Genetic and Molecular Control of Sexual and Asexual Reproduction in Strawberries

Plants have developed both sexual and asexual reproduction modes to ensure their survival. Strawberry, a perennial crop species, offers an interesting model by combining both sexual reproduction and asexual reproduction by stolons. In addition, the woody diploid strawberry, F. vesca, as the cultivated octoploid F. x ananassa, present both an original trait with two modes of flowering: in once-flowering genotypes, floral transition happens once a year whereas continuous flowering genotypes flower continuously during the growing season, therefore offering a lengthened period of fruits and seeds production. Our objective was to decipher the genetic and molecular mechanisms of the continuous vs. once flowering in Fragaria and its relationship with asexual propagation.

We have found that in diploid and octoploid strawberry the continuous flowering trait is controlled by two different genetic 'keys' located at non-orthologous positions. In F. vesca, no direct genetic relationship was found between the two traits: continuous flowering is linked to the gene FvKSN homologous to the TFL1 floral repressor (Iwata et al. 2012) and located on LGVI whereas stolon production is linked to the R (Runnering) locus located on LGII. In F. x ananassa, both traits are genetically linked and share common physiological control since a major QTL located on LGIV is linked to both continuous flowering and stolon production. This major QTL displays opposite effects on flowering (positive effect) and on stolon production (negative effect). We can conclude that this region is the site for the control of competition between vegetative and reproductive development in the octoploid strawberry.

These results offer new insights to understand the genetic and molecular pathway that control the balance between sexual and asexual reproduction in strawberries.