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Meiosis and fertilization are two hallmarks of sexual reproduction in eukaryotic species. Meiosis leads to the generation of recombined, haploid, spores. In sexual plants, the fusion of genetically unique gametes – by fertilization - leads to restitution of the sporophytic phase and infinitely diverse progeny. In contrast, some plant species have abandoned sex, skip meiosis and fertilization, and produce clonal seeds by apomixis. Here I will explore mechanisms of sexual and apomictic reproduction in the nightshade (Solanaceae) and sunflower (Asteraceae) plant families, respectively.

Using the cultivated tomato (S. lycopersicum), and hybrids with related wild species, we explore how recombination and meiosis can succeed despite more than two million years of evolutionary divergence. Direct modulation of several F₁ hybrid genotypes by CRISPR/Cas9 allows us to explore how different genetic factors contribute to the stabilization of meiosis in wide hybrids.

Using naturally apomictic triploid dandelion (T. officinale) we have identified a genetic factor that allows embryogenesis in egg cells in the absence of fertilization. The PARTHENOGENESIS (PAR) gene encodes a K2-2 Zinc Finger-EAR domain protein. Loss of PAR mutants revert to sexual reproduction and require cross-fertilization for viable embryo and seed formation. The evolution of apomixis in dandelion and related species will be discussed.