Optimization of chloroplast microsatellite PCR conditions and primer screening for endangered Rheum officinale, Rheum palmatum, and Rheum tanguticum.

Chloroplast microsatellite primers were developed in order to provide more population genetic information of endangered Rheum officinale, R. palmatum, and R. tanguticum for conservation. The dried roots and rhizomes of these plants are important in traditional Chinese medicine. The results showed that the optimum concentrations of Mg(2+), Taq DNA polymerase, dNTPs, template DNA, and primers in a 25-μL reaction system were 2.0 mM, 1.0 U, 0.10 mM, 20 ng, and 0.8 μM, respectively. Fourteen of 53 primer combinations were chosen for their high clarity and repetition in three species, and their annealing temperatures ranged from 56 to 58°C. These primers and the optimized polymerase chain reaction system may provide a tool for understanding the demography and genetic variation of these endangered plants.