The Effect of GABA in Induction of Chilling Resistance in Cucumber (Cucumis sativus L.) Seedlings

In order to investigate the possibility of chilling resistance induction and reduce the chilling injury of cucumber seedlings, a factorial experimental based on completely randomized design with three replications was conducted in a greenhouse at Ilam University, Ilam Iran in 2018. The experimental factors were included concentrations of 0, 5, 10 and 15 mM gamma-aminobutric acid (GABA) and two methods of application including seed priming and foliar application at four true leaf stages. Treated plants were incubated at 3 °C for six nights and then investigated for different characteristics. Results showed that all GABA treatments reduced chilling injury in cucumber seedlings. Moreover, although there were no significant differences among the different GABA concentrations for most of the studied characteristics, seed priming was better than foliar application. The lowest chilling index, lipoxygenase activity and highest shoot fresh weight were observed in seed priming application of GABA but with no significant differences among GABA concentrations. The highest shoot dry weight (6.77 and 6.68 g.plant-1), chlorophyll index (20.57 and 21.07 mg.g-1 FW: leaf fresh weight), total protein (1.29 and 1.25 g.kg-1), proline (21.92 and 22.42 μmol.g-1 FW), catalase activity (115.67 and 126.9 U.g-1 FW) peroxidase (0.61 and 0.63 U.g-1 FW) and the lowest ion leakage (30.22 and 29.22 %), malondialdehyde (0.65 and 0.60 μmol.g-1 FW) and hydrogen peroxide (1.27 and 1.19 μmol.g-1 FW), were observed in seed priming application of 10 and 15 mM GABA concentrations, respectively. Therefore, seed priming application of 10 mM GABA is recommended for reducing the chilling injury in cucumber seedlings.