Effects of ultrasonic treatment on yield and aroma synthesis mechanism of fragrant rice under different mechanical transplanting methods

Abstract BACKGROUND Fragrant rice has high economic value because of the special aroma of its seeds, and how to economically and environmentally enhance the aroma of rice is a topic of significant concern for researchers. In the present study, we investigated the effects of ultrasonic treatment and different mechanical transplanting methods on the yield and aroma substance 2‐acetyl‐1‐pyrroline (2‐AP) of fragrant rice, with the aim of improving the aroma content and final yield in a more efficient, convenient and environmentally friendly manner. The treatments included ultrasonication (ultrasound‐treated seeds: U1; ultrasound‐treated seedlings: U2l; ultrasound‐treated seeds and seedlings: U12) and mechanical transplanting (potting machine transplanting: B; blanket transplanting: T). RESULTS The results showed that potting machine transplanting treatments (B) resulted in higher yields (4.38–6.04 t ha −1 ) and 2‐AP content (276.82–345.61 μg kg −1 ) in fragrant rice compared to blanket transplanting treatments (T) by affecting yield components, photosynthetic characteristics and the content of aroma‐related precursors. Ultrasonic treatment of rice led to a higher net photosynthetic rate, increased activity of resistance and aroma enzymes, and a higher content of aroma‐related precursors compared to non‐ultrasonic treatment, ultimately resulting in higher yield (4.54–6.04 t ha −1 ) and 2‐AP content (286.76–345.61 μg kg −1 ) than the control. However, the ultrasonic treatment of both seeds and seedlings (U12) did not exhibit a ‘stacking effect’ and there were no significant changes in yield and aroma content compared to the control. CONCLUSION Therefore, for the cultivation of fragrant rice, it is recommended to use potting machines for transplanting and to choose to ultrasonicate seeds or seedlings separately. © 2025 Society of Chemical Industry.