Sodium and chloride accumulation and repartition differed between the cultivated tomato (Solanum lycopersicum) and its wild halophyte relative Solanum chilense under salt stress

Salinity is of growing global concern and affects the yield of several crop species, including tomato (Solanum lycopersicum). Halophyte wild relatives could be used to improve salt tolerance of crop species. Among wild tomato relatives, Solanum chilense was shown to be NaCl-tolerant but its strategy for Na+ accumulation and repartition remained poorly understood, and its Cl-accumulation was never investigated. In this study, both species were cultivated under salinity (0, 60 and 120 mM NaCl) during vegetative and reproductive phases. We investigated the ion (Na+, K+, Cl-) accumulation and repartition in the different organs (leaves, stems, roots, inflorescences), the expression of Na+ and Cl- transporters in vegetative organs and the role of these ions in osmotic management. Solanum chilense accumulated mainly Na+ in the shoots while S. lycopersicum accumulated it mainly in the roots so that the Na+ shoot/root ratio was 10 times higher in S. chilense than in S. lycopersicum. This suggests that S. chilense had an includer strategy while S. lycopersicum had an excluder strategy towards Na+. The excluder behavior of S. lycopersicum was linked to the high expression of HKT1;2 and SOS pathway genes in roots. In contrast to Na+, both species accumulated Cl- in a similar way and Cl- content was higher in the shoots than in the roots in both species. In addition, both species limited the entry of Na+ and Cl- in the inflorescences. The Na+ and Cl- concentrations were respectively about 3 and 2 times lower in the inflorescences than in the leaves. Ions also contributed to osmotic adjustment, mainly Cl- in S. lycopersicum and Na+ and K+ in S. chilense. Overall, our results highlight the salt-tolerance characteristics of S. chilense compared to the cultivated tomato.