Genetic diversity and structure of walnut (Juglans regia L.) genotypes from Middle and High Atlas mountains of Morocco as investigated by Inter-Simple Sequence Repeat (ISSR) markers

Abstract

The genetic diversity and genotypes structure of walnut (Juglans regia L.) are essential to understand and manage genetic resources of this species, as well as for further progress in breeding programs. ISSR markers were used to assess the genetic diversity of 66 individuals’ trees from 11 accessions, representing the main cropping area of walnut belonging to two ranges types of Mountain in Morocco: middle and high Atlas. Eleven ISSR primers rendered a total of 135 bands (91%) with 0.88 polymorphic information content. The utilization of 123 polymorphic bands revealed a high level of genetic variation within and among the examined accessions. The multi-locus values of Ht and Hs were 0.25 and 0.20, respectively. The AMOVA analysis showed that 71.30% of total genetic variability is accounted within accessions and 28.70% between accessions. This was congruent with the coefficient of genetic differentiation (GST=0.16). Bayesian model-based clustering approach identified three gene pools that were not correlated with mountain range type. This is the first application of ISSR markers for the assessment of genetic diversity in Moroccan germplasm of walnut. This information will be useful to define conservation strategies and improvement programs of this species.