Genetic conservation programs in arid environments rely on molecular methods for diversity assessments. DNA-based molecular profiling will aid in conservation and protection of species from genetic erosion. Obtaining intact genomic DNA from Calligonum species, of sufficiently high-quality that is readily amplifiable using PCR, is challenging because of the presence of the exceptionally large amount of oxidized polyphenolic compounds, polysaccharides, and other secondary metabolites. The present method involves a modification of the available CTAB method employing higher concentrations of NaCl and CTAB, and incorporating PEG 6000 (1%) and glucose. The yield of DNA was 60-670 μg g(-1) of fresh tissue. The protocol has been tested with two species from the arid region. The DNA isolated was successfully amplified by two ITS primer pairs. PCR-RFLP analysis of the ITS1-5.8S-ITS2 region among and within Calligonum species followed by sequencing is under way.

The species of the genus Calligonum L. (Polygonaceae) that appear in Tunisian deserts play an important role in maintaining local ecosystems and supply important natural resources in these regions. In this study, 31 individuals belonging to the 3 hypothetical species of the genus Calligonum (Calligonum arich Le Houér., Calligonum azel Maire, and Calligonum comosum L'Hér.) were collected from 12 populations in 6 localities of the Tunisian desert and examined to assess the relationship between species. Phylogenetic analyses using 1 nuclear (ITS) and 2 plastid regions (trnL-trnF and rbcL) and genome size assessments are used in this study to evaluate the relationships between these hypothetical species. C-value results suggest the existence of 3 different species, which is also supported by phylogenetic tree topology. The paraphyletic pattern of C. comosum and the plausible origin of C. arich from C. azel suggest the existence of several mechanisms of isolation and speciation in the Sahara Desert for this genus. Additional studies are necessary to evaluate the population size, demographic tendency, and conservation status of these desert species and their genetic relationships with other congeners.

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