Selective embryo abortion hypothesis revisited - A molecular approach

Many plant species abort a large fraction of their embryos. it has often been suggested that embryos of genotypes that would perform worse later in life are preferentially aborted. Such selective embryo abortion would lead to investment of resources only in the offspring with the highest potential fitness. Many studies have shown that otherwise viable embryos are aborted. However, only few manipulative studies have indeed shown a correlation between the level of abortion and offspring quality and these studies have been challenged for their experimental design. Molecular techniques open new opportunities to study selective embryo abortion. Non-random abortion at the level of molecular markers can be observed as a deviation from Mendelian segregation: over- or under-representation of markers in the offspring. Subsequently, the over-or under-re presented markers can be related to offspring quality later in life. We reviewed the literature on the genetic maps of intraspecific crosses of wild plant species and the selection of cultivated species. The level of non-Mendelian segregation we found in these maps is high. On average, 11.5% of the tested markers in the genetic maps of wild species and 14.6% in the cultivated ones, show a departure from Mendelian segregation. From six studies, providing sufficient data, it was calculated that in 68% of loci segregating in non-Mendelian fashion post-fertilization selection is involved. We propose that the deviation from Mendelian segregation can be partly explained by selective embryo abortion. We describe an experimental design that allows for attributing selective embryo abortion to the non-Mendelian segregation that is found in a genetic map.