Changes in mineral elements and starch quality of grains during the improvement of japonica rice cultivars

Analysis of Erect-Panicle Japonica Rice in Northern China: Yield, Quality Status, and Quality Improvement Directions

China is the only country that extensively cultivates the indica and japonica rice varieties, with the largest japonica rice production area being in northeast China. A study of the relationship between the yield and quality of japonica rice and the effect of nitrogen fertilizer application on this relationship is important. In this paper, we aimed to assess the current yield and quality of japonica rice in northeast China. We selected erect-panicle varieties as the test materials. Field experiments were conducted using different nitrogen fertilizer levels for two consecutive years to analyze the rice varieties' yield, quality, interrelationship, and nitrogen fertilizer response. The average yield following high- and low-nitrogen treatments exceeded 10,000.00 kg/hm2, with a maximum of 12,285.63 kg/hm2. The high-yield-high-nitrogen treatment group had more panicles, a higher seed-setting rate, and a higher 1000-grain weight than the other groups. The high-yield-low-nitrogen group had a higher number of panicles and seed-setting rate than the other groups. The low-yield-high-nitrogen group had a lower number of whole grains, grain length-to-width ratio, and taste value than the other groups. The low-yield-low-nitrogen group had fewer primary branches than the other groups; excluding the primary branch-setting rate and 1000-grain weight, the values of the other panicle traits of the group were significantly higher than those of the other groups. The high-nitrogen-high-flavor group had lower panicle and spikelet numbers and higher spikelet fertility rates than the other groups. The low-nitrogen-high-flavor group had higher spikelet fertility rates and 1000-grain weight than the other groups. Compared to the other groups, the low-nitrogen-high-flavor group had a higher head rice yield, and the high-nitrogen-high-flavor group had a lower chalkiness rate. The main goal of the breeding and cultivation of high-yield and high-quality erect-panicle japonica rice in northern China is to achieve "dual high, dual low, and one high and one low" conditions, signifying a high yield with high or low nitrogen levels, low protein and amylose contents, high head rice rates, and low chalkiness. This study provides a new technique for enhancing the taste of northern erect-panicle japonica rice to promote the sustainable, high-yield, and high-quality development of japonica rice in northern China.

Silicon nutrition improves the quality and yield of rice under dry cultivation

BACKGROUND

Dry cultivation of rice is a water-saving, emission reduction and labor-saving rice farming method. However, the development of rice under dry cultivation is hampered by the limitations of dry cultivation on rice yield and rice quality. We hypothesized that additional silicon (Si) would be a measure to address these limitations or challenges.

RESULTS

In the present study, we set up field trials with three treatments: flooded cultivation (W), dry cultivation (D) and dry cultivation plus Si. Yield and quality were reduced under D treatment compared to W treatment. The addition of Si promoted root development, increased plant height and leaf area, increased photosynthetic enzyme activity, net photosynthetic rate and SPAD values, and increased biomass under dry crop conditions. Under the drought conditions, silica up-regulated the expression of AGPSI, SBEI, SBEIIb, SSI and SSII-1 genes and the activities of ADP-glucose pyrophosphorylase (AGPase), soluble starch synthetase (SSS) and starch branching enzyme (SBE) enzymes, which reduced protein, amylose, chalkiness percentage and chalkiness degree, increased brown rice rate, milled rice rate and head milled rice rate, and also improved rice quality. In addition, the increase of AGPase, SSS and SBE enzyme activities promoted the filling rate and the number of spikes was guaranteed, whereas the yield was improved by promoting the seed setting rate and 1000-grain weight.

CONCLUSION

The results of the present study indicate that adding appropriate amounts of Si fertilizer can improve the yield and quality of rice under dry cultivation by regulating source supply capacity and grain starch synthesis. © 2023 Society of Chemical Industry.

Differences in rice component distribution across layers and their relationship with taste

BACKGROUND

Rice taste is closely associated with endosperm composition, which varies among different rice layers. Although clarifying the relationship between this difference and nutritional taste can guide rice breeding and cultivation practices, research on this topic is limited.

RESULTS

Here, typical rice varieties having excellent and poor taste characteristics were selected to analyze the distribution characteristics and differences of their components. The varieties with excellent taste exhibited lower apparent amylose content (AAC) and protein content (PC), lesser short-chain (Fa) and long-chain (Fb3 ) amylopectin (AP) and more medium-chain (Fb1+2 ) AP, higher long-to-short chain ratio (Fa:Fb3 ), and higher nitrogen (N), magnesium (Mg) and calcium (Ca) content in layer 1 (L1) than the varieties with poor taste. Layer 2 (L2) played a key role in AAC and PC regulation in the varieties with excellent taste by reducing AAC and appropriately increasing PC, consequently improving rice taste. AP structure in layer 3 (L3) substantially affected the taste of the two types of varieties. The mineral content was the highest in L1, and increased potassium (K), Ca, and Mg content improved taste in all varieties.

CONCLUSION

AAC in each layer contributes to rice taste. PC and minerals primarily act on L1 and L2, whereas AP acts on L2 and L3. Therefore, the endosperm formation process should be exploited for improving rice taste. Furthermore, key resources and cultivation should be identified and regulated, respectively, to improve rice taste. © 2023 Society of Chemical Industry.

Effects of different phosphorus fertilizers on cadmium absorption and accumulation in rice under low-phosphorus and rich-cadmium soil

Rice is the main food crops with the higher capacity for cadmium (Cd) uptake, necessitating the urgent need for remediation measures to address Cd in paddy soil. Reasonable agronomic methods are convenient and favorable for fixing the issue. In this study, a pot experiment was employed to evaluate the effects of two foliar (NaH2PO4, SDP; KH2PO4, PDP) and two solid phosphate fertilizers (double-superphosphate, DSP; calcium-magnesium phosphate, CMP) on uptake and remobilization of Cd in rice plants under the low-P and rich-Cd soil. The results revealed that these four phosphorus fertilizer significantly down-regulated the relative expression of OsNRAMP5 involved in Cd absorption, while up-regulated OsPCS1 expression and increased distribution of Cd into the cell wall in roots. Furthermore, phosphorus fertilizer resulted in a significant decrease in the relative expression of OsLCT1 in stems and OsLCD in leaves, decreased the transfer factor of Cd from shoots to grains, and ulterior reduced the Cd accumulation in three protein components of globulin, albumin, and glutelin, making the average Cd concentration of brown rice decreased by 82.96%. These results comprehensively indicate that in situations with similar soil backgrounds, the recommended application of solid CMP and foliar PDP can alleviate the toxicity of Cd by reducing its absorption and remobilization.

Combined amendment improves soil health and Brown rice quality in paddy soils moderately and highly Co-contaminated with Cd and As

In situ remediation technology applied aims to not only decrease cadmium (Cd) and arsenic (As) uptake by rice but also improve soil health and rice quality in contaminated paddy soils. Here the effects of a combined amendment, consisting of limestone, iron powder, silicon fertilizer, and calcium-magnesium-phosphate fertilizer, with three application rates (0, 450, and 900 g m^-2) on soil health, rice root system, and brown rice quality were compared in moderately versus highly Cd and As co-contaminated paddy fields. After the amendment application, soil pH, cation exchange capacity, four kinds of soil enzyme activities increased (sucrase, urease, acid phosphatase, and catalase), and concentrations of leached Cd/As decreased, as measured by the DTPA (diethylene triamine pentaacetic acid) and TCLP (toxicity characteristic leaching procedure). Changes in the above soil indicators promoted soil health. In both fields, the dithionite-citrate-bicarbonate (DCB)-Fe and DCB-Mn concentration in iron plaque increased and root length became longer. Changes in the above root system indicators reduced the root system's absorption of Cd and As but increased that of nutrients. Under 900 g m^-2 treatment, the Cd concentration in brown rice of two sites decreased by 55.8% and 28.9%, likewise inorganic As (iAs) decreased by 50.0% and 21.1%, whereas essential amino acids increased by 20.4% and 20.0%, respectively. Furthermore, the Cd and iAs concentrations in brown rice were <0.2 mg kg^-1 (maximum contaminant level of Cd and iAs in the Chinese National Food Safety Standards GB2762-2017 for brown rice) under the 900 g m^-2 in the moderately contaminated field. These results suggest the combined amendment can improve soil health and brown rice quality in the moderately and highly Cd- and As-co-contaminated paddy soils, offering potential eco-friendly and efficient remediation material for applications in such polluted paddy soils.

Mutation in OsFWL7 Affects Cadmium and Micronutrient Metal Accumulation in Rice

Micronutrient metals, such as Mn, Cu, Fe, and Zn, are essential heavy metals for plant growth and development, while Cd is a nonessential heavy metal that is highly toxic to both plants and humans. Our understanding of the molecular mechanisms underlying Cd and micronutrient metal accumulation in plants remains incomplete. Here, we show that OsFWL7, an FW2.2-like (FWL) family gene in Oryza sativa, is preferentially expressed in the root and encodes a protein localized to the cell membrane. The osfwl7 mutation reduces both the uptake and the root-to-shoot translocation of Cd in rice plants. Additionally, the accumulation of micronutrient metals, including Mn, Cu, and Fe, was lower in osfwl7 mutants than in the wildtype plants under normal growth conditions. Moreover, the osfwl7 mutation affects the expression of several heavy metal transporter genes. Protein interaction analyses reveal that rice FWL proteins interact with themselves and one another, and with several membrane microdomain marker proteins. Our results suggest that OsFWL7 is involved in Cd and micronutrient metal accumulation in rice. Additionally, rice FWL proteins may form oligomers and some of them may be located in membrane microdomains.

Utilization of Pepeta, a locally processed immature rice-based food product, to promote food security in Tanzania

Consumption of pepeta, a traditionally processed immature rice product, is common in Tanzania, where it contributes to food security as an early rice food i.e. when there is no other food available at the household while the crops in the field not yet fully ripe. Many production steps are needed to guarantee a consistent, good quality pepeta product, and this hinders its utilization in other rice-growing sub-Saharan regions. This study aims to gain insight into the pepeta processing knowledge and final product, and assess variations in the processing conditions and parameters across the study area. A survey among 257 Tanzanian processors and consumers revealed that the pepeta product is widely known, rated second (73.5% respondents) as rice-based food after wali (cooked white rice, (100%)) and linked to traditions of the communities in the study area. Harvest of immature rice grain, roasting, pounding, cleaning, and packing are the main process steps of pepeta production. Method of rice harvest, rice suitability for pepeta production after optimum harvest, dryness of grains and number of pounding as indicator to terminate roasting and pounding process respectively, and packaging materials used varied significantly across respondents in the study area. Reported criteria considered by respondents for product acceptability did not vary significantly across study area. The criteria include colour (76.5%), general appearance (60.8%), texture (64.7%) and taste (52.9%). Immature rice paddy and pepeta were sold at a higher price than mature rice paddy and white rice, respectively, which implies that options to facilitate pepeta processing through, for instance, standardization of processing conditions and parameters could lead to increased income.

Combination of High Zn Density and Low Phytic Acid for Improving Zn Bioavailability in Rice (Oryza stavia L.) Grain

BACKGROUND

Zn deficiency is one of the leading public health problems in the world. Staple food crop, such as rice, cannot provide enough Zn to meet the daily dietary requirement because Zn in grain would chelate with phytic acid, which resulted in low Zn bioavailability. Breeding new rice varieties with high Zn bioavailability will be an effective, economic and sustainable strategy to alleviate human Zn deficiency.

RESULTS

The high Zn density mutant LLZ was crossed with the low phytic acid mutant Os-lpa-XS110-1, and the contents of Zn and phytic acid in the brown rice were determined for the resulting progenies grown at different sites. Among the hybrid progenies, the double mutant always displayed significantly higher Zn content and lower phytic acid content in grain, leading to the lowest molar ratio of phytic acid to Zn under all environments. As assessed by in vitro digestion/Caco-2 cell model, the double mutant contained the relatively high content of bioavailable Zn in brown rice.

CONCLUSIONS

Our findings suggested pyramiding breeding by a combination of high Zn density and low phytic acid is a practical and useful approach to improve Zn bioavailability in rice grain.

Nutritional quality and in vitro digestion of immature rice-based processed products

The nutritional contents of rice decreased as grains matured, and pepeta-type processing improves the nutritional properties and in vitro protein digestibility of rice.