Genetic mapping of monoterpene composition in an interspecific eucalypt hybrid

Genetic control of foliar oil composition was investigated amongst half-sib progeny of an interspecific eucalypt hybrid. The oil was found to be largely composed of the monoterpenes, limonene, α−pinene, γ−terpinene, 1,8 cineole and p-cymene. Due to difficulties in the interpretation of the compositional data based on raw proportions, further analysis was conducted using log-ratio variables. A high degree of intercorrelation amongst log-ratios was thought to be a consequence of commonality in the biosynthetic origins of the monoterpenes. Quantitative trait locus (QTL) analysis of log-ratio variables indicated that a significant (68–81%) proportion of the variation in four out of the ten possible log-ratios were controlled by a single genomic region of the maternal Eucalyptus grandis parent. The impact of this genomic region upon oil composition was thought to be a consequence of a gene, or genes, controlling the production of limonene, as limonene was the predominant oil constituent in many hybrid individuals and was common to all log-ratios associated with the identified genomic region.