Independent genetic control of drought resistance, recovery and growth of Eucalyptus globulus seedlings.

Drought is a major stress impacting forest ecosystems world-wide. We utilised quantitative trait loci (QTL) analysis to study the genetic basis of variation in i) drought resistance and recovery, and ii) candidate traits which may be associated with this variation in the forest tree Eucalyptus globulus. QTL analysis was performed using a large outcrossed F mapping population from which 300 trees were phenotyped based on the mean performance of their open-pollinated F progeny. Progeny were grown in a glasshouse in a randomised complete block design. A subset of seedlings was subjected to a drought treatment after which they were rewatered and scored for damage and post-drought growth. Non-droughted seedlings were assessed for growth traits as well as lignotuber size and resprouting following severe damage to the main stem. QTL were detected for most traits. Importantly, independent QTL were detected for i) drought damage and plant size; ii) drought damage and growth recovery, and iii) lignotuber size and resprouting capacity. Such independence argues that trade-offs are unlikely to be a major limitation to the response to selection and at the early life history stage studied there are opportunities to improve resilience to drought without adverse effects on productivity.