Assessment of genetic diversity and relatedness among Tunisian almond germplasm using SSR markers

H Gouta,A Mliki,E Ksia,M Zarrouk,T Buhner,M Á Moreno,Y Gogorcena

doi:10.1111/j.1601-5223.2009.02147.x

Abstract

Genetic diversity of 50 Tunisian almond (Prunus dulcis Mill.) genotypes and their relationships to European and American cultivars were studied. In total 82 genotypes were analyzed using ten genomic SSRs. A total of 159 alleles were scored and their sizes ranged from 116 to 227 bp. The number of alleles per locus varied from 12 to 23 with an average of 15.9 alleles per locus. Mean expected and observed heterozygosities were 0.86 and 0.68, respectively. The total value for the probability of identity was 4 × 10(-13) . All SSRs were polymorphic and they were able all together to distinguish unambiguously the 82 genotypes. The Dice similarity coefficient was calculated for all pair wise and was used to construct an UPGMA dendrogram. The results demonstrated that the genetic diversity within local almond cultivars was important, with clear geographic divergence between the northern and the southern Tunisian cultivars. The usefulness of SSR markers for almond fingerprinting, detection of synonyms and homonyms and evaluation of the genetic diversity in the Tunisian almond germplasm was also discussed. The results confirm the potential value of genetic diversity preservation for future breeding programs.

Highlights

The almond tree, dating back to ancient times, has been grown extensively in Tunisia since the Carthaginian era, 8th century B.C. (Jaouani 1976)
The results demonstrated that the genetic diversity within local almond cultivars was important, with clear geographic divergence between the northern and the southern Tunisian cultivars
As only little information is available about the genetic diversity and relatedness within Tunisian almond cultivars and their relationship with almond cultivars originated from other countries, the aims of this work are to : 1) identify by simple sequence repeat markers (SSRs) analysis the accessions preserved in the Tunisian National Collection and those collected directly from different sites of the country (Sidi Bouzid and Bizerte); 2) determine their relatedness to European and American cultivars; and 3) estimate the level of genetic diversity

Summary

Introduction

The almond tree, dating back to ancient times, has been grown extensively in Tunisia since the Carthaginian era, 8th century B.C. (Jaouani 1976). In the last five years, more than three million almond trees were lost because of the long period of drought (2000–2002) This has increased the need to preserve as much as possible the Tunisian almond genetic diversity, in order to prevent genetic erosion. (Downey and Iezzoni 2000) These markers have been used for the molecular characteri zation and estimation of genetic diversity among peach, almond and other Prunus species (Aranzana et al 2002; Dirlewanger et al 2002; Martínez-Gómez et al 2003a; Bouhadida et al 2007), sweet cherry (Wünsch and Hormaza 2002) and apricot cultivars (Hormaza 2002; Maghuly et al 2005). SSRs are currently being employed for molecular characterization, estimation of genetic diversity and genetic relationships among almond cultivars and related Prunus species (Martínez-Gómez et al 2003b; Xu et al 2004; Sánchez-Pérez et al 2006; Shiran et al 2007; Zeinalabedini et al 2008)

Objectives

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Results

Conclusion