CONICET | Buscador de Institutos y Recursos Humanos

(*Authors 1 and 2 contributed equally to the work), Sunflower has been rated as moderately salt tolerant and variability for salt tolerance has been detected within this crop, however, variability in salt tolerance mechanisms has not been assessed. Osmotic tolerance, the relation of salt tolerance with whole plant Na+ and K+ distribution and tissue Na+ tolerance were investigated in several sunflower inbred lines. Plants were grown under controlled conditions, in pots with sand and perlite irrigated with salinized (NaCl, -0.65 MPa) nutrient solution. Osmotic tolerance was assessed from the initial effects of the salt treatment on plant elongation in eleven sunflower lines. Long-term salinity responses were evaluated in four of those lines, by assessing whole plant growth. A Principal Components Analysis (PCA) was run on relative-to-control growth data and this information was used to establish a relative tolerance ranking, which indicated lines HAR2>HAR1>HA64>HAR5. Osmotic tolerance was observed in HA64 and HAR2. The lines showed different degrees of Na+ accumulation, it was very low in some of them, but relative salt tolerance was not associated to this trait. Tissue Na+ tolerance was deduced by comparing the percentage of dead leaves as a function of leaf blade Na+ 14 accumulation, and it was higher in HAR1 than in the rest. These results indicate that variability for salt tolerance mechanisms exists in sunflower, osmotic tolerance and tissue Na+ tolerance, were detected in different lines, highlighting that such variability may be exploited for increasing salt tolerance in this crop. Keywords Sunflower, salt tolerance, osmotic tolerance, Na+ 20 tissue tolerance 21 Page 3 of 33 Wiley-VCH Journal of Plant Nutrition and Soil Science