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Selenium (Se) is one of the human essential elements and the input of Se for its biofortification is common in rice production to meet the demand for Se in the population. Biological nano-selenium (nano-Se) is a new type of nanoscale microbial synthetic material. However, the effects of biological nano-Se on aromatic rice performance metrics, such as yield formation, grain quality parameters, and the biosynthesis of 2-acetyl-1-pyrroline (2-AP, the key component of aromatic rice aroma), have rarely been reported. Therefore, this study conducted a field experiment with two cropping seasons and two aromatic rice genotypes to explore the effects of the foliar application of biological nano-Se on aromatic rice performance metrics. The results showed that the foliar application of biological nano-Se at 3–4 days before panicle differentiation or the heading stage increased the grain yield of aromatic rice. Dry matter accumulation and the leaf area index increased under Nano-Se application. Furthermore, the foliar application of Nano-Se at 3–4 days before panicle differentiation significantly enhanced the activity of peroxidase, superoxide dismutase, catalase and reduced malondialdehyde content. The foliar application of Nano-Se at the grain-filling stage also increased 2-AP content. In addition, nano-Se application substantially increased the grain Se content in aromatic rice. [ABSTRACT FROM AUTHOR]

Rapeseed–rice rotation is a cropping system that improves the land-use rate. The present study conducted a field experiment with winter planting of rapeseed as treatment (WR) and winter fallow as control (CK) to investigate the effects of winter planting of rapeseed on growth, yield formation, and 2-acetyl-1-pyrroline (2-AP) biosynthesis of fragrant rice in the two subsequent cropping seasons. The results show that WR treatment improved alkali-hydro nitrogen and rapidly available phosphorus contents in soil. Compared with CK, WR treatment significantly increased grain yield and effective panicle number per plant by 21.16–27.26% and 7.33–21.24%, respectively. Higher net photosynthetic rate, leaf area index, and dry matter accumulation of fragrant rice plants were recorded in WR treatment and CK. Furthermore, compared with CK, WR treatment significantly increased grain 2-AP content, which could be explained by increased content of pyrroline-5-carboxylic acid, methylglyoxal, 1-pyrroline, and enhanced activity of proline dehydrogenase. In addition, future studies should be conducted at a molecular level to reveal the regulation mechanism in 2-AP biosynthesis of fragrant rice under conditions of winter planting of rapeseed. [ABSTRACT FROM AUTHOR]

Improved tillage management in fragrant rice cropping systems can enhance soil organic carbon (SOC) and the content of 2-Acetyl-1-Pyrroline (2-AP), a crucial volatile compound contributing to the aroma of fragrant rice. Despite this, the interplay between 2-AP content in fragrant rice and SOC metabolism, alongside the influences exerted by soil microbial functions, remains poorly understood. This study introduces a comprehensive 6-year field experiment which aims to correlate SOC with rice grain 2-AP content by analyzing soil microbial KEGG functions, such as carbon and amino acid metabolism, using metagenomic sequencing. The experiment assessed three tillage practices, conventional tillage (CT), reduced tillage (RT), and no tillage (NT), with soil samples collected on three dates in 2022. The results indicated that NT significantly (p < 0.05) enhanced SOC content and modified carbon metabolism by upregulating the Calvin cycle (K01601) and reducing hemicellulose degradation (K01710). Additionally, NT notably increased the soil levels of alkaline amino acids, such as histidine and ornithine, which were 165.17% and 1218.42% higher, respectively, than those in CT, possibly linked to an increase in soil pH. Furthermore, the 2-AP content in fragrant rice under NT was significantly higher by 52.02% and 13.90% compared to under RT and CT, respectively. NT also upregulated K00250 (alanine, aspartate, and glutamate metabolism) and K00290 (valine, leucine, and isoleucine biosynthesis), leading to significantly higher levels of 2-AP biosynthesis-related amino acids proline and glutamate in fragrant rice grain. This study links SOC and 2-AP biosynthesis via soil microbial functions, presenting a novel strategy for improving the quality of fragrant rice through soil management practices. [ABSTRACT FROM AUTHOR]