Nitrogen application and different water regimes at booting stage improved yield and 2-acetyl-1-pyrroline (2AP) formation in fragrant rice

Regulation of 2-Acetyl-1-pyrroline Content in Fragrant Rice under Different Temperatures at the Grain-Filling Stage

2-Acetyl-1-pyrroline (2-AP) is a key volatile organic compound in fragrant rice aroma. However, the effects of temperature on 2-AP biosynthesis in fragrant rice and its regulation mechanism have been rarely reported. In the present study, three fragrant rice varieties were used as plant materials, and four temperature treatments during the grain-filling stage, i.e., (T1) 22/17 °C, (T2) 27/22 °C, (T3) 32/27 °C, and (T4) 37/32 °C, were adopted. The results showed that grain contents of 2-AP, proline, and γ-aminobutyric acid (GABA) significantly (P < 0.05) increased with decreased temperature, while the lowest and highest 2-AP contents were recorded in the T4 and T1 treatments, respectively. Higher pyrroline-5-carboxylic acid (P5C) content was recorded in low-temperature treatments (T1 and T2) than in high-temperature treatments (T3 and T4). The transcript levels of genes BADH2, PRODH, and OAT significantly (P < 0.05) decreased with decreased temperature. Lower transcript levels of genes P5CR, P5CS2, DAO2, DAO4, and DAO5 were recorded in low-temperature treatments (T1 and T2) than in high-temperature treatments (T3 and T4). In conclusion, low temperature increased 2-AP content and high temperature decreased 2-AP content in fragrant rice. We deduced that temperature regulated 2-AP biosynthesis through the metabolism of proline and GABA.

l-Glutamate Seed Priming Enhances 2-Acetyl-1-pyrroline Formation in Fragrant Rice Seedlings in Response to Arsenite Stress

2-Acetyl-1-pyrroline (2-AP) is a fragrance compound and flavor in fragrant rice whose precursors are generally glutamate (Glu) and proline (Pro). Our previous study revealed that exogenous Glu enhanced the arsenic (As) tolerance in fragrant rice by improving the ascorbic acid-glutathione cycle and the Pro content in roots. However, less is known about how Glu is involved in 2-AP biosynthesis in fragrant rice under As stress. Herein, a hydroponic experiment of L-Glu seed priming with 0, 100, and 500 μM l-glutamic acid solutions was conducted with two fragrant rice varieties. After that, the 10-day-old seedlings were cultured under 0 and 100 μM arsenite stress for 10 d. Results showed that the 2-AP and Pro contents were increased by 18-30% and 21-78% under As100 μM-Glu100 μM treatment in comparison to the control As100 μM to Glu0 μM, while the activities of pyrroline-5-carboxylate synthetase (P5CS) and proline dehydrogenase (ProDH) were increased by 19-46% and 3-19%, respectively. Furthermore, the 2-AP, Pro contents, and P5CS activity were correlated positively. Correspondingly, a significant abundance of differential expressed metabolites (18) and differential expressed genes (26) was observed in amino acid metabolism and glutathione metabolism pathways. In addition, several essential genes were verified and grouped into the pathways of glutathione metabolism, proline, and arginine metabolism with antioxidant defense system to comodulate 2-AP biosynthesis and stress detoxification. Therefore, the Glu seed priming treatment had a positive impact on the 2-AP biosynthesis of fragrant rice under 100 μM arsenite toxicity.

Optimization of liquid fertilizer management improves grain yield, biomass accumulation, and nutrient uptake of late-season indica fragrant rice

BACKGROUND

The use of liquid fertilizer is an effective measure to increase rice yield and nitrogen use efficiency. There has been a lack of information regarding the effects on the grain yield, biomass accumulation, and nutrient uptake in late-season indica fragrant rice of split fertilizer application and of nitrogen management in liquid fertilizer application.

RESULTS

A 2-year field experiment was carried out during 2019 and 2020 with two fragrant rice cultivars grown under differing fertilizer management treatments. Results showed that the fertilization treatments affected the grain yield, yield components, biomass accumulation, and nutrient accumulation significantly. The mean nitrogen recovery efficiency with liquid fertilizer management was greater than in a control treatment corresponding to a practice commonly used by farmers (H2). The effects of nitrogen metabolism enzymes in the leaves of both rice cultivars were stronger with liquid fertilizer treatments than with H2. Grain yield was positively associated with the effective panicle number, spikelets per panicle, dry matter accumulation, N and K accumulation, and the nitrogen metabolism enzymes.

CONCLUSIONS

Optimized liquid fertilizer management increases biomass accumulation, nitrogen utilization efficiency, and nitrogen metabolism. It stabilizes yields and increases the economic benefits of late-season indica fragrant rice. © 2023 Society of Chemical Industry.

Nitric oxide confers cadmium tolerance in fragrant rice by modulating physio-biochemical processes, yield attributes, and grain quality traits

Cadmium (Cd) stress causes serious disruptions in plant metabolism, physio-biochemical processes, crop yield, and quality characters. Nitric oxide (NO) improves the quality features and nutritional contents of fruit plants. However, how NO confers Cd toxicity in fragrant rice plants, is sparse. Hence, the present study investigated the effects of 50 µM NO donor sodium nitroprusside (SNP) on physio-biochemical processes, plant growth attributes, grain yield, and quality traits of fragrant rice under Cd stress (100 mg kg^-1 soil). The results revealed that Cd stress diminished rice plant growth, impaired photosynthetic apparatus and antioxidant defense system, and deteriorated the grain quality traits. However, foliar application of SNP mitigated Cd stress by improving plant growth and gas exchange attributes. Higher electrolyte leakage (EL) was accompanied with elevated levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) under Cd stress; however, exogenous application of SNP reduced them. The activities and relative expression levels of enzymatic antioxidants; superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) and non-enzymatic antioxidants, glutathione (GSH) contents were reduced by Cd stress, while SNP application regulated their activity and transcript abundances. SNP application improved fragrant rice grain yield and 2-acetyl-1-pyrroline content by 57.68 % and 75.54 % respectively, which is concomitant with higher biomass accumulation, photosynthetic efficiency, photosynthetic pigment contents, and an improved antioxidant defense system. Collectively, our results concluded that SNP application regulated the fragrant rice plant physio-biochemical processes, yield traits and grain quality characters under Cd-affected soil.

Biosynthesis of 2-Acetyl-1-pyrroline in Fragrant Rice: Recent Insights into Agro-management, Environmental Factors, and Functional Genomics

Rice is a staple food for more than half of the world's population, and rice fragrance is a key quality attribute which is highly desired by consumers and attracts premium prices in the international market. There are around 200 volatile compounds involved in rice fragrance, but 2-acetyl-1-pyrroline (2-AP) has been considered a master regulator of aroma in fragrant rice. Consequently, efforts were made to increase the 2-AP contents in the grain by managing agronomical practices or by using modern functional genomic tools, which successfully converted nonfragrant cultivars to fragrant rice. Furthermore, environmental factors were also reported to influence the 2-AP contents. However, a comprehensive analysis of 2-AP biosynthesis in response to agro-management practices, environmental factors, and the application of functional genomic tools for fragrant rice production was missing. In this Review, we summarize how micro/macronutrients, cultivation practices, amino acid precursors, growth regulators, and environmental factors, such as drought, salinity, light, and temperature, influence the 2-AP biosynthesis to modulate the aroma of fragrant rice. Furthermore, we also summarized the successful conversion of nonfragrant rice cultivars to fragrant rice using modern gene editing tools, such as RNAi, TALENS, and CRISPR-Cas9. Finally, we discussed and highlighted the future perspective and challenges related to the aroma of fragrant rice.

Increasing basal nitrogen fertilizer rate improves grain yield, quality and 2-acetyl-1-pyrroline in rice under wheat straw returning

Straw returning plays an essential role in crop yields and the sustainable development of agriculture. However, the effects and mechanisms of nitrogen (N) fertilizer management on grain yield, quality and aroma substance 2-acetyl-1-pyrroline (2-AP) content under wheat straw returning are still unclear. In this field experiment, two japonica rice cultivars were used as materials, wheat straw non-returning (NS) and wheat straw full returning (WS) were designed coupled with two N application ratios, namely basal fertilizer: tiller fertilizer: panicle fertilizer =5:1:4 (local farmers' fertilizer practice, LFP) and 7:1:2 (increasing basal fertilizer rate, IBF) under the total N application rate of 270 kg ha^-1. The effects of the four treatment combinations (NS-LFP, NS-IBF, WS-LFP, WS-IBF) on yield, cooking and eating quality, and 2-AP content in rice were investigated. The two-year (2020, 2021) results showed that: 1) WS-IBF significantly increased the number of panicles and grains per panicle, leading to the increase in grain yield by 6.67%-12.21%, when compared with NS-LFP, NS-IBF and WS-LFP. 2) WS-IBF enhanced the taste value, peak viscosity, breakdown value, the ratio of amylopectin to amylose, and the ratio of glutelin to prolamin while reducing the setback value and amylose content of rice flour. 3) Compared with NS, WS increased the activities of proline dehydrogenase and ornithine transaminase, the synthetic precursors of 2-AP, and finally increased 2-AP content in rice grains. WS-IBF slightly decreased 2-AP content, but there was no significant difference with WS-LFP. The above results indicated that adjusting the N regime and increasing basal N fertilizer rate under wheat straw returning is conducive to improving grain yield, cooking and eating quality, and 2-AP content in rice.

Insights of Improved Aroma under Additional Nitrogen Application at Booting Stage in Fragrant Rice

Plant mineral nutrition substantially affects the growth, yield and quality of rice, whereas nitrogen (N) application contributes significantly in this regard. Undoubtedly, N application improves rice aroma biosynthesis; however, the molecular mechanism underlying the regulation of grain 2-acetyl-1-pyrroline (2-AP) biosynthesis in the presence of nitrogen application at the booting stage has remained largely unexplored. The present study examined the effects of three N levels, i.e., 0 g per pot (N0), 0.43 g per pot (N1) and 0.86 g per pot (N2) on intermediates, enzymes and genes involved in 2-AP biosynthesis, as well as on the yield of two fragrant rice cultivars viz, Meixiangzhan2 and Xiangyaxiangzhan. N was additionally applied at the booting stage. The results depicted that the levels of precursor, such as proline, and the activity of enzymes involved in 2-AP biosynthesis, such as Δ1-pyrroline-5-carboxylate synthetase (P5CS) and diamine oxidase (DAO), and P5CS1 gene expression were comparatively higher under N1 than N0 in both fragrant rice cultivars. Moreover, the N2 treatment increased the grain panicle-1, filled grain percentage and grain yield of both rice cultivars, while the grain yield of Meixiangzhan2 and Xiangyaxiangzhan was increased by 15.87% and 12.09%, respectively, under N2 compared to N1 treatment. Hence, 0.43 g per pot of N showed positive performances in yield and aroma accumulation in fragrant rice and should be further employed in the practice and production for better cultivation in the rice market.

Foliar application of procyanidins enhanced the biosynthesis of 2-acetyl-1-pyrroline in aromatic rice (Oryza sativa L.)

BACKGROUND

Procyanidins is a polyphenolic compound with multiple properties. However, the application of exogenous procyanidins in crops has not been reported. Aromatic rice is a high-quality rice with a special aroma and popular with consumers. The 2-acetyl-1-pyrroline (2-AP) is a key compound of aromatic rice aroma. In the current study, aromatic rice plants were sprayed with procyanidins solutions at 0.25 (Pr0.25), 0.50 (Pr0.50), 1.00 (Pr1.00), 2.00 (Pr2.00) g L^-1, respectively and treatment sprayed with distilled water was taken as control (CK). The effects of exogenous procyanidins on growth and 2-AP biosynthesis of aromatic rice plants were explored.

RESULTS

Compared with CK, Pr1.00 and Pr2.00 treatments significantly increased 2-AP content by 16.67% and 37.68%, respectively. Higher proline, 1-pyrroline-5-carboxylic acid (P5C), 1-pyrroline, methylglyoxal contents, and lower γ- aminobutyric acid (GABA) content were recorded in Pr1.00 and Pr2.00 treatments than CK. Compared with CK, Pr1.00 and Pr2.00 treatments significantly improved the activities of P5CS and OAT and diminished the activity of BADH. Furthermore, compared with CK, Pr1.00 and Pr2.00 treatments significantly up-regulated the transcript levels of P5CS2, P5CR, OAT, DAO4 and down-regulated the transcript levels of BADH2. Exogenous procyanidins had no substantial effects on plant height, stem diameter, fresh weight, and dry weight of aromatic rice plants.

CONCLUSIONS

In conclusion, our findings reported the increment of 2-AP content in aromatic rice under exogenous procyanidins. Our results indicated that the application of exogenous procyanidins enhanced 2-AP biosynthesis by improving proline biosynthesis and inhibiting GABA formation.

The Regulatory Mechanism of 2-Acetyl-1-Pyrroline Biosynthesis in Fragrant Rice (Oryza sativa L.) Under Different Soil Moisture Contents

2-acetyl-1-pyrroline (2-AP) is the key compound of rice aroma. However, the responses of 2-AP biosynthesis in fragrant rice under different soil moisture and the corresponding mechanism are little known. The present study evaluated the effects of different soil moisture on 2-AP biosynthesis through a pot experiment. Four soil moisture contents, that is, 50% (SM50), 40% (SM40), 30% (SM30), and 20% (SM20), were adopted, and SM50 treatment was taken as control. The pots were weighed and watered to maintain the corresponding soil moisture content. The results showed no significant difference in growth parameters (plant height, stem diameter, and plant dry weight) among all treatments. Compared with SM50, SM40, SM30, and SM20 treatments significantly (p<0.05) increased 2-AP content by 32.81, 23.18, and 53.12%, respectively. Between 20 to 90% higher proline content was observed in SM40, SM30, and SM20 treatments than in SM50. Enzymes including proline dehydrogenase, ornithine transaminase, and 1-pyrroline-5-carboxylate synthetase exhibited lower activities with soil moisture declined. Higher diamine oxidase activity was observed in SM40, SM30, and SM20 treatments compared with SM50, and real-time PCR analyses showed that transcript level of DAO1 was greatly increased under low soil moisture treatments, especially in SM20 treatment. Transcript levels of PRODH, DAO2, DAO4, DAO5, OAT, P5CS1, and P5CS2 decreased or maintained in SM40, SM30, and SM20 treatments compared with SM50. We deduced that low soil moisture content enhanced 2-AP biosynthesis mainly by upregulating the expression of DAO1 to promote the conversion from putrescine to 2-AP.

Transcriptomic Analysis Provides Insights into Foliar Zinc Application Induced Upregulation in 2-Acetyl-1-pyrroline and Related Transcriptional Regulatory Mechanism in Fragrant Rice

The involvement of zinc (Zn) in terms of aroma formation has been rarely investigated. This study shows that the regulation of 2-acetyl-1-pyrroline (2AP) biosynthesis was evaluated in two different rice cultivars under foliar Zn application. The results showed that the 2AP and Zn contents in leaves and grains were improved substantially under foliar Zn application. The 2AP content was positively related to the expression P5CS2 gene, contents of proline, 1-pyrroline, and Δ1-pyrroline-5-carboxylate (P5C), and the activity of pyrroline-5-carboxylate synthase (P5CS) under Zn application in fragrant rice. Multiple transcription factors (TFs) were differently expressed, such as bZIPs, NACs, and MYBs, to play a role under Zn treatments in fragrant rice, suggesting the crucial role of 46 differently expressed TFs in 2AP improvements in fragrant rice. Furthermore, this study showed that the optimal foliar Zn application at a concentration of 30 mg L^-1 could increase the 2AP content of aromatic rice and keep the yield stable or increase the yield. TFs were involved in regulating to promote the 2AP formation in aromatic rice under the foliar Zn application. However, the relationship between 2AP biosynthesis pathway genes and TFs in fragrant rice remains to be further studied.

Silicon Application Modulates the Growth, Rhizosphere Soil Characteristics, and Bacterial Community Structure in Sugarcane

Silicon (Si) deficiency, caused by acidic soil and rainy climate, is a major constraint for sugarcane production in southern China. Si application generally improves sugarcane growth; however, there are few studies on the relationships between enhanced plant growth, changes in rhizosphere soil, and bacterial communities. A field experiment was conducted to measure sugarcane agronomic traits, plant nutrient contents, rhizosphere soil enzyme activities and chemical properties, and the rhizosphere bacterial community diversity and structure of three predominant sugarcane varieties under two Si treatments, i.e., 0 and 200 kg of silicon dioxide (SiO₂) ha^-1 regarded as Si0 and Si200, respectively. Results showed that Si application substantially improved the sugarcane stalk fresh weight and Si, phosphorus (P), and potassium (K) contents comparing to Si0, and had an obvious impact on rhizosphere soil pH, available Si (ASi), available P (AP), available K (AK), total phosphorus (TP), and the activity of acid phosphatase. Furthermore, the relative abundances of Proteobacteria showed a remarkable increase in Si200, which may be the dominant group in sugarcane growth under Si application. Interestingly, the AP was noticed as a major factor that caused bacterial community structure differences between the two Si treatments according to canonical correspondence analysis (CCA). In addition, the association network analysis indicated that Si application enriched the rhizosphere bacterial network, which could be beneficial to sugarcane growth. Overall, appropriate Si application, i.e., 200 kg SiO₂ ha^-1 promoted sugarcane growth, changed rhizosphere soil enzyme activities and chemical properties, and bacterial community structures.

Lanthanum (La) improves growth, yield formation and 2-acetyl-1-pyrroline biosynthesis in aromatic rice (Oryza sativa L.)

BACKGROUND

Lanthanum (La) is a rare earth element that can influence plant growth and development. However, the effect of La on growth, yield formation and 2-acetyl-1-pyrroline (2-AP, a key compound responsible for the aroma of rice) biosynthesis in aromatic rice (Oryza sativa L. subsp. japonica Kato) has not been reported. Therefore, the present study investigated the effects of La on growth, photosynthesis, yield formation and 2-AP biosynthesis in aromatic rice through three experiments.

RESULTS

Two pot experiments and a two-year field trial were conducted with different rates of La application (20-120 LaCl3 mg kg-1 and 12 kg ha-1 LaCl3), and treatments without La application were used as controls. The results showed that the application of LaCl3 at 80 and 100 mg kg-1 and at 12 kg ha-1 greatly increased the 2-AP content (by 6.45-43.03%) in aromatic rice seedlings and mature grains compared with the control. The La treatments also increased the chlorophyll content, net photosynthetic rate and total aboveground biomass of rice seedlings. Higher antioxidant enzyme (superoxide, peroxidase, and catalase) activity was detected in the La treatments than in the control. The La treatments also increased the grain yield, grain number per panicle and seed-setting rate of aromatic rice relative to the control. Moreover, the grain proline and γ-aminobutyric acid contents and the activity of betaine aldehyde dehydrogenase significantly decreased under the La treatment. The application of La to soil enhanced the activity of proline dehydrogenase by 20.62-56.95%.

CONCLUSIONS

La improved the growth, yield formation and 2-AP content of aromatic rice and enhanced 2-AP biosynthesis by increasing the conversion of proline to 2-AP and decreasing the conversion of GABald to GABA.

Molybdenum-Induced Regulation of Antioxidant Defense-Mitigated Cadmium Stress in Aromatic Rice and Improved Crop Growth, Yield, and Quality Traits

Cadmium (Cd) stress causes serious disruptions in plant metabolism, physio-biochemical responses, crop yield, and grain quality characteristics. A pot experiment was conducted to investigate the role of molybdenum (Mo) in mitigating Cd-induced adversities on plant growth, yield attributes, and grain quality characteristics of a popular aromatic rice cultivar ‘Xiangyaxiangzhan’. The Mo was applied at 0.15 mg kg⁻¹ soil in both control (no Cd) and Cd-contaminated (100 mg kg⁻¹) soils. A treatment with Mo-free (−Mo) soil was also maintained for comparison. The results showed that Cd toxicity significantly (p < 0.05) reduced plant dry biomass, grain yield, photosynthetic efficiency, and pigment contents, and impaired chloroplast ultra-structural configuration and simultaneously destabilized the plant metabolism owing to higher accumulation of hydrogen peroxide, electrolyte leakage, and malondialdehyde contents. However, Mo supply improved grain yield and 2-acetyl-1-pyrroline content by 64.75% and 77.09%, respectively, under Cd stress, suggesting that Mo supply mitigated Cd-provoked negative effects on yield attributes and grain quality of aromatic rice. Moreover, Mo supply enhanced photosynthesis, proline, and soluble protein content, and also strengthened plant metabolism and antioxidant defense through maintaining higher activities and transcript abundance of ROS-detoxifying enzymes at the vegetative, reproductive, and maturity stages of aromatic rice plants under Cd toxicity. Collectively, our findings indicated that Mo supply strengthened plant metabolism at prominent growth stages through an improved enzymatic and non-enzymatic antioxidant defense system, thereby increasing grain yield and quality characteristics of aromatic rice under Cd toxicity.

Molybdenum improves 2-acetyl-1-pyrroline, grain quality traits and yield attributes in fragrant rice through efficient nitrogen assimilation under cadmium toxicity

Cadmium (Cd) toxicity causes severe perturbations in nitrogen (N) uptake and assimilation, and thereby interrupts normal plant growth. Molybdenum (Mo), a necessary trace element, plays important roles in N metabolism through regulating N assimilatory enzymes activities and expressions in higher plants. Taking this into account, a pot experiment was performed to explore the role of Mo in alleviating Cd-induced inhibitory effects on physio-biochemical processes, N metabolism, yield attributes and grain quality characters of two fragrant rice cultivars; Guixiangzhan and Meixiangzhan-2. Both the fragrant rice cultivars were treated with two levels of each Cd concentrations (0 and 100 mg/kg) and Mo treatments (0 and 0.15 mg/kg). The results revealed that Cd toxicity significantly reduced (p < 0.05) plant dry biomass, gaseous exchange attributes, chlorophyll contents, N utilizing and assimilatory enzymes activities, 2-acetyl-1-pyrroline (2AP) contents and grain yield in both cultivars; however, more severe inhibitions were observed in Meixiangzhan-2 than Guixiangzhan. Nevertheless, Mo application alleviated Cd stress and enhanced 2AP content and grain yield by 75.05% and 67.94% in Guixiangzhan and 87.71% and 83.51% in Meixiangzhan-2, respectively compared with no Mo application. Moreover, Mo application improved photosynthesis, chloroplast configuration, soluble protein and proline contents and also strengthened the N assimilatory pathway through efficient NO₃^- utilization, higher nitrate reductase, nitrite reductase, glutamine synthetase and glutamate synthase activities and transcript levels under Cd stress. Collectively, our results imply that Mo-induced enhancement in N utilization and assimilation improved yield and grain quality characters of fragrant rice cultivars under Cd stress.

Differential response of fragrant rice cultivars to salinity and hydrogen rich water in relation to growth and antioxidative defense mechanisms

Salinity negatively effects the growth and productivity of crop plants; however, the effects of hydrogen rich water (HRW) on the early growth of fragrant rice under salinity stress are rarely investigated. In present study, two HRW treatments: foliar application (F-HRW) and irrigation (I-HRW) were applied on the two fragrant rice cultivars, Yuxiangyouzhan and Xiangyaxiangzhan, grown under normal and salt stress conditions, i.e., 0 and 150 mmol NaCl L^-1, respectively. Plants without HRW application were grown as control (CK). Results showed that the dry weight per unit plant height (mg cm^-1) was increased by 12.6% and 23.0% in F-HRW and I-HRW, respectively under salt stress as compared with CK. Application of HRW, regardless of the application method, modulated the antioxidant activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) while reduced malondialdehyde (MDA) contents under salt stress. Moreover, significant and positive relations were observed among total dry weight and shoot dry weight, dry weight per unit plant height, SOD and CAT activity in root. Overall, F-HRW application modulated the early growth and related physiological attributes in fragrant rice under salt stress whereas I-HRW was found to mitigate salt stress. Novelty statement: Involvement of endogenous H₂ in plants for regulating various physiological functions is of great importance to stimulate and/or activate the antioxidant defense responses against oxidative stress; however, there is a lack of research in this aspect. The present study investigated the effects of hydrogen rich water (HRW) on the growth and physiological attributes of two fragrant rice cultivars grown under salt-stress. It was noteworthy to find that application of HRW either foliar application or irrigation improved the morphological characters, i.e., dry weight per unit plant height and enhanced the activities of antioxidants, i.e., peroxidase, superoxide dismutase and catalase whilst decreased the malonaldehyde content. Overall, the application of HRW modulates plant growth and physiological attributes in fragrant rice cultivars under salt-stress conditions. This study will be helpful in improving the early growth and/or stand establishment of fragrant rice nursery under saline conditions.

Selenium-silicon (Se-Si) induced modulations in physio-biochemical responses, grain yield, quality, aroma formation and lodging in fragrant rice

Fragrant rice is a high-valued quality rice type which is gaining much popularity over the globe due to its better cooking qualities and special aromatic characteristics. Selenium (Se) and silicon (Si) could improve the growth and yield of rice; however, the combine effects of Se and Si (Se-Si treatments) on rice grain quality, aroma and lodging in fragrant rice were rarely investigated. The pot and field experiments were conducted with two fragrant rice cultivars i.e., Xiangyaxiangzhan and Yuxiangyouzhan, grown under three Se levels i.e., 0, 120, and 240 mg kg^-1 of soil (for pot experiment) and 0, 300, and 600 kg ha^-1 (for field experiment) regarded as LSe, MSe and HSe, respectively and two Si levels i.e., 0 and 60 mg kg^-1 of soil (for pot experiment) and 0 and 150 kg ha^-1 (for field experiment) regarded as -Si and +Si, respectively. Results depicted that the Se-Si treatments regulated head rice yield, grain yield and yield related traits and the HSe+Si treatment sustainably improved the grain yield and head rice yield by regulating plant growth, antioxidant response and malondialdehyde (MDA) contents in fragrant rice. The Se-Si treatments also improved the grain 2AP contents owing to regulation in the proline, pyrroline-5-carboxylate (P5C) and γ-aminobutyric acid (GABA) contents. Besides, Se-Si treatments also regulated the grain quality attributes and influenced the plant Se contents. Moreover, the Si mitigated Se-induced lodging resulted from changes in the lodging parameters i.e., lodging index, fresh weight per tiller, pushing resistance force, plant height and bending moment. Overall, the Se and Si application improved the grain yield and regulated the dry weight accumulation, antioxidant attributes and quality attributes. Meanwhile, the Si application mitigated the negative effect of Se-induced lodging in fragrant rice.

Correction to: Nitrogen application and different water regimes at booting stage improved yield and 2-acetyl-1-pyrroline (2AP) formation in fragrant rice

It was highlighted that the original article (Mo et al. 2019) contained an error in Fig. 1f which revealed the biosynthesis pathway of 2AP. This Correction article shows the correct Fig. 1 and incorrect Fig. 1. The original article has been updated.