Genetic analysis of the near-infrared spectral phenome of a global Eucalyptus species

Understanding the genetic-based variability in plant phytochemical compounds provides insight into the evolutionary and ecological processes affecting those traits. In some cases, it is an advantage to quantify the holistic phytochemical profile of a sample rather than focus on individual compounds of known interest. Near-infrared (NIR) reflectance spectroscopy provides a means to rapidly characterise the holistic physicochemical profile of biological materials (known as the spectral phenome). To date, most studies examining differences in the spectral phenome between groups and species have not been conducted in such a way as to enable the quantitative genetic basis of the variation in the spectral phenome to be determined. Here, we investigate the genetic-based variation in the spectral phenome of eucalypts focussing on comparisons at multiple scales of the genetic hierarchy using a tree species of global economic importance, Eucalyptus globulus. Using foliage collected from common-environment field trials we were able to use the spectral phenome to accurately differentiate advanced generation inter-specific hybrids and their parents and examine the pattern of inheritance of the holistic chemical profile. We also found intra-specific variability in the spectral phenome at the race, sub-race and family within race levels, and could identify clear genomic positions influencing the spectral phenome. We have used Eucalyptus as a test system to demonstrate the general approach of using the spectral phenome in genetic-based analyses, an approach that is readily transferrable to other plant systems.