Fengqin Hu

Paclobutrazol (PBZ) is extensively used to modulate plant architecture in rice. However, its comprehensive effects on grain yield and aroma in aromatic rice have not been thoroughly investigated. This study used the local aromatic rice cultivars (Meixiangzhan 2 and Xiangyaxiangzhan) as experimental materials to evaluate the impacts of foliar-applied PBZ at three concentrations (0 (CK), 150 (T1), and 300 (T2) mg L⁻¹) on grain yield, photosynthetic characteristics, fragrance formation, and radiation use efficiency (RUE). Field experiments revealed that T1 significantly reduced the leaf area index (LAI) by 10.12% and intercepted photosynthetically active radiation (IPAR) by 10.74%, meanwhile significantly increasing SPAD values by 12.94% and net photosynthetic rate (Pn) by 9.95%, leading to improved RUE up to 25.21%. These changes contributed to a larger number of grains per panicle and increased 1000-grain weight, ultimately enhancing grain yield. In contrast, T2 resulted in a sharp reduction by 24.84% in IPAR and a significant decline in Pn by 10.07% during the late grain-filling stage, thus limiting the supply of photosynthetic assimilates, eventually reducing grain yield. PBZ application also significantly elevated 2-acetyl-1-pyrroline (2-AP) content by 28.74% under T1 and 17.51% under T2, compared to the control. The increase in 2-AP was mainly associated with elevated levels of key precursors, including proline, Δ1-pyrroline-5-carboxylic acid, and Δ1-pyrroline. In spite of differences in traits between cultivars, the traits responded to PBZ in the same pattern. These results indicate that foliar application of PBZ at 150 mg L⁻¹ can effectively improve both yield and aroma of aromatic rice, offering a promising cultivation strategy for high-quality aromatic rice production.

Aromatic rice has gained significant attention due to its high economic and nutritional value. 2-Acetyl-1-pyrroline (2-AP), a key aroma compound in aromatic rice, plays a crucial role in elucidating the aroma characteristics of aromatic rice. However, there is no report on the effect of aromatic rice in rice–potato rotation on aroma characteristics. In order to study the influences of winter-planted potatoes on the yield, quality, and 2-AP biosynthesis of aromatic rice grains, the commonly cultivated aromatic rice variety Meixiangzhan-2 and the potato cultivar Huashu-5 were selected as experimental materials for a three-year consecutive field experiment with different tillage patterns consisting of rice–winter fallow as the control group (CK) and rice–potato rotation as the experimental group (RP). The results indicated that the RP treatment enhanced the soil nutrient content and decreased the bulk density. Compared with CK, RP treatment increased the effective panicle number by 10.88% and grain number per panicle by 8.82%, thereby increasing the yield by 11.99%. Meanwhile, RP treatment improved the brown rice rate by 2.61%, milled rice rate by 4.53%, head milled rice rate by 7.51%, and crude protein content by 6.98%. Regarding 2-AP biosynthesis in grains, in contrast to CK, the RP treatment raised the levels of related precursors (Δ1-pyrroline, Δ1-pyrrolidine-5-carboxylic acid, and proline increased by 8.95%, 18.14%, and 13.75%, respectively) and enzymes (proline dehydrogenase, ornithine transaminase, and diamine oxidase increased by 18.37%, 14.61%, and 11.36%, respectively) in its synthesis pathway, thereby facilitating the accumulation of 2-AP. Furthermore, we also observed a more stable yield and grain 2-AP content in aromatic rice under RP treatment. Overall, with regard to enhancing the aromatic rice yield and aroma, the rice–potato rotation system can be contemplated for vigorous promotion.