Microsatellite polymorphism in Pisum sativum

Pisum sativum sequences were retrieved from Genbank/EMBL databases and searched for all possible dinucleotide and trinucleotide tandem repeats. One-hundred and seventy-one simple sequence repeats (SSRs) were found among 663 sequences. The different dinucleotide or trinucleotide motifs occurred at varying frequencies. CT/AG was the most frequent dinucleotide, and TCT/AGA the most frequent trinucleotide. Forty-three microsatellite markers were generated from these sequences and used to assess the genetic variability among 12 pea genotypes. Thirty-one were polymorphic among the genotypes and the average number of variants per marker was 3.6 when considering only polymorphic markers. Overall, the number of variants for a given SSR marker was correlated with the length of the SSR but some 12-bp long SSRs showed the same degree of polymorphism as longer ones. The groupings resulting from the SSR genotyping among the 12 genotypes gave an interesting insight into the possible origin of one recent cultivar. Database-derived SSR markers are highly variable. They can provide useful information on the genetic diversity among P. sativum cultivated types.