Abiotic and Biotic Factors Controlling Grain Aroma along the Value Chain of Fragrant Rice: A Review

The aroma of fragrant rice is one of the grain quality attributes that significantly influence consumer preferences and prices in world markets. The volatile compound 2-acetyl-1-pyrroline (2AP) is recognized as a key component of the aroma in fragrant rice. The variation in grain 2AP content among fragrant rice varieties is associated with the expression of the badh2 gene, with 19 alleles having been identified. The grain 2AP content is strongly influenced by environmental and management factors during cultivation as well as post-harvest conditioning. This review identified the major abiotic and biotic factors that control grain 2AP content. Abiotic factors, such as water, temperature, light quality, fertilizer application (both macro- and micro-nutrients), and soil properties, including salinity, contribute to the aroma of fragrant rice. The grain 2AP content is also affected by biotic factors, including microorganisms that produce aromatic compounds, thus influencing the grain aroma in fragrant rice. Post-harvest management, including storage and drying conditions, can significantly impact the grain 2AP content, and proper post-harvest conditions can enhance the intensity of the grain aroma. This review suggests that there are rice varieties that serve as potential sources of genetic material for breeding rice varieties with high grain aroma content. However, the trait is strongly influenced by both abiotic and biotic factors, as well as post-harvest management. This review provides a summary of recent research on the major factors affecting aroma content in fragrant rice. This knowledge will facilitate further research on the production of high-quality rice to meet the demands of farmers and consumers.