Exogenous γ-aminobutyric acid (GABA) application at different growth stages regulates 2-acetyl-1-pyrroline, yield, quality and antioxidant attributes in fragrant rice

The aim of this study was to investigate the optimum time for γ-aminobutyric acid (GABA) application to improve the yield and quality in fragrant rice. Pot and field experiments were conducted during 2016–17 with two fragrant rice cultivars (for pot experiment), and five fragrant rice cultivars (for field experiment) which were applied with five GABA levels i.e. no GABA application (CK), application of GABA at 250 mg l−1 with 25 ml pot−1 at tillering stage (S1), panicle initiation stage (S2), heading stage (S3), and at tillering, panicle initiation and heading stages (S4) in the pot experiment. Similarly, the same treatments with 100 ml m−2 were applied to all rice cultivars in the field experiment. The S3 treatment significantly increased the 2-acetyl-1-pyrroline (2AP) contents in Meixiangzhan2 (14.76%) and Yuxiangyouzhan (20.19%) in pot experiment, Meixiangzhan2 (27.27%), Yuxiangyouzhan (40.24%), Basmati (43.07%) and Yungengyou14 (13.66%) in field experiment owing to regulations in the contents of proline, Δ1-pyrroline-5-carboxylic acid (P5C), GABA and the activities of enzymes involved in 2AP formation. The GABA treatments improved yield and modulated the antioxidant enzyme activities. This study provides a reference for the GABA application to improve yield and quality in fragrant rice