Effect of Timing and Duration of Salt Treatment during Growth of a Fragrant Rice Variety on Yield and 2-Acetyl-1-pyrroline, Proline, and GABA Levels

In greenhouse experiments, Aychade, a fragrant rice variety, was grown under one level of salt solution (EC of 3800 ± 400 μS·cm–1) sufficient to induce salt stress in rice. Timing and duration of salt solution application varied according to the growth stages. 2-Acetyl-1-pyrroline (2AP), a characteristic flavor compound of fragrant rice as well as biogenetically related compounds, proline, and γ-aminobutyric acid (GABA) were quantified. Salt treatments induced 2AP synthesis in the leaves, but the increase was often higher in the vegetative phase. This increase was correlated with proline level but not with that of GABA. Interestingly the grains from all the salt treated plants contained significantly higher levels of 2AP (733–998 μg·kg–1) than those from the control (592 μg·kg–1). The highest 2AP synthesis occurred when the plants were subjected to salt treatment during whole vegetative or reproductive phases. However in the latter case crop yield decreased significantly.