Complex mutational patterns and size homoplasy at maize microsatellite loci

VERONICA V. LIA; MARIANA BRACCO; ALEXANDRA GOTTLIEB; LIDIA POGGIO; VIVIANA CONFALONIERI

THEORETICAL AND APPLIED GENETICS

Springer-Verlag

Año: 2007 vol. 115 p. 981 - 991

0040-5752

Microsatellite markers have become one of the most popular tools for germplasm characterization, population genetics and evolutionary studies. To investigate the mutational mechanisms of maize microsatellites, nucleotide sequence information was obtained for ten loci. In addition, Single-Strand Conformation Polymorphism (SSCP) analysis was conducted to assess the occurrence of size homoplasy. Sequence analysis of 54 alleles revealed a complex pattern of mutation at 8/10 loci, with only 2 loci showing allele variation strictly consistent with stepwise mutations. The overall allelic diversity resulted from changes in the number of repeat units, base substitutions, and indels withinrepetitive and non-repetitive segments. Thirty-one electromorphs sampled from six maize landraces were considered for SSCP analysis. The number of conformers per electromorph ranged from 1 to 7, with 74.2% of the electromorphs showing more than one conformer. Size homoplasy was apparent within landraces and populations. Variation in theamount of size homoplasy was observed within and between loci, although no diVerences were detected among populations. The results of the present study provide useful information on the interpretation of genetic data derived from microsatellite markers. Further eVorts are still needed to determine the impact of these Wndings on the estimation of population parameters and on the inference of phylogenetic relationships in maize investigations.