Variation of the Impact Aroma Compound, 2-Acetyl-1-Pyrroline, Content in Thai Fragrant Rice Plants and its Enhanced Accumulation by Soil Nutritional Elements

This study investigated the accumulation characteristics of 2-acetyl-1-pyrroline (2AP) in the Thai Jasmine rice cultivar, Khao Dawk Mali 105 (KDML 105) under different soil types and addition of soil nutritional elements. There was significant variation in the 2AP contents of rice leaves, not only among different growth stages, but also among different leaf positions at each growth stage. The highest 2AP content was seen in the third leaves at booting stage (25.10±0.90 µg g-1), whilst for flag leaves it was seen at mature grain stage (8.00±0.72 µg g-1). During the ripening stage, plants in sandy soil acquired higher 2AP content in flag leaves, spikelets, and seeds than in clay soil, with the highest 2AP content in flag leaves at 25.00±0.70 µg g-1. The accumulation of 2AP in basal, middle, and upper branches of panicles showed no significant differences, whereas a steady decrease in 2AP content was detected in the panicle axis and branches. The effects of individual mineral elements (B, Cr, Cu, Mg, Mn, and Se) on 2AP content was different at each growth stage. B enhanced the 2AP content by more than two-fold in the leaves at the heading stage (63.84±4.56 µg g-1) compared to that of the control set, followed by Mn, Cu, and Se. Similar to the above results, the 2AP content was also heightened in grains. The extended knowledge gathered in this study will assist farmers who wish to improve the fragrance qualities of their rice varieties.