Genetic control of Eucalyptus globulus seed germination

Key message: The maternal genotype has a significant effect on most germination traits of Eucalyptus globulus seeds. These differences can be partly explained by genetic-based differences amongst races, including differences in sensitivity to high temperatures which may be of adaptive significance. Context: Slow and uneven germination of Eucalyptus globulus seeds in commercial nurseries can be a problem which has been linked with periods of high temperature. Aims: This study aimed to determine whether maternal genotype affects the germination of E. globulus seeds. Methods: By sampling seeds over two seasons from multiple randomised ramets (trees) of maternal genotypes from three races of E. globulus growing in a seed orchard, the extent of genetic control of seed germination responses was assessed at different germination temperatures. Results: Maternal genotype had a significant effect on most germination traits but a differential response to temperature was more evident for germination proportion than rate traits. Maternal races differed in their rate of seedling development regardless of temperature, but differences in the germination proportion were only detected at high temperatures. Conclusion: The present study highlights the potential adaptive significance of the germination response and the need for seed lot-specific germination testing as both genetics and maternal environment vary.