Fifty‐eight mature Persian walnut ( Juglans regia ) seedlings growing at six sites in the mountainous regions of Taft, in central Iran, were evaluated to determine their morphological variation and to identify promising individuals. The traits investigated included phenological characteristics, such as budbreak and nut maturity time, and nut characteristics, such as nut and kernel weight, kernel ratio, and shell thickness. Yield efficiency and fruit‐bearing habit were also investigated. The average fruit characteristics: nut weight, kernel weight, kernel ratio, and shell thickness were in the range of 6.0–15.2 g, 2.6–9.1 g, 38.4–79.6%, and 0.4–1.4 mm, respectively. The promising genotypes were AA ₃₃ , AA ₃₅ , AA ₁₁₅ , AA ₁₁₆ , and BA ₁₅₀ . These trees had larger nuts (AA ₁₁₆ ), heavier nuts (15.2 g, AA ₃₃ ), heavier kernels (9.1 g, AA ₃₃ and AA ₁₁₅ ), higher kernel ratio (79.6%, AA ₃₅ ), and later budbreak (BA ₁₅₀ ). A few significant correlations were found between nut weight and nut length (0.57), nut width (0.68), nut thickness (0.67), kernel weight (0.75), and shell thickness (0.32); whereas a negative correlation was detected between shell thickness and kernel ratio (‐0.34). The data correlation matrix was subjected to principal component analysis, a technique that reduced the dimensionality of the data set and revealed the dominating variables. Cluster analysis of the selected genotypes detected three cluster groups. However, no significant relationship was found between morphological diversity and site geography. The promising selected genotypes identified in central Iran will be further exploited by walnut breeding programmes for their tree and nut characteristics.

Physio-biochemical responses of pistachio varieties including Pistacia vera L. ‘Ghazvini’ (GH), P. vera ‘Ghermez-Pesteh’ (GP) and P. atlantica subsp. mutica (M) were assessed under salt stress to understand the common mechanisms of salt tolerance in two popular Pistacia species. In the experiment, half-sib seedlings of the varieties were subjected to high (100 mM) and severe (200 mM) levels of NaCl-induced salinity for 90 days. Growth, physiological, biochemical and ionic parameters in the roots and shoots of plants were measured in the experiment. Salinity markedly declined plant growth, and increased the number of necrotic leaves (NL) and leaf abscission. In terms of physiological responses, salinity reduced the relative water content (RWC), membrane stability index (MSI) and the concentrations of photosynthetic pigments, but increased carbohydrates and proline content in the leaves. MSI of the leaves was positively correlated with the concentrations of anthocyanins and carotenoids. Salinity increased sodium content in root and shoot tissues of the plants, and decreased potassium concentration and K/Na ratio. Among the rootstocks, GH had better performance on all parameters. Despite the high concentration of Na⁺ and low K/Na ratio in the shoots, the lowest number of NL was found in GH under both salinity levels. The results indicated that salt tolerance in GH was most likely related to compartmentation of Na⁺ ions. Finally, accumulation of osmolytes and sodium compartmentation were considered to be the most important mechanisms in the salt tolerance of pistachio rootstocks.

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. 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). 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.

Selecting salt tolerant rootstocks is a sustainable approach for developing fruit trees in salinity prone areas. 60-day-old seedlings of Pistacia vera ‘Akbari’ and ‘Ghazvini’, and P. vera ‘Ghazvini’ × P. atlantica (G×A) were subjected to 0, 50, 100 and 150 mM NaCl in half strength Hoagland’s nutrient solution. After 45 days, the growth, water relations, and oxidative damage parameters were investigated. Salt stress reduced plant biomass, height, crown diameter and leaf number, but increased specific leaf area (SLA) of the seedlings. Under salt stress, the growth of ‘Akbari’ seedlings was higher than the other genotypes. Accumulation of malondialdehyde (MDA) and proline was observed in the leaves of salt affected seedlings. ‘Ghazvini’ seedlings had the highest MDA concentration and the lowest cell membrane stability in their leaves. Degredation of photosynthetic pigments under salt stress was lower in the leaves of ‘Akbari’ seedlings than that in other genotypes. Increase in leaf succulence was observed in ‘Akbari’ and G×A seedlings in response to salt stress. Relative water content and concentration of anthocyanins in the leaves of pistachio genotypes remained unchanged under salt stress. The results revealed that monitoring leaf abscission, SLA, leaf succulence, MDA concentration, and photosynthetic pigments provide suitable contrast for screening salt tolerance in pistachio. Furthuremore, ‘Akbari’ was found to be the most salt tolerant genotype.

In protected cultivation, increasing the light level via supplementary lighting (SL) is critical to improve external quality, especially in periods with low light availability. Despite wide applications, the effect of light quality remains understated. In this study, the effect of SL quality and nutrient solution electrical conductivity (EC) on growth and flowering of three bromeliad species was investigated. Treatments included solar light, and this supplemented with R90B10 [90% red (R) and 10% blue (B)], R80B20 (80% R and 20% B), and R70B30 (70% R and 30% B). These were combined with an EC of 1 and 2 dS m^-l. Irrespective of the light treatment, the higher EC promoted growth, inflorescence emergence, and development in Aechmea fasciata (Lindl.) Baker, whereas adverse effects were noted in Guzmania and Vriesea. The higher EC-induced negative effect in Guzmania and Vriesea was slightly alleviated by SL. With few notable exceptions, SL exerted limited effects on photosynthetic functionality. Depending on the species, SL improved external quality traits. In all species, SL increased root and inflorescence weight and stimulated biomass allocation to generative organs. It also accelerated inflorescence emergence and promoted inflorescence development. In this way, the time to commercial development stage was considerably shortened. These effects were more prominent at R80B20 and R70B30. Under those conditions, for instance, inflorescence emergence occurred 3–5 weeks earlier than in the control, depending on the species. In conclusion, SL with increased B proportion leads to shorter production period owing to faster emergence and improved development of the inflorescence and is recommended for commercial use.

Grafting type and covering method of the graft union have significant effects on grafting success. Two experiments were conducted to determine the best method of grafting and the covering of graft union in walnuts during 2014 and 2015. In the first experiment, plants were grafted under a shade-house with 50% reduction of sunlight. Two methods of saddle and tongue grafting, and three covering methods of graft union including moist sawdust, moist mixed coverage (cocopeat + soil + manure) and plastic cover (control) were used. In the second experiment, two walnut cultivars, ‘Chandler’ and ‘Franquette’ were used as scions along with four grafting methods, including saddle, tongue, omega and V under outdoor conditions. In this experiment, graft unions were covered with moist sawdust. The results of the first experiment showed that, 4 weeks after grafting, the rate of graft-take was better in saddle grafting compared to tongue grafting (76.8 and 62%, respectively). Covering by moist sawdust was better than the other two covers. In the second experiment, the omega method caused the best quality of callus, the highest callused grafts (89.1%) and the most successful graft-take (81.6%). Meanwhile, V grafting caused the highest survival percentage (65.8%) and growth of scions (107.9 cm) after 6 months. Therefore, we recommend this method for grafting walnuts under outdoor conditions.