Genetic diversity of blue grama, Bouteloua gracilis, and little bluestem, Schizachyrium scoparium, as affected by selection

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Phan, Anh T.
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There is a renewed interest in the use of native grasses in North America for agronomic, environmental, and ecological purposes. The need for commercial sources of genetically diverse native grass seed prompted the present research. The objectives of this study were threefold: (1) To determine variation in seed yield traits of 11 blue grams and 14 little bluestem plant collections from sites across southern Manitoba, Canada; (2) To develop a simple and effective selection method to improve seed yield potential and maintain genetic diversity in blue grams and little bluestem; (3) To use RAPD molecular markers to assess genetic diversity among and within the 11 blue grams plant collections, and to determine shifts in genetic diversity caused by selection. Analysis of individual plant measurements revealed variation in plant size, culm number, seedhead number, seed yield, caryopsis weight, and anthesis date among all original blue grams and little bluestem plant collections. Genetic variation was found for allmeasured seed yield component traits, and variation among collections was consistent between years, which suggested that collections were genetically distinct. Four selection criteria--seed yield, harvest index, kernel index, and a 'combined index', and three methods of pooling (stratified selection with equal pooling, unstratified with equal pooling, and mass selection) or improving seed production potential on a per plant basis were compared. Selection with a combined index that included seed yield and kernel index for blue grama and one combining kernel index with harvest index for little bluestem, and equal pooling across all plant collections, was shown to improve overall seed production potential while maintaining genetic diversity. A genetic study of the blue grama populations utilized RAPDs. The populations compared included the Original, which was comprised of a random sample of individuals from all original plant collections, the Ecovar, which was derived from a polycross containing an equal number of selections from all pla t collections selected for seed yield and kernel index; and the Cultivar, which was derived from a polycross of individuals selected by a simple mass selection without regard to equal representation from all original plant collections. The RAPD analysis revealed high levels of genetic variation in the Original plant collections. Ecovar and Cultivar populations showed similar levels of genetic variation despite differences in selection intensity and genetic contribution from the original collections. (Abstract shortened by UMI.)