Aroma is a primary determinant of rice quality and market value, yet its evaluation in breeding programs remains constrained by labor-intensive milling, cooked-grain sensory methods, binary screening assays, and the limited seed availability of early generation selection. Moreover, aromatic rice breeding has historically focused narrowly on 2-acetyl-1-pyrroline-mediated popcorn aroma, potentially overlooking valuable alternative aromatic profiles. In this study, we developed a rapid sensory phenotyping approach for paddy rice that enables quantitative assessment of the aroma intensity and qualitative aroma characterization without milling or cooking. A diverse panel of 126 rice genotypes was evaluated using 1 g of ground paddy rice heated under controlled conditions coupled with sensory analysis and targeted HS-SPME-GC-MS/MS quantification of 164 volatile compounds. The method discriminated the aroma intensity and enabled characterization of aroma quality. Hierarchical clustering integrating sensory and chemical data resolved five distinct aroma classes, including popcorn-dominant, fruity-floral, nutty-grainy, woody-floral, and oxidation-driven phenotypes. While 2AP showed the strongest association with popcorn aroma and overall intensity (r = 0.50), several high-intensity genotypes exhibited minimal 2AP, yet strong aroma perception driven by esters, alcohols, indole, and ketones. Interestingly, two genotypes (R125 and R126) showed strong popcorn perception despite much lower 2AP than typical aromatic rice, indicating the contribution of non-2AP popcorn-like aroma drivers. Conversely, genotypes with elevated lipid oxidation aldehydes exhibited high volatile abundance but poor aroma quality characterized by rancid, phenolic, and musty notes. These results demonstrate that superior rice aroma is a multivariate trait and is not related to only 2AP. The rapid phenotyping framework presented here provides breeding programs with an employable, information-rich tool for early generation screening, accelerating the identification of aromatic rice cultivars with expanded sensory diversity.
Rani et al. (Mon,) studied this question.