Variability in Salt Tolerance Mechanisms In Sunflower

CÉCCOLI G; SENN, ME; BUSTOS, DA; ORTEGA LI; CÓRDOBA, A.; VEGETTI AC; TALEISNIK E.

Mar del Plata

Congreso; XVIII International Sunflower Conference; 2012

International Sunflower Association

• Salinity has always been considered a serious constraint to agricultural productivity and it is one of the criteria for classifying lands as marginal for agriculture. The purpose of this work was to assess sunflower salt tolerance at the vegetative stage in a group of sunflower lines that had been previously characterized in response to drought. Salt tolerance conceptually results from three concurrent general mechanisms: osmotic tolerance, ion uptake control and compartmentation, and tissue ion tolerance, which were evaluated in this study. • Eleven non-branching sunflower inbred lines which had been previously characterized for their response to water deficit (Pereyra-Irujo et al., 2008) were used trials 1 and 2, and, from those, four were studied in trial 3: HA64, HAR1, HAR2 and HAR5. Experiments were carried out in the greenhouse or growth room, plants were grown in pots with sand and perlite irrigated with salinized (0.65 MPa) nutrient solution. Na+ and K+ concentrations, whole plant growth and leaf expansion kinetics were assessed. A Principal Components Analysis (PCA) was run on relative-to-control growth data to get a summary of the effects of salinity and establish a relative tolerance ranking. Osmotic tolerance was evaluated as the initial effects of the salt treatment on plant elongation, ion uptake control was assessed by determining Na+ concentration distribution among different organs, and tissue Na+ tolerance was deduced by comparing the percentage of dead leaves as a function of leaf blade Na+ accumulation. • Lines HA64 and HAR2 were more tolerant to osmotic stress than the others, while lines HAR1 and HAR5 were the least tolerant. None of the lines showed leaf Na+ exclusion, only different degrees of Na+ accumulation: it was very low in HAR2, high in HAR1 and intermediate in the other two lines. Tissue Na+ tolerance was higher in HAR1 than in the rest. The analysis of leaf expansion kinetics indicated that, aside from expected decreased growth rates, growth duration tended to increase in several leaves of salt treated plants. • A tolerance ranking based on relative growth responses indicated HAR2>HAR1=HA64>HAR5. Osmotic tolerance was observed in lines HA64 and HAR2, and tissue Na+ tolerance, in HAR1.The increase in leaf expansion duration could partially buffer the negative effects of salt stress on leaf area expansion. No association was apparent between these effects and leaf blade Na+ accumulation. • The information derived from this study identified two salt tolerance mechanisms in four sunflower lines, which, if combined, could lead to genotypes with increased salt tolerance.