Effect of exogenous application of Glycine Betaine on physiological traits and tomato yield in drought condition

In order to determine the best time and amount of Glycine Betaine (GB) in increasing tomato yield in drought stress condition, an experiment was carried out in Split Plots on RCBD design with four replications, during 2016. The experimental factors included main factor (irrigation period in 6 and 12 days) and sub factors including time (in 3 levels including sowing, flowering and fruit set) and amount (in 3 levels including 0, 3 and 6 kgha-1) of GB application. The results from RWC, leaf area and electrolyte leakage showed the efficiency of GB application in stress condition. Using GB in non-stress condition led to decrease in fruit weight and no significant difference was observed between 3 and 6 kgha-1 dosages. In stress condition, 3 kgha-1 GB application in sowing, flowering and fruit set stage increased fruit weight by 33%, 40% and 60% respectively compare to average fruit weight of control treatments. Although the positives effect of 3 kgha-1 GB at flowering time on fruit yield was obvious (62% higher) in this study, it seems that the application of this amino acid in non-stress conditions had some toxic effects on tomato fruit yield.