AGRONOMIC EVALUATION OF A COLLECTION OF FRENCH PERENNIAL RYEGRASS POPULATIONS - MULTIVARIATE CLASSIFICATION USING GENOTYPE-X ENVIRONMENT INTERACTIONS

Five hundred and forty-seven natural populations of perennial ryegrass were collected as seeds from all over France in 1983 and 1984, then evaluated at 9 sites in spaced plant nurseries. Ten traits of agronomic interest were observed over a 3-yr life cycle. An analysis of variance of these traits for 3 sites with a complete data set revealed the considerable importance of population x location interactions in the total variation for 6 out of the 10 traits: the susceptibilities and vigor traits. Principal component analyses were carried out on the interaction terms in 8 locations for each trait, which allowed the reduction to 4 as the minimum number of locations required to describe the most important part of interactions. A hierarchical clustering method was thus carried out using adjusted means of the 4 stable traits (absence of vernalisation requirement for flowering, growth habit, aftermath heading and heading date) or phenotypic means of the 6 others (rust susceptibility, frost susceptibility, spring, summer and autumn growth and persistence) in each of the 4 locations retained. A partition into 11 clusters was chosen from the view of the tree, accounting for more than 50% of the inertia. Each cluster was described by the mean of each trait and by its location on the map. One cluster (10) show a good performance in every location compared with control cultivars for every trait which show significant deviation from the general mean, except persistence in one location. Other clusters show more specific adaptation, ie they are above average in only one evaluation site. Good behavior at Mont de Marsan (South France) of the local populations of the surrounding region was observed. The evolutionary implications and usefulness of this type of typology for genetic resource management and plant breeding are discussed.