Application of Silicon Influencing Grain Yield and Some Grain Quality Features in Thai Fragrant Rice

Silicon (Si) is a beneficial nutrient that has been shown to increase rice productivity and grain quality. Fragrant rice occupies the high end of the rice market with prices at twice to more than three times those of non-fragrant rice. Thus, this study evaluated the effects of increasing Si on the yield and quality of fragrant rice. Also measured were the content of proline and the expression of the genes associated with 2AP synthesis and Si transport. The fragrant rice varieties were found to differ markedly in the effect of Si on their quality, as measured by the grain 2AP concentration, while there were only slight differences in their yield response to Si. The varieties with low 2AP when the Si supply is limited are represented by either PTT1 or BNM4 with only slight increases in 2AP when Si was increased. Si affects the gene expression levels of the genes associated with 2AP synthesis, and the accumulation of 2AP in fragrant rice mainly occurred through the upregulation of Badh2, DAO, OAT, ProDH, and P5CS genes. The findings suggest that Si is a potential micronutrient that can be utilized for improving 2AP and grain yield in further aromatic rice breeding programs.

Multiple regulators were involved in glutelin synthesis and subunit accumulation in response to temperature and nitrogen during rice grain-filling stage

Rice glutelin is sensitive to temperature and nitrogen, however, the regulatory mechanism of glutelin response to temperature and nitrogen is unclear. In this study, we conducted the open field warming experiment by the Free-air temperature enhancement facility and application of nitrogen during grain filling. In three-year field warming experiments, glutelin relative content was significantly increased under elevated temperature and application of nitrogen. Temperature and nitrogen and their interaction increased the glutelin accumulation rate in the early and middle grain filling stages (10-25d after flowering), but decreased the glutelin accumulation rate in the middle and late grain filling stages (25-45d after flowering). Elevated temperature promoted pro-glutelin levels whereas application of nitrogen under warming increased the amount of α-glutelin. At the transcriptional level, the expression levels of the glutelin-encoding genes and protein disulphide isomerase-like enzyme (PDIL1-1), glutelin precursor accumulation 4 (GPA4), glutelin precursor mutant 6 (GPA2), glutelin precursor accumulation 3 (GPA3) and vacuolar processing enzyme (OsVPE1) of glutelin folding, transport and accumulation-related genes were up-regulated by nitrogen under natural temperature as early as 5d after flowering. However, elevated temperature up-regulated glutelin-encoding genes before 20d after flowering, and the expression of endoplasmic reticulum chaperone (OsBip1), OsPDIL1-1, small GTPase gene (GPA1), GPA2-GPA4 and OsVPE1 were significantly increased post 20d after flowering under warming. In addition, the increase in glutelin content worsened grain quality, particularly chalkiness and eating quality. Overall, the results were helpful to understand glutelin accumulation and provide a theoretical basis for further study the relationship between rice quality and glutelin under global warming.

Rice seed storage proteins: Biosynthetic pathways and the effects of environmental factors

Rice (Oryza sativa L.) is the most important food crop for at least half of the world's population. Due to improved living standards, the cultivation of high-quality rice for different purposes and markets has become a major goal. Rice quality is determined by the presence of many nutritional components, including seed storage proteins (SSPs), which are the second most abundant nutrient components of rice grains after starch. Rice SSP biosynthesis requires the participation of multiple organelles and is influenced by the external environment, making it challenging to understand the molecular details of SSP biosynthesis and improve rice protein quality. In this review, we highlight the current knowledge of rice SSP biosynthesis, including a detailed description of the key molecules involved in rice SSP biosynthetic processes and the major environmental factors affecting SSP biosynthesis. The effects of these factors on SSP accumulation and their contribution to rice quality are also discussed based on recent findings. This recent knowledge suggests not only new research directions for exploring rice SSP biosynthesis but also innovative strategies for breeding high-quality rice varieties.

Comprehensive Evaluation of 17 Qualities of 84 Types of Rice Based on Principal Component Analysis

Rice quality is a complex indicator, and people are paying more and more attention to the quality of rice. Therefore, we used seven rice varieties for twelve nitrogen fertilizer treatments and obtained eighty-four rice types with seventeen qualities. It was found that 17 quality traits had different coefficients of variation. Among them, the coefficient of variation of chalkiness and protein content was the largest, 44.60% and 17.89% respectively. The cluster analysis method was used to define four categories of different rice qualities. The principal component analysis method was used to comprehensively evaluate 17 qualities of 84 rice. It was found that rice quality was better under low nitrogen conditions, Huanghuazhan and Lvyinzhan were easier to obtain better comprehensive rice quality during cultivation. Future rice research should focus on reducing protein content and increasing peak viscosity.

Yield, Grain Quality, and Starch Physicochemical Properties of 2 Elite Thai Rice Cultivars Grown under Varying Production Systems and Soil Characteristics

Rice production systems and soil characteristics play a crucial role in determining its yield and grain quality. Two elite Thai rice cultivars, namely, KDML105 and RD6, were cultivated in two production systems with distinct soil characteristics, including net-house pot production and open-field production. Under open-field system, KDML105 and RD6 had greater panicle number, total grain weight, 100-grain weight, grain size, and dimension than those grown in the net-house. The amounts of reducing sugar and long amylopectin branch chains (DP 25–36) of the RD6 grains along with the amounts of long branch chains (DP 25–36 and DP ≥ 37), C-type starch granules, and average chain length of the KDML105 were substantially enhanced by the open-field cultivation. Contrastingly, the relative crystallinity of RD6 starch and the amounts of short branch chains (DP 6–12 and DP 13–24), B- and A-type granules, and median granule size of KDML105 starch were significantly suppressed. Consequently, the open-field-grown RD6 starch displayed significant changes in its gelatinization and retrogradation properties, whereas, certain retrogradation parameters and peak viscosity (PV) of KDML105 starches were differentially affected by the distinct cultivating conditions. This study demonstrated the influences of production systems and soil characteristics on the physicochemical properties of rice starches.

Plant DNA methylation is sensitive to parent seed N content and influences the growth of rice

BACKGROUND

Nitrogen (N) is an important nutrient for plant growth, development, and agricultural production. Nitrogen stress could induce epigenetic changes in plants. In our research, overexpression of the OsNAR2.1 line was used as a testing target in rice plants with high nitrogen-use efficiency to study the changes of rice methylation and growth in respond of the endogenous and external nitrogen stress.

RESULTS

Our results showed that external N deficiency could decrease seed N content and plant growth of the overexpression line. During the filial growth, we found that the low parent seed nitrogen (LPSN) in the overexpression line could lead to a decrease in the filial seed nitrogen content, total plant nitrogen content, yield, and OsNAR2.1 expression (28, 35, 23, and 55%, respectively) compared with high parent seed nitrogen (HPSN) in high nitrogen external supply. However, such decreases were not observed in wild type. Furthermore, methylation sequencing results showed that LPSN caused massive gene methylation changes, which enriched in over 20 GO pathways in the filial overexpression line, and the expression of OsNAR2.1 in LPSN filial overexpression plants was significantly reduced compared to HPSN filial plants in high external N, which was not shown in wild type.

CONCLUSIONS

We suggest that the parent seed nitrogen content decreased induced DNA methylation changes at the epigenetic level and significantly decreased the expression of OsNAR2.1, resulting in a heritable phenotype of N deficiency over two generations of the overexpression line.

Green Labelled Rice Shows a Higher Nutritional and Physiochemical Quality Than Conventional Rice in China

In China, green food refers to a wide array of certified agricultural and processed edible commodities that are produced strictly following defined standard protocols and labelled with a specified “Green Food” logo. The demand for green labelled rice is rapidly growing due to its higher quality and adherence to safety standards compared to conventional rice. Therefore, the physicochemical and nutritional quality of green rice needs to be further investigated for consumers’ benefits. Using Daohuaxiang 2, one of the most famous types of green rice, we found that green rice was significantly superior to conventional rice in terms of thousand kernel weight, chalkiness, amylose content, and rheological properties. Green rice contained lower levels of heavy metals than conventional rice due to a dramatic reduction in chemical inputs during its cultivation. The concentrations of Cr, As, Cd, Pb in green rice decreased, respectively, from 98.7 to 180.1 μg/kg, 49.8 to 62.3 μg/kg, 7.8 to 9.1 μg/kg, and 29.0 to 42.8 μg/kg on average. Gas chromatography coupled with mass spectrometry (GC–MS)-based metabolomics, in combination with multivariate analysis, revealed that 15 metabolites differentially accumulated when comparing green and conventional rice. Among these, 12 metabolites showed a high accumulation in green rice, including seven amino acids, two sugars, and three fatty acids. Overall, our results suggest the superior quality of a type of green rice that is popular in China, which may boost green rice consumption and facilitate the further expansion of green rice production in China.

Impact of physicochemical properties on duration and head rice yield during abrasive and friction milling of rice

The physicochemical properties of four rice varieties representing high amylose (Jyothi and IR64), intermediate amylose (Taraori Basmati) and waxy (Agonibora) were evaluated to understand their influence on milling. Based on the grain dimensions, Jyothi and Agonibora were classified as long and medium, IR64 as long and slender, and Basmati as extra-long and slender. The head rice yield (HRY) was higher with abrasive milling (61-75%) compared to friction milling (10-60%) although it required longer milling duration. Lower grain thickness, hardness and, amylose and higher bran fat content reduced the friction milling duration while these properties prolonged the duration in abrasive milling. Agonibora variety with low amylose content and high-fat content exhibited the highest HRY in both the types of milling. The study revealed that the selection of milling process should be made with due importance to grain geometry as well as its chemical properties.

Effects of Cultivar, Nitrogen Rate, and Planting Density on Rice-Grain Quality

To achieve superior rice-grain quality, more emphasis has been placed on the genetic diversity of breeding programs, although this improvement could be seriously restricted in the absence of comparable agricultural management practices. Nitrogen (N) application and planting density are two important agronomic practices influencing rice growth, yield, and grain quality. This study investigated the four main aspects of rice-grain quality, namely, milling (brown-rice, milled-rice, and head-rice percentage), appearance (length/width ratio, chalky-kernel percentage, and chalkiness), nutrition (protein content), and cooking and eating quality (apparent amylose content, gel consistency, and pasting viscosities) of two rice cultivars (Shendao 47 and Jingyou 586) under four N rates (0, 140, 180, and 220 kg ha−1), and three planting densities (25 × 104, 16.7 × 104, and 12.5 × 104 hills ha−1) in a field trial from 2015 to 2016. The four main aspects of rice-grain quality were significantly influenced by cultivar. Several aspects were affected by the interactions of N rate and cultivar. No significant interaction between N rate and plating density was detected for all grain-quality parameters. A higher N rate increased the percentages of brown rice and head rice, chalky-kernel percentage, and setback and peak time values, but reduced the length/width ratio, chalkiness, apparent amylose content, gel consistency, and peak-, trough-, and final-viscosity values. These results indicate that the N rate has a beneficial effect on milling and nutritional quality, but a detrimental effect on appearance and cooking and eating quality. Jingyou 586 and Shendao 47 had different responses to planting density in terms of grain quality. Our study indicates that low planting density for Jingyou 586, but a medium one for Shendao 47, is favorable for grain quality.

Rice single cropping or ratooning agro-system: which one is more environment-friendly?

Sustainable development of food production depends on damping the environmental impacts of agricultural production. The aim of this study was to investigate the environmental performance of rice production in single crop and ratooning (main rice + ratoon crop) agro-systems through life cycle assessment (LCA) methodology in Guilan province, Northern Iran, in 2015. The flooding irrigation regime was the dominant irrigation method for single cropping system and main crop rising in ratooning agro-system. The data were gathered through a face to face interview with 215 single crop and 115 ratoon breeder paddy farmers. The environmental risks were determined in six impact categories including global warming, terrestrial eutrophication, acidification, and depletion of fossil fuels, phosphate, and potash resources. The functional unit (FU) was set as 100 kg protein. Results indicated that the CO₂, N₂O, and CH₄ emissions of the rice ratooning agro-system (661.44, 1.96, and 5.42 kg 100 kg^-1 protein) were less than the corresponding values in the rice single cropping agro-system (1341.63, 2.88, and 9.20 kg 100 kg^-1 protein, respectively). Among all the environmental impact categories, the terrestrial eutrophication had the widest negative environmental effect followed by depletion of phosphate resources in single cropping agro-system with weighted indices of 0.51 and 0.41, respectively. Moreover, the terrestrial eutrophication had the largest negative environmental effect followed by acidification in rice ratooning agro-system with weighted indices of 0.48 and 0.29, respectively. Overall, the results highlighted that the rice ratooning ago-system is more environmentally beneficial than the single cropping system, particularly in terms of depletion of fossil fuels, global warming, and depletion of phosphate and potash resources categories. This priority may be improved through adopting proper management of agronomic practices for main and ratoon rice in ratooning agro-system. Graphical abstract ᅟ.

Applying nitrogen fertilizer increased anthocyanin in vegetative shoots but not in grain of purple rice genotypes

BACKGROUND

Anthocyanin is a major antioxidant compound in purple rice, with properties that can protect against oxidative damage in some human diseases. This study was undertaken to determine if nitrogen (N) fertilizer can enhance anthocyanin and antioxidant levels in four purple Thai rice genotypes.

RESULTS

The anthocyanin concentration and antioxidant capacity were increased in the shoots of N120 plants compared with plants without N. The leaves had higher anthocyanin concentration and antioxidant capacity than the stem+leaf sheath. Maximum shoot anthocyanin concentrations occurred at tillering and then declined by 87-94% at maturity. Antioxidant capacity was high at tillering and panicle initiation and declined by 26% in leaves and by 98% in the stem+leaf sheath at maturity. Unlike in the vegetative shoot, grain anthocyanin was not affected by the addition of N fertilizer. The response of grain antioxidant capacity to N fertilizer was affected by genotype, increasing in KPY by 45% but decreasing in K19959 by 30% in N120 plants.

CONCLUSION

Applying N fertilizer could be a promising way to improve the antioxidative properties in vegetative parts for use in rice-grass juice, cosmetics and other products, especially the young leaves, which contained high values of anthocyanin as well as antioxidant capacity. However, further field studies should be undertaken to optimize N utilization for anthocyanin and antioxidant capacity in purple rice genotypes. © 2018 Society of Chemical Industry.

Identification of quantitative trait loci for rice grain quality and yield-related traits in two closely related Oryza sativa L. subsp. japonica cultivars grown near the northernmost limit for rice paddy cultivation

Quantitative trait loci (QTLs) associated with eating quality, grain appearance quality and yield-related traits were mapped in recombinant inbred lines (RILs) derived from closely related rice (Oryza sativa L. subsp. japonica) cultivars, Yukihikari (good eating quality) and Joiku462 (superior eating quality and high grain appearance quality). Apparent amylose content (AAC), protein content (PC), brown grain length (BGL), brown grain width (BGWI), brown grain thickness (BGT), brown grain weight per plant (BGW) and nine yield-related traits were evaluated in 133 RILs grown in four different environments in Hokkaido, near the northernmost limit for rice paddy cultivation. Using 178 molecular markers, a total of 72 QTLs were detected, including three for AAC, eight for PC, two for BGL, four for BGWI, seven for BGT, and six for BGW, on chromosomes 1, 2, 3, 4, 6, 7, 8, 9, 11 and 12. Fifteen intervals were found to harbor multiple QTLs affecting these different traits, with most of these QTL clusters located on chromosomes 4, 6, 8, 9 and 12. These QTL findings should facilitate gene isolation and breeding application for improvement of eating quality, grain appearance quality and yield of rice cultivars.

Impact of volunteer rice infestation on yield and grain quality of rice

BACKGROUND

Volunteer rice (Oryza sativa L.) grains may differ in physicochemical traits from cultivated rice, which may reduce the quality of harvested rice grain. To evaluate the effect of volunteer rice on cultivated rice, fields were surveyed in Arkansas in 2012.

RESULTS

Cropping history that included hybrid cultivars in the previous two years (2010 and 2011) had higher volunteer rice infestation (20%) compared with fields planted previously with inbred rice (5.5%). The total grain yield of rice was reduced by 0.4% for every 1% increase in volunteer rice density. The grain quality did not change in fields planted with the same cultivar for three years. Volunteer rice density of at least 7.6% negatively impacted the head rice and when infestation reached 17.7%, it also reduced the rice grain yield. The protein and amylose contents of rice were not affected until volunteer rice infestation exceeded 30%.

CONCLUSION

Crop rotation systems that include hybrid rice are expected to have higher volunteer rice infestation than systems without hybrid rice. It is predicted that, at 8% infestation, volunteer rice will start to impact head rice yield and will reduce total yield at 18% infestation. It could alter the chemical quality of rice grain at >30% infestation. © 2016 Society of Chemical Industry.

Effect of different doses of nitrogen on protein profiling, pasting and quality attributes of rice from different cultivars

Effect of different level (60, 120 and 180 kg N/ha) of nitrogen (N) application on protein profiling, pasting and cooking quality characteristics of milled rice from different paddy cultivars was evaluated. N dose showed positive correlation with protein content and negative correlation with L*, whiteness and amylose content. N application significantly affected the protein profile, textural and pasting properties of different cultivars. All the cultivars expect PR120 and PAU201, showed an increase in the amount of accumulation of 60 kDa polypeptide with increase in N application. Accumulation of prolamines (16 and 14 kDa) and polypeptides of 38 and 35 kDa increased in all the cultivars. Size exclusion chromatography revealed decrease in low molecular weight subunits and increase in medium molecular weight subunits in all the cultivars upon N application. However, high molecular weight subunits increased in IET21214 and decreased in PR120 and PAU20 upon N application. N application resulted in increase in glutelins and decrease in peak and breakdown viscosity. PAU201 and PR120 showed lower AAC due to low accumulation of 60 kDa granule-bound starch synthase (GBSS), in response to N application. Gumminess and hardness of cooked rice increased with the increase in N dose and the increase was significant at 60 kg N/ha.

The Usefulness of Known Genes/Qtls for Grain Quality Traits in an Indica Population of Diverse Breeding Lines Tested using Association Analysis

BACKGROUND

A number of studies reported major genes/QTLs for rice grain shapes, chalkiness and starch physicochemical properties. For these finely mapped QTLs or cloned genes to make an impact in practical breeding, it is necessary to test their effects in different genetic backgrounds. In this study, two hundred nineteen markers for 20 starch synthesis genes, 41 fine mapped grain shape and related traits QTLs/genes, and 54 chalkiness QTLs/genes plus 15 additional markers and a large indica population of 375 advanced lines were used to identify marker-trait associations under 6 environments that can be used directly in breeding for grain quality traits.

RESULTS

The significant associations detected by the QK model were used to declare the usefulness of the targeted genes/QTLs. A total of 65 markers were detected associations with grain quality trait at least in one environment. More phenotypic variations could be explained by haplotype than single marker, as exemplified by the starch biosynthesising genes. GBSSI was the major gene for AC and explained up to 55 % of the phenotypic variation, which also affected GC and accounted up to 11.31 % of the phenotypic variation. SSIIa was the major gene for chalkiness and explained up to 17 and 21 % of variation of DEC and PGWC, respectively. In addition, RMw513 and RM18068 were associated with DEC in 6 environments as well. Four markers (RGS1, RM15206, RMw513 and Indel1) tightly linked to GS3, gw5, and qGL7-2 were the most important ones for grain shapes. Allelic combinations between SSIIa and RMw513 revealed more variations in DEC.

CONCLUSIONS

The validated markers for genes/QTLs with major effects could be directly used in breeding for grain quality via marker-assisted selection. Creating desirable allelic combinations by gene pyramiding might be an effective approach for the development of high quality breeding lines in rice.

Effect of fertiliser on functional properties of flour from four rice varieties grown in Sri Lanka

BACKGROUND

Fertiliser is an essential agro-chemical input in modern rice farming. Fertiliser affects the grain quality and yield of rice. Although much research has been carried out to investigate the influence of fertiliser (recommended NPK addition) on yield and quality of rice grain, little is known about the effect of fertiliser on thermal, pasting, gelling and retrogradation properties of rice flour. The aim of this study was to investigate the influence of recommended fertilisation on functional properties of rice flour from four popular high yielding rice varieties grown in Sri Lanka.

RESULTS

Fertiliser (recommended NPK addition) increased the protein content but reduced the apparent amylose content in rice flour except in BG 357. Swelling power and amylose leaching were decreased by fertilizer. [corrected] Pasting onset temperature, cold paste viscosity and setback were increased but peak viscosity and granular breakdown decreased. In response to the fertiliser application, gelatinisation peak temperature was reduced in all varieties except BG 300. However, compared to pasting properties, gelatinisation parameters were not much affected by fertilisation. The extent of amylopectin retrogradation was decreased by fertiliser in BG 305 and BG 352 but unchanged in the other two varieties. Except in BG 305, fertiliser reduced the gel hardness of rice flour but increased the gel cohesiveness.

CONCLUSION

It is apparent that the increased protein and reduced amylose content caused by fertiliser affect the functional properties of rice flour.