Explore the vast range of titles available.

Background Pistachio ( Pistacia vera L.) growth, yield and quality are affected by abiotic stress especially drought. Understanding the strategies that improve dehydration tolerance is essential for developing resistant pistachio rootstocks. In the experiment, nine-month-old saplings of seven clonal interspecies hybrids of Pistacia atlantica × P. integerrima (C1, C2, C16-1, C8-3, C4-2, C9-4 and UCB1) were assessed for growth and physiological responses to water withholding and recovery. Result Water deficit negatively impacted growth parameters, including shoot dry weight, root dry weight and leaf area, in all hybrids; however, the C1 demonstrated relatively minor reductions compared to the other hybrids. Glycine betaine content in leaves increased by 49.4% in C9-4 and 47% in C1, while only 7% and 11% increases were found in the most sensitive clones, C8-3 and C4-2. Notably, C9-4, identified as the most tolerant clone, displayed the highest proline levels, with increases of 29.5% in leaves and 41.5% in roots, in contrast to C8-3, which showed minimal increases of 6% and 11% in leaves and roots, respectively. Clones with higher compatible solutes maintained higher relative water content (RWC), lower osmotic potential and smaller reductions in leaf water potential. RWC declined by just 6% in C9-4, whereas it dropped by 88% in C8-3. Osmotic potentials in C9-4 were − 1.61 MPa in leaves and − 0.271 MPa in roots, while in C8-3, they were − 0.93 MPa and − 0.11 MPa in leaves and roots, respectively. Following recovery, evaluations of growth, physiological traits and visual observations indicated that C8-3 had poor recovery ability. Heatmap and PCA analyses categorized the clones into three groups: “tolerant” (C9-4, C1 and C2), “moderately tolerant” (UCB1) and “sensitive” (C8-3, C4-2 and C16-1). Conclusion The results of this study underscore the significance of osmotic adjustment as a more critical trait compared to growth and stomatal parameters in effectively differentiating tolerant clones from sensitive ones.

As one of the main origin centers of nut trees, Iran is the fourth leading nut crops producer in the world (6% of total nut production). Due to the high genetic diversity, development of new varieties and rootstocks with desirable characteristics have been highly considered by fruit breeders in Iran. In this regard, molecular breeders concentrate on filling the gaps in the conventional breeding with the aim of accelerating breeding programs. Recent advancements in molecular breeding such as next-generation sequencing (NGS) techniques, high-throughput genotyping platforms and genomics-based approaches including genome wide association studies (GWAS), and genomic selection (GS) have opened up new avenues to enhance the efficiency of nut trees breeding. Over the past decades, Iranian nut crops breeders have successfully used advanced molecular and genomic tools such as molecular markers, genetic transformations and high-throughput genotyping to explore the genetic basis of the desired traits and eventually to develop new varieties and rootstocks. Due to a broad international cooperation, a clear perspective is envisaged for the nut breeding programs in Iran, especially based on new biotechnology techniques. The propagation of nut trees in Iran have also been dramatically improved. Different types of grafting and tissue culture (micropropagation or somatic embryogenesis) techniques for propagation of nut crops have been studied intensively in the last 30 years in Iran and the successful techniques have been commercialized. Several certified nurseries are producing grafted and micropropagation plants of walnut, pistachio and other nut crops commercially. A part of the grafted and micropropagaited plants of nut crops in Iran is being exported to the other countries. Establishing modern orchards of nut crops using new cultivars and rootsocks is presently being advised by professional consultants.

Simplified prediction of the interactions of plant tissue culture media components is of critical importance to efficient development and optimization of new media. We applied two algorithms, gene expression programming (GEP) and M5’ model tree, to predict the effects of media components on in vitro proliferation rate (PR), shoot length (SL), shoot tip necrosis (STN), vitrification (Vitri) and quality index (QI) in pear rootstocks (Pyrodwarf and OHF 69). In order to optimize the selected prediction models, as well as achieving a precise multi-optimization method, multi-objective evolutionary optimization algorithms using genetic algorithm (GA) and particle swarm optimization (PSO) techniques were compared to the mono-objective GA optimization technique. A Gamma test (GT) was used to find the most important determinant input for optimizing each output factor. GEP had a higher prediction accuracy than M5’ model tree. GT results showed that BA (Γ = 4.0178), Mesos (Γ = 0.5482), Mesos (Γ = 184.0100), Micros (Γ = 136.6100) and Mesos (Γ = 1.1146), for PR, SL, STN, Vitri and QI respectively, were the most important factors in culturing OHF 69, while for Pyrodwarf culture, BA (Γ = 10.2920), Micros (Γ = 0.7874), NH 4 NO 3 (Γ = 166.410), KNO 3 (Γ = 168.4400), and Mesos (Γ = 1.4860) were the most important influences on PR, SL, STN, Vitri and QI respectively. The PSO optimized GEP models produced the best outputs for both rootstocks.

Persian walnut ( Juglans regia L.) frequently encounters simultaneous drought and heat stress in its natural habitat, impacting its physiology and biochemistry. Therefore, understanding the physiological and molecular responses to these combined stresses is essential for improving stress resilience in this species. The present study investigates the effects of drought stress (DS), heat stress (HS), combined drought-heat stress (DH) and control condition (CC) on the antioxidant defenses and gene expression in own-rooted walnut plants (cv. Chandler) under controlled greenhouse conditions. Combined stress significantly increased malondialdehyde and hydrogen peroxide by 2.55- and 2.05-fold, respectively, while reducing membrane stability index by 0.43-fold compared to CC. Total chlorophyll declined by 0.18- and 0.09-fold under DS and HS, respectively, with the greatest reduction (0.37-fold) under DH. Levels of phenylalanine ammonia-lyase, polyphenol oxidase, superoxide dismutase, catalase, and guaiacol peroxidase rose 2.5- to sixfold under DH compared to CC. Similarly, phenolic compounds and antioxidant capacity increased between 1.49- and 3.55-fold relative to CC. Gene expression analyses of NCED6 , PPO , and GST revealed 2- to sixfold upregulation under both individual and combined stress conditions compared to control. These results highlight the crucial roles of these genes in activating antioxidant defense pathways and detoxification processes that mitigate oxidative damage in walnut under stress. Following stress relief, walnut seedlings displayed notable recovery in photosynthetic function and antioxidant activity. These findings indicate that combined drought and heat stress exerts a stronger impact than either stress alone, underscoring key adaptive mechanisms that may enhance walnut resilience to climate variability.

Background Root system architecture is a key determinant of plant establishment, particularly in species such as Pistachio ( Pistacia vera L.), which inherently display limited lateral root formation and low survival rates after transplanting. This study evaluated the impact of radicle-tip excision on root architecture and overall seedling vigor in ‘Ohadi’ pistachio cultivar. A factorial experiment was conducted using five distinct radicle length categories at the time of excision: L1 (0.5–1.0 cm), L2 (1.01–2.0 cm), L3 (2.01–3.0 cm), L4 (3.01–4.0 cm) and L5 (4.01–5.0 cm), and three cutting sizes of 1 mm (CS1), 3 mm (CS3) and 5 mm (CS5) while untreated seedlings were used as the control group. Following radicle-tip excision, the seedlings were grown in perlite-filled pots and irrigated weekly with half-strength Hoagland’s nutrient solution. Growth, vitality, and root architectural traits were assessed at end of the experiment. Result Remarkably, the L3CS3 treatment involving excision of 3 mm from the radicle tip when its length reached L3 (2.01–3.0 cm) resulted in significant enhancements in key morphological traits, including shoot and root fresh/dry weights, leaf area and plant height. In addition, root system characteristics such as the number of lateral roots (NLR), network depth (NWDP), network volume (NWVL), and convex area (NWCA) showed substantial improvement. Ordinal regression analysis revealed a strong relationship between lateral root traits and overall seedling vigor, confirming the physiological relevance of the root manipulation. Complementary correlation analysis further supported the notion that improved root traits positively influence shoot growth, indicating an integrative effect. Conclusion These findings underscore the potential of radicle-tip excision as a cost-effective and scalable approach to improve root functionality and transplant performance in pistachio, with broader applicability to other species that exhibit limited lateral root development in nursery production systems. Graphical abstract

Pistachio ( Pistacia vera L.) is a valuable nut crop that faces significant challenges due to drought stress, which can severely impact its growth, yield, and quality. Understanding the physiological and molecular mechanisms underlying drought tolerance is crucial for developing resilient pistachio rootstock. In this study, among nine-month-old saplings of seven clonal interspecies hybrids of Pistacia atlantica × Pistacia integerrima , two contrasting hybrids, ‘C4-2’ (sensitive) and ‘C9-4’ (resistant), were assessed for their morphological, physiological and molecular responses to 30 days of withholding irrigation. Water withholding induced alterations in root architecture in the resistant clone, accompanied by an increase in compatible solutes, including glycine betaine, proline, and total soluble carbohydrates. Enzyme activities of guaiacol peroxidase (GPX) and catalase (CAT) were elevated in the resistant clone under water stress. Both clones exhibited increased levels of malondialdehyde (MDA) and hydrogen peroxide (H 2 O 2 ) during the stress period, with these changes being more pronounced in C4-2 compared to C9-4. In the resistant clone, both CDPK and ZEP genes were upregulated, suggesting their role in enhancing stress signaling and osmotic regulation under drought stress. The upregulation of CDPK indicates its involvement in calcium-mediated signaling pathways, which likely contribute to improved drought tolerance. Similarly, DHN expression was strongly influenced by CDPK activity, further emphasizing its role in maintaining cellular integrity during stress conditions. The findings provide valuable insights for developing more resilient pistachio rootstocks capable of thriving in water-limited environments. Specifically, C9-4 demonstrated significant drought tolerance in this study. Nonetheless, further research is necessary to validate the broader applicability of these findings and to evaluate its performance across various stress environments.

Background Predicting impact of plant tissue culture media components on explant proliferation is important especially in commercial scale for optimizing efficient culture media. Previous studies have focused on predicting the impact of media components on explant growth via conventional multi-layer perceptron neural networks (MLPNN) and Multiple Linear Regression (MLR) methods. So, there is an opportunity to find more efficient algorithms such as Radial Basis Function Neural Network (RBFNN) and Gene Expression Programming (GEP). Here, a novel algorithm, i.e. GEP which has not been previously applied in plant tissue culture researches was compared to RBFNN and MLR for the first time. Pear rootstocks (Pyrodwarf and OHF) were used as case studies on predicting the effect of minerals and some hormones in the culture medium on proliferation indices. Results Generally, RBFNN and GEP showed extremely higher performance accuracy than the MLR. Moreover, GEP models as the most accurate models were optimized using genetic algorithm (GA). The improvement was mainly due to the RBFNN and GEP strong estimation capability and their superior tolerance to experimental noises or improbability. Conclusions GEP as the most robust and accurate prospecting procedure to achieve the highest proliferation quality and quantity has also the benefit of being easy to use.

Walnut production is challenged by climate change and abiotic stresses. Elucidating the genomic basis of adaptation to climate is essential to breeding drought-tolerant cultivars for enhanced productivity in arid and semi-arid regions. Here, we aimed to identify loci potentially involved in water use efficiency (WUE) and adaptation to drought in Persian walnut using a diverse panel of 95 walnut families (950 seedlings) from Iran, which show contrasting levels of water availability in their native habitats. We analyzed associations between phenotypic, genotypic, and environmental variables from data sets of 609 000 high-quality single nucleotide polymorphisms (SNPs), three categories of phenotypic traits [WUE-related traits under drought, their drought stress index, and principal components (PCs)], and 21 climate variables and their combination (first three PCs). Our genotype–phenotype analysis identified 22 significant and 266 suggestive associations, some of which were for multiple traits, suggesting their correlation and a possible common genetic control. Also, genotype–environment association analysis found 115 significant and 265 suggestive SNP loci that displayed potential signals of local adaptation. Several sets of stress-responsive genes were found in the genomic regions significantly associated with the aforementioned traits. Most of the candidate genes identified are involved in abscisic acid signaling, stomatal regulation, transduction of environmental signals, antioxidant defense system, osmotic adjustment, and leaf growth and development. Upon validation, the marker–trait associations identified for drought tolerance-related traits would allow the selection and development of new walnut rootstocks or scion cultivars with superior WUE.

The main aim of the present investigation is modeling and optimization of a new culture medium for in vitro rooting of G×N15 rootstock using an artificial neural network-genetic algorithm (ANN-GA). Six experiments for assessing different media culture, various concentrations of Indole – 3- butyric acid, different concentrations of Thiamine and Fe-EDDHA were designed. The effects of five ionic macronutrients (NH 4 + , NO 3 − , Ca 2+ , K + and Cl − ) on five growth parameters [root number (RN), root length (RL), root percentage (R%), fresh (FW) and dry weight (DW)] were evaluated using the ANN-GA method. The R 2 correlation values of 0.88, 0.88, 0.98, 0.94 and 0.87 between observed and predicted values were acquired for all five growth parameters, respectively. The ANN-GA results indicated that among the input variables, K + (7.6) and NH4 + (4.4), K + (7.7) and Ca 2+ (2.8), K + (36.7) and NH 4 + (4.3), K + (14.7) and NH 4 + (4.4) and K + (7.6) and NH 4 + (4.3) had the highest values of variable sensitivity ratio (VSR) in the data set, for RN, RL, R%, FW and DW, respectively. ANN-GA optimized LS medium for G×N15 rooting contained optimized amounts of 1 mg L −1 IBA, 100, 150, or 200 mg L −1 Fe-EDDHA and 1.6 mg L −1 Thiamine. The efficiency of the optimized culture media was compared to other standard media for Prunus rooting and the results indicated that the optimized medium is more efficient than the others.

Persian plateau (including Iran) is considered as one of the primary centers of origin of walnut. Sampling walnut trees originating from this arena and exploiting the capabilities of next-generation sequencing (NGS) can provide new insights into the degree of genetic variation across the walnut genome. The present study aimed to explore the population structure and genomic variation of an Iranian collection of Persian walnut ( Juglans regia L.) and identify loci underlying the variation in nut and kernel related traits using the new Axiom J. regia 700K SNP genotyping array. We genotyped a diversity panel including 95 walnut genotypes from eight Iranian provinces with a variety of climate zones. A majority of the SNPs (323,273, 53.03%) fell into the “Poly High Resolution” class of polymorphisms, which includes the highest quality variants. Genetic structure assessment, using several approaches, divided the Iranian walnut panel into four principal clusters, reflecting their geographic partitioning. We observed high genetic variation across all of the populations (H O  = 0.34 and H E  = 0.38). The overall level of genetic differentiation among populations was moderate (F ST  = 0.07). However, the Semnan population showed high divergence from the other Iranian populations (on average F ST  = 0.12), most likely due to its geographical isolation. Based on parentage analysis, the level of relatedness was very low among the Iranian walnuts examined, reflecting the geographical distance between the Iranian provinces considered in our study. Finally, we performed a genome-wide association study (GWAS), identifying 55 SNPs significantly associated with nut and kernel-related traits. In conclusion, by applying the novel Axiom J. regia 700K SNP array we uncovered new unexplored genetic diversity and identified significant marker-trait associations for nut-related traits in Persian walnut that will be useful for future breeding programs in Iran and other countries.