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

Abstract

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.

The Correlation between 2-Acetyl-1-pyrroline Content, Biological Compounds and Molecular Characterization to the Aroma Intensities of Thai Local Rice

“…Mo et al 19 found that a decrease in solar intensity shade treatment leads to an increased proline content and 2AP content in rice. The 2AP content was also correlated with the proline content of Aychade rice under salt condition 20 .…”

“…Previously published work has reported the association between proline content and 2AP content in rice. Poonlaphdecha et al 20 found that the 2AP content increases andis correlated withthe proline content under salt stress. Recently, Mo et al 19 reported that an increased 2AP content in grains is correlated with a higher proline concentration under low light intensity conditions.…”

“…2AP can be synthesized from other parts of rice and can be translocated to the grain during grain formation. 2AP synthesis can occur inrice grains after translocation of the proline precursor from another part of the rice into the grains 19,20,23,37 . 2AP accumulation may be affected by environmental factors.…”

Effect of gamma irradiation on the 2-acetyl-1-pyrroline content during growth of Thai black glutinous rice (Upland rice)

“…The highest 2AP content was found at seedling stage II, and the lowest 2AP content found at seedling stage I. These results were contrasting to the Aychade fragrant rice variety, where the highest 2AP content of rice was obtained from panicle initiation stage, and the lowest 2AP content was obtained from middle tillering stage (Poonlaphdecha et al, 2012). The different accumulation trend of 2AP content in different rice variety could be explained by several factors such as different condition of growth and difference between rice varieties (Yoshihashi et al, 2004;Poonlaphdecha et al, 2012;Mo et al, 2015).…”

“…For example, Gay et al (2010) and Poonlaphdecha et al (2012) reported that 2AP formation increased due to increase in salt concentration. Moreover, Yoshihashi et al (2004) reported that drought stress has an effect on increasing 2AP concentration in grains during period of grains formation.…”