Acetic acid application timing on strawberry: an alleviator for salinity adverse effect

Salinity is an important abiotic stress which limits normal plant growth and productivity, particularly in arid and semi-arid areas. The foliar spray of acetic acid has recently been considered to enhance tolerance of abiotic stress, especially drought stress in plants but its effect on increased salinity tolerance in horticultural crops remains elusive. Hydroponically grown strawberry plants that were subjected to 40 mM sodium chloride for 90 days, were sprayed with 1- or 2-mM acetic acid (AA) three times including a week before, simultaneously and a week after application of salinity treatment. According to the results the electrolyte leakage, lipid peroxidation, and hydrogen peroxide, were increased by 45%, 46%, and 54%, respectively, under saline condition. While, the maximum quantum yield of PSII (Fv/Fm) decreased to 14% under salinity treatment. The maximum alleviation effect of salt stress was recorded in 1 mM foliar application of acetic acid, especially when applied 1 week before and simultaneous with salinity stress, resulting in significant decreases in electrolyte leakage to 13% and 15%, hydrogen peroxide to 30% and 32%, respectively, while the decline in lipid peroxidation was only observed in 1 week before salt stress to 39% compared to the control. The fruit yield reduced about 71% under 40 mM NaCl compared to the control, however, yield reduction was quite lower under 1- and 2-mM acetic acid treatments (31% and 45%, respectively). Acetic acid considerably increased antioxidant enzymes' activity including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) as well as the concentration of non-enzymatic antioxidants such as phenolic compounds under salinity stress conditions, especially when applied 1 mM AA a week before and simultaneously with salinity (25% and 24%, respectively). These results confirmed that acetic acid treatment especially with 1 mM concentration a week before and simultaneously with salinity treatment can be considered to improve the salt tolerance in strawberry under saline conditions.