Cross-amplification and sequence variation of microsatellite loci in Eurasian hard pines.

Microsatellite transfer across coniferous species is a valued methodology because de novo development for each species is costly and there are many species with only a limited commodity value. Cross-species amplification of orthologous microsatellite regions provides valuable information on mutational and evolutionary processes affecting these loci. We tested 19 nuclear microsatellite markers from Pinus taeda L. (subsection Australes) and three from P. sylvestris L. (subsection Pinus) on seven Eurasian hard pine species ( P. uncinata Ram., P. sylvestris L., P. nigra Arn., P. pinaster Ait., P. halepensis Mill., P. pinea L. and P. canariensis Sm.). Transfer rates to species in subsection Pinus (36-59%) were slightly higher than those to subsections Pineae and Pinaster (32-45%). Half of the trans-specific microsatellites were found to be polymorphic over evolutionary times of approximately 100 million years (ten million generations). Sequencing of three trans-specific microsatellites showed conserved repeat and flanking regions. Both a decrease in the number of perfect repeats in the non-focal species and a polarity for mutation, the latter defined as a higher substitution rate in the flanking sequence regions close to the repeat motifs, were observed in the trans-specific microsatellites. The transfer of microsatellites among hard pine species proved to be useful for obtaining highly polymorphic markers in a wide range of species, thereby providing new tools for population and quantitative genetic studies.