Caracterizacion y evaluacion preliminar del germoplasma de alfalfa de la Republica Argentina.

There is increasing interest in collection, conservation and utilization of genetic resources. Alfalfa (Medicago sativa L.) is the main forage legume crop in Argentina, having a considerable number of ecotypes and landraces. However, during the last decade, there has been a massive introduction of foreign cultivars which is jeopardizing the purity and perdurability of those valuable germplasm resources. The objectives of this study were to characterize and evaluate a collection of 71 alfalfa accessions collected in different regions of Argentina and to group accessions by similarity using multivariate analysis techniques. The experiment was established at Anguil Experiment Station of INTA on March 1992 according to a RCB design with four replications. The alfalfa collection was evaluated during the first growing season (1992/93). Seven cultivars, representing the different fall dormancy groups used in Argentina, were included as checks. Characterization and evaluation were based on 28 agronomic, forage quality, pest resistance, and root and crown morphology traits. A statistical description (univariate procedure) of information was calculated. Stepwise discriminant analysis (SDA) was used to identify variables that best discriminated among preassigned geographical origin groups. The 28 traits were included in a cluster analysis (average linkage method) to define similarity groups among accessions. Accessions exhibited greater variability than checks for most traits. Nine traits (Fall growth, Mildew damage, Summer growth habit, Pea aphid resistance, Summer dry matter yield, Leaf Shape, Number of secondary roots, Summer growth, Crown width) were identified by SDA as the most powerful variables to discriminate among geographical origins. Cluster analysis defined seven similarity groups in the collection with most of the Pampean region accession in one big group. A new cluster analysis including only Pampean accessions allowed a better separation between Cordobesas and Bonaerense. The materials included in this study were divided into 8 well defined similarity groups. Although there was an association between geographical origin and similarity groups, it was not absolute. This could indicate a certain degree of exchange among regions.