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Genetic and epigenetic aspects of somaclonal variation: flower colour bud sports in azalea, a case study
S de Schepper, P Debergh, E van Bockstaele, M de Loose, A Gerats, A Depicker
Abstract
Bud sporting
is the consequence of sudden variations in gene expression of somatic cells,
leading to the occurrence of phenotypically altered shoots on plants. This
phenomenon can be observed in most vegetatively propagated plant species
and finds its origin in genetic as well as epigenetic events. In azalea the
frequent occurrence of flower colour sports is appreciated as a valuable
additional source of variation; more than half of the commercial assortment
consists of flower colour bud sports. However, when clonal uniformity is
desired for registration (Distinctness Uniformity Stability, DUS) and mass
propagation, this somaclonal variation is perceived as a hindrance. Insight
into the molecular mechanism(s) underlying the induction of bud sporting
might improve breeding strategies, towards the appropriate choice of cultivars
in hybridisation experiments. The complex beauty of sport phenotypes clearly
indicates interactions within and between genetic and epigenetic mechanisms.
Therefore, using azalea somaclonal variation as a model, a review of the
literature on various genetic and epigenetic phenomena that regulate or influence
gene expression, as well as on the links that exist between them is presented.
South
African Journal of Botany 2002, 69(2): 117–128
is the consequence of sudden variations in gene expression of somatic cells,
leading to the occurrence of phenotypically altered shoots on plants. This
phenomenon can be observed in most vegetatively propagated plant species
and finds its origin in genetic as well as epigenetic events. In azalea the
frequent occurrence of flower colour sports is appreciated as a valuable
additional source of variation; more than half of the commercial assortment
consists of flower colour bud sports. However, when clonal uniformity is
desired for registration (Distinctness Uniformity Stability, DUS) and mass
propagation, this somaclonal variation is perceived as a hindrance. Insight
into the molecular mechanism(s) underlying the induction of bud sporting
might improve breeding strategies, towards the appropriate choice of cultivars
in hybridisation experiments. The complex beauty of sport phenotypes clearly
indicates interactions within and between genetic and epigenetic mechanisms.
Therefore, using azalea somaclonal variation as a model, a review of the
literature on various genetic and epigenetic phenomena that regulate or influence
gene expression, as well as on the links that exist between them is presented.
South
African Journal of Botany 2002, 69(2): 117–128
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South African Journal of Botany. ISSN: 0254-6299