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Fructify or grow: the dilemma faced by strawberry plants

In the strawberry, the balance between flowering and vegetative development (runnering) conditions the yield of a plant. INRA has demonstrated the influence of plant hormones (gibberellins) on the fate of the axillary meristem.

Fraises variété

The strawberry is a model plant with dual development

After the apple and pear, the production of strawberries (Fragaria spp) with high added value ranks third among fruit species, according to the turnover figures for France. The plant has the specific feature of being able to propagate itself either vegetatively (production of daughter plants via stolons) or sexually (production of fruits carrying seeds). In this important fleshy fruit plant, which suffers from inbreeding depression, the production of above-ground stolons (runners) is essential for the clonal propagation of commercial varieties. The balance between these two types of reproduction thus conditions both the production of plants and fruit yields. Environmental factors, temperature and photoperiod are also known to affect the fate of apical meristems (floral transition) of axillary meristems (as runners). However, this balance is also influenced by plant hormones, or gibberellins, as has recently been demonstrated by scientists.

Gibberellins 20-oxidase: plant hormones that condition strawberry yields

The endogenous molecular mechanisms underlying the production of stolons had until now remained unknown. Thanks to a runnerless mutant (r) of the wild strawberry (Fragaria vesca), the scientists were able to demonstrate that a deficit in vegetative reproduction was due to a deletion in the active site of a gibberellin 20-oxydase synthetic gene (GA20ox). This gene, FeGA20ox4, is mainly expressed in the axillary meristem and in developing stolons. When it is mutated, the axillary meristems remain "dormant" or produce secondary shoots terminated by fruit-bearing inflorescences. An exogenous application of bioactive gibberellins restored vegetative reproduction in the mutated strawberry, thus clearly confirming the important of these hormones to differentiation of the axillary meristem to vegetative shoots and hence to the compromise between vegetative propagation and fruit production.

Improvements to the productivity of strawberry plants under the crucial control of mechanisms for stolon or inflorescence production

The results showed that depending on the allelic status of GA20ox4, the axillary meristem produces either a stolon (active allele) or inflorescences (inactive allele). This mutation, which is found in r mutants, goes back more than three centuries. Thus the production of inflorescences by the axillary meristem corresponds to initiation of a default development programme which could be exploited to modulate stolon production and increase strawberry fruit yields. The possibility to regulate the balance between runnering and flowering in the strawberry through mutation of the FveGA20ox4 gene is particularly important because both reproductive modes are necessary in this species: asexual reproduction to provide producers with different varieties obtained by selection, and sexual reproduction to ensure fruit yield.
An understanding of the specific role of gibberellin 20-oxiydase in axillary meristem differentiation now opens opportunities to identify breeding goals and define optimised cultivation practices that will meet both the needs of producers and the demands of consumers. Work on the transfer of this knowledge from wild to cultivated strawberry is ongoing.

These results were obtained in the context of the PhD thesis of Tracey Tenreira: Contrôle génétique et moléculaire du stolonnage – Balance entre reproduction sexuée et multiplication végétative chez le fraisier diploïde (Genetic and molecular control of runner production: the balance between sexual reproduction and vegetative propagation in the diploid strawberry), Université de Bordeaux (defended in December 2015). This research benefited from funding for 3 years from the Ministry for Higher Education, Research and Innovation (Doctoral School competition). It was carried out in partnership with the IRTA Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB6UB) in Barcelona and the Institut für Pfanzenbiologie de Braunschweig (Germany).

Contact(s)
Scientific contact(s):

  • Béatrice Denoyes INRA-Université de Bordeaux Joint Research Unit for Fruit Biology and Pathology (UMR-1332 BFP)- Inra et Université de Bordeaux, Campus de la Grande Ferrade, 71 av Edouard Bourlaux, 33883 VILLENAVE D'ORNON
  • Christophe Rothan INRA-Université de Bordeaux Joint Research Unit for Fruit Biology and Pathology (UMR-1332 BFP)-, Inra et Université de Bordeaux, Campus de la Grande Ferrade, 71 av Edouard Bourlaux, 33883 VILLENAVE D'ORNON
Associated Division(s):
Plant Biology and Breeding, Plant Health and Environment
Associated Centre(s):
Nouvelle-Aquitaine-Bordeaux

Bibliographical references

  • Lockhart J (2017) Flowering Versus Runnering: Uncovering the Protein Behind a Trait That Matters in Strawberry. The Plant Cell Vol 29. DOI:
    https://doi.org/10.1105/tpc.17.00709
  • Mach J (2017) A Time to Divide and a Time to Expand: Histone Deacetylases Flip a Gibberellin Oxidase-Mediated Switch in Root Meristem Cells. The Plant Cell Vol 29.
    https://doi.org/10.1105/tpc.17.00732
  • Tenreira T et al (2017). A Specific Gibberellin 20-oxidase Dictates the Flowering-Runnering Decision in Diploid Strawberry. The Plant Cell. Vol. 29: 2168–218.
    https://doi:10.1105/tpc.16.009
  • Verma S et al (2017). Detection of fruit quality and flowering QTLs in Eastern and Western U.S. strawberry (Fragaria ×ananassa) breeding populations using pedigree-based analysis. Horticulture Research, 4, 17062.
    https://doi:10.1038/hortres.2017.62
  • Martins AO et al (2018). To Bring Flowers or Do a Runner: Gibberellins Make the Decision. Molecular Plant. 2018 Jan 8; 11(1): 4-6.

The French strawberry sector

INRA research programmes have always been closely followed by the strawberry sector, and particularly in the Aquitaine region which produces 50% of French strawberries. In 1988, INRA’s Nouvelle Aquitaine-Bordeaux Research Centre, in collaboration with the entire profession, initiated research on resistance to pathogens and fruit quality in the cultivated strawberry. More recently, to support adaptation of the crop to new cultivation practices and climate change, research was started on understanding the genetic, physiological and molecular mechanisms underlying the balance between reproductive and vegetative growth. This research is carried out by the Joint Research Unit for Fruit Biology and Pathology in partnership with professionals from the strawberry sector in Aquitaine (CIREF, Invenio and AOPn Fraise). Thanks to the strong links created in the context of common regional and international projects, the research results can now be discussed rapidly and implemented by the sector.