Adaptation in Congo Brazzaville of Eucalyptus citriodora from Australia: Tree-to-tree yield and composition variability

Abstract

The adaptation of five lines of Eucalyptus citriodora from Australia (14713, S and W of Mt. Garnet OLD, Australia), introduced in Congo-Brazzaville in 1989 was evaluated on a seeded plantation using starter fertilizer (NPK,13-13-21, at 300 g/plant), set up in 2003 and monitored for about 2 years. Here, we report results for the first 25 months of growth. The analysis of a large number of samples of essential oils obtained showed that their chemical composition was highly stable. Their content varied by harvesting season and tree age, with an average production ranging from 9.83 to 13.28 kg/ha of essential oil. The best results were obtained in the rainy season. The essential oil contents of the different lines were, in descending order: Z444(3.17%), Z442(3.11%), Z439(2.88%), Z443(2.83%), and Z438(2.46%). The level of citronellal, the major constituent of these essential oils, ranged from 54 to 88% in trees 12 years old, and from 81 to 94% in test plants aged 6 to 25 months. Citronellal, citronellol and isomers of pulegol together made up more than 95% of the essential oil. Key words: Eucalyptus citriodora, sylviculture, essential oil composition, citronellal, Congo-Brazzaville.