Influence of γ-Aminobutyric Acid (GABA) Application on Aromatic Rice Under Shading and Drought Stress Conditions: Effects on Crop Yield, Grain Quality, and 2-Acetyl-1-Pyrroline Biosynthesis

Enhancing aroma retention is pivotal for the production and exportation of aromatic rice in Bangladesh. In this study, a 2-year pot experiment was conducted to assess the effects of gamma-aminobutyric acid (GABA) application on aromatic rice under shading and drought stress conditions. The rice variety, BRRI (Bangladesh Rice Research Institute) dhan80 was used as the planting material to investigate with the following eight treatments: (T1) no GABA, shading, or drought stress treatment; (T2) GABA application at 250 mg/L during panicle initiation; (T3) shading at the grain filling stage; (T4) drought stress at the grain filling stage; (T5) shading and drought stress at the grain filling stage; (T6) GABA application at 250 mg/L at panicle initiation and shading at the grain filling stage; (T7) GABA application at 250 mg/L at panicle initiation and drought stress at the grain filling stage; and (T8) GABA application at 250 mg/L at panicle initiation as well as shading and drought stress at the grain filling stage. A randomized complete block design was followed, with treatments replicated five times. Results revealed GABA application along with shading and drought stress significantly influenced most studied traits. Notably, 250 mg/L GABA application at panicle initiation, alongside shading and drought stress at the grain filling stage, resulted in favorable outcomes for the brown rice yield, head rice recovery, amylose and protein content, grain 2-acetyl-1-pyrroline content, grain aroma, and taste of BRRI dhan80 rice compared with the control group (T1). However, the control treatment exhibited the highest grain yield compared with the other treatments. Overall, GABA application combined with shading and drought stress markedly improved grain quality and aroma of BRRI dhan80 but affected grain yield in an inverse manner.