Abstract Through the last decades, environmentally and
health-friendly production methods and conscientious use
of resources have become crucial for reaching the goal of a
more sustainable plant production. Protection of the environment
requires careful consumption of limited resources
and reduction of chemicals applied during production of
ornamental plants. Numerous chemicals used in modern
plant production have negative impacts on human health and
are hazardous to the environment. In Europe, several compounds
have lost their approval and further legal restrictions
can be expected. This review presents the more recent
progress of genetic engineering in ornamental breeding,
delivers an overview of the biological background of the
used technologies and critically evaluates the usefulness of
the strategies to obtain improved ornamental plants. First,
genetic engineering is addressed as alternative to growth
retardants, comprising recombinant DNA approaches targeting
relevant hormone pathways, e.g. the gibberellic acid
(GA) pathway. A reduced content of active GAs causes
compact growth and can be facilitated by either decreased
anabolism, increased catabolism or altered perception.
Moreover, compactness can be accomplished by using a
natural transformation approach without recombinant DNA
technology. Secondly, metabolic engineering approaches
targeting elements of the ethylene signal transduction
pathway are summarized as a possible alternative to avoid
the use of chemical ethylene inhibitors. In conclusion,
molecular breeding approaches are dealt with in a way
allowing a critical biological assessment and enabling the
scientific community and public to put genetic engineering
of ornamental plants into a perspective regarding their
usefulness in plant breeding.