Résumé
An oil palm experiment was set up in the Ivory Coast to compare the effects of crossing and selfing within two origins, Deli and La Me, on the mean and the variability of Deli x Me between-origin hybrids. The originality of the experiment lay in the crossing plan, which provided access to genetic parameters related to additivity, dominance and different components of epistasis. This first part covers the analysis of the components of the mean. The parents used were obtained from four palms, two from each origin. Those of La Me origin were half-sibs. The common parent came from a wild stand in the Ivory Coast. Those of Deli origin were from two different populations bred in Southeast Asia for several generations from a narrow genetic base. These four parents gave rise to nine Deli x La Me hybrid populations with double-cousin-type links. The additive component is more important within the Deli origin than within the La Me origin. This may be explained by the large genetic divergence between the two Deli parent palms. On the other hand, the additive*additive epistasis is more substantial within the La Me origin, probably because of inbreeding. The discussion concentrates on how this information should be used when choosing parents to be crossed and tested and to produce improved populations. The crossing plan proposed can be of general use and is suitable for other species in a reciprocal recurrent selection programme.