Backhousia citriodora F. Muell.—Rediscovery and chemical characterization of the L‐citronellal form and aspects of its breeding system

Abstract The rare L ‐citronellal form of Backhousia citriodora F. Muell. was first reported in 1950 but attempts to relocate it were unsuccessful until 1996. The quest to relocate trees of this type has been driven by interest in L ‐citronellal for perfumery. The common, citral form of the species is already under cultivation for oil production in Australia. This paper reports on the rediscovery of the L ‐citronellal form, first in 1996 in a year‐old provenance/progeny trial of B. citriodora in south‐eastern Queensland, and then in a natural population on Queensland's Sunshine Coast in 1998. The three L ‐citronellal trees in the trial gave foliar oil concentrations (g/100 g dry weight) of 3.2, 2.2 and 1.8, respectively, when sampled in November 1996. The same trees sampled in March 1999 gave pale yellow oils consisting of 85–89% citronellal, 6–9% isopulegol isomers with small quantities of citronellol (approx. 3%) and several other compounds. Data on the physicochemical properties of these oils are given in the paper. Seed from a single mature L ‐citronellal tree gave progeny of both the L ‐citronellal and citral form in a ratio of approximately 1 : 1. Propagation material from many more plants of the L ‐citronellal form needs to be collected and assembled in breeding populations. This would form the basis of a selection and breeding programme, should this chemotype show economic potential. Copyright © 2001 John Wiley & Sons, Ltd.