THE BREAK -THROUGH IN THE REDUCTION OF JUVENILE PHASE IN APPLE USING TRANSGENIC APPROACHES

In contrast to herbaceous plants, fruit trees such as apple [Malus x domestica (Borkh.)] flower and set fruit only after an extended juvenile phase that lasts several years.
In the course of studying juvenility in apple, we have cloned the MdTFL gene homologous to Arabidopsis TERMINAL FLOWER1 (TFL1) gene, which suppresses floral meristem identity genes, LEAFY (LFY) and APETALA1 (AP1). The expression of MdTFL (Malus x domestica TFL1) mRNA was strong in sepals and mature leaves, and highest in early July, about two weeks before flower induction, in apical buds in apple.
Transgenic apples expressing antisense MdTFL gene flowered at about eight to 15 months after grafting onto rootstocks.
On the other hand, non-transformed control plants have not flowered in five years.
The flower organs of the transgenic apples were normal and fertile.
These results demonstrate that the suppression of the expression of MdTFL gene reduces the juvenile phase and can induce precocious flowers in apple.