Breeding strategies for woody ornamentals.

摘要

Besides classical cross breeding and selection, more modern breeding techniques offer an extended potential to introduce new genetic variation in woody ornamentals. Artificial polyploidisation can by itself be used to create new variation. Polyploid plants in general are more robust and more sturdy than diploids. Frequently, larger flowers, bigger leaves and more vigorous growth can be observed. The induction of polyploidy is also a common technique in interspecific crosses to overcome the sterility in F₁-progenies or to generate genotypes with equal ploidy level when interploidy crosses are problematic. Interspecific and even intersubgeneric hybridizations are highly interesting to combine desired traits from genetically distinct genotypes. In vitro protocols are also available to induce in some species somaclonal variation or are used in mutation breeding or for genetic transformation. In several woody ornamentals genetic modification has already been demonstrated, but until now practical use is hampered by legislation and public acceptance. Molecular markers and cytogenetic techniques can unravel genetic relationships between species and genera in advance. The same techniques assist afterwards to prove the hybrid status of the progeny or to indicate DNA introgression. Also the development and validation of robust, simple and reliable selection protocols are very important for practical breeding programmes. Especially bio-assays and screening methods for selection towards both biotic and abiotic stress resistance are desired. For disease resistance screening this implies knowledge about the pathogen and pathogen-host interactions, as well as the availability of artificial infection protocols.