Fruit Acidity Research Articles

Effects of Long-Term Nitrogen Fertilization and Application Methods on Fruit Yield, Plant Nutrition, and Soil Chemical Properties in Highbush Blueberries

Nitrogen (N) fertilizer is routinely applied in highbush blueberry (Vaccinium corymbosum L.) production. The recommended N fertilizer rate increases as the plants mature, and is usually determined based on regional growing conditions. However, the effects of N fertilizer rates and application methods over the long term remain poorly understood. In this study, ammonium sulfate was applied as an N source at the recommended rate (100%), which corresponds to a maximum of 155 kg N ha−1 for plants older than eight years, along with higher rates at 150% and 200% of the recommended level, as well as a control treatment of no N. Treatments were applied to the blueberry cultivar ‘Duke’ as either broadcast (BROAD) or fertigation (FERT), and impacts were analyzed after 12 and 13 years of treatment. In the 14th year, the 100% N rate was uniformly applied as BROAD across all plants to separate the effects of different N rates from those caused by long-term soil condition changes. The BROAD treatment at the 100% N rate achieved the highest yield, and the FERT treatment at 200% resulted in the lowest yield in the 12th year, suggesting that excessive N rates can reduce fruit yield. However, no significant yield differences were observed in the 13th year. Higher N rates were associated with reduced titratable acidity in fruits and fewer flower buds. The soil pH declined across all N treatments, with the FERT at 200% showing the most significant reduction. All N treatments generally increased soil electrical conductivity (EC). High N rates also decreased plant accumulation of magnesium, calcium, and copper, with the latter reaching deficiency levels. These findings emphasize the importance of adhering to recommended N application rates and adjusting soil pH and EC to mitigate the adverse effects of prolonged N treatments.

Changes in total soluble solids concentration, fruit acidity, and yeast assimilable nitrogen in response to altered leaf area to fruit weight ratio in Pinot noir

The increasing consumer demand for lower alcohol wine and the need to mitigate against a warming climate presents new challenges for winegrowers and the desire to produce grapes with lower total soluble solids (sugar) or earlier harvesting, while preserving other wine compounds and attributes, particularly for varieties intended for red wine production. We investigated how reducing vine leaf area through shoot trimming and leaf removal, applied at different severities and timings to modify the leaf area to fruit weight (LA) ratio, affects fruit composition for producing lower alcohol quality Pinot noir wine. Shoot trimming treatments (half canopy, H in 2015/16 and 2016/17, and quarter canopy, Q in 2016/17 by alternately removing leaves after trimming shoots to half) were applied shortly before veraison (V-, E-L 34), during veraison (V, E-L 35) and post-veraison (V+, E-L 36) in three different vineyard locations (Marlborough, Canterbury and Central Otago, New Zealand). Untrimmed vines served as the control. Lateral shoots were removed during treatment application, and regrowth was removed to maintain a consistent leaf area. Results showed that reducing the LA:FW ratio delayed the accumulation and concentration of total soluble solids (reduction of 1.0 to 2.7 °Brix) at harvest in all trimmed vines over both seasons. Berry weight, malic acid concentration, titratable acidity, and pH at harvest were unaffected by trimming. At target TSS levels of 18 °Brix (10 % ethanol, v/v) in the Marlborough vineyard and 20 °Brix (11 % v/v) in the Central Otago vineyard, V+ vines showed malic acid and titratable acidity levels comparable to the control. At the Canterbury vineyard, these parameters remained similar across all treatments at 16 °Brix (8.9 % v/v). Yeast-assimilable nitrogen concentration increased (188 to 411 mg/L) in early trimmed vines. At Central Otago, roots showed lower carbohydrate reserves across all trimming treatments, likely due to the high yield at the site, while at Canterbury, trimming did not result in significant differences in carbohydrate reserves, likely due to the low yield at the site. At the Marlborough vineyard, vines trimmed early and more severely had less starch in their roots, while HV+ vines maintained similar levels of starch to controls. In conclusion, halving the canopy post-veraison (HV+, LA 0.70 m²/kg as observed in Marlborough) could be considered a viable viticultural option to lower sugar accumulation, thereby reducing potential alcohol content, without affecting titratable acidity and pH. This practice offers significant potential for adapting to a warming climate and producing lower alcohol Pinot noir wines in a sustainable manner.

Multi-Omics Analysis Uncovers the Mechanism for Enhanced Organic Acid Accumulation in Peach (Prunus persica L.) Fruit from High-Altitude Areas.

The early-ripening peach industry has undergone rapid development in the Panxi region of the Sichuan Basin in recent years. However, after the introduction of some new peach varieties to the high-altitude peach-producing areas in Panxi, the titratable acid content in peach fruit has significantly increased. This study compared the fruit quality indicators of early-ripening peach varieties cultivated in Xide County (a high-altitude peach-producing area) and Longquanyi District (a low-altitude peach-producing area) in Sichuan Province and analyzed the differences in organic acid metabolism by combining primary metabolomic and transcriptomic approaches. The results showed that the 'Zhongtaohongyu' fruit from the high-altitude peach-producing area had a much higher accumulation of malic acid and, accordingly, a significantly higher organic acid content than the other samples. The lower annual average temperature and stronger ultraviolet radiation in high-altitude peach-producing areas may lead to the increased expression of genes (PpNAD-ME1, PpNADP-ME3, and PpPEPC1) in the organic acid synthesis pathway and the decreased expression of genes (PpACO2, PpNAD-MDH2/3/4/5, and PpPEPCK2) in the organic acid degradation pathway in peach fruit, ultimately resulting in the accumulation of more organic acids. Among them, the downregulation of the key genes PpNAD-MDH3/4/5 involved in malic acid metabolism may be the main reason for the higher malic acid accumulation in peach fruit from high-altitude peach-producing areas. Overall, this study elucidates the mechanism by which environmental factors enhance the accumulation of organic acids in peach fruit from high-altitude peach-producing areas from a multi-omics perspective, as well as providing a theoretical basis for screening key genes involved in organic acid metabolism in peach fruit.

Hibiscus: A Multipurpose Medicinal Plant

The continent of Africa made up of numerous countries of which Cameroon is part, is naturally endowed with several plant species which have nutritional and medicinal benefits [1] Hibiscus being one of them. The genus Hibiscus consists of about 300 species that are grown throughout the tropical and subtropical regions of the world [2] such as Hibiscus syriacus, Hibiscus sabdariffa, Hibiscus rosa-sinensis, just to name a few. The various species of this plant grow in different climatic zones and all provide diverse medicinal or therapeutic benefits for the population in these areas in which they thrive. This is because they contain various ingredients or components such as fruit acids [3], antioxidants [4] and polyphenolic compounds [5]. These substances have positive effects in the treatment of ailments as the term “medicinal” implies, which simply means they posess healing properties.

A Smartphone-Enabled Colorimetric Microneedle Sensing Platform for Rapid Detection of Ascorbic Acid in Fruits.

Achieving rapid extraction and detection of analytical solutions from plant tissues to circumvent cumbersome procedures and reduce the dependence on detection instruments remains a challenge. Herein, a colorimetric microneedle integrated platform was developed for the rapid extraction and detection of plant fluids for testing purposes. Colorimetric microneedle patches (CMPs) offer a swift and effective method to swiftly extract and detect ascorbic acid (AA) within 10 min from various fruit crops like mango, nectarine, apple, pear, and kiwifruit, facilitated by a smartphone application. CMPs are constructed for the rapid and sensitive analysis of AA with good linearity amid the range 0.05-25 μM and a low limit of detection of 30 nM. The novel CMPs demonstrate significant potential as a rapid detection platform for AA in plants. CMPs offer significant advantages over traditional ultraviolet spectrophotometry, such as simplified operational procedures and accelerated extraction and detection processes. This establishes robust groundwork for conducting in situ extraction and molecular detection of diverse crops across a spectrum of application scenarios.

Low-cost digital colorimetric sensor for rapid on-site determination of ascorbic acid in vegetable- and fruit-based purees and juices

Ascorbic acid is essential for human health due to its potent antioxidant properties; however, excessive intake can lead to adverse effects. This has created a high demand for simple and cost-effective analytical techniques to determine this analyte outside of laboratory settings for food quality control. In this study, a portable colorimetric sensor was developed for the quantitative on-site determination of ascorbic acid. The technique is based on the reduction of phosphorus heteropoly acid by ascorbic acid, resulting in the formation of a blue-colored product. The heteropoly acid was immobilized on a polymer template in the sensor's indicator zone with menthol used as an environmentally friendly extractant to enhance the device’s stability and extend its shelf life. The colorimetric sensor demonstrated reliable detection with a low limit of detection of 5 mg kg−1, calculated based on a blank test using 3σ. Under optimized conditions, the linear detection range was 15–150 mg kg−1. The disposable sensors were applied to determine ascorbic acid in fruit and vegetable juices and purees for baby food, with recovery rates between 88 % and 110 %. This easy-to-produce and ready-to-use technique presents significant potential for mass on-site screening of ascorbic acid in food samples.

Metabolome and transcriptome reveal the biosynthesis of flavonoids and amino acids in Isatis indigotica fruit during development.

Isatis indigotica Fort. is a famous medicinal plant that is also used as a natural dye and functional vegetable. The characteristics of the I. indigotica fruit during development are largely unknown, information that is essential for the exploitation and seedlings cultivation of I. indigotica. In this study, the biochemical, metabolite characteristics and gene expression profiling of I. indigotica at four developmental stages were investigated. A total of 428 metabolites were detected and categorized into 17 categories. High contents of anthocyanins, especially cyanidin 3-glucoside, might contribute to the purple colouration of I. indigotica fruits. Moreover, dozens of flavonoid components, including taxifolin, quercetin, astragalin and isovitexin 2″-O-beta-D-glucoside, and several other active components were also up-regulated in mature fruits. The abundance of antioxidants might endow a significantly stronger antioxidant activity of mature I. indigotica fruits compared to many other reported species. Enrichment analyses revealed that flavonoid and anthocyanin biosynthesis genes were mostly enriched in up-regulated gene sets during fruit development. The up-regulated structural genes, including IiCHS, IiCHI, IiF3H, IiDFR, IiANS, IiFLS, IiUGT, and transcription factors such as IiMYBs, IibHLHs and IiNACs were identified as candidate regulators of flavonoid and anthocyanin biosynthetic pathway. Furthermore, biosynthesis of amino acids was enriched in all pairwise comparisons of metabolites in fruits at four developmental stages. The differential accumulation of amino acids might result from the differentially expressed genes involved in amino acid biosynthesis. Taken together, these findings provide a comprehensive understanding of metabolite profiling and gene expression patterns in I. indigotica fruit during maturity, which is useful for pharmaceutical extractions and seedling cultivation of I. indigotica.

ZF protein C2H2-71 regulates soluble solids content by inhibiting LIN5 in tomato

Soluble solids content (SSC) plays an important role in determining the flavor of tomato fruits. Tomato fruit SSC has been shown to be transcriptionally regulated via sugar metabolism. Previous studies have been predominantly focused on the role of C2H2-type zinc finger proteins in tomato growth and development. However, the specific regulatory mechanism of C2H2 in the accumulation of soluble solids in tomato fruits are yet to be fully understood. This study involved the selection of eight tomato accessions with varying levels of SSC to study the expression of SlC2H2 family genes in red ripe fruits. The study found that the levels of SlC2H2-71 expressions were significantly reduced in high-SSC accessions compared to low-SSC accessions. The Slc2h2-71 mutant lines were developed using the CRISPR-Cas9 system, leading to elevated levels of soluble solids, fructose, glucose, malic, and citric acids in mature red ripe fruits. However, sucrose content in the edited Slc2h2-71 mutant lines generally decreased. RNA-seq analysis revealed that fruits from the mutant lines had altered expression of genes related to sugar and acid metabolic pathways, which was further confirmed by quantitative real time PCR. Specifically, there was an observed increase in the expression of SlLIN5 encoding the cell wall invertase (CWIN). The yeast one-hybrid (Y1H) assay, 35S::UAS-GUS, dual-luciferase reporter systems and electrophoretic mobility shift assay (EMSA) demonstrated that SlC2H2-71 regulates tomato sugar metabolism by directly binding to the promoter region of SlLIN5, culminating in the repression of its transcriptional activity. The activity of acid invertase in the SlC2H2-71 knock-out lines exhibited a significantly higher level compared to that observed in the control lines. In summary, the regulation of tomato fruit SSC by SlC2H2-71 involves the inhibition of SlLIN5 expression.

Prestorage hot water treatments retard papaya fruit deterioration and enhanced fruit quality in cold storage

Papaya (Carica papaya) fruit has a short shelf life and suffers significant postharvest losses due to climacteric, instant ripening and perishable nature. Pre-storage hot water treatment (HWT) has significant potential to delay decay incidence in horticultural commodities. The present study was designed to evaluate effectiveness of HWT on ‘Red lady’ papaya fruit for minimizing the fruit decay and maintaining the quality during storage. Physiologically mature unripe ‘Red lady’ papaya fruit harvested from a commercial papaya orchard. Selected fruits were treated at three different hot water temperatures (50 °C, 52 °C and 54 °C) along with a control (room temp) for 10 minutes thereafter stored at 12 °C and 85–90% RH for four weeks. Different sensory evaluation, fruit quality scales and enzymatic activities were observed at weekly intervals. Fruit stored after 54 °C HWT showed lower weight loss (4.63%), decay incidence (5.1%) and higher fruit firmness (12.92 N) relative to control. Fruit treated at 52 °C HWT improved the fruit acidity, but total soluble solids decreased than control. The results revealed that ascorbic acid (33.33 mg/100 g), total phenolic contents (35 mg/g FW) total antioxidants (47.50% DPPH inhibition), and antioxidative enzyme activities were improved by 52 °C HWT. It is concluded that pre storage papaya fruit treatment (HWT @ 52 °C) preserves the quality of fruit throughout storage on the other hand at 54 °C HWT helps in decreased fruit decaying. It can be summarized that papaya fruit can be treated with hot water in the range of 52–54 °C to support the fruit shelf life and suppress fruit decay along with maintaining fruit quality. Practical applications: Papaya (Carica papaya L.) is a climacteric fruit which is highly susceptible to fungal attacks after harvest. Due to its perishable nature, it becomes decayed and huge amount of highly nutritious and medicinally important fruit is wasted. Recently people are more concerned about food safety which limits the use of fungicides for controlling the fruit decay in papaya. However, heat treatment has tremendous potential to control microbial decay, and keep food commodities safe from hazardous chemicals. In this study, the hot water treatment has successfully suppressed the fruit decay and maintained fruit quality of papaya in the course of entire period of cold storage. These findings indicated that use of hot water treatment is a practical approach for increasing the shelf life of papaya fruit.

Identification and Functional Analysis of Key Genes Regulating Organic Acid Metabolism in Jujube Fruit

Organic acids are crucial indicators of fruit flavor quality, but the metabolic characteristics and regulatory genes of organic acids during jujube fruit development remain largely unexplored. In this study, the cultivar ‘Heigeda’ with a high organic acid content was used as the experimental material. The organic acid content was quantified, and key candidate genes were identified through transcriptome analysis. The results indicated that malic acid and citric acid were the main organic acid content in jujube fruit and increased gradually with fruit development. Transcriptome analysis identified nine genes associated with malic acid and seven with citric acid, with four genes co-regulating malic acid and citric acid. Functional assays by transient overexpression and silencing of these four genes in the jujube fruits revealed that overexpression significantly upregulated the malic and citric acid content. However, only the silencing of aconitase1 (ZjACO1) and aconitase3 (ZjACO3) significantly downregulated the content of malic and citric acids. Therefore, aconitase1 (ZjACO1) and aconitase3 (ZjACO3) are considered the key genes that regulate the metabolism of citric acid and malic acid in jujube fruits. Our study can enrich the regulation mechanism of the organic acid metabolism of jujube fruit and provide theoretical support for the efficient cultivation of jujube fruit.

Determination of naturally derived propionic, benzoic, and sorbic acids in seafood, meats, and fruits during storage

Propionic acid, benzoic acid, and sorbic acid are common preservatives in processed foods, but their natural concentrations in raw foods are not well understood. In Korea, if propionic acid or benzoic acid exceeds certain levels in processed plant-based foods, manufacturers must prove they are naturally occurring to avoid recalls. This regulation applies to both local and imported products, with non-compliance leading to economic costs and damage to brand reputation. To address this, further research is needed to build a database of naturally occurring preservatives in raw foods and develop food safety standards. This study quantified the levels of propionic, benzoic, and sorbic acids in 37 raw foods stored at different temperatures for 2 weeks, using gas chromatography and high-performance liquid chromatography. The changes in acid concentrations during storage were examined, with preservatives identified by mass spectrometry. Sensory evaluation and total viable count were used to assess spoilage in seafood and meat samples. The matrix effects were evaluated, and the quantification methods were validated using seven food matrices. The intra- and interday accuracies and precisions (% relative standard deviation, %RSD) values met the Codex guidelines. In general, the propionic acid contents of most seafood and meat samples increased during storage, with the highest content being found in manila clams. Interestingly, the fresh sea squirt sample contained a higher propionic acid content (456 mg/kg) than the other samples. However, benzoic acid and sorbic acid were not detected in most samples, with the exception of the jujube and apple samples.

Brinjal (Solanum melongena) rootstocks improve photosynthetic rate, fruit yield and quality parameters in grafted tomato (Solanum lycopersicum)

The experiment was conducted during winter (rabi) seasons of 2021–22 and 2022–23 at ICAR-Indian Institute of Vegetable Research, Varanasi, Uttar Pradesh to study the improvement in yield and quality parameters in tomato (Solanum lycopersicum L.) cultivar using brinjal (Solanum melongena L.) rootstock. Three improved cultivars of tomatoes i.e. Kashi Aman, Kashi Adarsh and Kashi Chayan were grafted over three brinjal rootstocks, IC-111056, IC- 354557, and Surya. Experimental findings revealed that brinjal rootstocks significantly affected photosynthetic traits, root architectures, fruit yields and quality traits of tomatoes. Maximum photosynthetic rate (23.8 µmol/m2/s) and stomatal conductance (492.74 mmol/m2/s) were recorded in Kashi Chayan grafted over Surya rootstock, whereas chlorophyll fluorescence yields (Fv/Fm) was significantly higher in Kashi Aman self-rooted plants (0.452–0.457). Grafting tomato onto brinjal rootstocks significantly enhanced most of the yield traits, such as fruit number, weight, size and yields. Surya + Kashi Chayan graft combination registered an enhancement in number of fruits and yields by 8.65% and 8.4%, respectively over self-rooted Kashi Chayan. Significantly higher root volumes were noticed in two graft combinations i.e. IC-354557 + Kashi Aman (28.53 cm2) and Surya + Kashi Chayan (27.98 cm2), while 63% and 44.5% higher root length density (RLD) were registered in graft combinations IC-354557 + Kashi Chayan and Surya + Kashi Chayan, respectively over self-rooted Kashi Chayan. Fruit quality such as lycopene and ascorbic acid contents were significantly affected in different rootstocks and scions, whereas fruit acidity was unaffected. From the present study it may be conclude that use of brinjal rootstock Surya significantly improved most of the physiological, yield, root architecture and fruit quality in Kashi Chayan tomato cultivars.

Identification of key gene networks controlling organic acid and sugar metabolism during star fruit (Averrhoa carambola) development

The sugar and organic acid content significantly impacts the flavor quality of star fruit, and it undergoes dynamic changes during development. However, the metabolic network and molecular mechanisms governing the formation of sugar and organic acid in star fruit remain unclear. In this study, 23 of 743 components were detected by metabonomic analysis. The highest metabolites contents were organic acids and derivatives. The highest sugar content in the fruit was fructose and glucose, followed by sucrose, which proved that A. carambola is a hexose accumulation type fruit. Genome identification preliminarily screened 141 genes related to glucose metabolism and 67 genes related to acid metabolism. A total of 7,881 unigenes were found in transcriptome data, 6,124 differentially expressed genes were screened, with more up-regulated than down-regulated genes. Transcriptome and metabolome association analysis screened seven core candidate genes related to glucose metabolism and 17 core genes highly related to organic acid pathway, and eight differentially expressed sugar and acid genes were selected for qRT-PCR verification. In addition, 29 bHLHs and eight bZIPs transcription factors were predicted in the glucose metabolism pathway, and 23 MYBs, nine C2H2s transcription factors and one GRAS transcription factor was predicted in the acid metabolism pathway, and transcription factors have both positive and negative regulatory effects on sugar and acid structure genes. This study increased our understanding of A. carambola fruit flavor and provided basic information for further exploring the ornamental and edible values of star fruit.

Phytohormonal dynamics in the abscission zone of Korla fragrant pear during calyx abscission: a visual study.

Phytohormones play a crucial role in regulating the abscission of plant organs and tissues. In this study, the ultrastructure of the sepals of Korla fragrant pears was observed using a transmission electron microscope, and high-performance liquid and gas chromatography were used to analyze the dynamic changes of phytohormones in the abscission zone during the calyx abscission process of Korla fragrant pears, and mass spectrometry imaging was applied to ascertain the spatial distribution of phytohormones. The results revealed that the mitochondria in the abscission zone of the decalyx fruits were regularly distributed around the cell wall, and the chloroplasts were moderately present. In contrast, in the persistent calyx fruit, the corresponding parts of the abscission zone showed a scattered distribution of mitochondria within the cells, and there was a higher number of chloroplasts, which also contained starch granules inside. Mass spectrometry imaging revealed that ABA was enriched in the abscission zone of the decalyx fruit, and their ionic signal intensities were significantly stronger than those of the persistent calyx fruit. However, the ionic signal intensities of Indole-3-acetic acid (IAA) and Gibberellin A3 (GA3) of the persistent calyx fruit were significantly stronger than those in the abscission zone of the decalyx fruit and were concentrated in the persistent calyx fruit. 1-Aminocyclopropanecarboxylic Acid (ACC) did not show distinct regional distribution in both the decalyx and persistent calyx fruits. Furthermore, before the formation of the abscission zone, the levels of IAA, GA3, and zeatin (ZT) in the abscission zone of the decalyx fruits were significantly lower than those in the persistent calyx fruits by 37.9%, 57.7%, and 33.0%, respectively, while the levels of abscisic acid (ABA) and ethylene (ETH) were significantly higher by 21.9% and 25.0%, respectively. During the formation of the abscission zone, the levels of IAA, GA3, and ZT in the abscission zone of the decalyx fruits were significantly lower than those in the persistent calyx fruits by 41.7%, 71.7%, and 24.6%, respectively, while the levels of ABA and ETH were significantly higher by 15.2% and 80.0%, respectively. After the formation of the abscission zone, the levels of IAA and GA3 in the abscission zone of the decalyx fruits were lower than those in the persistent calyx fruits by 20.8% and 47.8%, respectively, while the levels of ABA and ETH were higher by 271.8% and 26.9%, respectively. In summary, during the calyx abscission process of Korla fragrant pears, IAA and GA3 in the abscission zone inhibited abscission, while ABA and ETH promoted calyx abscission. These research findings enrich the understanding of the regulatory mechanism of plant hormones on calyx abscission and provide a theoretical basis for the study of exogenous plant growth regulators for regulating calyx abscission in Korla fragrant pear.

Bioactives in Berry Fruits with Emphasis on In Vitro Bioaccessibility for Human Nutrition

This study aimed to investigate the bioaccessibility and biostability of carotenoids, vitamin E isomers, and individual polyphenolic compounds after the in vitro gastrointestinal digestion of two types of berries (raspberry and blackberry fruits). The results of the polyphenols analysis showed that raspberry fruits contained higher concentrations of hydroxybenzoic acids, hydroxycinnamic acids, flavanols, and flavonols compared to blackberry fruits, but exhibited the lowest bioaccessibility values for all the studied polyphenol classes. Ellagic acid represented 13.63% and 2.65% of the hydroxybenzoic acids in raspberry and blackberry fruits. The hydroxybenzoic acids exhibited the highest bioaccessibility index in the intestinal phase of both types of berries, and gallic acid emerged as one of the most bioaccessible phenolic compounds. The bioaccessibility of carotenoids ranged between 15.7 and 17.30% for lutein, 5.52 and 7.56% for astaxanthin, and 7.85 and 9.93% for canthaxanthin, with elevated values being observed in raspberry fruits. Although vitamin E and carotenoids follow a similar path for absorption, the bioaccessibility of vitamin E isomers was higher than that of carotenoids, with γ-tocopherol being the most bioaccessible isomer in both raspberries and blackberries. Knowing the bioaccessibility of food constituents during digestion is crucial, as the potential effectiveness of bioactives for human health largely depends on the bioavailability of these molecules.

Validated high performance thin layer chromatographic method for simultaneous quantification of betulinic acid, β-sitosterol and lupeol in fruits, leaves, root bark and stem bark of Dillenia indica Linn

AbstractDillenia indica is one of the important medicinal plants and is extremely popular in many systems of medicine including ayurvedic, homeopathic, and siddha. Traditionally, different parts of this plant have been used to treat cancer, wound healing, diabetes, diarrhea, bone fractures, abdominal pains, cuts and burns. In the present study, a simple, precise, accurate and validated high performance thin layer chromatographic (HPTLC) method was developed for simultaneous estimation of three pharmaceutically active compounds i.e., betulinic acid (BE), β-sitosterol (BT) and lupeol (LP) in fruits, leaves, root bark and stem bark of D. indica. Standards and plant samples were applied on TLC aluminum plate precoated with 0.2 mm layer of silica gel 60F254. The plate was run in a twin glass chamber comprising toluene:methanol:chloroform (8:1:1, v/v/v) as a mobile phase which resulted in better separation of compounds. The plates were immersed in anisaldehyde-sulfuric reagent and then heated at 105 °C for 5 min in CAMAG TLC plate heater for appearance of bands. Densitometric scanning was performed at λmax = 525 nm using tungsten light source in CAMAG TLC Scanner4 armed with WinCATS software. RF values of BE, BT and LP standards and those of plant samples were found to be 0.38 ± 0.01, 0.54 ± 0.01 and 0.65 ± 0.02 respectively. The method was further validated by following the International Conference of Harmonization (ICH) guidelines. For BE, BT and LP, the linear regression data for the calibration plots revealed a satisfactory linear association with correlation coefficients (r2) = 0.9736, 0.9989 and 0.9957, respectively. Linear ranges for BE, BT and LP were 2,000–6,000 ng/band, 200–1,000 ng/band, and 200–600 ng/band respectively. Accuracy of the method was assessed by recovery study conducted at three different levels with the average recovery of 99.19, 99.69 and 100.95% for BE, BT and LP, respectively. The results exhibited the highest content of BE (0.148 ± 0.01%), BT (0.031 ± 0.01%) and LP (0.047 ± 0.01%) in stem bark. The developed method will be useful for routine and quality control analysis of fruits, leaves, root bark and stem bark of D. indica species.

Low soil pH enhances fruit acidity by inhibiting citric acid degradation in lemon (Citrus lemon L.)

Fruit acidity significantly influences fruit flavor, but the specific impact of soil pH on fruit acidity remains unclear. This study investigated the effects of various soil pH levels on fruit acidity and citric acid (CA) metabolism in lemon (Citrus limon L.). High soil pH (pH 8) decreased total soluble solids concentrations in lemon fruits, while low soil pH (pH 4) increased titratable acid and CA concentrations. Although low soil pH reduced the synthesis of CA due to the decreased citrate synthase and phosphoenolpyruvate carboxylase activities, the elevated fruit acidity under low soil pH conditions is not directly related to CA synthesis. Instead, low soil pH was found to suppress the activity of cytosolic aconitase (Cyt-ACO), an iron-dependent enzyme, indicating a potential role for CA degradation inhibition in low soil pH-induced CA accumulation. Furthermore, low soil pH significantly reduced cytosolic iron (Cyt-Fe) concentration, which was positively correlated with Cyt-ACO activity. In conclusion, low soil pH contributes to increasing fruit acidity in lemon, partially by inhibiting CA degradation due to the reduced Cyt-Fe concentrations. Our work unravels the influence of soil pH on CA accumulation and provides important clues for modulating CA levels through microelement fertilization in citrus.

Enhancing sweet cherry resilience to spring frost and rain-induced cracking with pre-harvest melatonin treatments

Sweet cherry producers annually confront climatic challenges such as spring frost and fruit cracking. This vulnerability arises primarily from spring frost during bloom or cracking at critical maturity stages during persistent rainfall. With changing climate patterns, innovative strategies are essential to mitigate these adversities. Foliar applications of melatonin (MT) at 0, 0.01, 0.05 and 0.1 mM were tested on the ‘Prime Giant’ and ‘Sweetheart’ cultivars over four different production cycles (2020–2023) to evaluate the effect on frost resilience on flower buds and fruit cracking reduction. MT-treated flower buds showed reduced malondialdehyde content and increased fruit set in most seasons, reducing their vulnerability to extreme weather events. In addition, MT consistently decreased sweet cherry cracking incidence across all studied seasons, indicating a strong effect between the fruit ripening stage and susceptibility to fruit cracking, which was cultivar dependent. Quality parameters at harvest, including fruit firmness, and colour at harvest, were either delayed or unaffected in MT-treated fruits compared with controls. However, other ripening parameters were stimulated by pre-harvest MT applications in several growing cycles, such as total soluble solids, which slightly reduced total acidity in MT-treated fruits. In summary, pre-harvest MT treatments can be a promising strategy for climate change adaptation and stress mitigation, potentially increasing sweet cherry production under extreme weather conditions.

Distinctive acidity in citrus fruit is linked to loss of proanthocyanidin biosynthesis

The distinctive acidity of citrus fruit is determined by a regulatory complex of MYB and bHLH transcription factors together with a WDR protein (MBW complex) which operates in the unique juice vesicles of the fruit. We describe a mutation affecting the MYB protein, named Nicole, in sweet orange and identify its target genes that determine hyperacidification, specifically. We propose that the acidity, typical of citrus fruits, was the result of a loss of the ability of Nicole to activate the gene encoding anthocyanidin reductase, an enzyme essential for the synthesis of proanthocyanidins, which are absent in citrus fruit.

Combined application of the endophyte Bacillus K1 and sodium dehydroacetate alleviates postharvest gray mold in grapes

Botrytis cinerea, which causes postharvest gray mold, is a primary pathogen that limits grape shelf-life and consumption and causes substantial yield loss worldwide. The combined use of biocontrol agents and food additives has attracted increasing interest. The effects of combined treatment with the endophyte Bacillus subtilis K1 and sodium dehydroacetate (SD) on the occurrence of gray mold and maintenance of grape fruit quality were studied. Treatment with a K1 suspension (1 × 108 CFU/ml) combined with 0.32 g/L SD resulted in markedly improved control of B. cinerea on grapes. The disease incidence and severity in the groups treated with K1 alone or in combination with SD were significantly lower than those in the control groups (P < 0.05) when the mixtures were applied 2 h after pathogen inoculation. Moreover, application of the mixture could maintain the appearance, firmness, total soluble solid (TSS) content and titratable acidity (TA) of grape fruit. Furthermore, the combination triggered increases in the activities of defense-related enzymes such as peroxidase (POD), phenylalanine ammonia lyase (PAL), catalase (CAT), superoxide dismutase (SOD) and polyphenol oxidase (PPO). Additionally, it could increase the vitamin C content. Thus, appropriate combinations of biocontrol agents and chemical reagents can provide effective protection against postharvest decay.