Hormones as modulators of reproductive barriers between "Solanum lycopersicum" L. and "Solanum chilense" D.

Details

Supervisors

Quinet, Muriel

Faculty

Faculté des sciences

Degree label

Master [120] en biologie des organismes et écologie, à finalité approfondie

Abstract

enThe tomato (Solanum lycopersicum) is one of the most widely cultivated vegetable crops in the world, largely due to its nutritional importance. However, tomatoes have been domesticated to improve various characteristics, such as their productivity. This has led to a loss of genetic diversity, making S. lycopersicum highly susceptible to biotic and abiotic stresses. The introgression of genes from related wild species, such as Solanum chilense, could improve the tomato's sensitivity. Native to South America, specifically the Atacama Desert in Chile, this species is particularly well-adapted to salt and water stress. However, hybridization between these two species is severely limited by reproductive barriers. Indeed, Solanum lycopersicum is self-compatible, while Solanum chilense exhibits gametophyte self-incompatibility. Another important reproductive barrier, unilateral incompatibility, greatly limits the introduction of resistance genes into S. lycopersicum. This thesis investigates the potential role of gibberellins, auxins, and cytokinins in the reproductive barriers between S. lycopersicum and S. chilense. To this end, various exogenous hormonal treatments were carried out to evaluate, firstly, their impact on the floral morphology and fertility of the two species, and secondly, their effect on self-incompatibility barriers during interspecific crosses. The results show that these treatments do not affect the number of floral organs or the overall architecture of the flowers. Some moderate variations in organ size were observed, specific to the species and organ type. Pollen viability and stigmatic receptivity were not, or only minimally, affected by the hormonal treatments. This suggests that hormonal treatments did not induce any particular alteration in floral structure or fertility characteristics in S. lycopersicum and S. chilense. Due to technical problems, the impact of hormones on interspecific crosses did not yield conclusive results. A study of the expression of the genes IPT2, IPT3, IPT4, IPT6 and CYP735A1, involved in cytokinin metabolism, was conducted during inter- and intraspecific crosses. The expression profiles of these genes varied depending on the cross, suggesting specific regulation of cytokinin metabolism during pollination. Gibberellins, auxins, and cytokinins seem to be involved in controlling reproductive barriers between S. lycopersicum and S. chilense, but further studies are needed to understand the role of these hormones and whether their use could overcome these barriers.