Apomixis describes asexual types of reproduction through seeds and is wide spread in nature, naturally occurring in hundreds of plant species, especially in the Asteraceae (e.g. Common Dandelion), Rosaceae and the grasses. Apomictic seeds contain embryos, which are genetic copies of the mother plant. This is particularly interesting if the mother plant is a hybrid itself. There is a great commercial interest to use apomixis in plant breeding and seed production, because it would allow easy marketing of heterozygous hybrid plant material and an enorming decrease of breeding times and thus the possibility to generate crop plants adapted to numerous climatic and environmental conditions..
Our research activities in the field of apomixis focus on the comparison of gene expression pattern in sexual and parthenogenetic eggs with the aim to identify key genes involved in the induction of the embryonic program and/or to discover genes maintaining the undifferentiated stem cell character of the sexual egg cell. We are using maize and Tripsacum dactyloides (different sexual and apomictic lines) as model species.
 

Apomixis for hybrid seed production.

Parental inbred lines (P1 and P2) are crossed to generate hybrid seeds. Due to the heterosis-effect, F1 plants are more vigorous than parent plants and produce a higher yield. Genetic segregation occurs in F2 plants - but not in apomictic plants.

 

The mode of reproduction can be determined applying the flow cytometric seed screen (FCSS) using extracts of single mature seeds. The hight and relative position of peaks originating from seed nuclei in extracts after staining determine the reproduction mode: the example shows a seeds of a hexaploid Tripsacum dactyloides-linie, where the embryo developed parthenogenetically and the endosperm after fertilization of the central cell (pseudogamy).

 

Microdissection of reproductive cells from Tripsacum dactyloides for molecular analyses.

(a & b) male and female flowers, (c & d) ovule, (e) parthenogenetic egg cell, (f) synergids and (g) parthenogenetic embryo.