Exogenous γ-aminobutyric acid (GABA)-induced signaling events and field performance associated with mitigation of drought stress in Phaseolus vulgaris L

Abstract

Not much information is available to substantiate the possible role of γ -aminobutyric acid (GABA) signaling in mitigating water-deficit stress in snap bean (Phaseolus vulgaris L.) plants under semiarid conditions. Present work aims to investigate the role of exogenous GABA (foliar application; 0.5, 1 and 2 mM) in amelioration of drought stress and improvement of field performance on snap bean plants raised under two drip irrigation regimes (100% and 70% of water requirements). Water stress led to significant reduction in plant growth, leaf relative water content (RWC), cell membrane stability index (CMSI), nutrient uptake (N, P, K, Ca, Fe and Zn), pod yield and its content from protein and total soluble solids (TSS). Meanwhile, lipid peroxidation (malondialdehyde content- MDA), osmolyte content (free amino acids- FAA, proline, soluble sugars) antioxidative defense (activity of superoxide dismutase- SOD, catalase- CAT, peroxidase- POX and ascorbate peroxidase- APX) and the pod fiber content exhibited significantly increase due to water stress. Exogenous GABA application (especially at 2 mM) revealed partial normalization of the effects of drought stress in snap bean plants. GABA-induced mitigation of drought stress was manifested by improvement in growth, water status, membrane integrity, osmotic adjustment, antioxidant defense and nutrient acquisition. Furthermore, GABA application during water stress in snap bean plants resulted in improvement of field performance being manifested by increased pod yield and its quality attributes. To sum up, exogenous GABA appears to function as an effective priming molecule to alleviate drought stress in snap bean plants under semiarid conditions.

Keywords: phaseolus vulgaris; Crop yield; drip irrigation; drought; gamma-aminobutyric acid; osmolytes.

Figure 1.

Shoot fresh weight (a), shoot dry weight (b), leaf area (c), leaf relative water content “RWC” (d), cell membrane stability index “CMSI’ (e) and lipid peroxidation as indicated by malondialdehyde ”MDA” (f) of the snap bean plants at 60 DAS as influenced by the foliar application of GABA (0, 0.5, 1 and 2 mM) under two irrigation regime. Means were presented ± SD. Different letters are significant differences, according to LSD’s multiple range tests (P < .05)

Figure 2.

Free amino acids ”FAA” (a), Proline (b) and total soluble sugars (c) in the leaves of the snap bean plants at 60 DAS as influenced by the foliar application of GABA (0, 0.5, 1 and 2 mM) under two irrigation regimes Means were presented ± SD. Different letters are significant differences, according to LSD’s multiple range tests (P < .05)

Figure 3.

Superoxide dismutase ”SOD” (a), catalase “CAT” (b) peroxidase “POX” (c) and ascorbate peroxidase ”APX” (d) in the leaves of the snap bean plants at 60 DAS as influenced by the foliar application of GABA (0, 0.5, 1 and 2 mM) under two irrigation regimes. Means were presented ± SD. Different letters are significant differences, according to LSD’s multiple range tests (P < .05)

Figure 4.

Leaf mineral content including N (a), P (b), K (c) Ca (d), Fe (e) and Zn (f)in the leaves of the snap bean plants at 60 DAS as influenced by the foliar application of GABA (0, 0.5, 1 and 2 mM) under two irrigation regimes. means were presented ± SD. Different letters are significant differences, according to LSD’s multiple range tests (P < .05)

Figure 5.

Pod yield (a) and its content from protein (b), fibers (c) and total soluble solids “TSS” (d) of the snap bean plants as influenced by the foliar application of GABA (0, 0.5, 1 and 2 mM) under two irrigation regimes. Means were presented ± SD. Different letters are significant differences, according to LSD’s multiple range tests (P < .05)