Phenotypic Evaluation and Identification of Superior Persian Walnut (Juglans regia L.) Genotypes in Mazandaran Province, Iran

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.