Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2005
Publication Date: 10/27/2005
Citation: Mian, R.M., Zwonitzer, J.C., Chen, Y., Saha, M.C., Hopkins, A.A. 2005. AFLP diversity within and among hardinggrass populations. Crop Science. 45:2591-2597. Interpretive Summary: HARDINGGRASS (Phalaris aquatica L.), is a cool-season forage grass that grows well in the mild climates, and there is good potential for its adaptation to the southern Great Plains through breeding. Information on genetic diversity of hardinggrass will be very useful for improvement of this species. Currently, little information is available on the genetic diversity of hardinggrass. The objective of this study was to determine the genetic diversity within and among 22 promising hardinggrass populations (including plant introductions (PIs), breeding populations, and one cultivar) with amplified fragment length polymorphism (AFLP) markers. A high degree of genetic diversity was found, with a greater proportion of the diversity within (74%) rather than among (26%) populations. Substantial genetic variation that could be exploited for selection is present within these hardinggrass populations. Further, the evidence indicates that selection within hardinggrass populations need not result in a loss of genetic diversity. The clustering of the accessions from Morocco away from other populations in the study suggests that the Moroccan populations represent distinct germplasm and could be used to construct distinctive populations. Broad based populations could be constructed as well from combinations of several of the non-Moroccan accessions. Finally, the genetic differences between the Moroccan accessions and other populations in this research suggest a starting point for investigating possible heterosis in hardinggrass. Semi-hybrid cultivars might then be developed to take advantage of heterosis.
Technical Abstract: Little information is available on the genetic diversity of hardinggrass (Phalaris aquatica L.), a cool-season forage grass with potential for use in the southern Great Plains. The objective of this study was to determine the genetic diversity within and among 22 promising hardinggrass populations, including plant introductions (PIs), breeding populations, and one cultivar. Nine plants from each population (198 genotypes) were characterized with amplified fragment length polymorphism (AFLP) markers. Genotypes were evaluated with nine selective primer combinations of fluorescent-labeled PstI+3 and MseI+4 or MseI+3 primers, producing a total of 961 useful AFLP fragments. Genetic variation within and between population were estimated by AMOVA analysis and genetic distances were calculated using Jaccard’s coefficients and expressed as Euclidean distances with 961 AFLP fragments. Two hierarchical methods, unweighted paired group method using arithmetic averages (UPGMA) and Ward’s minimum-variance method, and multidimensional scaling (MDS) were applied to define the genetic relationships. A high degree of genetic diversity was found, with a greater proportion of the diversity within (74%) rather than among (26%) populations. Clustering of populations based on UPGMA closely followed the geographic origin and breeding history of the populations. Selections lead to genetic shifts between two breeding populations, HG PI C1 and HG PI C2, although genetic diversity changed little if at all within these populations based on polymorphism information content (PIC) scores of 0.22 versus 0.19, respectively. Two Moroccan PIs (PI 240248 and PI 517026) represent a distinct germplasm source, based on their genetic distances from other populations in the study. Genetic diversity data from this study will be helpful in grouping these accessions for development of breeding populations and various research purposes.