Genetic variability for responses to short- and long-term salt stress in vegetative sunflower plants

摘要

Sunflower (Helianthus annuus L.) has been rated as moderately salt-resistant, and variability for salt resistance has been detected within this crop. However, variability in salt-resistance mechanisms has not been assessed. Osmotic tolerance, the relation of salt resistance 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 resistance 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 resistance 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~+ accumulation, and it was higher in HAR1 than in the rest. These results indicate that variability for salt-resistance 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 resistance in this crop.