Rapid, non-destructive estimation of leaf chlorophyll content (SPAD) is crucial for assessing plant photosynthetic health and nutrient status. However, conventional methods rely on specialized instruments (e.g., SPAD meters and hyperspectral sensors) which are costly, cumbersome, or unsuitable for large-scale field deployment. While RGB image analysis offers a low-cost alternative, most existing approaches depend solely on color features, which are susceptible to environmental interference and lack robustness across growth stages. To address these limitations, this study proposes a novel machine learning framework that fuses both color and texture features from smartphone-captured RGB images for accurate SPAD estimation in walnut seedlings and explores its linkage with potassium nutrition. ‘Wen 185’ walnut seedlings were subjected to seven potassium concentration treatments to induce a chlorophyll gradient. From the leaf images, 22 color indices and 8 texture features based on the Gray-Level Co-occurrence Matrix (GLCM) were extracted. Prediction models were built and compared using Random Forest (RF), XGBoost, and a Support Vector Machine (SVM), with two fusion strategies: data-level and feature-level fusion. Results demonstrated that the RF model with feature-level fusion achieved optimal performance (validation set: R2 = 0.939, RMSE = 0.014, and RPD = 4.539), significantly outperforming models using single-feature types. SHAP analysis identified normalized red, normalized blue, and green-band correlation as the most influential features. This work fills a critical gap by establishing a robust, cost-effective, and interpretable method for SPAD monitoring using ubiquitous RGB imagery. Furthermore, the strong correlation between image-predicted SPAD and potassium levels confirms the method’s high potential for early and non-destructive diagnosis of potassium deficiency in orchard management.

Introduction:Tannin content is a key factor influencing the taste of walnuts and serves as an important index for evaluating walnut quality. Rapid and accurate detection of tannin levels in walnut kernels is therefore significant for quality assessment and management. This study aims to develop an efficient method for predicting tannin content in walnut kernels using near-infrared (NIR) spectroscopy combined with machine learning techniques. Methods:A total of 180 samples of 'Wen 185' walnut kernels were used as the research objects. The NIR reflectance spectra of the samples were measured within the range of 4000-10000 cm⁻¹. The spectral data were processed using mathematical transformations and continuous wavelet transform (CWT), both separately and in combination. Pearson correlation analysis was applied to extract characteristic bands related to tannin content. Based on these features, a random forest (RF) model was constructed to quantitatively predict tannin content. Additionally, the SHAP algorithm was employed to interpret and visualize the machine learning model. Results:The results indicated that within the spectral range of 4000-10000 cm⁻¹, the NIR reflectance of walnut kernels increased with tannin content under different orchard management modes. Both first-order differential transformation and CWT, as well as their combination, significantly enhanced the correlation between spectral data and tannin content. The combination of first-order differential transformation and CWT notably improved the model's prediction performance. The optimal prediction model was achieved using the feature lg'(1/R)_CWT_28, with training set metrics of R² = 0.880, RMSE = 1.188, RPD = 2.904, and validation set metrics of R² = 0.831, RMSE = 1.620, RPD = 2.459. Discussion:The study demonstrates that combining mathematical transformations with wavelet transform can effectively improve the prediction accuracy of models for tannin content in walnut kernels. The RF model based on processed spectral data showed strong performance, indicating its potential for rapid and non-destructive tannin quantification. The use of SHAP algorithm further enhances model interpretability. These findings provide a valuable reference for the accurate prediction of tannin content in walnut kernels and may support quality control in walnut production and processing.

BACKGROUND:The accumulation of nano-plastics in terrestrial environments raises urgent concerns for crop safety, but little is known about their bioavailability and impact in perennial plants like tea (Camellia sinensis L.). This study investigated the uptake and physiological effects of 80 nm polystyrene nano-plastics (PS-NPs) in hydroponically grown tea seedlings. RESULT:Confocal laser scanning microscopy (CLSM) visualized PS-NPs in root cortices and leaf tissues, confirming systemic translocation. Exposure to PS-NPs (10-100 mg L-1) for durations of 1, 3 and 7 days triggered concentration-dependent oxidative stress and defense responses: root catalase (CAT) activity was initially suppressed by 69.7% (50 mg L-1) but later induced 15-fold, while leaf glutathione S-transferase (GST) activity was significantly inhibited. Notably, theanine content in leaves increased by 77.6% at 10 mg L-1 but decreased by 70.1% at 100 mg L-1. CONCLUSION:The findings demonstrate PS-NPs uptake and their impact on tea seedling physiology and quality-related metabolites, underscoring potential risks to perennial crops. © 2026 Society of Chemical Industry.

Walnut is an important economic woody oil tree species, and anthracnose caused by Colletotrichum gloeosporioides is a devastating disease affecting walnut production in China. The MAPK-WRKY signaling pathway plays an important role in regulating plant disease resistance. However, the MAPK-WRKY pathway in walnut and the mechanism involved in anthracnose resistance remain unclear. Using ‘Taile’ and ‘Xiangling’ with significant differences in anthracnose resistance as materials, we identified a potential JrMAPK3-JrWRKY22 pathway related to anthracnose resistance through transcriptomics. Further analysis using yeast two-hybrid, bimolecular fluorescence complementation, pull-down, and in vitro phosphorylation assays revealed that JrWRKY22 interacts with and is phosphorylated by JrMAPK3. Transient injection results in walnut fruit revealed that overexpression of JrWRKY22 can inhibit Colletotrichum gloeosporioides infection, increase fruit anthracnose resistance, and significantly promote the expression of the β-1,3-glucanase gene JrGLU of the PR-2 family and the pathogenesis-related gene JrPR1. In contrast, silencing JrWRKY22 resulted in a significant increase in lesion size caused by Colletotrichum gloeosporioides and a corresponding decrease in gene expression levels. A dual-luciferase assay confirmed that JrWRKY22 can activate the promoter activity of JrPR1 and JrGLU and that phosphorylation by JrMAPK3 increases this activation. Further analysis using yeast one-hybrid assays, ChIP-PCR, and EMSA demonstrated that JrWRKY22 can bind to W-box elements in the promoters of JrPR1 and JrGLU. These findings elucidate the molecular mechanism by which the JrMAPK3-JrWRKY22 module increases walnut anthracnose resistance, broaden the understanding of resistance mechanisms, and provide a scientific basis for molecular breeding in the context of walnut disease resistance.

【Objective】Juglans regia L., commonly known as walnut, is a deciduous perennial fruit tree belonging to the Juglandaceae family and ranks among the world's“four major nuts”. Walnuts are prized not only for their high quality but also for their significant economic, nutritional, and medicinal value. The previous research has indicated that the primary cause of walnut kernel exposure is the relatively low levels of glucose and ferulic acid within the inner fruit peel during the initial hardening stage. This deficiency would inhibit the biosynthesis of lignin, cellulose, and hemicellulose, the principal structural components of the inner peel, thereby compromising its lignification. Consequently, incomplete development of the inner peel would lead to kernel exposure, highlighting its critical role in walnut growth, processing, transport, and storage. Concurrently, lignin accumulation is a pivotal step in the development of the walnut's inner peel. Lignin also serves as a key structural component providing robust mechanical support within plant cell walls. Earlier studies have revealed that cell wall formation is influenced by various factors, with phytohormones playing a particularly significant role. Hormones can regulate the formation of plant secondary cell walls by modulating genes associated with xylem development. Our research team observed that in Xinlu walnuts, the concentration of indole-3-acetic acid (IAA) in the inner fruit peel was significantly lower than in the mesocarp during the early hardening phase, but increased again later. This suggests that IAA(auxin)would play an important regulatory role in the hardening process of the inner peel. The AUX/IAA(Auxin/Indole-3-Acetic Acid)gene family represents one of the earliest responsive gene families to auxin signaling and is involved in regulating numerous aspects of plant growth and development.【Methods】Using the Arabidopsis AUX/IAA gene family as a reference, the AUX/IAA genes were identified within the walnut genome. The identity of these genes as the AUX/IAA family members was subsequently confirmed using a hidden Markov model (HMM)search. The comprehensive bioinformatics analysis of the identified gene family was performed utilizing various online tools, including ExPASy, MEGA 11, DNAMAN, Cytoscape, MEME, PlantCARE, STRING, and iTOL. This analysis encompassed the nucleotide sequence characteristics(chromosomal location, homology identification, gene structure, and promoter cis-elements) as well as the properties of the encoded proteins(physicochemical properties, conserved domains and motifs, proteinprotein interaction networks, and phylogenetic relationships). Furthermore, AUX/IAA gene expression patterns were analyzed using publicly available RNA-Seq databases. To investigate the role of auxin in endocarp development, the quantitative reverse transcription polymerase chain reaction(qRT-PCR)was employed to assess the expression levels of the AUX/IAA genes during walnut endocarp development under different concentrations of exogenous indole-3-acetic acid(IAA)treatment.【Results】A total of 63 walnut AUX/IAA genes were identified, and they were unevenly distributed across 16 chromosomes. The protein lengths ranged from 90 to 1296 amino acids, the isoelectric points(pI)ranged from 4.79 to 10.47, and the molecular weights ranged from 10.24 to 144.92 kilodaltons (kD). All family members were hydrophilic proteins. The prediction results for subcellular localization indicated that 47 JrAUX/IAA proteins were localized in the nucleus,12 in the chloroplast, and four in the cytoplasm(JrAUX4/13/40/63). The phylogenetic tree analysis grouped the proteins into four subgroups(Ⅰ-Ⅳ), and the members of the same subgroup typically exhibited similar gene structures and conserved domains. The Analysis of conserved domains revealed that all 63 JrAUX proteins possessed the AUX/IAA family domain, the B3 DNA-binding domain, and the auxin response factor domain. Most proteins also contained the AUX/IAA family domain. The promoter cis-acting elements indicated that members of this family were associated with numerous light-, stress-, hormone-, and other responsive elements. The combined transcriptome data and qRT-PCR analysis were used to study the expression patterns of the AUX family members under various hormone treatments at different time points. The results showed that the JrAUX2 andJrAUX27 exhibited significantly higher expression levels than the control after treatment with 150 and 200 mg · L-1 IAA, respectively, reaching 50.67 and 89.95 times of the level of the control.Meanwhile, the JrAUX16 exhibited the most significant downregulation after treatment with 200 mg · L-1 NPA, reaching 89.74 times of that of the control.【Conclusion】This study identified 63 JrAUX/IAA genes and analyzed their gene structure, chromosomal localization, similarity, and expression patterns at various concentrations and stages of walnut development. The genes were found to be unevenly distributed across 16 chromosomes. The subcellular localization analysis revealed that the genes were primarily localized in the cell nucleus. The phylogenetic analysis grouped the AUX/IAA family members into four subfamilies with similar gene structures and conserved motifs. The collinearity analysis revealed two pairs of tandem repeat genes and three pairs of fragment repeat genes within the AUX/IAA family. Through an analysis of the expression patterns of the 63 identified genes combined with quantitative reverse transcription PCR(qRT-PCR)analysis, it was speculated that the JrAUX2 and JrAUX27 might be the key genes influencing lignin synthesis during walnut endocarp development, auxin signaling potentially coordinates lignin biosynthesis through transcriptional control of pathway genes, with differential expression patterns observed across auxin concentration gradients.

【Objective】The aim of this study was to investigate the effects of exogenous N-carbonyloctanoyl homoserine lactone (3OC8-HSL) on salt tolerance of Malus robusta seedlings by evaluating growth performance, physiological parameters, and the expression of salt-responsive genes under salt stress.【Methods】A greenhouse pot experiment was conducted with four treatment groups: Including the control group(CK,0 mmol·L-1NaCl+water), the 3OC8-HSL treatment group(AC,0 mmol·L-1 NaCl+10 μmol·L-13OC8-HSL), salt stress group(Salt,200 mmol·L-1NaCl+water), and 3OC8-HSL+salt stress group(AS,200 mmol·L-1NaCl+10 μmol·L-13OC8-HSL). Each treatment was applied to the seedlings for 45 days.3OC8-HSL solution(10 μmol·L-1)was drench-applied to the root zone on days 1,7, and 14, while salt stress was imposed by watering with 200 mmol·L-1NaCl every 3 days. The growth parameters(plant height and fresh mass)were measured at the end of the experiment. The leaf chlorophyll content was determined (total chlorophyll, as well as chlorophyll a and b) as an indicator for photosynthetic status. The malondialdehyde(MDA)content in seedling roots was quantified to assess lipid peroxidation(oxidative stress damage). The leaf Na+and K+concentrations were measured,and the Na+/K+ratio was calculated to evaluate ionic homeostasis under each treatment. For molecular analysis, the root samples from salt-stressed seedlings with and without 3OC8-HSL were subjected to RNA sequencing(RNA-seq). Differentially expressed genes(DEGs)between the AS treatment and Salt treatment were identified using DESeq2(standard: |log2fold change|＞1 and adjusted p-value＜0.05). The gene Ontology(GO)enrichment analysis was performed to characterize the biological processes enriched among these DEGs. Furthermore, four DEGs associated with stress responses were selected for validation by quantitative real-time PCR (RT-qPCR): MdPAL, MdGST, MdHKT1, and MdLRR-RLK.【Results】The Growth and Physiological Responses: Under non-saline conditions, the exogenous 3OC8-HSL markedly promoted the growth of Malus robusta seedlings. The treated seedlings exhibited a 23.74% increase in plant height and a 17.23% increase in fresh mass compared with the untreated controls, along with a slight but significant rise in the leaf chlorophyll content(+4.06%). These results indicated that 3OC8-HSL itself had a growth-promoting effect even without stress. Under salt stress (200 mmol·L-1NaCl),3OC8-HSL application substantially improved seedling performance and stress tolerance. The 3OC8-HSL-treated salt-stressed seedlings grew taller(+11.61% plant height)and heavier (+26.38% fresh mass than those under salt stress alone. Notably, 3OC8-HSL alleviated salt-induced damage: the treated seedlings maintained significantly higher chlorophyll levels (total chlorophyll +36.98% vs salt control), indicating better photosynthetic capacity under stress. In addition,3OC8-HSL reduced oxidative damage, as evidenced by a 36.20% reduction in root MDA accumulation under salt stress relative to untreated seedlings. This lower MDA level suggested that 3OC8-HSL would enhance the antioxidant defense, thereby protecting cellular membranes from peroxidation damage caused by salt stress. The Ion Homeostasis:3OC8-HSL also improved ionic balance in Malus robusta under salinity. In the salt-stressed seedlings,3OC8-HSL treatment led to significantly lower Na+accumulation and higher K+retention in plant tissues. Specifically, the Na+content in the 3OC8-HSL-treated seedlings was 11.01% lower than that in the untreated salt-stressed controls, while the K+content was 19.46% higher. Consequently, The Na+/K+ratio, a key indicator of ion homeostasis under salt stress, was reduced by 22.17% in the 3OC8-HSL group compared with the salt treatment alone. This improvement in Na+/K+homeostasis reflected a better maintenance of ionic equilibrium, which is crucial for salt tolerance. The results suggested that 3OC8-HSL would help seedlings limit sodium uptake or transport and/or enhance potassium uptake, thereby mitigating ion toxicity under high salinity. Consistently, the treated seedlings showed healthier morphology and less salt injury than the untreated ones(greener leaves, less wilting), as observed qualitatively during the experiment. The Gene Expression and Pathway Activation: The transcriptome profiling of roots under salt stress revealed significant molecular changes due to 3OC8-HSL. A total of 560 genes were differentially expressed in the 3OC8-HSL-treated vs. untreated salt-stressed roots, with 177 genes upregulated and 383 downregulated(adjusted P＜0.05). The GO enrichment analysis of these DEGs indicated that 3OC8-HSL activated multiple stress-responsive pathways. Many of the upregulated genes were associated with secondary metabolite biosynthesis and defense-related processes. In particular, biological process categories such as phenylpropanoid biosynthetic and metabolic pathways(involved in the synthesis of lignin and other phenolics), glutathione metabolism, response to wounding, and cuticle development were significantly enriched among the 3OC8-HSL-induced genes. These results implied that 3OC8-HSL would trigger a broad reprogramming of the plant's stress response at the molecular level, enhancing both structural and chemical defenses under the salt stress. Importantly, several key salt-tolerance genes were strongly upregulated by 3OC8-HSL treatment. For instance, transcripts of the MdPAL(phenylalanine ammonia-lyase, a rate-limiting enzyme in the phenylpropanoid pathway leading to lignin synthesis)increased 4.6-fold in the 3OC8-HSL-treated roots (after 7 days of salt stress) compared with the untreated controls. The MdHKT1, encoding a high-affinity K+transporter involved in Na+/K+homeostasis, was upregulated 9.6-fold, and the MdLRR-RLK, encoding a leucine-rich repeat receptor-like kinase implicated in stress signal perception, rose by 8.4-fold(both after 7 days). Additionally, the MdGST(glutathione S-transferase, involved in detoxification and ROS scavenging via the glutathione pathway) showed a 6.4-fold induction at 24 hours after treatment. The robust induction of these genes, which would play roles in lignin biosynthesis(cell wall fortification), antioxidant activity, ionic transport, and stress signaling, would underscore the multi-faceted mechanism by which 3OC8-HSL would enhance salt tolerance.【Conclusion】This study demonstrated that the exogenous 3OC8-HSL improved the salt tolerance of Malus robusta seedlings by promoting growth, enhancing photosynthetic capacity, maintaining Na+/K+homeostasis, and reducing oxidative damage. The transcriptome and RT-qPCR analysis showed that the 3OC8-HSL upregulated the expression of the MdPAL, MdGST, MdHKT1, and MdLRR-RLK, and activated pathways related to phenylpropanoid metabolism and glutathione metabolism under the salt stress. These results would provide a theoretical basis for the application of AHL signals in improving salt resistance of apple rootstocks.

[This corrects the article DOI: 10.3389/fpls.2026.1746869.].

Alpine ecosystems are distinguished by nutrient-poor soils and low temperatures, short growing seasons, and harsh environmental conditions that have strong influence on plant growth and survival. Soil nutrient dynamics, especially the cycling of carbon (C) and the nutrients (N), play a central role in controlling the productivity, diversity and resilience of alpine vegetation. Microbial communities are important mediators of nutrient transformations that influence nutrient availability under the conditions of limited decomposition and mineralization. This chapter discusses the role of soil microbes, nutrient constraints and biogeochemical processes in determining plant distribution in the alpine communities. It highlights how changes in C and N cycling with climate change affect vegetation resilience and ecosystem functioning. This chapter provides evidence-based insights into soil–plant interactions and the role of microbes in enhancing biodiversity and informing conservation strategies to improve nutrient stability in alpine landscapes.

Background Caffeoyl-CoA O-methyltransferase (CCoAOMT) is a key rate-limiting enzyme in plant lignin biosynthesis. Walnut (Juglans regia L.) shell hardness is largely determined by endocarp lignification, but the underlying molecular mechanism remains poorly understood. Results In this study, we performed genome-wide identification and systematic bioinformatics analysis of the CCoAOMT family in walnut, and verified the biological function of JrCCoAOMT3 via heterologous overexpression in Arabidopsis thaliana (ecotype Col-0). A total of 11 JrCCoAOMT genes were identified, unevenly distributed on 5 chromosomes, all encoding proteins containing the complete conserved O-methyltransferase domain. Promoter cis-element analysis revealed abundant light-responsive and phytohormone signaling-related elements. JrCCoAOMT3 was highly expressed during the lignification stage of walnut endocarp (peaking at PD and PE stages, 78 and 92 days after full bloom), and its encoded protein was localized in the cytoplasm. Overexpression of JrCCoAOMT3 in A. thaliana altered stem and silique morphology, significantly increased hemicellulose content in roots and siliques, and enhanced lignin accumulation in leaves and stems. Notably, JrCCoAOMT3 overexpression significantly reduced H-type lignin content across tissues, while it had no significant effect on S-type lignin and only increased G-type lignin in stems. Conclusion This study systematically characterizes the walnut CCoAOMT gene family and confirms the key regulatory role of JrCCoAOMT3 in lignin biosynthesis, with a particular effect on H-type lignin monomer composition. The results provide a theoretical foundation for elucidating the molecular mechanism of walnut endocarp lignification and offer candidate gene resources for shell trait improvement.

Soybean crude oils (SCO) were detected by ultra-performance liquid chromatography-high-definition mass spectrometry (UPLC-HDMS) for discovering novel compounds. Numerous chromatographic peaks in ESI+ and ESI- modes showed that SCO was rich in numerous compounds. A total of 215 potential compounds with accurate mass-to-charge ratio, MSMS spectrum and CCS value were detected in SCOs. Among them, 105 compounds (47 known and 58 novel compounds) were identified and other 110 compounds weren't identified. Compared to peanut, sesame and olive oils, 65 compounds (genistein, foeniculoside X, 5,7-Dimethoxyflavone) were only detected in SCO; the types of fatty acids (32) and flavonoids (8) were higher in SCO. SCO was rich in fatty acids, fatty acid amides, flavonoids, stigmasterol, tocopherol, and soybean phospholipids. Overall, numerous novel and unique compounds with biological functions were first found in SCOs by UPLC/HDMS. Our results suggested the higher potential nutritional value of soybean oil.

Using 'Wen 185' paper skin walnuts as the raw material, walnut albumin, globulin, prolamin, and glutelin were separated using a solubility gradient method. The study investigates the effect of oil extraction temperature on their structural characteristics. Infrared spectroscopy was employed to analyze the changes in the secondary structure of proteins, while fluorescence and ultraviolet spectroscopy were used to examine the changes in the tertiary structure. The results from infrared. spectroscopy showed that the secondary structure of albumin was minimally affected by the oil extraction temperature. However. the secondary structure of globulin, prolamin, and gluten underwent significant changes when the extraction temperature reached 130 C-omicron. Additionally, the total content of alpha helix and beta-sheet structures in gluten was lower than in the other three protein components, indicating that its secondary structure stability is weaker than that of the other proteins, Fluorescence spectroscopy results revealed that the maximum fluorescence peak of albumin and globulin shifted to a longer wavelength (red shift) after the oil extraction temperature exceeded 130 C-omicron indicating that their tertiary structure unfolded, exposing more hydrophobic amino acids on the protein surface. The fluorescence peak of prolamin shifted slightly to a shorter wavelength (blue shift) after the extraction temperature exceeded 100 C, suggesting that the hydrophobic amino acids on its surface were buried within the protein molecule. However, when the extraction temperature exceeded 130 (omicron) C , a noticeable red shift occurred, indicating an increase in hydrophobic amino acids on the protein surface. The maximum fluorescence peak of gluten exhibited a red shift within the oil extraction temperature range of 40 to 70(omicron) C indicating that changes in its tertiary structure led to increased exposure of hydrophobic groups. However, when the temperature exceeded 130(omicron)C a blue shift in the fluorescence peak was observed. suggesting a reduction in the exposure of surface hydrophobic groups. This indicates that the tertiary structure of gluten is relatively more unstable compared to the other three types of proteins, Furthermore, the overall fluorescence intensity of albumin and globulin was higher than that of prolamin and gluten, suggesting that albumin and globulin contain more hydrophobic groups than prolamin and gluten. Ultraviolet spectroscopy results showed that all four protein components exhibited a significant UV absorption around 275 nm. As the oil extraction temperature increased, there was little change in the peak intensity of albumin, globulin, prolamin, and gluten, However, the number of UV absorption peaks in albumin and globulin was greater than in prolamin and gluten, suggesting that albumin and globulin contain more exposed hydrophobic amino acid groups, which is consistent with the conclusion drawn from fluorescence spectroscopy that albumin and globulin have more hydrophobic groups on their surfaces. In conclusion, when the oil extraction temperature reaches 130 C-omicron , it significantly affects the structure of albumin, globulin, and prolamin. The structural stability of gluten is relatively low, and at an oil extraction temperature of 70 C, its structure is already noticeably impacted. This study provides useful insights for understanding the effect of oil extraction temperature on walnut protein structure and for the development of walnut cake protein component products.

To effectively address the issues of poor ventilation, light deficiency, increased pest and disease pressure, and declining fruit quality in closed-canopy walnut orchards, this study was conducted in a standard, densely planted ‘Xinwen 185’ walnut orchard. Three treatments were established: an unthinned control (CK), a 1-year thinning treatment (T1), and a 2-year thinning treatment (T2). All parameters were uniformly investigated during the 2023 growing season to analyze the effects of thinning on orchard population structure, microenvironment, leaf physiological characteristics, fruit quality, and yield. The results demonstrated that tree thinning significantly optimized the population structure: crown width expanded by 6.22–6.76 m, light transmittance increased to 27.74–33.64%, and orchard coverage decreased from 100% to 75.94–80.51%. The microenvironment was improved: inter-row temperature increased by 2.34–4.08 °C, light intensity increased by 5.38–25.29%, and relative humidity decreased by 2.15–3.30%. Furthermore, leaf physiological functions were activated: in the T2 treatment, the chlorophyll content in outer-canopy leaves increased by 15.23% and 12.45% at the kernel-hardening and maturity stages, respectively; the leaf carbon-to-nitrogen ratio increased by 18.67%; the net photosynthetic rate (Pn) during fruit expansion increased by 34.21–46.10%; and the intercellular CO2 concentration (Ci) decreased by 10.18–10.31%. Fruit quality and yield were synergistically enhanced: single fruit weight increased by 23.39~37.94%, and kernel weight increased by 26.79–41.13%. The total sugar content in inner-canopy fruits increased by 16.50–16.67%, while the protein and fat content in outer-canopy fruits increased by 0.69–12.50% and 0.60–2.18%, respectively. Yield exhibited a “short-term adjustment and long-term gain” pattern: the T2 treatment (after 2 years of thinning) achieved a yield of 5.26 t·ha−1, which was 20.38% higher than the CK. The rates of diseased fruit and empty shells decreased by 65.71% and 93.22%, respectively, and the premium fruit rate reached 90.60%. This study confirms that tree thinning is an effective measure for improving the growing environment and enhancing overall productivity in closed-canopy walnut orchards, providing a scientific basis for sustainable orchard management and increased orchard profitability.

Drought, salt, high temperatures, pH imbalances in the soil, heavy metal toxicity, and floods are examples of abiotic stresses that pose serious challenges to agricultural sustainability and crop output worldwide. Plant physiological, biochemical, and molecular processes are negatively impacted by these environmental stresses, which are made worse by the rapid rate of climate change. This results in stunted development, decreased photosynthetic efficiency, disturbed nutrient balance, and eventually significant yield losses. The fundamental processes via which abiotic stressors affect plant systems are thoroughly examined in this chapter, with special attention paid to oxidative stress, hormone signaling, osmotic and ionic imbalances, and stress-induced metabolic reprogramming. It also clarifies crop-specific susceptibilities and geographical differences in stress exposure, emphasizing the disproportionate impacts on rainfed agricultural systems and staple food crops in areas like the Middle East, South Asia, and sub-Saharan Africa. The chapter offers an integrative framework of mitigation strategies in addition to evaluating the environmental and economic effects of prolonged abiotic stress, such as soil degradation and biodiversity decline. These consist of microbial inoculants, sophisticated biotechnology treatments, traditional agronomic techniques, and sustainable land management strategies. In the context of creating resilient agroecosystems, the function of precision technology, climate-smart agriculture, and international policy frameworks is also covered. The chapter emphasizes the critical need for flexible, science-based approaches to protect global food security in the face of growing environmental stressors via multidisciplinary insights and case studies tailored to certain regions.

Cinnamoyl-coenzyme A reductase (CCR) is the first important enzyme in the lignin monomer synthesis pathway, but we have little research on its characteristics in walnuts. To better understand its role, we conducted genome-wide identification of walnut JrCCRs. The experimental results identified 30 JrCCR members in the CCR gene family and clustered them into 6 subfamilies distributed on 13 different chromosomes. Chromosomes 14 and 5 contained 5 JrCCR genes each, and most chromosomes contained 1 or 2 JrCCR genes. The cis-acting elements showed that most of the promoter regions of the JrCCR genes contained predicted cis-acting elements responsive to hormones, with the most common being the abscisic acid-responsive element. The gene structure showed that the JrCCR genes contain two to five introns. Conserved motif and evolutionary analysis indicated that the JrCCR protein sequence is both conserved and altered during the evolutionary process. In addition, collinearity analysis showed a certain correlation and specificity between the JrCCR gene family and Arabidopsis. Moreover, there are different expression patterns of JrCCR in the transcriptome of tissues during the full developmental stage of walnut endocarp, indicating certain differences in the expression of JrCCR genes in different parts of the same tissue during endocarp hardening. The CCR gene is involved in the developmental process of walnut lignin synthesis and has a certain synergistic regulatory mechanism, laying the foundation for further research on the function of the JrCCR gene and providing a refer-ence for the regulatory genes of walnut endocarp development.

Climate change is worsening drought, salinity and extreme heat across MENA, threatening food security. Microbial biotechnology offers a sustainable solution by harnessing beneficial soil microbes like PGPR, AMF and endophytes that enhance crop resilience through nutrient mobilization, stress hormone regulation and antioxidant protection. Field trials in key crops (wheat in Egypt, olives in Morocco, date palms in Saudi Arabia) show 15-28% yield increases, though challenges remain in strain optimization, farmer adoption and policy support. Scaling up requires region-specific microbial consortia, advanced delivery systems like nano-encapsulation, and integration with digital agriculture. By overcoming these barriers, microbial solutions can become vital for climate-smart agriculture in MENA, supporting both food security (SDG 2) and climate action (SDG 13) amid growing environmental stresses.

Given the increasingly serious diseases [anthracnose mainly caused by Colletotrichum gloeosporioides (C. C. gloeosporioides)] )] of walnut plants in recent years and the environmental pollution caused by chemical pesticides, phosphites had been shown to be new environmental friendly chemical agents for plants. In this study, seven-year-old 'Xiangling' and 'Xifu 4' walnut trees were treated with different concentrations of potassium phosphite foliar fertilizer. The treatments were T1 (1500-fold dilution fluid of potassium phosphite), T2 (1000- fold dilution fluid of potassium phosphite) and CK (water). The results showed that the disease incidence rates of fruit treated with potassium phosphite were lower than CK. Moreover, the diseased fruit rates of 'Xiangling' (4) and 'Xifu 4' (14) in T2, lower than they (28 and 38) in CK. Metabolome and transcriptome further analysis revealed that potassium phosphite significantly increased the expression level of genes in the photosynthesis pathway and accumulated terpeniods, phenolic, salicylic acid and other secondary metabolic pathways. In addition, as salicylic acid content significantly increased, the expression level of the gene encoding the disease resistance-related protein (PR1) showed a corresponding trend. In vitro antibacterial tests of six related metabolites on C. gloeosporioides showed that hederagenin, 23-hydroxybetulinic acid, ursolic acid, eriodictyol, and salicylic acid had effect on C. gloeosporioides spores, among which salicylic acid and ursolic acid significantly inhibited the growth of C. gloeosporioides. Further experiments revealed that the minimum inhibitory concentrations of salicylic acid and ursolic acid were 2 and 5 g L- 1 , respectively. In addition, potassium phosphite could directly inhibit the growth of C. gloeosporioides spores in vitro tests. In conclusion, potassium phosphite enhanced walnut fruit disease resistance through up-regulated the genes related to photosynthetic performance and abundant in secondary metabolites, such as salicylic acid, terpenoids and phenolics, which were antibacterial effects on C. gloeosporioides. .

Streptomyces is a biocontrol agent capable of protecting walnut from stem rot disease caused by the fungal pathogen Cytospora chrysosperma. Antagonistic strains were selected from walnut rhizosphere soil for biocontrol of the disease. The strains were screened using C. chrysosperma as the target pathogen. Using dilution coating plate separation method, plate confrontation method, growth rate method and in vitro branch protection experiment, screening the antagonistic actinobacteria with inhibitory effect and control effect on walnut tree rot disease. Strains were identified based on their morphological, physiological, and biochemical characteristics, 16S rDNA sequencing, and phylogenetic analysis. The strain F-02 was identified as Streptomyces Lavendulae. Plate confrontation method tests showed that the inhibition rates of the Streptomyces strain F-02 on the pathogens were approximately 80.30%. Further study showed that the filtrate of strain F-02 couldinhibit the C.chrysosperma, and the widths of their inhibition zone reached 1.24±0.15 mm, the prevention effect of 71.03%. For the first time, S.lavendulae was used for the biological control of walnut tree rot. It provides strain resources for the development of walnut rot agents. It has potential applications for biological control of walnut tree rot disease.

Red walnut has broad market prospects because it is richer in anthocyanins than ordinary walnut. However, the mechanism driving anthocyanin biosynthesis in red walnut is still unknown. We studied two types of red walnut, called red walnut 1 (R1), with a red pericarp and seed coat, and red walnut 2 (R2), with a red seed coat only. R1 mostly contained cyanidin-3-O-galactoside, while R2 contained a various amounts of cyanidin-3-O-galactoside, cyanidin-3-O-arabinoside, and cyanidin-3-O-glucoside. The LDOX-2 (LOC109007163) and LDOX-3 (LOC109010746) genes, which encode leucoanthocyanidin dioxygenase/anthocyanidin synthase (LDOX/ANS), were preliminarily indicated as the crucial genes for anthocyanin biosynthesis in R1 and R2, respectively. The MYB differential genes analysis showed that MYB27 and MYB113 are specifically expressed in the red parts of R1 and R2, respectively, and they are regarded as candidate regulatory genes. Ectopic expression in Arabidopsis and transient injection in walnut showed that both MYB27 and MYB113 were located in the nucleus and promoted anthocyanin accumulation, while MYB27 promoted the expression of LDOX-2, and MYB113 promoted the expression of LDOX-3 and UAGT-3. Yeast one-hybrid and electrophoretic mobility shift assays showed that MYB27 could only bind to the LDOX-2 promoter, while MYB113 could bind to the promoters of both LDOX-3 and UAGT-3. In addition, we also identified an HD-Zip transcription factor, ATHB-12, which is specifically expressed in the pericarp. After silencing the expression of ATHB-12, the R2 pericarp turned red, and MYB113 expression increased. Further experiments showed that ATHB-12 could specifically interact with MYB113 and bind to its promoter. This suggests that MYB27 controls R1 coloration by regulating LDOX-2, while MYB113 controls R2 coloration by regulating LDOX-3 and UAGT-3, but ATHB-12 can specifically bind to and inhibit the MYB113 of the R2 pericarp so that it becomes unpigmented. This study reveals the anthocyanin biosynthetic mechanisms in two different types of red walnut and provides a scientific basis for the selection and breeding of red walnut varieties.

为探讨不同植物生长调节剂对"温185"核桃种子萌发及幼苗生长的影响,以核桃预处理后的带壳种子和去壳种子为试材,GA3和NAA分别设50、150、250、350、450 mg/L等5个浓度梯度,对种子的萌芽率、发芽率、烂种率及幼苗生长指标进行分析.结果表明,种子去壳处理对种子萌发和幼苗生长指标的促进作用优于带壳种子;与对照相比,GA3和NAA处理均能显著提高种子的萌芽率和发芽率,去壳种子经GA3350 mg/L处理后,萌芽率和发芽率最高达到86.03％和93.06％,苗高达21.55 cm,叶片数达17.40片,腋芽为3.1个;去壳种子经NAA 350 mg/L处理后,幼苗主根长和须根数最多,分别为11.4 cm和22.4条.研究表明,经外源植物激素浸种后,去壳处理能有效提高核桃种子萌发能力,并能促进幼苗各项指标的生长,适宜浓度GA3处理有利于去壳种子萌发及幼苗地上部分生长,而NAA处理相对有利于促进地下根系的生长.