Evaluating Genetic Variation of Brassica tournefortii Gouan Collections Via Microsatellite Marker Analysis

Plants can differ in phenotypes, but genetic variation may not always reflect phenotypic differentiation. In this study, we tested if native, invasive and landrace population types of Brassica tournefortii Gouan diverged genetically. We performed this comparison by genotyping individuals derived from our own field collections (invasive populations) and from USDA accessions (plants from the native range and landraces). We used two polymorphic microsatellite loci to analyze allelic diversity (Question 1), genetic differentiation, admixture, inbreeding (Question 2) and evolutionary relationships (Question 3) of three population types and of 17 populations of B. tournefortii. Comparison of allelic diversity indices and observed heterozygosity among population types, revealed that native populations had, on average, the highest estimates of genetic diversity (Question 1). Overall, the native, invasive and landrace population types had low levels of genetic differentiation and significantly varied in amount of admixture (Question 2). Differences in self-fertilization rates among individuals within populations may have accounted for the microsatellite variation detected. The two microsatellite loci contained enough variability to detect genetic divergence between the native, invasive and landrace population types (Question 3).