Salinity tolerance in strawberry (Fragaria spp) as influenced by genotype

Cultivated strawberry is considered a salt sensitive crop, while its progenitors Fragaria chiloensis and Fragaria virginiana differ in sensitivity, with F. chiloensis being more salt tolerant than F. virginiana. Salinity stress influences many aspects of plant physiology including photosynthetic rate, growth rate and the accumulation of certain metabolites to counteract the osmotic imbalance initially imposed by the increased salt concentration in the root medium. We sought to investigate the effect of salinity stress and recovery on the photosynthetic performance, leaf area production, and the accumulation of specific metabolites and inorganic ions of strawberry selections that differ in salt sensitivity, in an attempt to elucidate some of the mechanisms that are involved in salinity tolerance. At early stages of salt imposition reduction in stomatal conductance limited net assimilation rate (A) in all selections tested. Later, carboxylation efficiency was strongly affected in the F. virginiana plants (MR 10 and NC 95-21-1), but not in F. chiloensis (FRA 24), and the effect was not reversible after the stress was released. Toxicity symptoms were apparent in both F. virginiana selections, starting approximately the second week of the treatments and the severity was correlated to the amount of salt present in the irrigation water. No symptoms developed in F. chiloensis until the end of the experiment. High levels of Na+ and Cl− were detected in leaves of both F. virginiana selections treated with 50 and 100 mM NaCl while in F. chiloensis only Cl− was increased in the 100 mM treatment. Sodium appears to accumulate much slower than chloride in the leaf tissues. Increased salt levels brought about a reduction in leaf area growth and runner production and an increase in the total soluble carbohydrates in the two selections tested. Resumption of growth and leaf area production was evident after the stress was released and it was accompanied by a decrease in total soluble carbohydrates in F. virginiana selection, but not in F. chiloensis . Glucose and fructose accounted for 70% of the total soluble carbohydrates accumulated in leaves of both selections due to salinity stress but no substantial amount of proline was detected during the stress or the recovery periods.