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

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