Early flowering in trees
Shortening the vegetative phase in trees by cultural and genetic methods
Biosafety studies with transgenic forest plants suffer from the long generation times of trees. To analyze gene technologically induced sterility within a given time frame of two to three years it is desirable to shorten the vegetative phase of the poplars considerably.
Background and Objective
The induction of early flower formation is very important with transgenic poplars within the scope of the investigations for sterility and for spruce for breeding purposes. A gene technologically approach is tested beside physiological attempts for the production of early-flowering poplar lines with the help of the genes which have caused an early flowering already in other plant species. Up to now all attempts have missed to stimulate flowering in one-year-old to three-year-old poplars by means of physiological attempts (application of growth retardants, demethylation agents and hormones). In contrary, transgenic poplar carrying “early-flowering” genes formed flowers either already some months after the gene technologically change or as three-year-old plants. Different genetic constructs were used for the transformation by poplars.
The gene BpMADS4 from birch was tested in poplars for the first time. In transgenic birches this gene has caused a precocious flower formation. First BpMADS4 transgenic poplars were generated in the beginning of 2002, transferred into greenhouse and molecularly examined. Some transgenic plants are cultivated since middle of 2002 in climate chambers. However, a flower-inducing effect of this construct has not been found in transgenic poplars up to now. Nevertheless, during the culture in greenhouse it was observed that the BpMADS4 transgenic poplar lines didn’t loose their leaves completely. The expression of the two Arabidopsis thaliana genes Leafy and FT has promoted flowering in different plant species. In poplar, early flowering has been observed for both genes in in-vitro culture as well as in soil in the first year. The early-flowering Leafy- and FT-transgenic poplar lines are fertile under greenhouse conditions. Nevertheless, Leafy-and FT-induced reduction of the juvenility as well as the maintenance of fertility are strongly influenced by the genotype of the used poplar line. Additional flower-inducing genes are also being tested.
The gene BpMADS4 from birch was tested in poplars for the first time. In transgenic birches this gene has caused a precocious flower formation. First BpMADS4 transgenic poplars were generated in the beginning of 2002, transferred into greenhouse and molecularly examined. Some transgenic plants are cultivated since middle of 2002 in climate chambers. However, a flower-inducing effect of this construct has not been found in transgenic poplars up to now. Nevertheless, during the culture in greenhou
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