Chemical and morphological variation within a population of Eucalyptus radiata (Myrtaceae) exhibiting leaf volatile oil chemical forms

Abstract

Fifty trees were collected from a population of Eucalyptus radiata subsp. radiata known to contain leaf volatile oil chemical forms. These were studied for leaf volatile oil composition, flavonoid composition, and leaf and fruit morphology. Three distinct groups were detected on the basis of leaf volatile oil composition, representing low, medium and high percentages of piperitone, with 43, 3 and 4 plants in each respectively. The low piperitone group contained two subgroups differing in the inversely varying amounts of α-phellandrene and p-cymene. While there was variation in leaf and fruit morphological characters and in flavonoid composition, there was no correlation between any of these characters and the leaf volatile oil chemical groups. Groups could also be distinguished on the basis of morphological characters, especially fruit characters, but these morphological groups were not as distinct as those based on volatile oil characters. There was no association between the morphological groups and the chemical groups on the basis of group membership. The nature and importance of this variation within a Eucalyptus population are discussed.