Genetic diversity in natural populations and corresponding seed collections of little bluestem as revealed by AFLP markers

Little bluestem [Schizachyrium scoparium (Michx.) Nash] is one of the most widespread native grasses in North America. Little is known about the genetic diversity of this species in natural populations and in seed collections. The amplified fragment length polymorphism (AFLP) technique was applied to assess the comparative genetic diversity of six natural populations of little bluestem in Manitoba and Saskatchewan and their corresponding seed collections. Five AFLP primer pairs were employed to screen a total of 180 samples representing about 15 tillers per population and 15 seeds per collection, and 158 polymorphic AFLP bands were scored for each sample. Analyses of these scored bands revealed that >91% of the total AFLP variation was present within the natural populations and within the seed collections. The among-population and among-collection variation components, although relatively small (7-9%), were statistically significant from zero. Comparisons of AFLP profiles between the seed and tiller samples revealed the seed samples had fewer polymorphic bands, higher average band frequencies, and more bands with extremely high or low frequencies. A significant association of AFLP variation with geographical origin was detected in the seed, but not the tiller samples. These results indicate collecting seeds may not be as effective as collecting tillers in sampling genetic diversity from natural populations for the improvement of little bluestem germplasm for rangeland seeding.