in late harvest fruit and, in the production year with the highest index, in fruit stored at 0.5 °C. Leather blotch was highest in early harvest fruit and in fruit stored at 0.5 °C. 1-MCP treatment did not affect disorders other than FB and cracking. These results suggest that interactions among harvest and postharvest factors influence the development of ‘Gala’ FB and other disorders and indicate a possible relationship of chilling in FB development. The information may be useful for implementing practical strategies to reduce the development of these postharvest disorders in ‘Gala’ apple fruit.

Vegetative growth, yield quality, and phytochemical accumulation of Abelmoshus esculentus L. (Moench) influenced by priming with potassium nitrate

Seed priming is a promising technique that can improve the growth and yield of plants under optimum conditions. The specific priming duration and concentration required for adequate vegetative growth, yield quality, and phytochemical accumulation of Abelmoshus esculentus need clarification. This study was evaluated under screen house conditions, using a completely randomized design (CRD) approach. The seeds of Abelmoshus esculentus were subjected to priming with potassium nitrate for 6 and 12 h duration at a concentration of 0.5 and 1.00 mM while unprimed seeds served as the control. The results revealed that the primed seeds showed improved vegetative growth, yield components, and phytochemical constituents compared to the unprimed control seeds. This observation was irrespective of the priming duration and concentration of potassium nitrate used. Moreover, seeds primed for a 6 h duration at 1 mM were significantly higher in yield, fruit mineral, and phytochemical constituents compared to other treatments. At 12 h priming duration, seeds primed in 0.5 mM of potassium nitrate had higher growth and yield than at 1 mM. Priming with inorganic salts such as KNO3 induces faster growth and maximum crop yield of Abelmoshus esculentus. Priming for a short duration (6 h) 3 and at high concentration is sufficient to enhance the growth process and increased yield of Abelmoshus esculentus and has practical implications in the production of Abelmoshus esculentus .

Internal Flesh Browning in Apple and Its Predisposing Factors—A Review

This review article is focused on internal flesh browning (IFB)-related physiological disorders affecting apple (Malus domestica Borkh.) fruit. The expression of different physiological and metabolic IFB-related disorders during post-harvest storage are investigated along with the pre-harvest factors contributing to development. The effectiveness of commercially available pre-harvest technologies for preventing IFB-related disorders are also examined. Internal flesh browning-related disorders are erratic and devastating disorders that result in post-harvest deterioration of fruit quality in apples. Internal flesh browning-related disorders can result in severe economic losses to the apple industry through reduced consumer trust and market acceptability of susceptible cultivars. There are several IFB-related disorders and incidence can range from 0 to 100% of a crop, with severity ranging from no brown flesh to browning of the entire fruit flesh. While IFB-related disorders are found in several apple cultivars, some cultivars are more prone than others. The development of IFB-related disorders involve complex mechanisms depending upon the different types and causes, or factors involved in loss of structural integrity and functional stability of the cell membranes and cell components. Membrane disruption followed by enzymatic oxidation of fruit phenolic compounds by polyphenol oxidases and the production of brown polymers is considered to be the general underlying mechanism causing the browning of flesh tissue. It can be observed in different patterns based on the injured portion of the fruit flesh and the cause of membrane disruption. Three broad categories of IFB-related disorders, including chilling injury, internal CO2 injury, and senescent-related browning disorders, are discussed along with their sub-types. The development of IFB-related disorders can be influenced by both pre-harvest factors and post-harvest conditions and their interactions. Although commonly associated with storage, IFB can also be found immediately after harvest and sometimes in unharvested fruit prior to full maturity. As pre-harvest conditions are a strong contributor to IFB-related disorders, the influence of several pre-harvest orchard conditions, including fruit size, crop load, maturity at harvest, cultivar, climatic conditions, seasonal temperatures, growing degree days, and major mineral nutrients, such as nitrogen (N), phosphorus (P), potassium (K), and calcium (Ca) are reported. Although there are contradictory findings in the studies reported, in general, factors such as larger fruit size, light crop load and delayed harvesting, along with cool temperatures after bloom and warmer temperatures before harvest, increase the risk of IFB-related disorders. In relation to fruit mineral concentrations, high N and low Ca have been associated with increasing IFB, while there is conflicting evidence in relation to the impact of both P and K. This review also examines the effectiveness of commercial pre-harvest technologies such as 1-methylcyclopropene, aminoethoxyvinylglycine and diphenylamine in the prevention of IFB-related disorders, but none of these technologies were found promising due to varied and contradictory results.

Improvement of the Physico-Chemical Properties, Nutritional, and Antioxidant Compounds of Pomegranate Fruit cv. ‘Wonderful’ Using Integrated Fertilization

This study comprised of five different integrated fertilizers of calcium nitrate Ca(NO3)2 with ammonium sulphate (NH4)2SO4 ratios (0%:100%, 10%:90%, 20%:80%, 30%:70%, and 40%:60%) to enhance the physico-chemical properties, and the antioxidant and nutritional compounds of pomegranate fruits cv. ‘Wonderful’. The results discovered that the application of Ca(NO3)2:(NH4)2SO4 in different ratios significantly affected all measured parameters. Among integrated fertilizers, the 30%:70% combination showed an increment of 10.8% in fruit weight, 2.9% in fruit length, 11.8% in fruit volume, and 7.0% in fruit diameter. Similarly, total soluble solids, vitamin C, anthocyanin, total sugars, and reduced sugars, were also increased by 11.2%, 14.6%, 20.2%, 7.4%, and 5.2%, respectively. Likewise, values of both color variations from green to red (a*) and from blue to yellow (b*), and chroma, were also increased by 13.8%, 16.6%, and 14.4%, respectively. Moreover, the application of Ca(NO3)2:(NH4)2SO4 at a ratio of 40%:60% showed 25.1% decrease in titratable acidity, and 45.4% and 27.0% increase in maturity index and peel luminosity, respectively. Additionally, the 30%:70% combination showed an increment of 30.9% in total phenolic content, 70.5% in total tannin content, and 43.6% in total flavonoid content. Additionally, it showed 25.8% and 1.7% decrease in pH and moisture content, respectively. Moreover, P, K, Ca, Mg, Na, Fe, Mn, Zn, Cu, and Ni in fruit increased by different increments by application of the 30%:70% with an increasing range of 28% to 175%. A non-reducing sugar increase was observed at an application of Ca(NO3)2:(NH4)2SO4 at a ratio of 20%:80% by 47.0%. The findings of this study suggest that using calcium nitrate with ammonium sulphate at a ratio of 30%:70%, using the fertigation approach during the growth season, could be a safe, natural, and novel method for the pomegranate cv. ‘Wonderful’ to improve fruit quality, and its amount of antioxidants—specifically, phenolics, vitamin C, anthocyanin, and fruit minerals—with health benefits at harvest.

A systematic assessment of how rootstock growth characteristics impact grafted tomato plant biomass, resource partitioning, yield, and fruit mineral composition.

The appropriate selection of rootstock-scion combinations to improve yield and fully realize grafting benefits requires an in-depth understanding of rootstock-scion synergy. Toward this end, we grafted two determinate-type scions [grape tomato ('BHN 1022') and beefsteak tomato ('Skyway')] onto four rootstocks with different characteristics to examine plant growth, yield performance, biomass production, and fruit mineral nutrient composition. The study was conducted during two growing seasons (spring and fall plantings in Florida) under organic production in high tunnels with the non-grafted scions as controls. Rootstocks had previously been designated as either "generative" ('Estamino') or "vegetative" ('DR0141TX') by some commercial suppliers or had not been characterized ['RST-04-106-T' and 'SHIELD RZ F1 (61-802)']. Also, 'Estamino', 'DR0141TX', and 'RST-04-106-T' had been described as more vigorous than 'SHIELD RZ F1 (61-802)'. In both planting seasons (with low levels of soilborne disease pressure), the "vegetative" and "generative" rootstocks increased marketable and total fruit yields for both scions except for the beefsteak tomato grafted with the "vegetative" rootstock in fall planting. Positive effects of 'RST-04-106-T' on fruit yield varied with scions and planting seasons, and were most manifested when grafted with the beefsteak tomato scion in fall planting. 'SHIELD RZ F1 (61-802)' led to similar yields as the non-grafted controls except for grafting with the grape tomato scion in fall planting. For vegetative and fruit biomass, both the "vegetative" and "generative" rootstocks had positive impacts except for the beefsteak tomato in fall planting. For fruit mineral composition, the "vegetative" and "generative" rootstocks, both highly vigorous, consistently elevated fruit P, K, Ca, Zn, and Fe contents on a dry weight basis, whereas the other rootstocks did not. Overall, although the more vigorous rootstocks enhanced tomato plant productivity and fruit minerals, the evidence presented here does not support the suggestion that the so-called "vegetative" and "generative" rootstocks have different impacts on tomato scion yield, biomass production, or fruit mineral contents. More studies with different production systems and environmental conditions as well as contrasting scion genotypes are needed to further categorize the impacts of rootstocks with different vigor and other characteristics on plant biomass production and their implications on fruit yield development.

Foliar application of nanoceria attenuated cadmium stress in okra (Abelmoschus esculentus L.)

Foliar application of nanoparticles (NPs) as a means for ameliorating abiotic stress is increasingly employed in crop production. In this study, the potential of CeO2-NPs as stress suppressants for cadmium (Cd)-stressed okra (Abelmoschus esculentus) plants was investigated, using two cycles of foliar application of CeO2-NPs at 200, 400, and 600 mg/l. Compared to untreated stressed plants, Cd-stressed plants treated with CeO2-NPs presented higher pigments (chlorophyll a and carotenoids). In contrast, foliar applications did not alter Cd root uptake and leaf bioaccumulation. Foliar CeO2-NPs application modulated stress enzymes (APX, SOD, and GPx) in both roots and leaves of Cd-stressed plants, and led to decreases in Cd toxicity in plant’s tissues. In addition, foliar application of CeO2-NPs in Cd-stressed okra plants decreased fruit Cd contents, and improved fruit mineral elements and bioactive compounds. The infrared spectroscopic analysis of fruit tissues showed that foliar-applied CeO2-NPs treatments did not induce chemical changes but induced conformational changes in fruit macromolecules. Additionally, CeO2-NPs applications did not alter the eating quality indicator (Mg/K ratio) of okra fruits. Conclusively, the present study demonstrated that foliar application of CeO2-NPs has the potential to ameliorate Cd toxicity in tissues and improve fruits of okra plants.

Mineral Nutrients, Physiological Disorders, Postharvest Water Loss, and PR Gene Expression in Bell Pepper (Capsicum annuum L.) Fruit under Shade Nets

Abstract Shade nets can be an effective technology for producing bell pepper (Capsicum annuum L.) under hot climatic conditions. However, the effects of shading on fruit quality are still unclear. The objectives were to evaluate the effects of shade level on fruit mineral nutrient content, physiological disorders, and postharvest water loss. Trials were conducted in the spring–summer of 2016, 2017, and 2018 in Tifton, Georgia, USA, following a randomized complete block design with five shade levels: 0% (open field), 30%, 47%, 63%, and 80%. Shading increased the bell pepper fruit dimensions (length, diameter, and weight) in 2016 and mineral nutrient content in 2017. Fruit sunscald incidence decreased with increasing shade level, while blossom-end rot showed inconsistent responses. Postharvest fruit water loss and transpiration rates were highest in fruits from the unshaded treatment in 2016; there were no differences in fruit water loss among the shade levels. NONEXPRESSOR OF PATHOGENESIS-RELATED 1 (NPR1) and PATHOGENESIS-RELATED 1 (PR1) genes expressed more than 1.5-fold and 10-fold, respectively, at 47% shade level compared to 80%, though not significantly. Therefore, plants grown under shading had fruit with greater size, increased mineral nutrient content, and reduced sunscald incidence compared with the unshaded control.

Investigations of Multiple Approaches to Reduce Green Spot Incidence in ‘WA 38’ Apple

A pre-harvest apple (Malus × domestica Borkh.) disorder named “green spot” (GS) was recently identified on ‘WA 38’ apples. Previous work indicated a tentative association between GS and fruit mineral imbalance, and an influence of rootstock selection on GS frequency; however, the specific causes, risk factors, and mitigation steps have not been explored. In this study, the role of microclimate, modified using netting or fruit bagging, on GS incidence in ‘WA 38’ apples over two years on two different dwarfing rootstocks, ‘Geneva 41’ (‘G.41’) and ‘Malling 9-Nic29’ (‘M.9’), was investigated. Early season fruit bagging reduced GS appearance, but netting showed mixed results between year and rootstock. Rootstock selection influenced GS incidence, especially in the 2021 season. Fruit mineral analyses highlighted some differences of mineral composition between symptomatic and asymptomatic apples, which helped to corroborate earlier reports; however, within the full context of these results, it is not clear that nutrient imbalance directly influences disorder incidence. Further work to understand the mechanisms behind GS emergence should consider environmental factors, including light, humidity, and wind, as well as anatomical features of ‘WA 38’ fruit, such as lenticel morphology and physiology.

Plant Growth and Fruit Nutrient Changes in Carica papaya L. Genotypes Subjected to Regulated Deficit Irrigation.

The current genotypes of Carica papaya L. cultivated worldwide are considered relatively tolerant or sensitive to drought conditions, depending specifically on the cultivar features and the severity of water shortage. In this work an experimental field was established by subjecting "Intenzza" and "Siluet" to the following water regimes: Control ("CT"), plants irrigated at field capacity (100%); Moderate Deficit Irrigation ("MDI", watered at 66%); and Severe Deficit Irrigation ("SDI", watered at 50%). The results indicated that water deficit decreases leaf number leading to a decline of total leaf area, being "Intenzza" equally affected by "SDI" and "MDI", whereas in "Siluet" the major decrease was induced by "SDI". Regarding fruit development, in "Intenzza", "MDI" and "SDI" did not affect fruit number except two dates (120 and 202 DAT), decreased fruit fresh weight (FW), and increased total soluble solutes (TSS) levels, while in "Siluet" only "SDI" reduced fruit FW and watering systems did not change TSS, suggesting a better performance of this cultivar under "MDI". In addition, drought did not impair fruit mineral concentrations excepting in few dates, and in such cases stressed fruits accumulated a slight minor or even major concentration of some nutrients than control, maintaining consequently suitable organoleptic quality.

Tree age and maturity stage affect reducing sugars, organic acids and minerals in Ziziphus jujuba Mill. cv. Huping fruits

Ziziphus jujuba Mill. is a fruit native to China, and widely distributed in the world for its nutritional value. In this study, Jujube Huping fruits were collected from tree with ages (5, 13, 30, 100-years old) at two different ripening stages. The results showed that the contents of reducing sugars increased with tree age except for 5 years old tree. Citric and malic acids were the predominant organic acids with the highest contents in the green stage of 100-year-old trees (3500 mg/100 g FW) and the red stage of 13-year-old trees (4290 mg/100 g FW), respectively. There was no specific pattern for minerals affected by the tree ages. Ca (156–397 mg/kg DW), Al (144–156 mg/kg DW), Mg (512–680 mg/kg DW) and K (7105–4617 mg/kg DW) were the main minerals in fruits. Based on Hierarchical cluster analysis and principal component analysis, the eight samples were classified into four groups: Cluster 1 (SR-5, SR-100, SG-5, and SG-13), Cluster 2 (SG-30), Cluster 3 (SR-13, SR-30), and Cluster 4 (SG-100). The study showed how the age of jujube trees affected the levels of nutrients in jujube fruits, as well as provided insights on how to grow and cultivate jujube trees of various ages.

Evaluation of substrates for cucumber production in the Dutch bucket hydroponic system

The Dutch bucket system is commonly used for production of high-wire crops such as tomatoes, peppers, and cucumbers in controlled environment agriculture. It is a hydroponic system that utilizes containers typically filled with perlite as the substrate. Perlite provides good aeration however has higher leachate in the systems. Furthermore, demand for regional and sustainable substrates is increasing. Our preliminary study showed growth parameters in vegetative and early fruiting stages of cucumber grown with five regionally accessible substrates are comparable to perlite. Thus, the current study evaluated the performance of five organic substrates in comparison to perlite in the Dutch bucket system for the full production cycle of cucumber (Cucumis sativus ‘Picolino F1’). The substrates evaluated were sphagnum peat, medium grade pine bark (Bark-M), coarse grade pine bark (Bark-C), coir, and wood fiber. Leachate rates in Bark-M, coir, and peat were lower than perlite by 18.0%, 24.0%, and 38.1%, respectively. Plant leaf area indicated better vegetative growth of cucumber with wood fiber, but pine bark had higher yield and fruit quality than perlite. Bark-M resulted in greater yield and fruit vitamin C content, which were 23.9% and 48.3% higher than perlite, respectively. On the other hand, although Bark-C had a similar yield to perlite, its fruit mineral nutrient content including nitrogen (except wood fiber), phosphorus, potassium, calcium (except Bark-M and wood fiber), sulfur (except Bark-M and wood fiber), iron (except Bark-M), zinc, boron, copper (except wood fiber), and manganese (except Bark-M), as well as total anthocyanin and total phenols were highest among all substrates. In summary, organic substrates investigated could provide equal or higher cucumber yields and quality than perlite in the Dutch bucket hydroponic system.