Fire blight cases in Almaty Region of Kazakhstan in the proximity of wild apple distribution area.

Fire blight caused by Erwinia amylovora reached Kazakhstan in 2008. Here, the disease poses a threat not only to agricultural production of apples and pears, but also to the forests of wild Malus sieversii, the progenitor of most domesticated apple varieties worldwide. In the period 2019-2021, the spread of fire blight in the growth area of wild apples was limited by the weather conditions. In 2022, late spring and early summer were characterized by increased rainfall and moderate temperatures favorable for the disease. The goal of this study was to monitor the distribution of fire blight in private households and small orchards in the zones adjacent to wild apple distribution areas. A total of 91 samples with fire blight-compatible symptoms were collected from cultural apples (68), wild apple (10), pear (5), hawthorn (7), and quince (1) in south-eastern and eastern Kazakhstan, resulting in 21 isolates (one from pear, one from quince, and 19 from apple) of E. amylovora. All isolates belonged to the archetypal CRISPR genotype A. Considering the relative proximity of the infections to the forests of wild M. sieversii, additional measures for fire blight control and prevention will have to be implemented, including state monitoring of the wild apple forests for disease symptoms and awareness campaigns for specially protected natural territories that safeguard M. sieversii, as well as for local pomaceous-fruit growing communities.

MdNAC5: a key regulator of fructose accumulation in apple fruit.

The sweetness of apple fruit is a key factor in the improvement of apple varieties, with fructose being the sweetest of the soluble sugars, playing a crucial role in determining the overall sweetness of the apple. Therefore, uncovering the key genes controlling fructose accumulation and deciphering the regulatory mechanisms of fructose are vitally important for the improvement of apple varieties. In this study, through BSA-seq and transcriptome analysis of the 'Changfu 2' × 'Golden Delicious' F1 hybrid population, MdNAC5 was identified as a key regulatory gene for fructose content. MdNAC5 was shown to significantly influence fructose accumulation in both apples and tomatoes. Furthermore, we conducted a detailed identification of sugar transporters and metabolic enzymes in apples, discovering that MdNAC5 can enhance fructose accumulation in vacuoles and the conversion of sucrose to fructose by binding to and activating the promoters of the vacuolar sugar transporter MdTST2 and the neutral invertase MdNINV6. Additionally, MdNAC5 regulated the MdEIN3.4-MdSWEET15a module, strengthening the unloading of sucrose in the phloem of the fruit. Our results reveal a new mechanism by which MdNAC5 regulates fructose accumulation in apples and provide theoretical foundations for improving apple sweetness through genetic modification.

Smart watch applications in atrial fibrillation detection: Current state and future directions.

INTRODUCTION: Atrial fibrillation (Afib) is a prevalent chronic arrhythmia associated with severe complications, including stroke, heart failure, and increased mortality. This review explores the use of smartwatches for Afib detection, addressing the limitations of current monitoring methods and emphasizing the potential of wearable technology in revolutionizing healthcare. RESULTS/OBSERVATION: Current Afib detection methods, such as electrocardiography, have limitations in sensitivity and specificity. Smartwatches with advanced sensors offer continuous monitoring, improving the chances of detecting asymptomatic and paroxysmal Afib. The review meticulously examines major clinical trials studying Afib detection using smartwatches, including the landmark Apple Heart Study and ongoing trials such as the Heart Watch, Heartline, and Fitbit Heart Study. Detailed summaries of participant numbers, smartwatch devices used, and key findings are presented. It also comments on the cost-effectiveness and scalability of smartwatch-based screening, highlighting the potential to reduce healthcare costs and improve patient outcomes. CONCLUSION/RELEVANCE: The integration of wearable technology into healthcare can lead to earlier diagnosis, improved patient engagement, and enhanced cardiac health monitoring. Despite ethical considerations and disparities, the potential benefits outweigh the challenges. This review calls for increased awareness, collaboration with insurance companies, and ongoing research efforts to optimize smartwatch accuracy and encourage widespread adoption of Afib detection. With insights from major trials, this review serves as a comprehensive reference for healthcare professionals and policymakers, guiding future strategies in the early diagnosis and management of atrial fibrillation.

An asymptomatic geminivirus activates autophagy and enhances plant defenses against diverse pathogens.

Plant viral diseases cause great losses in agricultural production. Virus cross-protection is a strategy in which a mild virus is employed to shield plants against subsequent infections by severe viral strains. However, this approach is restricted to protection against the same viruses. In this study, we observed that pre-inoculation with apple geminivirus (AGV) reduced the accumulation of secondarily infected heterologous viruses, such as cucumber mosaic virus, potato virus X, and tobacco mosaic virus in Nicotiana benthamiana, tomato, and pepper plants. Transcriptional expression analysis showed that autophagy-related genes were transcriptionally up-regulated upon AGV inoculation at an early stage of infection. Accordingly, autophagic activity was observed to be elevated following AGV infection. Interestingly, AGV accumulation was reduced in autophagy-deficient plants, suggesting that autophagy activation promotes AGV infection in the plant. Moreover, pre-inoculation with AGV provided cross-protection against infection with a phytopathogenic bacterium (Pseudomonas syringae) and fungus (Botrytis cinerea) in Nicotiana species. In summary, our study showed that AGV, an asymptomatic virus, could protect plants against severe viral, fungal, and bacterial diseases to some extent through the activation of autophagy pathways, highlighting its potential as a biocontrol agent for managing a wide range of plant crop diseases in the field.

An integrated approach for assessing the health risks of pesticide residues on apple: From field dynamics to human exposure.

The apple (Malus domestica), a cultivated fruit extensively grown in temperate regions worldwide, is abundant in nutrients and phytochemicals that promote health. However, the application of pesticides in apple cultivation raises significant concern regarding their influence on food safety. This study investigated the dynamic behavior of five pesticides, including chlorpyrifos, imidacloprid, acetamiprid, carbendazim, prochloraz, in apple trees, utilizing both field experiments and predictive modeling to analyze their distribution, transfer, and degradation patterns. Results from the field experiment revealed that at harvest, the residue levels of the five pesticides on apple were below international and national maximum residue limits. The dynamiCROP modeling results, corresponding to the field trial findings, demonstrated that these pesticides exhibited comparable dissipation patterns across various environmental compartments. The primary sources of pesticides in apples were the air and the fruit surface up to 10 days after application, while the soil and leaf surface became the main sources over time. The transferred pesticides adhered to the apple fruits at varying rates and persist therein. Choosing pesticides with lower impact scores helped reduce the impacts on human health and the environment. The assessment of health risks associated with consuming apples containing pesticide residues suggested that the impact on human health is acceptable. These findings were crucial for apple producers, as they enable the optimization of pesticide application timing to ensure compliance with food safety standards and help improve pesticide management strategies in agriculture. This study is essential for minimizing the environmental impact of pesticides and enhancing sustainable agricultural practices.

Oxygen saturation measurement in cyanotic heart disease with the Apple watch.

BACKGROUND: Accurate measurement of transcutaneous oxygen saturation is important for the assessment of cyanosis in CHD. Aim of this study was the evaluation of a supplementary transcutaneous oxygen saturation measurement with an Apple watch® in children with cyanotic heart disease. MATERIAL AND METHODS: During a six-minute walk test, measurement of transcutaneous oxygen saturation was performed simultaneously with an Oximeter (Nellcor, Medtronic, USA) and an Apple watch® Series 7 (Apple inc, USA) in 36 children with cyanotic heart disease. RESULTS: Median age was 9.2 (IQR 5.7-13.8) years. Transcutaneous oxygen saturation measurement with the Apple watch® was possible in 35/36 and 34/36 subjects before and after six-minute walk test. Children, in whom Apple watch® measurement was not possible, had a transcutaneous oxygen saturation < 85% on oximeter. Before six-minute walk test, median transcutaneous oxygen saturation was 93 (IQR 91-97) % measured by oximeter and 95 (IQR 93-96) % by the Apple watch®. After a median walking distance of 437 (IQR 360-487) m, transcutaneous oxygen saturation dropped to 92 (IQR 88-95, p < 0.001) % by oximeter and to 94 (IQR 90-96, p = 0.013) % measured with the Apple watch®. CONCLUSION: In children with mild cyanosis measurement of transcutaneous oxygen saturation with an Apple watch® showed only valid results if transcutaneous oxygen saturation was > 85%, with higher values being measured with the smart watch. In children with moderate or severe cyanosis transcutaneous oxygen saturation, measurement with the Apple watch® was not reliable and cannot be recommended to monitor oxygen saturation at home.

Bioaccumulation and toxicological effects of dietborne arsenic exposure on the apple snail (Pomacea canaliculata).

An eight-compartment physiologically based pharmacokinetic (PBPK) model was used to simulate the bioaccumulation and distribution of arsenic (As) within the apple snail (Pomacea canaliculata) following the ingestion of As-contaminated lettuce. The bioaccumulation results revealed that the shell contained the majority (67.21 %) of the total As content, with the liver and the head-foot containing approximately 11.14 % and 10.45 % of the total As content in the snail, respectively. Modeling quantified the process of intestine-stomach absorption of dietborne As and revealed its crucial role in the subsequent distribution of As within the body. The liver is the primary metabolic site, whereas the shell is the primary storage site. Exposure to dietborne As leads to pronounced physiological and biochemical alterations in apple snails. Total protein levels decreased by 24.06 %, superoxide dismutase (SOD) activity decreased by 24.43 %, malondialdehyde (MDA) content increased by 47.51 %, glutathione (GSH) content decreased by 46.99 %, and glutathione S-transferase (GST) activity decreased by 42.22 %. Furthermore, the subcellular-level results indicated that dietborne As exposure altered subcellular distribution in the liver. Additionally, dietborne As exposure significantly reduced the abundance of gut microbiota in apple snails.

A novel RAV transcription factor from pear interacts with viral RNA-silencing suppressors to inhibit viral infection.

In plants, RNA silencing constitutes a strong defense against viral infection, which viruses counteract with RNA-silencing suppressors (RSSs). Understanding the interactions between viral RSSs and host factors is crucial for elucidating the molecular arms race between viruses and host plants. We report that the helicase motif (Hel) of the replicase encoded by apple stem grooving virus (ASGV)-the main virus affecting pear trees in China-is an RSS that can inhibit both local and systemic RNA silencing, possibly by binding double-stranded (ds) siRNA. The transcription factor related to ABSCISIC ACID INSENSITIVE3/VIVIPAROUS1 from pear (PbRAV1) enters the cytoplasm and binds Hel through its C terminus, thereby attenuating its RSS activity by reducing its binding affinity to 21- and 24-nt ds siRNA, and suppressing ASGV infection. PbRAV1 can also target p24, an RSS encoded by grapevine leafroll-associated virus 2 (GLRaV-2), with similar negative effects on p24's suppressive function and inhibition of GLRaV-2 infection. Moreover, like the positive role of the PbRAV1 homolog from grapevine (VvRAV1) in p24's previously reported RSS activity, ASGV Hel can also hijack VvRAV1 and employ the protein to sequester 21-nt ds siRNA, thereby enhancing its own RSS activity and promoting ASGV infection. Furthermore, PbRAV1 neither interacts with CP, an RSS encoded by grapevine inner necrosis virus, nor has any obvious effect on CP's RSS activity. Our results identify an RSS encoded by ASGV and demonstrate that PbRAV1, representing a novel type of RAV transcription factor, plays a defensive role against viral infection by targeting viral RSSs.

Sustainable Jam with Apple Pomace: Gelling, Rheology, and Composition Analysis.

Fruit juice processing can generate significant waste, but efficiently repurposing some of its byproducts not only reduces environmental impact but also adds value, thereby enhancing sustainability in the food industry. This work assesses the use of hydrocolloids in jam preparation and the influence of time and temperature on gelation in the presence of apple pomace. The effects of different processing conditions were analyzed using response surface methodology. Viscosity, elastic modulus (G'), viscous modulus (G″), and firmness were measured. Results indicated that both time and temperature significantly improved rheological and textural properties. The optimal conditions (35.6 min and 84.2 °C) yielded a viscosity of 3.66 × 104 ± 4.49 × 102 Pa·s and a G' at 1 Hz of 2596 ± 128 Pa. The final product exhibited the desirable texture, was free of added sugars, had low lipid content, and retained its bioactive compounds. Applying apple pomace in the formulation allows a more efficient hydrocolloid system, promotes a circular economy, and combats food waste.

New insights into the relationship between optical response and physicochemical properties in apple flesh: Hyperspectral microscope imaging technology.

Hyperspectral microscope imaging (HMI) technique was employed to assess the changes in physicochemical parameters and microstructure of 'Golden Delicious' apples flesh during storage. Four regions of interest (ROIs), including whole-cell ROI, intercellular space ROI, cytoplasm ROI, and cell wall ROI were investigated to assess their relationships with physicochemical parameters. Different ROIs presented similar vibrational profiles, but with slight differences in spectral intensity, especially in the range of 800-1000 nm. Spectral angle mapper (SAM) was applied to the HMI of apple tissues at different storage stages to clearly show the structural changes of parenchyma cells, while principal component analysis (PCA) could highlight the distribution of sugars, water and pigments in apple flesh at the cellular scale. Simultaneously with the degradation of acid-soluble pectin (ASP), middle lamella dissolution and increased intercellular space were observed using SEM and TEM. Single feature variables were used to construct linear models based on pearson correlation analysis, with R2 of 0.96 for moisture at 982 nm, 0.85 for water-soluble pectin (WSP) at 420 nm, 0.82 for L* at 946 nm, 0.77 for soluble solids content (SSC) at 484 nm, and 0.66 for firmness at 490 nm. This work demonstrated the great potential of HMI technology as a fast, accurate and efficient solution for assessing the quality of 'Golden Delicious' apples.

Unveiling a Sour Truth: Acute Pancreatitis Linked to Apple Cider Vinegar Supplement.

Acute pancreatitis, a common gastrointestinal ailment in the United States, often lacks a clear etiology, with one-third of cases deemed idiopathic. We discuss an 84-year-old woman with acute pancreatitis possibly linked to a recently introduced weight loss supplement containing apple cider vinegar. Literature review unveils scant data regarding the risks of acute pancreatitis associated with less rigorously studied and regulated supplements, such as apple cider vinegar products. Considering the morbidity and financial burden associated with acute pancreatitis, there is a pressing need to report and disseminate awareness of diverse etiologies, encompassing drug and supplement-induced cases. This case report endeavors to address this need.

Determination of leaf nitrogen content in apple and jujube by near-infrared spectroscopy.

The nitrogen content of apple leaves and jujube leaves is an important index to judge the growth and development of apple trees and jujube trees to a certain extent. The prediction performance of the two samples was compared between different models for leaf nitrogen content, respectively. The near-infrared absorption spectra of 287 apple leaf samples and 192 jujube leaf samples were collected. After eliminating the outliers by Mahalanobis distance method, the remaining spectral data were processed by six different preprocessing methods. BP neural network (BP), random forest regression (RF), least partial squares (PLS), K-Nearest Neighbor (KNN), and support vector regression (SVR) were compared to establish prediction models of nitrogen content in apple leaves and jujube leaves. The results showed that the determination coefficient (R2), root mean square error (RMSE) and residual prediction deviation (RPD) of the models established by different combined pretreatment methods were compared among the five methods. Compared with the performance of the other four models, the modeling method of SG + SD + CARS + RF was suitable for the prediction of nitrogen content in apple leaves, and its modeling set R2 was 0.85408, RMSE was 0.082188, and RPD was 2.5864. The validation set R2 is 0.75527, RMSE is 0.099028, RPD is 2.1956. The modeling method of FD + CARS + PLS was suitable for the prediction of nitrogen content in jujube leaves. The modeling set R2 was 0.7954, RMSE was 0.14558, and RPD was 2.4264; the validation set R2 is 0.81348, RMSE is 0.089217, and RPD is 2.4552.In the prediction modeling of apple leaf nitrogen content in the characteristic band, the model quality of RF was better than the other four prediction models. The model quality of PLS in predictive modeling of nitrogen content of jujube leaves in characteristic bands is superior to the other four predictive models, These results provide a reference for the use of near-infrared spectroscopy to determine whether apple trees and jujube trees are deficient in nutrients.

γ-Aminobutyric acid mediated by MdCBF3- MdGAD1 mitigates low temperature damage in apple.

Low temperatures can seriously affect apple yield and can also cause chilling injury to apple fruit. γ-aminobutyric acid (GABA) plays an important role in improving plant stress resistance. Some studies have reported that GABA can improve cold resistance in plants, only through exogenous treatment; however, the molecular mechanism of its resistance to low temperature is still unknown. This result suggested that exogenous GABA treatment of both apple seedlings and fruit could improve the resistance of apple to low temperatures. MdGAD1, a key gene involved in GABA synthesis, was overexpressed in tomato plants and apple callus to improve their cold tolerance. Both yeast one-hybrid and luciferase assay showed that MdCBF3 could bind to the MdGAD1 promoter to activate its expression and promote GABA synthesis. These results revealed a molecular mechanism utilizing the MdCBF3-MdGAD1 regulatory module that can enhance cold resistance by increasing endogenous GABA synthesis in apple.

Apple polyphenols prevent patulin-induced intestinal damage by modulating the gut microbiota and metabolism of the gut-liver axis.

Patulin (PAT), a foodborne toxin, causes severe intestinal damage. To mitigate this health threat, mice were pretreated with apple polyphenols (AP) in their drinking water (0.01 % and 0.05 %) for eight weeks, followed by exposure to PAT during the last two weeks. Subsequently, histopathological and biochemical evaluations of intestinal tissues were conducted, alongside assessments of alterations in gut microbiota, colonic content metabolome, and hepatic metabolome. Consequently, AP alleviated PAT-induced villus and crypt injury, mucus depletion, GSH level decline, GSH-Px and SOD activity reduction, and MPO activity elevation. Notably, AP counteracted PAT-mediated microbiota disruptions and promoted the abundance of beneficial bacteria (Dubosiella, Akkermansia, Lachnospiraceae, and Lactobacillus). Furthermore, AP counteracted PAT-induced metabolic disorders in the colonic contents and liver. Ultimately, AP prevented intestinal injury by regulating the gut microbiota and amino acid, purine, butanoate, and glycerophospholipid metabolism in the gut-liver axis. These results underscore the potential of AP to prevent foodborne toxin-induced intestinal damage.

Molluscicidal activity and biochemical impacts of borrelidins against an aquatic invasive snail Pomacea canaliculata for crop protection.

The invasive golden apple snail Pomacea canaliculata is one of the devastating threats to aquatic ecosystems and wetland agriculture worldwide. Macrolides from microbes display various advantages over other compounds in controlling snails. However, emergence of antibiotic-resistant phenotypes against certain macrolides in the field appeals for exploring more effectively molluscicidal macrolides. Here, two borrelidins, borrelidin BN1 and BN2, from the extract of a Streptomyces strain fermentation were evaluated for molluscicidal potential against P. canaliculata using both immersion and contact bioassay methods. Borrelidin BN1 (borrelidin A) presented a significant molluscicidal activity comparable to the chemical pesticide metaldehyde, and had a much lower median lethal concentration value (LC50, 522.984 µg·ml-1) than avermectin B1 at 72 h of contact-killing treatment. Snail growth was inhibited by borrelidin BN1 more than by metaldehyde at sublethal concentrations, consistent with responses of key biochemical parameters. Exposure to borrelidin BN1 decreased the activity of acetylcholinesterase (AChE), glutathione S-transferase (GST), aspartate aminotransferase (AST), alanine aminotransferase (ALT) as well as the levels of energy reserves and sex steroids in snail tissues, while increased the activity of superoxide dismutase (SOD), catalase (CAT), lactate dehydrogenase (LDH) and the level of lipid peroxidation (LPO). Further application assay confirmed that borrelidin BN1 protected crop plant Zizania latifolia from P. canaliculata damage via suppressing snail population density. These findings suggest great potential of borrelidin BN1 as a molluscicide. Additionally, its higher activity than the stereoisomeric borrelidin BN2 (borrelidin F) implied better molluscicidal borrelidins could be acquired through structural optimization.

Rapid Identification of Phytotoxins Produced by Glomerella cingulata Using High-Resolution Mass Spectrometry-Based Qualification, Targeted Structural Confirmation and Their Characteristics Investigation.

Glomerella cingulata is a pathogenic fungus that can cause apple Glomerella leaf spot (GLS), a new and destructive apple disease in China. Phytotoxins are important factors closely related to the disease process, but there is still no report on the phytotoxins of G. cingulata. The aim of this study was to rapidly identify the phytotoxins of this pathogen using a strategy of HRMS-based preliminary qualification, followed by targeted structure confirmation and also investigation of phytotoxicity characteristics. First, the crude toxin sample was directly analyzed by the UPLC-HRMS and GC-MS, and the data were processed to screen for possible phytotoxic compounds using MS library and the phytotoxicity-related literature. The reference standards of credible phytotoxic compounds were then subjected to targeted structure validation (signal comparison between standards and compounds in crude toxin via HPLC-DAD, UPLC-MS/MS, and GC-MS), and also the phytotoxicity assay. The results confirmed six phytotoxins produced by G. cingulata, namely 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), 2,5-bis(hydroxymethyl)furan (BHMF), 2-furoic acid (FA), 2,3-butanediol, trans-aconitic acid (TAA), and cis-aconitic acid (CAA). Of these, HMFCA and TAA exhibited greater phytotoxicity. Main characteristics: All of them were non-host-selective toxins, and toxins were synergistically phytotoxic to the host when mixed. BHMF, HMFCA, FA, TAA, and CAA could be commonly produced by all tested strains, and their phytotoxicity can be significantly inhibited or even eliminated at high temperatures or high pH. The elucidation of the phytotoxins of G. cingulata in this work could provide information on the pathogenesis and control of apple GLS.

Utilization and Effect of Apple Pomace Powder on Quality Characteristics of Turkey Sausages.

The present study was conducted to develop turkey sausages by incorporating freeze-dried apple pomace (FDAP) at 3, 5, and 8% by replacing turkey breast meat. Three sausage formulations and the control of turkey sausages were subjected to physicochemical properties: proximate content, water-holding capacity (WHC), cooking yield, pH, color, textural parameters, antioxidant activity, and microbiological and sensory properties. The parameters were analyzed during storage from days 0 to 7. The addition of FDAP to turkey sausages resulted in a significant (p ≤ 0.05) decrease in moisture and protein contents, whereas no significant difference was found in fat and ash contents. The increased incorporation of FDAP resulted in decreased pH, cooking loss, lightness, redness, and yellowness in turkey sausages, whereas an increase in total phenolic content, fiber content, ABTS, and DPPH values was observed. FDAP, as a low-cost source of valuable phenolic content, strongly inhibited microorganism growth during the storage of turkey sausages. The sensory scores of turkey sausages containing 3% FDAP for other sensory traits, such as flavor, texture, juiciness, tenderness, and overall acceptability, were comparable to those of the control. Scores for sensory attributes declined significantly with a further increase in FDAP in turkey sausages. It is concluded that turkey sausages with very good acceptability can be prepared by incorporating freeze-dried apple pomace each at a 3% level.

Validation of Optimization Methods for Sensory Characteristics Using Rate-All-That-Apply and Intensity Scales: A Case Study of Apple Juice.

Preference mapping (PM), which integrates consumer and descriptive analysis (DA) data to identify attributes that drive consumer liking, is widely employed for product optimization. However, a limited group of trained panelists cannot fully represent the diverse consumer population or reliably predict market acceptance. Consequently, numerous studies have explored consumer-based methodologies as potential replacements for DA; however, their efficacy for product optimization remains limited. Therefore, this study was conducted to explore the potential of optimizing products using two consumer-based profiling techniques as alternatives to DA in external preference mapping (EPM). Overall, 8 trained panelists profiled 12 sensory attributes of 7 commercial apple juices, whereas 160 consumers assessed the same attributes using a 5-point rate-all-that-apply (RATA) scale and a 10 cm intensity scale (IS). Danzart's response surface ideal modeling was employed to identify optimal products using DA, RATA, and IS through barycenter calculations, focusing on three products from the original consumer test located around the group ideal point. Overall, the ideal products of the group and their sensory characteristics were successfully identified using DA, RATA, and IS. Regarding sensory intensities, high concordance was observed between DA and RATA (Rv = 0.92) and between DA and IS (Rv = 0.91). Overall liking and preference scores for products mixed at the optimal ratio for each method showed no significant differences in preference among the ideal products identified using DA, RATA, and IS. This study suggests that both RATA and IS are viable alternatives to DA in EPM for identifying ideal sensory profiles.

Effects of Water and Nitrogen Regulation on Apple Tree Growth, Yield, Quality, and Their Water and Nitrogen Utilization Efficiency.

Apple tree productivity is influenced by the quantity of water and nutrients that are supplied during planting. To enhance resource utilization efficiency and optimize yields, a suitable strategy for supplying water and nitrogen must be established. A field experiment was conducted using a randomized block group design on five-year-old apple trees in Ningxia, with two irrigation lower limit levels (55%FC (W1) and 75%FC (W2)) and four N application levels (0 (N1), 120 (N2), 240 (N3), and 360 (N4) kg·ha-1). Our findings showed that leaf N content increased with a higher irrigation lower limit, but the difference was not statistically significant. However, the leaf N content significantly increased with increasing N application. The growth pattern of new shoots followed logistic curve characteristics, with the maximum new shoot growth rate and time of new shoot growth being delayed under high water and high nitrogen treatments. Apple yield and yield components (weight per fruit and number of fruits per plant) were enhanced under N application compared to no N application. The maximum apple yields were 19,405.3 kg·ha-1 (2022) and 29,607 kg·ha-1 (2023) at the N3 level. A parabolic relationship was observed between apple yield and N application level, with the optimal range of N application being 230-260 kg⸱ha-1. Apple quality indicators were not significantly affected by the irrigation lower limit but were significantly influenced by N application levels. The lower limit of irrigation did not have a significant impact on the quality indicators of the apples. Water and N utilization efficiencies improved with the W2 treatment at the same N application level. A negative relationship was observed between the amount of nitrogen applied and the biased productivity of nitrogen fertilizer. The utilization of nitrogen fertilizer was 127.6 kg·kg-1 (2022) and 200.3 kg·kg-1 (2023) in the W2N2 treatment. The apple yield was sustained, the quality of the fruit improved, and a substantial increase in water productivity was achieved with the W2N3 treatment. The findings of this study can be used as a reference for accurate field irrigation.

Dopamine Regulates Its Own Synthesis via MdORG2 to Improve Low-Nitrogen Tolerance in Apple Plants.

Nitrogen (N) is crucial for plant growth and development. Exogenous dopamine has been shown to improve the N-deficiency tolerance of apple. However, the potential regulatory mechanisms by which dopamine mitigates low-N stress remain unclear. Our data indicated that the dopamine levels in apple (Malus domestica) were elevated by the overexpression (OE) of MdTYDC, which encodes tyrosine decarboxylase, a key enzyme in dopamine biosynthesis. The photosynthetic capacity of the OE lines was enhanced, and the root system was more extensive under low-N stress compared with the wild-type (WT) plants. This enhancement contributed to a greater net nitrate influx at the root surface in the OE lines compared with the WT. Transcriptomic and carbohydrate analyses suggested that the OE of MdTYDC in apple enhanced N-deficiency tolerance by promoting the expression of carbohydrate-related genes, which increased the content of soluble sugars and sorbitol. Both exogenous dopamine and MdTYDC OE activated the expression of MdORG2 (a bHLH transcription factor), which, in turn, directly binds to the promoter of MdTYDC, activating its expression, increasing dopamine levels, and consequently conferring strong low-N tolerance in apple. Thus, this reveals the molecular pathways by which dopamine regulates low-N tolerance in apple through pathways involving MdTYDC and MdORG2.