Interspecific hybridization effect on the content and the chemical composition of essential oils of eucalyptus grown in Morocco

In this work, the quality and quantity of the leave essential oils of five Eucalyptus hybrids were determined. The crosses of Eucalyptus globulus ssp. maideni, Eucalyptus globulus ssp. globulus, Eucalyptus grandis, Eucalyptus cladocalyx and Eucalyptus diversicolor with Eucalyptus camaldulensis have been studied. The average yield of parental species samples varies according to species. It is 3.4/ for Eucalyptus globulus spp. maideni, 2.5/ for Eucalyptus globulus spp. globulus and 1.6/ for Eucalyptus diversicolor. Eucalyptus camaldulensis, Eucalyptus grandis and Eucalyptus cladocalyx are characterized by an average yield less than 1/, i.e. 0.8/, 0.4/ and 0.3/, respectively. The average yields of the two hybrids Eucalyptus camaldulensis x Eucalyptus globulus spp. maideni and Eucalyptus camaldulensis x Eucalyptus diversicolor are 2.9/ and 1.4/ respectively. The combinations Eucalyptus camaldulensis x Eucalyptus globulus spp. globulus, Eucalyptus camaldulensis x Eucalyptus cladocalyx and Eucalyptus camaldulensis x Eucalyptus grandis are characterized by the lowest yields, i.e. 1/, 0.8/ and 0.8/ respectively. The analysis of the chemical composition shows that the hybrids Eucalyptus camaldulensis x Eucalyptus globulus spp. maideni give 1,8-cineole rates superior to 70/, which is required by the users. Comparatively to Eucalyptus camaldulensis, the essential oils of the other crosses reveal a slight decrease in percentage of this product. However, increases of the alpha-pinene and p-cymene contents have been recorded. In general, all products detected in essential oils have average percentages intermediate between those of parental species. Hybridization of eucalyptus can improve the quality and the quantity of eucalyptus essential oils.