Huge genetic diversity of Persian walnut in Iran provides a great opportunity for walnut breeders to use it for introducing varieties with desirable traits. In this regard, evaluating the genetic diversity and introducing superior genotypes is the foundation step of a walnut breeding program. This study was conducted to exploit the genetic diversity in Savadkuh county, Mazandaran province, Iran to identify some superior genotypes during 2013-2016. In the first step, 91 seed-originated genotypes were selected based on questionnaire. In the second stage, the morphological characteristics of the selected genotypes were studied using two IPGRI and UPOV descriptors in 2015. The results showed that nut and kernel weight ranged between 7.3-16.7 g and 3.2-8.6 g, respectively. Also, kernel percentage and shell thickness varied from 36 to 60.74% and from 0.8 to 2.8 mm, respectively. According to the morphological evaluation, 9 out of 91 genotypes (SR7, SR8, SR14, SR23, SR24, SR33, SR52, SR60 and SR83) were selected as superior genotypes. The selected superior genotypes were morphologically evaluated for two consecutive years (2015-2016). These superior walnut genotypes had high yield, lateral bearing habit (45-60%), heavy (13.4-16.7 g) and large nuts, high kernel percentage (48.6-56.6%), thin to moderate shell (1.1-1.6 mm) with light kernel color. Due to distinct and desirable characteristics, the selected superior genotypes can not only be used as parents in the further breeding program, but also some of them have the potential to release as commercial varieties. Manuscript profile

There are diverse types of gelling agents that are used in media cultures. Agar and Gelrite are among the gelling agents used in DKW culture medium, as the common culture medium for the micropropagation of walnut plants. The effects of these gelling agents have not been investigated on the successful production ofin vitroexplants and the response of the explants to ex vitro evaporative demand is overlooked so far. Stomata and water relations of tissue culture medium determine the successful production ofin vitroplants, therefore this experiment was conducted to investigate the effect of two types of gelling agents (Agar and Gelrite) on the stomatal characteristics, transpiration rate (E), and desiccation responses ofin vitrowalnut explants. Stomatal morphology, transpiration rate, RWC, and some morpho-physiological traits such as shoot length, chlorophyll content, osmotic potential (ψs), proline, and glycine betaine content were evaluated in micropropagated walnut explants cultured on Agar or Gelrite. Analysis of results indicated no considerable changes in the morpho-physiological characteristics of explants grown in DKW medium containing Agar or Gelrite gelling agents. Compared with the medium containing Agar, adding Gelrite to the DKW medium caused a decrease in E and an increase in relative leaf water content (RWC) of the walnut explant's leaves during desiccation. Gelrite induced generation of more closed stomata leading to a reduction in E and increase in RWC during desiccation. This resulted in improvement of walnut plantlet's capacity to conserve their water content and as the consequence promoted ability to prevent ex vitro wilting. Manuscript profile

There are numerous challenges associated with the large-scale production of walnut In vitro-plantlets. It is imperative to develop new environmental control systems for its In vitro propagation. Additionally, there is a lack of knowledge regarding the impacts of lighting systems on the morpho-physiological traits and biomass accumulation in walnut tissue-cultured explants. In this study, walnut nodal shoots were subjected to eight different light spectra, including white, blue, red, green, far-red, blue-red combination, red-far-red combination, and a fluorescent lamp serving as a control, over a period of 28 days. The results indicated that combined spectra treatments, such as blue-red and red-far-red, led to improved biomass accumulation (total fresh and dry weight) compared to other monochromatic light spectral treatments. Furthermore, Light-emitting diode (LED) treatments had a discernible impact on the morpho-physiological traits of walnut In vitro-explants. Specifically, white light spectra enhanced Specific leaf area (SLA), while the green light spectra increased leaf water content (LWC) when compared to other light treatments. Additionally, the application of far-red light elevated leaf mass area (LMA) and water content per unit leaf area (LWCA). The findings of this study demonstrate that the quality, morphological, and growth characteristics of In vitro explants of walnut can be enhanced by utilizing specific light spectra. Manuscript profile

High genetic diversity is the guarantee of success in a breeding program. Therefore, it is important to study the genetic diversity in plant populations. Because Iran consider as one of the primary walnut origin centers, this study was conducted to evaluate the genetic diversity of the walnut population in the Bavanat region in the Southwestern Iran during the 2010-2015 growing season. For this purpose, 349 walnut seed-originated walnut trees from seven different regions of Bavanat were pre-selected based on local information. After primary evaluation, 92 walnut genotypes were selected to be further studied. The phenological and pomological characteristics of the genotypes were evaluated based on IPGRI descriptor. The results showed that high genetic diversity was observed in the studied germplasm in terms of important horticultural traits, especially nut and kernel weight, kernel percentage, nut size, shell thickness, lateral bearing, leafing date, and harvest date. The nut weight, kernel percentage, kernel weight, and shell thickness varied between 6.75-16.33 g, 40.15-67.22%, 3.30-8.15 g, and 0.58-2.30 mm, respectively. Cluster analysis classified the studied genotypes into six main groups. Furthermore, correlations among some horticultural traits indicated that kernel weight, nut weight, difficulty of removal of kernel halves, and shell thickness are main traits in determining kernel percentage. Also, lateral bearing, leafing date, nut weight, and nut size determine the final yield of walnut trees. In conclusion, high biodiversity in the walnut population of Bavanat region provides unique plant genetic resources for walnut genetic improvement programs to achieve desirable commercial cultivars and rootstocks. Manuscript profile

Walnut (Juglans regia L.) is a tree with significant economic value and usage for human health and various food industries. However, fresh walnut kernels are a less widespread product than the dried kernels. This study aimed to determine the fresh walnut kernel properties including, fatty acid composition, proximate composition, total phenolics (TPs), total antioxidant capacity (TAC), acidic, peroxide and saponification values of extracted oil and minerals of fresh walnuts kernels. Green walnut fruits were harvested on commercial maturity. The content of different fatty acids (%) was determined as 16:0; 5.91, 18:1; 77.7, 18.2; 11.13 and 18:3; 2.84. Also, the essential nutritional compounds such as protein content (16 ± 0.67), ash (3± 0.32), water (20 ± 0.49), fat (40 ± 0.22) and total carbohydrate (21 ± 0.23) were quantified and reported in percentages. The energy content was 508 ± 0.48 kcal. Acidic values, peroxide values and saponification values in walnut oil were 3 ± 0.14, 0.3 ± 0.06 and 130 ± 0.54 respectively. Furthermore, the average mineral contents were also determined. In general, it can be claimed that fresh walnuts have significant amounts of protein, oil and minerals, and higher water content in comparison with dry nuts. Nonetheless, our results in comparison with the information available about dry walnuts showed that fresh walnuts contained less oil content compared to dried fruits. Manuscript profile

This study was conducted to determine the best pollinizer for five selected pecan cultivars in southwest of Iran at Safiabad Agricultural Research Center in 2014-2015. The cultivars included: 'GraTex', '10J', 'Wichita 6J', 'GraKing', 'Choctaw' as pollinated cultivars (♀) and 'GraTex', 'Peruque', 'Comanche 4M', '10J', 'Wichita 6J', 'Mohawk', 'Mahan', 'Stuart 2J', '3J', 'Stuart 4J', 'GraKing', 'Choctaw', 'Apache', '6M', 'Wichita 7J' and 'Comanche 5M.' as pollinizer cultivars (♂). In the first step, a pollination chart of cultivars was determined in two years. The pollination chart of cultivars showed that all the cultivars investigated during this study were dichogamous and also protogynous except for the 'Peruque'. ‘GraKing’ had the longest duration of shedding pollen. Pollination chart showed that 'Peruque', ‘GraKing’, and 'Stuart 2J' had flowering overlap with the selected cultivars. Pollen germination test showed that the germination ability was different among the cultivars. It was 45% for 'GraKing' and 35% for 'Peruque', which were both recommended as pollinizers in this study. '6M', 'GraTex' and 'Stuart 4J' cultivars had the highest pollen germination percentage of 65%, 60% and 60%, respectively. The results of controlled pollinationtest showed that different pollen sources had no significant effect on nuts per cluster but self-pollinated all of the cultivars significantly reduced fruit set in first and second years. Based on the present research, pollination in pecan orchard was necessary for adequate yield. Also, 'Peruque', 'GraKing' and 'Stuart 2J' were the best pollinizers for five selected cultivars in southwest of Iran. Manuscript profile

Grafting on epicotyl of young seedlings has been introduced as a simple and rapid method for walnut propagation. Although this technique improves the grafting success and propagation efficiency, it is technically more demanding than the conventional walnut grafting procedures and is yet to be optimized. This study was aimed to investigate the influence of rootstock type (dwarf and standard genotypes), graft union covering materials (perlite, sawdust, coco-peat and perlite at 1:1 ratio, and without cover - control) and different epicotyl grafting procedures (Gandev-Arnaudov and Frutos) on grafting success and performance of the grafted plants in order to optimize the walnut epicotyl grafting. Walnut seedlings were grown in a greenhouse. After four weeks, dormant shoots of walnut ‘Chandler’ were grafted to the epicotyl of young walnut seedlings. Grafting success and callusing quality were recorded 30 days after grafting. Growth parameters of the grafted plants, including number of nodes and length of internodes, height and diameter of scion, and survival of the grafted plants, were determined 150 days after grafting. Enhanced grafting success and performance of the grafted scions were obtained by following the Frutos’s procedure. Moreover, the highest grafting success (75.1%) and survival of the plants (91.7%) were obtained by using the dwarf rootstock and application of sawdust as graft union cover. In conclusion, performing walnut epicotyl grafting according to Frutos’s procedure by using dwarf genotypes as rootstock and covering the graft union with sawdust was suggested to obtain maximum propagation efficiency (68.7%). Manuscript profile

In 2007 and 2008, the influence of pollen source on the shell and kernel traits of resulting seeds and on fruit set was examined to evaluate the potential for Xenia or Metaxenia in Persian walnut. Pistillate flowers of ‘Jamal’, ‘Chandler’, ‘Hartley’ and ‘Pedro’ were crossed with the pollen of ‘Serr’, ‘Z60’ and ‘Damavand’. The pistillate flowers on each female parent were covered about one week before starting the reception period of the flowers, and the bags remained 7-10 days after pollination. The catkins of the male parents were collected just prior to pollen shedding, and they were kept in room temperature for 24- 48 hours. Collected pollen was refrigerated until use. Pollination was done when the stigmas were expanded and were pinkish in color. Data recording were started after removing the bags and measuring the percent of fruit set and recording the fruit growth and time of ripening. The fruits, nut and kernel weight, length, diameter, length to diameter, shell thickness, shell weight and kernel percentage were evaluated after harvest. The result showed that nut and kernel diameter, kernel weight, length to diameter, shell-thickness and shell weight were affected by pollen source. There were also significant differences in the fruit set of the different pollen parents. Pollens of ‘Damavand’ and ‘Z60’ significantly decreased the nut diameter and weight in some female parents. Total fat and protein content of kernels were significantly affected by the type of pollen parent. Manuscript profile