Enhancement of 2-acetyl-1-pyrroline (2AP) concentration, total yield, and quality in fragrant rice through exogenous γ-aminobutyric acid (GABA) application

The effects of exogenous application of gamma-aminobutyric acid (GABA) on yield and quality characteristics, especially 2-acetyl-1-pyrroline (2AP) biosynthesis, are rarely investigated. Two field experiments, i.e., experiment 1 (EXP.1) and experiment 2 (EXP.2), were conducted, and four GABA levels, i.e., 0, 50, 500, 1000 mg l(-1), classified as CK, T1, T2, and T3, respectively, were sprayed at the initial heading stage of a fragrant rice cultivar, Yuxiangyouzhan. The results showed that exogenous GABA application increased the 2AP content in grains 8.58%-19.44% in EXP.1 and 0.010/0-6.22% in EXP.2. Exogenous GABA treatments also increased the GABA concentration in the grains and proline content in fragrant rice. Significant correlations between the grain 2AP content and proline content in leaves at 5 days after spraying were also detected in EXP.1, whereas GABA application did not significantly affect leaf dry weight, total dry weight, or grain yield. Moreover, gas exchange parameters, soil-plant analyses development values, and antioxidant activities were improved under GABA treatments. Additionally, the GABA applications substantially improved the grain quality characteristics, including milled rice percentage, head rice percentage, and protein content. Overall, exogenous GABA application was effective in the improvement of quality characteristics in fragrant rice, especially that of grain 2AP contents.