Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/29/2001
Publication Date: 1/1/2002
Citation: Johnson, R.C., Johnston, W.J., Golob, C.T., Nelson, M.C., Soreng, R.J. 2002. Characterization of the usda poa pratensis collection using rapd markers and agronomic descriptors. Genetic Resources and Crop Evolution. 49:349-361. Interpretive Summary: Characterization of germplasm collections is critical to assess collection diversity and enhance utilization. This paper reports work in which the USDA Kentucky bluegrass collection was characterized for both molecular variation at the DNA level as well as agronomic variation. The results showed that both the molecular and agronomic characterizations were useful in determining overall diversity in the Kentucky bluegrass collection. The molecular technique was, however, better at determining misidentified accessions. Both approaches showed that not two accessions in the collection were duplicates but highly diverse material was generally under represented. The correlation between the molecular and agronomic-based techniques was significant but both molecular and agronomic characterizations were needed to assess overall diversity.
Technical Abstract: Characterization of germplasm collections is critical to assess collection diversity and enhance utilization. A Poa pratensis L. germplasm collection of 228 accessions representing 26 countries, along with 17 commercial check cultivars, was characterized using 86 random amplified polymorphic DNA (RAPD) markers and 17 agronomic descriptors. The Dice similarity coefficient used for RAPD data ranged from 0.56 to 0.95 and average Euclidean distance used for agronomic data ranged from 0.28 to 2.52. No two accessions had a similarity of one or a distance of zero, showing there were no duplicate entries. Cluster analysis of RAPD data using the unweighted pair-group method using arithmetic average (UPGMA) revealed 11 accessions with particularly low similarity values. These were subsequently found to be misidentified Poa species (one each of P. aplina, P. compressa P. glauca, P. urssulensis, and seven P. trivialis). For RAPD data, 62% of the entries were in one large cluster with 46 additional clusters containing one to 13 accessions. For agronomic data, 89% of the entries were in four main clusters. This clustering pattern for RAPD and agronomic data suggested unique genotypes were generally under represented in the collection. The agronomic-based clusters showed some broad separation by accession origin, but in general, origin did not correspond closely with the clustering pattern. The correlation between the RAPD and agronomic- based distance matrices, excluding misidentified accessions, was highly significant (P<0.01) (n=234, r=-0.14). However, the correlation represented a relatively small fraction of the total variation, indicating that both molecular and agronomic characterizations were needed to assess overall diversity.