Biotechnological approaches to shorten the juvenile period in fruit trees
Fruit trees have long generation intervals. Tree development from the juvenile (non-flowering) to the adult stages requires several years and is a disadvantage for plant breeders. To accelerate the onset of flowers by reducing the juvenile period is an important aim for research. Detailed understanding of genetic factors controlling the process of flower formation during tree development is basic to develop appropriate techniques to shorten the juvenile period. Several key genes were identified which regulate floral induction and flower development in Arabidopsis. Ectopical overexpression of LFY and AP1 resulted in precocious flowering in different plant species. The overexpression of BpMADS4, MdFT1 and MdFT2 in apple was successful in reducing the juvenile period. The down-regulation of MdTFL1 in apple resulted in the activation of floral pathway integrators and the development of flowers. Transgenic fruit tree plants obtained by overexpression or down-regulation of genes involved in flower induction and initiation are as interesting for breeders as for researchers. The paper presents an overview of flower induction using genetic engineering in fruit trees.