Development of an early flowering system for poplar breeding and biosafety research

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Tree species produce flowers (reproductive phase) only after a prolonged juvenile phase (vegetative phase), which is quite variable lasting in some tree species until 40 years. The long vegetative phase has impeded the development of forest tree breeding. Even though substantial breeding progress has been made with intensively bred pines, poplars, eucalypts and a few other taxa, forest tree ‘cultivars’ can still be considered as nearly ‘wild plants’ with few if any of the hallmarks of crop domestication. Probably one of the most promising prospects offered by genetic engineering of forest trees is on overcoming the long vegetative phase. Several approaches have been successful on the induction of early flowering in trees using flowering time (FTi) and meristem identity genes. However, hitherto available early flowering poplar systems often show many drawbacks, like disturbed growth, microsporogenesis, and unexpected effects on other developmental processes like wood formation. This project aims to generate a more efficient and reliable system for the induction of flowering in poplar. Early flowering would be very valuable to forest tree breeding and biosafety research on genetic containment. Several approaches will be tested using gene stacking of FTi and flower meristen/organ identity genes. Early flowering, growth performance and wood properties of the different transgenic lines, as well as gene expression of selected poplar FTi and meristem/organ identity genes will be evaluated.