Improving barley performance by proper foliar applied salicylic-acid under saline conditions

Despite general effect of salicylic-acid (SA) in improving plant growth and productivity in saline conditions, there have not been unanimity about the best concentration. In this 2-yr field study the effect of different SA concentrations (0, 0.5, 1.0, 1.5 and 2.0 mM) was examined on growth, grain yield and yield components of barley under two non-saline (2 dS m-1) and saline (12 dS m-1) conditions. By using response curves and regression analyses the best concentration was also determined. The results showed that salt stress decreased barley plant height (22.7%), fertile tillers (19.0%), ear length (21.6%), grain number per ear (22.5%), thousand grain weight (19.9%), biological yield (29.6%) and grain yield (37.6%). Since salinity treatment when imposed the tillers were at their rapid growth phase; therefore, fertile tiller number per unit area was found to be the most sensitive trait to salt stress. Nonetheless, SA foliar application in different concentrations could ameliorate some of these negative impacts on growth, yield and yield components. Reduction percentage of grain yield due to salinity was the lowest at 1.5 mM in first and 1.0 mM SA concentration in second year corresponding to 27.3% and 33.8%, respectively; while those were highest at no-SA treatments (42.2% and 43.8% in first and second year, respectively). Modulating role of SA for adverse effect of salinity could be attributed to enhanced grain number. Based on the result of regression analysis, it can be concluded that SA foliar application at 2.0 mM under non-saline and at 1.41 mM under saline conditions could be considered as the best concentrations for improving barley performance.