Molecular analyses of evolution and population structure in a worldwide almond [Prunus dulcis (Mill.) D.A. Webb syn. P. amygdalus Batsch] pool assessed by microsatellite markers

A total of 158 almond accessions representative of the diversity of almond across the five continents were included for analysis using 17 microsatellite polymorphic markers. Genetic relationships among genotypes were estimated using cluster analysis, allowing their differentiation in two main groups, one with the domesticated almond cultivars and selections and the other with all wild Prunus species close to almond. The unweighted pair group method average tree drawn from this analysis classified the genotypes according to their geographical origin, confirming the particular evolution of different almond ecotypes. Structure analysis showed a strong subpopulation structure and linkage disequilibrium decaying with increasing genetic linkage distance. Analysis of molecular variance confirmed that most of the genetic variability was within populations. Therefore the connection structure between the different populations and the possible bottlenecks in the expansion of almond cultivars could be established.