Effect of salicylic acid on morphological characteristics and yield of sorghum (Sorghum bicolor L.) cultivars under different irrigation regimes

To evaluate the effect of salicylic acid (SA) on morphological characteristics and yield of sorghum under drought stress, an experiment was conducted as split plot-factorial in randomize complete block design with three replications. Irrigation in three levels based on evaporation of40, 80 and 110 mm from the evaporation pan were considered as main plots and combinations of salicylic acid concentrations (0, 1, 2 mM) and sorghum cultivars (Speedfeed and Pegah) were considered as factorial in sub plots. The results showed that the effect of drought stress and SA were significant for all studied traits except for harvest index. The interaction of irrigation×SA was significant for grain yield and number of leaf as well as the interaction of irrigation×cultivar was significant for number of leaf. Also, significant differences were observed between sorghum cultivars for all studied traitsand Speedfeed cultivar had better performance compared with Pegah.Severe drought stress reduced plant height, leaf number, fresh forage yield, dry forage yield, seed weight, chlorophyll, grain yield and biological yield about 41.5, 37.7, 33.1, 26.0, 53.7, 33.7 and 32.5 percent, respectively,compared to control treatment. The results showed that application of 2 mM SA had the greatest impact on evaluated traits, so thatapplication of 2 mM SA caused an increasing of 15.0, 8.1, 8.2, 16.7, 15.3, 9.3 and 19.8 percent in plant height, fresh forage yield, dry forage yield, chlorophyll content (SPAD), 1000-grain weight, biological yield and grain yield, respectively,compared to the control. Also, foliar application ofSA has an effective role (37 %) in reducing drought stress damages on yield of sorghum cultivars, so that application of 2 mM SA under severe drought stress conditions reduced the effect of drought stress on grain yield about 37 percent. Therefore, foliar application of SA is recommended under water deficit conditions.