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2-acetyl-1-pyrroline (2AP) is recognized as the key aromatic compound in fragrant rice, however, the effect of light quality on rice aroma is not fully understood. In this study, two fragrant rice varieties (Xiangyaxiangzhan and Yuxiangyouzhan) were grown under four light quality treatments (CK: natural light, L1: red light, L2: blue light and L3: combined light). Results depicted that L1, L2 and L3 treatments enhanced the grain yield by 14.24–35.36%, compared to CK whilst L2 and L3 treatments reduced the 2AP content in grains by 17.18–28.68%. Moreover, L1, L2 and L3 treatments enhanced the grain yield owing to improved filled grain percentage and regulation in antioxidant enzyme activities. On the other hand, L2 and L3 reduced the 2AP content in grains by decreasing pyrroline-5-carboxylic acid content and modulating proline and γ-aminobutyric acid content. Overall, this study revealed that light quality substantially affects the grain yield and quality characters of fragrant rice. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the optimum time for γ-aminobutyric acid (GABA) application to improve the yield and quality in fragrant rice. Pot and field experiments were conducted during 2016–17 with two fragrant rice cultivars (for pot experiment), and five fragrant rice cultivars (for field experiment) which were applied with five GABA levels i.e. no GABA application (CK), application of GABA at 250 mg l−1 with 25 ml pot−1 at tillering stage (S1), panicle initiation stage (S2), heading stage (S3), and at tillering, panicle initiation and heading stages (S4) in the pot experiment. Similarly, the same treatments with 100 ml m−2 were applied to all rice cultivars in the field experiment. The S3 treatment significantly increased the 2-acetyl-1-pyrroline (2AP) contents in Meixiangzhan2 (14.76%) and Yuxiangyouzhan (20.19%) in pot experiment, Meixiangzhan2 (27.27%), Yuxiangyouzhan (40.24%), Basmati (43.07%) and Yungengyou14 (13.66%) in field experiment owing to regulations in the contents of proline, Δ1-pyrroline-5-carboxylic acid (P5C), GABA and the activities of enzymes involved in 2AP formation. The GABA treatments improved yield and modulated the antioxidant enzyme activities. This study provides a reference for the GABA application to improve yield and quality in fragrant rice. [ABSTRACT FROM AUTHOR]

The 2‐acetyl‐1‐pyrroline (2AP) is a key aroma compound in fragrant rice. The present study assessed the γ‐aminobutyric acid (GABA) and nitrogen (N) application induced regulations in the biochemical basis of rice aroma formation. Four N levels, that is, 0, 0.87, 1.75, and 2.61 g/pot, and two GABA treatments, that is, 0 mg/L (GABA0) and 250 mg/L (GABA250), were applied to three fragrant rice cultivars, that is, Yuxiangyouzhan, Yungengyou 14, and Basmati‐385. Results showed that GABA250 increased 2AP, Na, Mn, Zn, and Fe contents by 8.44%, 10.95%, 25.70%, 11.14%, and 43.30%, respectively, under N treatments across cultivars. The GABA250 further enhanced the activities of proline dehydrogenase (PDH), ornithine aminotransferase (OAT) (both at 15 days after heading (d AH), and diamine oxidase (DAO) (at maturity) by 20.36%, 11.24%, and 17.71%, respectively. Significant interaction between GABA and N for Mn, Zn, and Fe contents in grains, proline content in leaves, GABA content in leaves at 15 d AH and maturity stage (MS), Δ1‐pyrroline‐5‐carboxylic acid (P5C) contents in leaves at 15 d AH, and Δ1‐pyrroline‐5‐carboxylate synthase (P5CS), PDH, and OAT activities in leaves at MS was noted. Moreover, the 2AP contents in grains at MS showed a significant and positive correlation with the proline contents in the leaves at 15d AH. In conclusion, GABA250 enhanced the 2AP, Na, Mn, Zn, and Fe contents, as well as the enzyme activities involved in 2AP biosynthesis. Exogenous GABA and N application improved the 2AP contents and nutrient uptake in fragrant rice. [ABSTRACT FROM AUTHOR]

Water (W) and nitrogen (N) have pronounced effects on 2-acetyl-1-pyrroline (2AP) contents and nutrient acquisition in fragrant rice. Field experiments were conducted during the early (March–July) and the late (July–November) seasons of 2013. Two water regimes i.e., W0 (well-watered, soil water potential was 0 kPa) and W1 (soil water potential was −25± 5 kPa) and two nitrogen levels i.e., N0 (0 kg N/ha) and N1 (60 kg N/ha (applied in addition to basal dose) were applied to two fragrant rice cultivars i.e., 'Nongxiang 18' and 'Basmati 385' at booting stage. All treatments were applied with 90–90-195 kg N–P–K ha−1 as basal fertilizer and at five days after transplanting, more N was added at 30 kg/ha. Results showed that the interactive effects of W and N influenced 2AP content in grains of both aromatic rice cultivars in both seasons. Compared to W1N0, the 2AP contents of 'Nongxiang 18' and 'Basmati 385'were increased by 37.74% and 55.78% as well as 68.35% and 47.10% at W1N1 for early and late season, respectively. Moreover, W1N1 increased total nitrogen contents in leaves and total potassium contents in leaves and stem sheath of both rice cultivars, whereas, grain 2AP contents were significantly related to the total N and N/P ratio in leaves. • Soil water potential −25± 5 kPa improved the grain 2AP contents substantially. • Reduced water and additional N application increased N and K contents in leaves. • The grain 2AP contents are significantly associated with N and N/P ratio in leaves. • The grain 2AP contents in late season were substantial higher than early season rice. [ABSTRACT FROM AUTHOR]

When using predictive models to assess the risk posed by foodborne pathogens, certain strains exhibit resistance at low temperatures, which may affect the assessment result. To understand the influence of strain heterogeneity on growth dynamics, two Staphylococcus aureus strains, including comparatively low temperature tolerant BB-11 and sensitive BA-26, were inoculated into glutinous rice dough at temperatures ranging from 10 to 37 °C. The primary Gompertz model fit showed an obvious difference in the maximum specific growth (μ max) and duration of the lag phase (λ) values at 10 °C (0.071/h and 28 h for BB-11 and 0.049/h and 34 h for BA-26, respectively). When Huang and Ratkowsky models were compared as secondary models, a log-linear relationship was demonstrated between μ max and λ for both models. Ratkowsky's model fit was more accurate with a high R 2 of 0.95. The predicted minimum growth temperatures were 4.8 °C and 6.3 °C for BB-11 and BA-26, respectively. The time for achieving a 4-log increase (t 4.0) was 96 h for BB-11 at 10 °C, but only 2.4 log CFU/g increase was determined in BA-26 at 144 h. This study suggests that cold-tolerant strains should be considered when a predictive model is used for risk assessment of foodborne pathogens. • Cold tolerant and sensitive S. aureus exhibited different growth curves in glutinous rice dough. • The two strains showed an obvious difference in μ max and λ values at 10 °C. • Ratkowsky's model fit was more accurate when used as secondary model. • Cold-tolerant strains should be well considered when a predictive model is constructed. [ABSTRACT FROM AUTHOR]

The effect of the light quality on 2-acetyl-1-pyrroline (2AP) during the grain filling period in fragrant rice has rarely been investigated. A pot experiment was carried out with two fragrant rice varieties, Xiangyaxiangzhan and Yuxiangyouzhan, grown under three light treatments, 100% red light (L1), 100% blue light (L2), and compound light (L3), during the grain filling period, and natural light was taken as the control (CK). The yield, quality, and fragrance were investigated. The results showed that light quality treatments significantly decreased the 2AP content in mature grains by 16.67–32.82% but improved the grain yield by 2.70–21.41% compared to CK. The regulation effects of light quality treatments on grain yield and 2AP are linked to yield-related traits, biomass accumulation, antioxidant physiology, and 2AP formation-related physiology. Additionally, light quality treatments decreased the chalky rice percentage and chalkiness, and increased the length-to-width ratio. Overall, light quality treatments during the grain filling period had a positive effect on the grain yield but not on fragrance in fragrant rice. [ABSTRACT FROM AUTHOR]

Mechanical pot-seedling transplanting (PST) is an efficient transplanting method and deep nitrogen fertilization has the advantage of increasing nitrogen use efficiency. However, little information is available about the effect of PST when coupled with mechanized deep nitrogen (N) fertilization on grain yield, nitrogen use efficiency, and antioxidant enzyme activities in rice. A two-year field experiment was performed to evaluate the effect of PST coupled with deep N fertilization in both early seasons (March–July) of 2018 and 2019. All seedlings were transplanted by PST and three treatments were designed as follows. There was a mechanized deep placement of all fertilizer (MAF), broadcasting fertilizer (BF), no fertilizer (N0). MAF significantly increased grain yield by 52.7%. Total nitrogen accumulation (TNA) was enhanced by 27.7%, nitrogen partial factor productivity (NPFP) was enhanced by 51.4%. nitrogen recovery efficiency (NRE) by 123.7%, and nitrogen agronomic efficiency (NAE) was enhanced by 104.3%, compared with BF treatment. Moreover, MAF significantly improved peroxidase (POD), catalase (CAT), and notably reduced the malonic dialdehyde (MDA) content for both rice cultivars, compared to BF. Hence, the result shows that mechanical pot-seedling transplanting coupled with nitrogen deep placement is an efficient method with the increase of grain yield and nitrogen use efficiency in rice cultivation in South China. [ABSTRACT FROM AUTHOR]

Nitrate reductase is a nitric oxide (NO) induced enzyme in plants, NO acts as a signaling molecule under ZnO NPs-induced stress whereas melatonin (N-acetyl-5-methoxytryptamine) could improve morpho-physiological attributes of plants under adverse conditions. In present study, seedlings of two rice genotypes differed regarding nitrate reductase activities i.e., transgenic 'NR' and wild type 'WT' were applied with two melatonin levels i.e., 0, 10 μΜ regarded as M0, M10, respectively and three levels of ZnO NPs i.e., 0, 50, 500 mg L−1 regarded as ZnO NPs0, ZnO NPs50 and ZnO NPs500, respectively. Results revealed that melatonin application substantially increased the dry biomass accumulation of both rice genotypes under all ZnO NPs levels. The root growth, mineral absorption as well as the antioxidant responses were also improved by melatonin application under ZnO NPs stress. The interactive effects of melatonin and genotype on plant growth, antioxidant responses and mineral contents i.e., Zn, Na, Fe and Mn were also found significant under different ZnO NPs stress. Furthermore, total plant dry weight was significantly correlated with the leaf dry weight, root volume, catalase (CAT) activity in leaves, Na accumulation in stem sheath and Fe accumulation in root under both M0 and M10 treatments. Moreover, the comparative transcriptome analysis identified key genes which were responsible for melatonin and NO-induced modulations in plant growth under ZnO NPs stress. Overall, melatonin could improve the morphological growth of the rice plants by modulating root-shoot characteristics, antioxidant activities and mineral uptake in root and shoot of rice. • Melatonin could significantly increase dry biomass accumulation rice across three ZnO NPs. • Melatonin improved the root growth parameters, mineral absorption and the antioxidant responses. • Melatonin and genotype had interactive effect on morphology and biochemistry under ZnO NPs stress. • The comparative transcriptome analysis identified key genes. [ABSTRACT FROM AUTHOR]