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There is a need to comprehensively evaluate the rice quality of different rice varieties under different nitrogen treatments. Therefore, in this study, we used twenty-one hybrid indica rice varieties and twenty-three inbred japonica rice varieties with three nitrogen fertilizer levels to investigate differences in rice qualities. As compared with hybrid indica rice, inbred japonica rice had lower coefficient of variation values for grain shape, mild rice percentage, and head rice percentage, but relatively higher coefficient of variation values for chalkiness traits, appearance, and taste value of cooked rice. A principal component analysis and membership function method were used to comprehensively evaluate the qualities of rice. The overall eating quality value by sensory evaluation and head rice percentage explained 61.3% and 67.9% of the variations in comprehensive quality of hybrid indica rice and inbred japonica rice across different nitrogen levels, respectively. We also found that rice comprehensive quality was better under low nitrogen levels for hybrid indica rice, while for inbred japonica rice, properly increasing nitrogen application could improve the comprehensive quality. [ABSTRACT FROM AUTHOR]

Abstract Due to the sensitivity of chalk formation to high temperatures, the global warming will further threaten the improvement of high chalky grain rate in the southern japonica region of China. There have been many studies reported on the role of starch in the formation of chalkiness, but the relationship between nitrogen metabolites and chalkiness has not been given sufficient attention. In this study, we conducted the open field warming experiment and investigated the effects of temperature increase on grain protein metabolism. Results showed under the warming range of predicted global temperature increase (1.9 °C–4.0 °C), field warming apparently accelerated the development of grain endosperm, and the number of protein bodies were increased in both rice varieties, Furthermore, we clarified that the increased temperature regulated the key regulatory factors in protein synthesis and metabolism pathway, and the synthesis, transport, folding, assembly process of grain protein were further affected, and that further lead the component changes of grain storage protein. In conclusion, chalky traits are closely related to the grain storage materials and in this study, increased temperature induced the changes in the accumulation balance of storage proteins, amino acids and starches, which coordinately controls the formation of grain chalkiness. Highlights • We simulated climate warming with the field-warming system in actual rice field. • Endosperm and protein bodies were apparently increased under elevated temperatures. • Elevated temperature regulated regulatory factors in protein anabolism pathway. • Elevated temperatures affect balance of storage material and induce the chalkiness. • Proteins may play a certain role in chalkiness formation under elevated temperature. [ABSTRACT FROM AUTHOR]

To evaluate the actual and comprehensive response of rice grain quality to global warming in lower reaches of Yangtze River delta, a 3-year open-field warming experiment was conducted with two japonica rice cultivars using Free-air temperature enhancement (FATE) facility. Ningjing3 and Wuyunjing24 were planted under two temperature regimes (NT: natural temperature; ET: elevated temperature) during grain-filling. FATE facility increased rice canopy temperature by 2.7 °C (daytime 1.5 °C/nighttime 3.9 °C), 2.0 °C (daytime 1.6 °C/nighttime 2.5 °C) and 3.4 °C (daytime 2.0 °C/nighttime 4.9 °C) in 2012, 2013 and 2014, respectively. Compared with NT, head rice rate, occurrence of perfect grains, amylose content, setback and consistency were decreased by ET, while occurrence of chalky grains, breakdown, cool paste viscosity, pasting temperature were increased under ET. Response of different chalky types to warming were unstable among cultivars and years. Based on Wu-Gilbert model, we found that the relative activity of starch branching enzyme (SBE) to starch synthase (SS) was decreased by ET, which may contribute to longer average amylopectin chain length. ET increased protein content of rice grain but performed no influence on the relative proportion of amino acids. These results revealed that low-amplitude warming during grain-filling could deteriorate rice milling, appearance and cooking quality, but improved its nutritional quality. [ABSTRACT FROM AUTHOR]

This study investigated the chain length distribution (CLD) of two japonica rice cultivars under six nitrogen (N) treatments by high performance size exclusion chromatography, with the aims to elucidate the effect of N on rice quality and its biological mechanism. Results showed significant influence of N on CLD. In comparison with low N rate, high N lowered the percentage of short amylopectin branches. Fitting with the CLD model of Wu-Gilbert, it suggested that relative activity of SBE to SS was lower at high N rate, thus producing fewer short amylopectin branches. Comparison of CLD between N rates and between cultivars revealed that decrease in short amylopectin branches or the relative ratio of short to long amylopcetin branches correlated with increase in flour gelatinization temperatures (T o , T p , and T c ) and decrease in pasting values (except PaT) and amylose-lipid gelatinization temperatures. In addition, quality traits of Wuyujing3, a cultivar with premium eating quality, expressed stably across N treatments compared with the high-yielding cultivar Wuyunjing7. [ABSTRACT FROM AUTHOR]

Abstract: A field experiment involving six japonica rice cultivars with contrasting agronomic traits and seven nitrogen (N) fertilizer treatments was performed to determine the effects of N and genotype on distribution of four kinds of grain proteins and amino acids in milled and brown rice. For brown and milled rice, albumin and globulin were controlled more by genotype than N treatments, whereas prolamin and glutelin were largely determined by N. Substantial genotypic differences in response of milled/brown (M/B) ratios of proteins to N treatments were detected. In comparison with large panicle cultivars, small panicle cultivars such as Wuyujing3 had the lower ratio and exhibited more stability under contrasting N treatments. N had significant influence on amino acid composition of brown and milled rice, with contents of the 17 amino acids measured increasing with elevated N rate. However, cysteine and methionine in brown rice and lysine and methionine in milled rice were not significantly affected by N. In addition, N had little effect on ratios of M/B for most of the amino acids. [Copyright &y& Elsevier]

Abstract: Thirty-one japonica cultivars with contrasting agronomic traits were used and 5 nitrogen (N) fertilizer treatments of level and timing were performed to determine the effects of N application on grain phytic acid and proteins including albumin, globulin, prolamin, and glutelin. Variance analysis showed a large effect of N and a smaller effect of cultivar on grain phytic acid and proteins. With increased N level, grain phytic acid concentrations progressively reduced whereas concentrations of the 4 proteins and ratios of glutelin to total protein increased, indicating that N level has a beneficial effect on rice nutritional quality. In addition, substantial genotypic differences in response of grain phytic acid and proteins to N treatments were detected. Some cultivars such as Xiushui09, Zhendao10, and Yanjing5 exhibited more stability of grain proteins under contrasting N treatments, and the significance of this stability is discussed in regard to its use in rice quality improvement. [Copyright &y& Elsevier]