Abstract
Two forms of A. halimus shrubs: erect habit (A. halimus) and bushy habit shrub (A. schweinfurthii) are used naturally isolated by a considerable distance from each other and occupy the same area. To explore the effect of natural isolation on the genetic basis of the two forms, Start Codon Targeted (SCoT) and the phylogenetic relationships of A. halimus by sequencing ITS1-5.8S-ITS2 regions of the ribosomal DNA are used. Significant isolation-by-distance relationship was found (r = 0.62, P = 0.001). Soil factors did not influence molecular variations. The natural isolation of A. halimus habitats restricts gene flow among the populations and the observed high within-population genetic diversity (74.19%) in this species is best explained by its outcrossing behaviour, long-lived individuals and overlapping generations. The UPGMA analysis of the SCoT results showed that all the studied populations were divided into two discrete genetic groups with significant separation of the two forms in Burg El-Arab area (Populations 1 and 2) and insignificant separation between two forms in El-Hammam area (population 5 and 6). The sequencing of the ITS1-5.8S-ITS2 rDNA regions also showed the insignificant separation of the two A. halimus forms. We conclude that gene flow depending on habitat fragmentation was the main factor affecting the population genetic differentiation. We suggest that the two forms do not merit specific rank in presence of interference between the two forms and absence of a breeding barrier fail to separate the different populations when they become sympatric.
Highlights
Atriplex halimus L. (Chenopodiaceae), a C4 perennial shrub, highly outbreeding, is found in semi-arid and arid environments
For analysis of variability of A. halimus, 10 primers were used for studying the Start Codon Targeted (SCoT) banding patterns across the entire samples
This result agrees with Bouda et al [41] who suggested that A. halimus populations from Morocco are very largely differentiated based on RAPD data (Fst = 0.334, P = 0.000)
Summary
Atriplex halimus L. (Chenopodiaceae), a C4 perennial shrub, highly outbreeding, is found in semi-arid and arid environments. (Chenopodiaceae), a C4 perennial shrub, highly outbreeding, is found in semi-arid and arid environments. This species, well adapted to arid and salt-affected areas, is valued as livestock forage in low rainfall Mediterranean areas [1]-[4] and is considered as a promising forage plant for large-scale plantings [5]. The taxonomic revision of Atriplex halimus L. in Egypt revealed the presence of two subspecies namely: subsp. This treatment was based on the pollen diversity. Both subspecies of Atriplex halimus L., are extremely heterogenous in terms of their morphology, ecology and productivity [11]. Determination of DNA content showed that certain populations with morphologies intermediate between those considered typical of subsp. halimus and schweinfurthii were tetraploid [14]
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