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The objective of this study was to determine the effects of seed germination and the parboiling process at different temperatures and times on total anthocyanin concentration, antioxidant activity, γ‐aminobutyric acid (GABA), and the concentration levels of zinc (Zn) and iron (Fe) in the purple rice variety CMU 107. Germinated parboiled rice (GPR) and non‐germinated parboiled rice (NPR) samples were parboiled by being soaked under specific conditions involving a series of temperatures (25°C, 60°C, and 80°C) and times (2, 4, and 6 hr) then being analyzed for the nutritional values. The results showed that the total anthocyanin concentration levels in NPR were about 62.2% higher than those in GPR; however, the antioxidant activity, Zn and GABA concentration levels in GPR were 197.9%, 9.8%, and 5.8% higher than in NPR, respectively. The soaking temperatures and times did not significantly affect the Fe concentrations in all treatments. Practical applications The process of germination following by parboiling at the appropriate soaking temperature and time could be an effective approach to improve antioxidant capacity, grain Zn, and GABA concentration in purple rice. The successful approach would be applied to use in the individual household and/or scaling up into the industrial units and consequently improve nutritional intake among rice consumers. However, anthocyanin concentration in germinated parboiled grain should be preserved carefully by selecting a specific method.

Improving grain yield and zinc (Zn) concentration yields a double benefit for farmers and consumers, especially when accomplished through the common practice of nitrogen (N) and Zn application. The objective of this study was to evaluate responses of a modern improved rice variety (SPT1) to Zn and N fertilizer management of seed germination, seedling growth, yield, and grain Zn accumulation. A preliminary laboratory study was conducted by priming seeds with variation of N and Zn solutions, consisting of (1) 0% urea + 0% ZnSO4 (N0Zn0), (2) 0% urea + 0.07% ZnSO4 (N0Zn+), (3) 0.05% urea + 0.07% ZnSO4 (N0.05Zn+), (4) 0.10% urea + 0.07% ZnSO4 (N0.10Zn+), (5) 0.15% urea + 0.07% ZnSO4 (N0.15Zn+), (6) 0.20% urea + 0.07% ZnSO4 (N0.20Zn+), and (7) 0.25% urea + 0.07% ZnSO4 (N0.25Zn+). Priming seeds with N0.15Zn+ led to a higher germination rate and growth performance. Seedling Zn concentration increased linearly along with the dry weights of root and coleoptile during germination. A second experiment in the field included priming the seed with (1) 0% urea + 0% ZnSO4 (N0Zn0), (2) 0.15% urea + 0% ZnSO4 (N+Zn0), (3) 0% urea + 0.07% ZnSO4 (N0Zn+), and (4) 0.15% urea + 0.07% ZnSO4 (N+Zn+); this experiment showed that simultaneous priming of seeds with 0.15% urea and 0.07% ZnSO4 (N+Zn+) resulted in the highest coleoptile length and seedling dry weight. The highest seedling Zn concentration was observed when priming seeds with N0Zn+ followed by N+Zn+, but the effect disappeared at the later growth stages. A third experiment in the field was conducted by foliar application with four different treatments of (1) 0% urea + 0% ZnSO4 (N0Zn0), (2) 1% urea + 0.5% ZnSO4 (N+Zn0), (3) 0% urea + 0.5% ZnSO4 (N0Zn+), and (4) 1% urea + 0.5% ZnSO4 (N+Zn+). The highest grain yield increases were achieved by foliar application of N+Zn0 (28.5%) and foliar application of N+Zn+ (32.5%), as compared with the control (N0Zn0). Grain Zn concentration was the highest under foliar application of N+Zn+, with a 37.9% increase compared with N0Zn0. This study confirmed that seedling growth performance can be enhanced by initially priming seeds with N and Zn solution, while grain yield and Zn concentration can be improved by foliar application of N and Zn fertilizer. The information would be useful for the appropriate combined application of Zn and N fertilizers in the practical field to improve grain yield and Zn accumulation as well as Zn nutrition among humans with rice-based diets. The result should be extended to a wider range of rice varieties under suitable management of N and Zn fertilizer.

This study evaluated the variation in bioactive compounds (anthocyanins, phenols, and antioxidants) among 22 rice varieties in the same growing locations and among four varieties collected from eight different provinces in Northern Thailand. Wide variation in anthocyanins, phenols, and antioxidant capacity was established, ranging from 1.6 to 33.0 mg/100 g, 249.9 to 477.7 mg gallic acid/100 g, and 0 to 3,288.5 mg trolox equivalent/100 g, respectively. The highest straw anthocyanin and phenol concentrations were found in KDK (a traditional photoperiod-sensitive variety with purple pericarp and leaves) and K4 (an advanced, photoperiod-insensitive variety with purple pericarp and leaves), while the highest antioxidant capacity was found in KH CMU (an improved traditional photoperiod sensitive variety with a purple pericarp and green leaves) and K4. The variation of the bioactive compounds was also found in the same variety grown at different locations, e.g., the KDMl105 grown in Prayao province had a straw anthocyanin concentration higher than when grown in Mae Hong Son province. The effect was also observed in phenol content and antioxidant capacity when the same rice variety was grown across various locations. A significant correlation between total phenol and antioxidant capacity was observed across rice varieties and growing locations but was not found between anthocyanin and antioxidant capacity. This study found that the bioactive compounds in rice straw varied among rice varieties and growing locations. Straw phenol acts as a major antioxidant that can be used as a characteristic for the selection of rice varieties with high antioxidant capacity for use at the industrial scale for the processing of food, pharmaceuticals, and medicinal products.

Zinc (Zn) is an essential element involved in human metabolism, which can be supplied by an appropriate diet. Enhancing Zn enrichment in rice grains through agronomic biofortification is advocated as an immediate and effective approach to combat micronutrient malnutrition in hu-man. It has been well-documented that high grain Zn accumulation in rice can be achieved by Zn fertilizers management. This study evaluated the effects of foliar nitrogen (N) and Zn applied at the flowering and milky stages of brown rice plants with and without soil Zn application. A glasshouse pot experiment was conducted using a completely randomized design with four replicates. Soil Zn in the form of ZnSO4 was applied at 0 and 50 kg ha−1. Foliar fertilizer of 1% urea along with 0.5% ZnSO4 was applied and assigned as (1) nil foliar N and Zn (N0Zn0), (2) foliar N with nil Zn (N+Zn0), (3) nil foliar N with foliar Zn (N0Zn+), and (4) foliar N and Zn (N+Zn+) at flowering and milky stages. Foliar application of N and Zn increased grain yield and yield components in both soil Zn conditions. Grain Zn concentration in brown rice was the highest when foliar N and Zn were applied under nil soil Zn conditions; however, grain N concentration decreased by 13.1–28.5% with foliar application at flowering and 18.8–28.5% with application at the milky stage. The grain Zn content was increased by foliar application of N0Zn+ and N+Zn+ at flowering and milky stages. Applying foliar N and Zn at flowering or milky stages tended to increase the grain N content when Zn was applied to the soil, while nil soil Zn decreased the N content by 26.8% at flowering and milky stages under N0Zn+. The results suggest that the milky stage is the most suitable for foliar application of Zn for increasing (i) grain yield and (ii) N and Zn concentrations in brown rice without having a dilution effect.

This study examined the effect of B fertilizers applied by soil and foliar routes on the yield and total B uptake under glasshouse and field conditions. A high-yield rice variety, Sanpatong 1, was used in the experiments. In a pot experiment, soil B application produced a grain yield of 23.4 g pot−1, similar to the control treatment, but foliar B decreased grain yield by 14.9%. The total uptake of B was the highest at 2.5 mg pot−1 when soil B was applied, 66.7% higher than the in the control and foliar B application treatments, but there was no significant effect on the numbers of filled or unfilled grains. Similar responses of grain yield and total B uptake were observed in both conditions. Soil B application produced a grain yield of 4.7 t ha−1, similar to the control, but foliar B application decreased grain yield by 10.9%. The total uptake of B in the field was the highest at 4.7 mg m−2 when soil B was applied, being 42.4% higher than in the foliar B application and control treatments. This study indicates that the total uptake of B in rice plants can be successfully improved by applying soil B fertilizer, even though no effect was observed on productivity. The efficacy of B uptake in rice plants by soil B application is an interesting subject that should be further studied in greater detail to determine its utility in yield production, e.g., by splitting application times.