Eucalypts were first introduced in Congo-Brazzaville in 1953. Since then, 63 different species have been introduced that produce large quantities of firewood, charcoal and wood pulp. About 10 species thrive in Congolese ecosystems. Since 1960, successful hybrids have been developed from these species - a eucalyptus genetic improvement programme was therefore set up to create suitable hybrid populations. Eucalyptus urophylla is the species that produces the best hybrids after crossing (through a reciprocal recurrent selection programme ), with good biomass yields. There is especially high variability within suitable species, thus strengthening the "improved populations" for selection. In 1973, a CTFT (now CIRAD-Forêt) seed-gathering mission to the Sunda Isles focused on two eucalyptus species: E. urophylla and E. alba . Seventy different E. urophylla rootstocks were planted in 1973 at two locations in the southern Congo (Loudima and Loandjili). In Loandjili, seeds from different trees of the same origin, were planted together at random. In Loudima, seeds from the same tree were planted together, with two replicates. The "island origin" effects in Loandjili, and "island" "origin" and "block" effects in Loudima were analysed in terms of form and adaptability. Another test was conducted to check the effect of altitude on tree form and adaptability in the Congo. "Island", "origin", and "origin within the Island" affected both form and adaptability, with "island" having a significant effect. The "altitude effect" was significant after 21 years in Loudima.
Unité de recherche sur la productivité des plantations industrielles (UR2PI) ; Programme matériel végétal ; BP 1291 ; Pointe-Noire ; Congo.