γ-Aminobutyric Acid Regulates Grain Yield Formation in Different Fragrant Rice Genotypes Under Different Nitrogen Levels

The influences of γ-aminobutyric acid (GABA) and nitrogen on grain yield, yield-related traits, plant growth, grain–leaf ratio and NSC contents in different fragrant rice genotypes are not fully understood. A pot experiment was conducted with four nitrogen rates, i.e. 0, 0.87, 1.75, and 2.61 g pot −1 , two GABA levels, i.e. 0 and 250 mg L −1 , and three fragrant rice cultivars, i.e. Yuxiangyouzhan, Yungengyou 14 and Basmati. Results depicted that GABA treatment significantly increased the mean grain yield by 11.84% as a consequence of the increment of grain weight, spikelet per pot, grain weight per leaf area, stem sheath dry weight at HS, panicle dry weight at HS, panicle dry weight at MS and total dry weight at MS. Besides, significant effects of nitrogen and cultivar on yield and yield-related traits and some rice growth parameters were observed. Moreover, significant positive correlation relationships between yield and panicle number per pot, leaf area and dry weight for all the cultivars were observed. GABA application could alleviate the effects of nitrogen on grain yield in fragrant rice. These results suggest that GABA is feasible to increase grain yield and improve rice plant growth for fragrant rice varieties grown under different nitrogen conditions.