A breeding strategy based on molecular genetics to improve tea tree oil production

Tea tree oil production from leaves of Melaleuca alternifolia is a significant agricultural industry with the establishment in recent years of large plantation crops in Australia and several other countries. The oil is highly valued in the pharmaceutical and cosmetic industries for its broad-spectrum germicidal properties. Considerable differences in oil yield and composition are of particular interest to commercial producers, and suggest significant genotypic variability. However, apart from some limited varietal selection, little breeding work has been conducted. Sampling of M. alternifolia leaf material was undertaken from 40 sites throughout the geographic range of the species, which is endemic to north-eastern New South Wales and far south-east Queensland, Australia. Genotypic diversity within the species was studied utilising specifically developed microsatellite DNA markers. These were used to study the genotypic distribution within the species population and between subpopulations. Oil yield and quality analyses were conducted from more than 600 samples in order to identify superior varieties for future commercial production. More importantly, data from the research provides the foundation for a tea tree breeding program to pursue further varietal improvement. Analysis of the microsatellite genotype distributions and the oil phenotypes has facilitated the development of an optimal breeding strategy aimed at parent selection for efficient generation of elite tea tree varieties. The research also lends itself to the future possibility of marker-assisted breeding.