CONTENS - International Organization of Plant Biosystematists

O 49
Apomixis in Taraxacum: European and Himalayan taxa from the
cytogenetic viewpoint
Radim J. Vašut 1,2 , Kitty Vijverberg 3 , J. Hans de Jong 2 & Peter J. van Dijk 3
1 Department of Botany, Faculty of Science, Palacký University, Šlechtitelů 11, CZ-
78371 Olomouc, Czechia; 2 Department of Plant Sciences, Laboratory of Genetics,
Wageningen University, Arboretumlaan 4, NL-6703 BD Wageningen, the
Netherlands; 3 Keygene N.V., P.O. Box 216, 6700 AE Wageningen, the Netherlands.
The genus Taraxacum (dandelion; Asteraceae) combines three modes of
reproduction: two sexual ones (allogamy, autogamy) and apomixis. Autogamy is
known only in few ancestral taxa, whereas apomixis is widely distributed across all
continents and it covers most of phylogenetic groups of the genus. The dandelion’s
type of apomixis is diplosporous apomixis and it is confined to polyploids (mainly
triploids and tetraploids). One of three genes involved in its regulation is Diplospory
(DIP; first division restitution meiosis). We physically positioned DIP region to middle
of distal arm of one of the NOR chromosome in apomictic common dandelion (T.
sect. Ruderalia). In this study, we therefore aimed at answering the question: a) what
is the position of DIP region in other apomictic Taraxaca from different geographical
regions, b) not related phylogenetic groups and c) of different genome-size. In
addition, we studied NOR chromosomes in autogamic taxa. We address the
question, whether this can explain origin of apomixis. We used Fluorescence in situ
hybridisation (FISH) with BAC probes containing DIP-linked SCAR markers. In
autogamic species, increased number of NOR chromosomes was observed. In
apomictic taxa, the same position of DIP region in all our studied sections was
confirmed. We detected either unique strong signal or signal significantly larger then
remaining signals located in the middle of distal arm of one of the NOR
chromosomes. This indicates that DIP region has conserved position in the genus
Taraxacum and apparently has longer evolutionary history then apomictic taxa
themselves.
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