Fertilizer Deep Placement Significantly Affected Yield, Rice Quality, 2-AP Biosynthesis and Physiological Characteristics of the Fragrant Rice Cultivars

The management of fertilizers in a context of climate change and the preservation of the environment is strongly related to the regulation and accumulation of 2-acetyl-1-pyrroline (2AP) in fragrant rice. However, the feasibility of such management strategies in terms of enhancing the accumulation of 2AP has not yet been explored in aromatic cultivars. Here, we investigated the impact of the application of two fertilizers at three depth (surface, 5 cm and 10 cm) levels of placements to improve the aromatic rice quality, including such aspects as the 2AP content-, protein-, amylose- and yield-related traits. For this purpose, two known rice cultivars, Basmati 385 (B-385) and Yunjingyou (YJY), were grown in pots during 2019 and 2020 under fluctuating climates. The deep application of fertilizer at 10 cm significantly affected the 2AP content with such values as 127.53 μg kg⁻¹ and 111.91 μg kg⁻¹ obtained for Fragrant Fertilizer (FF) and Urea in B-385 cultivar, and 126.5 μg kg⁻¹ and 114.24 μg kg⁻¹ being observed for FF and Urea in YJY, respectively, during 2019. In addition, values of 108.41 μg kg⁻¹ and 117.35 μg kg⁻¹ were recorded for FF and Urea in B-385, while 125.91-μg kg⁻¹ and 90.71-μg kg⁻¹ were measured for FF and Urea in YJY, respectively, during 2020. Similarly, B-385 had better 2AP content and yield-related traits, as well as amylose content and cooked rice elongation, as compared to the YJY rice cultivar. The 2AP accumulation and its related biochemical parameters, and their relationships in different plant tissues at different growth stages under FF and Urea treatments, were also improved. Further, the 2AP content and the P5C activity demonstrated strong correlations during the grain filling periods in both fragrant rice cultivars. In conclusion, our findings have the potential to provide useful information to farmers and agriculture extension workers in terms of the saving of fertilizers and the improvement of rice grain quality under fluctuating climate conditions.