Internal transcribed spacer sequences analysis of genetic variation among and within populations of Atriplex halimus from different bioclimatic zones in Morocco

The genetic diversity of 12 Atriplex halimus L. populations collected throughout its natural range in Morocco has been studied by using sequences of nrDNA ITS region. Within-population genetic diversity was high in comparison to others species with similar life histories and ecological traits. Most of genetic variation detected by AMOVA resided within populations (94%), relative to the amount of variation among populations (6%). The level of populations differentiation (FST = 0.06) was low, which corresponds with the high level of gene flow (4.00) revealed between populations. Differentiation among ecological groups of populations accounted only for 1.23% of the total ITS variation, which indicates that climatic conditions did not have an effect of population's structuration or that this differentiation is obviously not related to ITS markers. Furthermore, very low genetic differentiation (FCT = 0.015) was observed between regions (Moroccan populations versus American population). Strangely enough, geographic distances were not correlated to genetic differentiation between the populations (r = 0.06, P = 0.5). The structuration of populations in five groups was not operated according to their bioclimatic type. The data obtained in this assay could play a crucial role to establish efficient strategies for genetic resources conservation and to work out the scheme of breeding programs of Atriplex