Submitted to: North American Alfalfa Improvement Conference
Publication Type: Abstract only
Publication Acceptance Date: 7/20/1998
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: A collection of 20,997 annual Medicago accessions, representing 34 species and 42 species, was evaluated for 27 agronomic characteristics from 1968 to 1994. We developed a method to assemble a core collection from these accessions by maximizing the selected diversity from within 793 groups of accessions defined by species, subspecies, and geographic origin. The mean Euclidian distance of each accession to all other accessions was calculated; each of the 793 groups was represented in the core collection by the extremes of average Euclidian distance found within the group. A small average Euclidian distance indicated "typical" accessions, while a large average Euclidian distance indicated the more unusual types. The mean Euclidian distances calculated ranged from 5.4 to 48.7. Retaining 0.5% of the typical end and 3.0% of the diverse end of each of the 793 groups resulted in the retention of 1705 accessions, or 10.4% of the entire collection. Associations of trait expression were evaluated by calculating correlation coefficients of all combinations of the evaluated traits. Coefficients greater than 0.71, i.e. more than 50% 50% of the variance of one trait is predicted by the other, were for: seedling vigor and average winter yield (r=0.74), average spring yield and average winter yield (r=0.78), grams of seed per plant and grams of pods per plant (r=0.91), number of seed per plant and number of pods per plant (r=0.74), 1000 seed weight and 1000 pod weight (r=0.75), number of seeds per plant and grams of seeds per plant (r=0.77), florets per peduncle and pods per peduncle (r=0.86). None of these relationships were surprising, but they do suggest that it may not be necessary to measure all of the traits involved in future germplasm evaluations.