How sexual are the asexuals?
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| Year of publication | 2010 |
| Type | Conference abstract |
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| Citation | |
| Description | Clonal reproduction is a common propagation strategy in higher plants; its most extreme type is apomixis. An apomictic embryo is (usually) developed from an unreduced megaspore in the absence of ovule fertilization. The offspring is genetically uniform and it causes taxonomic complexity. The distribution of apomicts is associated with the phenomenon of geographical parthenogenesis. However, the distribution of sexuals and apomicts overlap and form contact zones where they can hybridize. Apomicts serve as pollen donors for the sexuals, and novel apomictic clones are thus formed. Therefore, in order to elucidate the significance of apomictic taxa one requires an understanding of what the proportion of apomictic-sexual reproduction is in the mixed populations; additionally, to what extent the novel clones are apomictic. Obligate diplosporous lesser dandelions show a high transmission of apomixis into novel clones; whereas facultative aposporous-pseudogamous blackberries show significant variation. Taxa of Rubus ser. Radula are of hybridogeneous origin among taxa of the series Discolores (apomict) and Glandulosi (sexual). We have studied the offspring of the putative apomictic parents (Discolores), using flow-cytometric seed screen (FCSS). Triploids produce nearly 100% apomictic offspring; whereas tetraploids vary considerably in their reproduction modes. In Rubus bifrons, we detected three major types: i) sexual (including autogamy), ii) apomixis, and iii) pseudogamy (including polyspermy). Furthermore, we observed significant differences in the sex-apo ratio between two distinct regions, with the Sudeten plants showing a significantly higher proportion of apomixis (pseudogamy) then the Carpathian plants. This difference correlates with the occurrence of stabilized apomictic microspecies in the Sudeten, and their absence in the Carpathians. We tested the segregation of microsatellites in the F1 offspring in order to test what the prevailing origin of grown seedlings is. Although we do not know the genetic regulation of apomixis, we can suggest that variations in the proportion of apomictic reproduction in the putative parent species is in concert with the formation of novel stabilized apomictic clones in Rubus. |
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