STRUCTURE OF THE SPECIFIC COMBINING ABILITY BETWEEN 2 SPECIES OF EUCALYPTUS .2. A CLUSTERING APPROACH AND A MULTIPLICATIVE MODEL

The Eucalyptus breeding program of URPPI (a partnership between CIRAD- Foret. Centre National de la Recherche Forestiere du Congo, and Unite d'Aforestation Industrielle du Congo) consists of a reciprocal recurre nt selection scheme developed in the Congo between the two species Euc alyptus urophylla and Eucalyptus grandis. Two approaches are proposed in order to model and predict the specific combining ability (SCA) bet ween these species, The clustering approach uses a simultaneous cluste ring procedure of the two species based on SCA and reveals heterotic g roups coherent with the geographical origins of E. urophylla genotypes , The second approach uses a multiplicative model to partition the SCA into three multiplicative terms explaining 95% of the interaction.