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OCCURRENCE OF POLYEMBRYONY IN FRAGARIA X ANANASSA DUCH.
The last three were characterized by absence of stamens (male sterile).
On unfertilized ovules, we observed some additional uninucleate embryo sacs in ‘Tardive de Leopold’ and ‘Direktor Paul Wallbaum’ at a frequency ranging from 1 to 8% (of observed ovules). Moreover, some ovaries of ‘Direktor Paul Wallbaum’ contained two ovules.
Fifteen days post-pollination, 4% of the ovaries with one ovule showed two embryos in ‘Direktor Paul Wallbaum’ and ‘Tardive de Leopold’. When two ovules were observed in the same ovary (‘Direktor Paul Wallbaum’), each of them developed an embryo after pollination.
When polyembryony was observed, only one embryo seemed be able to produce a plantlet.
Thus, in the progenies issued from ‘Direktor Paul Wallbaum’ and ‘Tardive de Leopold’, each achene gave only one plantlet (with an hybrid phenotype).
These additional embryos may arise from cells of unreduced embryo sacs (apomitic embryo). To confirm this hypothesis, it will be necessary to determine the stage of abortion of the embryos in order to develop in vitro embryo rescue techniques.
Moreover, molecular markers should be used to determine the origin of the embryos (i.e. hybrid or maternal).