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In order to optimize N application and understand how the different combinations of water and N management affect grain filling characteristics and yield, we designed three irrigation regimes (W1 submerged irrigation, W2 alternate irrigation, W3 dry cultivation), and different N application strategies at 180 kg ha−1 in 2010 and 2011. The relationship between grain filling characteristics and grain yield formation were respectively investigated. The results revealed that there were obvious interacting effects of irrigation regime and N application strategies on grain yield and grain-filling characteristics as well. Compared with W1 and W3 treatments, under W2, the N-fertilizer should account for 30% base, 30% tillering, and 40% panicle fertilizer with the last being applied equally at 4th and 2nd leaves emerged from the top. Correlation analysis revealed that grain filling rate during middle grain-filling stage was the largest and contribute more than 50% to grain-filling. Grain yield was significantly related to grain filling rate (Gmax or Gmean), final weight of a kernel (A), and mean grain filling rate (MGR) of the early, mid and late stages during grain filling in inferior spikelets, which is the important reason for water and N coupling effect further to increase yield and fertilizer use efficiency. [ABSTRACT FROM AUTHOR]

In order to clarify yield formation mechanism of mechanical dry direct-sowing rice, the objective of this experiment was to study the effects of different mechanical dry direct-sowing modes on growth and development characteristics and yield of rice. Two different rice cultivars of indica hybrid rice F you 498 (143 days growth duration) and conventional japonica rice Xudao 4 (145 days growth duration) were planted with two mechanical dry direct-sowing modes, including a shallow rotary tillage land and mechanic drilling simultaneously (B1), regulating soil moisture and two rotary tillage before mechanic drilling (B2). Manual broad-cast sowing (B3) was set as control at the same time. We investigated and performed growth analysis during different growth periods, and determined yield formation and physiological characteristics under different direct-sowing treatments. The dry direct-sowing machine in this study was modified by Nanjing Agricultural University and was re-modified by Sichuan Agricultural University. This machine has six drills and sowed depth 2.0 cm, drill spacing 28.0 cm, working area 1.50 m. Motive power of this machine was the Shanghai New Holland tractor (SNH504). This test adopted row spacing 20 m × 1.5 m, each plot covered 30 m2 of seeding amount was 30.0 kg/hm2 of indica hybrid rice F you 498, 37.5 kg/hm2 of conventional japonica rice Xudao 4 respectively. The nitrogen fertilizer amount was 180 kg/hm2, and the amount of potash and phosphate were 90 and 180 kg/hm2, respectively. The N application ratios was applied on 4 splits: 50% basal, 30% tillering fertilizer at the third leaf stage, 10% panicle N-fertilizer at the 4th leaves emerged from the top, 10% ear granular fertilizer at the full heading stage. The phosphate fertilizer was applied as base fertilizer. The potash fertilizer application ratio of basic fertilizer, tillering fertilizer and ear granular fertilizer was 2:1:1. The other management measures were at a uniform with high-yield cultivation. The results showed that the variety difference and direct-sowing modes significantly affected dry matter accumulation and leaf area index (LAI) at the mainly growth periods, net photosynthetic rate (Pn) and protective enzyme activities of flag leaves, root bleeding intensity, culm lodging resistance during the grain filling stage and the grain yield. Under different direct-sowing modes, the various indicators on yield and growth characteristics of F you 498 were significantly higher than those of Xudao 4. Compared with B3 treatment, rice under mechanical direct-seeding modes could optimize the number of rice tillering, improve the percentage of earbearing tiller, maintain an appropriate LAI and increase efficient leaf area ratio at the full-heading stage. Besides mechanical direct-seeding could improve photosynthetic capacity at the grain filling stage and therefore increase the accumulation of photosynthetic products. In addition, Pn and protective enzyme activities in flag leaves, root bleeding intensity, culm lodging resistance during the grain filling stage under mechanical direct-seeding modes were superior, and rice could gain higher seed-setting rate and 1000-grain weight with a number of effective panicles. These outstanding traits should be the important reason for mechanical direct-sowing rice further to increase yield. Under different mechanical direct-sowing modes, compared with B3, B2 treatment was the best model in this study referred as the mechanical direct-sowing treatments, which could further promote the dry matter accumulation, alleviate LAI decay, increase root vigor and the ability of culm lodging resistance during grain filling stage, consequently, promoting the seed-setting rate and 1000-grain weight as well as the grain yield. [ABSTRACT FROM AUTHOR]

Rice lacks sufficient amounts of zinc despite its vitality for human health. Leaf senescence enables redistribution of nutrients to other organs, yet Zn retransfer during deficiency is often overlooked. In this hydroponic experiment, we studied the effect of Zn deficiency on rice seedlings, focusing on the fourth leaf under control and deficient conditions. Growth phenotype analysis showed that the growth of rice nodal roots was inhibited in Zn deficiency, and the fourth leaf exhibited accelerated senescence and increased Zn ion transfer. Analyzing differentially expressed genes showed that Zn deficiency regulates more ZIP family genes involved in Zn ion retransfer. OsZIP3 upregulation under Zn-deficient conditions may not be induced by Zn deficiency, whereas OsZIP4 is only induced during Zn deficiency. Gene ontology enrichment analysis showed that Zn-deficient leaves mobilized more biological pathways (BPs) during aging, and the enrichment function differed from that of normal aging leaves. The most apparent "zinc ion transport" BP was stronger than that of normal senescence, possibly due to Zn-deficient leaves mobilizing large amounts of BP related to lipid metabolism during senescence. These results provide a basis for further functional analyses of genes and the study of trace element transfer during rice leaf senescence. [ABSTRACT FROM AUTHOR]

As the human population grows rapidly, food shortages will become an even greater problem; therefore, increasing crop yield has become a focus of rice breeding programs. The maize gene, ZmDUF1645, encoding a putative member of the DUF1645 protein family with an unknown function, was transformed into rice. Phenotypic analysis showed that enhanced ZmDUF1645 expression significantly altered various traits in transgenic rice plants, including increased grain length, width, weight, and number per panicle, resulting in a significant increase in yield, but a decrease in rice tolerance to drought stress. qRT-PCR results showed that the expression of the related genes regulating meristem activity, such as MPKA, CDKA, a novel crop grain filling gene (GIF1), and GS3, was significantly changed in the ZmDUF1645-overexpression lines. Subcellular colocalization showed that ZmDUF1645 was primarily localized on cell membrane systems. Based on these findings, we speculate that ZmDUF1645, like the OsSGL gene in the same protein family, may regulate grain size and affect yield through the cytokinin signaling pathway. This research provides further knowledge and understanding of the unknown functions of the DUF1645 protein family and may serve as a reference for biological breeding engineering to increase maize crop yield. [ABSTRACT FROM AUTHOR]

Summary: More than half of the world's food is provided by cereals, as humans obtain >60% of daily calories from grains. Producing more carbohydrates is always the final target of crop cultivation. The carbohydrate partitioning pathway directly affects grain yield, but the molecular mechanisms and biological functions are poorly understood, including rice (Oryza sativa L.), one of the most important food sources. Here, we reported a prolonged grain filling duration mutant 1 (gfd1), exhibiting a long grain‐filling duration, less grain number per panicle and bigger grain size without changing grain weight. Map‐based cloning and molecular biological analyses revealed that GFD1 encoded a MATE transporter and expressed high in vascular tissues of the stem, spikelet hulls and rachilla, but low in the leaf, controlling carbohydrate partitioning in the stem and grain but not in the leaf. GFD1 protein was partially localized on the plasma membrane and in the Golgi apparatus, and was finally verified to interact with two sugar transporters, OsSWEET4 and OsSUT2. Genetic analyses showed that GFD1 might control grain‐filling duration through OsSWEET4, adjust grain size with OsSUT2 and synergistically modulate grain number per panicle with both OsSUT2 and OsSWEET4. Together, our work proved that the three transporters, which are all initially classified in the major facilitator superfamily family, could control starch storage in both the primary sink (grain) and temporary sink (stem), and affect carbohydrate partitioning in the whole plant through physical interaction, giving a new vision of sugar transporter interactome and providing a tool for rice yield improvement. [ABSTRACT FROM AUTHOR]

• This work provides a new model framework for predicting grain yield. • Combining spectral data and RGB images to develop the fusion models of grain yield. • Multi-source remotely sensed data can improve the estimation accuracy of rice LCC. • Multi-source remotely sensed data has the potential for grain yield prediction. Predicting rice grain yield using multi-source remotely sensed data is crucial for improving prediction accuracy, optimizing nitrogen management, and advancing precision agricultural development. However, the feasibility and reliability of using multi-source remotely sensed data to predict the grain yield remain unclear. Therefore, this study aimed to explore the possibility of providing rice leaf chlorophyll content (LCC) estimations and predictions of the grain yield using multi-source remotely sensed data. Two rice field experiments were conducted with various rice cultivars and nitrogen rates, and a field spectrometer and an unmanned aerial vehicle (UAV) equipped with a digital camera were employed to acquire the spectral reflectance and red–green–blue (RGB) images at the tillering, jointing, and full-heading stages. Destructive sampling was then conducted to measure the LCC and grain yield. The LCC was used as a bridge to develop remotely sensed prediction models for the grain yield. First, the linear relationship between grain yield and the LCC was determined at the tillering, jointing, and full-heading stages. A multiple linear regression (MLR) model was then developed to predict grain yield using multi-temporal LCCs at three growth stages. Second, multiple stepwise regression, support vector regression, and back propagation neural network were used to evaluate the estimation performance of spectral reflectance, RGB image data, and their combination for LCC. Third, the most accurate LCC estimation model was selected and coupled with the linear and MLR models of grain yield. The results showed that grain yield was significantly and positively related to the LCC at the tillering, jointing, and full-heading stages, and that the MLR model of grain yield achieved the best estimation accuracy using multi-temporal LCCs. The fusion models established by combining spectral reflectance and RGB image data improved LCC estimation accuracies. Using multi-growth stages, the most accurate predictions of grain yield were obtained from LCC estimation models (R 2 = 0.698, RMSE = 0.742 t ha−1, rRMSE = 9.004 %) compared to those using single growth stages. Our study concluded that multi-source remotely sensed data fused from ground-based spectral reference and UAV-based RGB images can better predict and explain the grain yield for both single and multi-growth stages. This study provides a novel method of estimating the crop chlorophyll content and grain yield. [ABSTRACT FROM AUTHOR]

To promote the reduction and efficiency of chemical fertilizers in rice production, two hybrid rice varieties with different amylose contents (16.43% and 27.58%) were selected to study the yield and quality performance of different quality rice varieties under reduced nitrogen/phosphorus conditions. Thus, the specific mechanism of the long‐term nitrogen/phosphorus reduction effect on the quality of low‐ and high‐amylose content (16.43% and 27.58%) rice was investigated by comparative analyses of the rapid visco analyzer and X‐ray diffraction patterns, amylose contents, and starch structures of the samples. The results revealed that the effect of nitrogen fertilizer on the quality and yield of the hybrid rice was greater than that of phosphorus fertilizer. Indeed, reducing the former increased the Wx gene expression and amylose content of the rice varieties. Moreover, it reduced the starch crystallinity of Yixiangyou 1108 (2.16%), increasing the space between the starch grains and thus, chalkiness. Reducing nitrogen/phosphorus application did not significantly affect the yield and quality of the high‐amylose rice but affected that of the high‐quality rice with lower amylose contents. Thus, for high‐amylose rice created for processing, appropriate chemical fertilizer reduction will not affect their yield and processing demand. Practical applications: Fertilization with different nitrogen and phosphorus fertilizers will seriously affect rice quality. The rice varieties with low amylose content (AC) could produce high taste quality rice by increasing nitrogen fertilizer and decreasing phosphorus fertilizer. The rice varieties with relatively high ACs should reduce the application of nitrogen/phosphorus fertilizer to appropriately increase AC, which can be used to produce healthy food with high resistant starch. [ABSTRACT FROM AUTHOR]

In this study, field data from 148 farmers were combined with energy equivalents, greenhouse gas emission factors, and product prices obtained from the literature and official statistics to evaluate and compare the energy use, environmental impact, and economic benefits between smallholders' rice production mode (SHM) and scale rice production modes (Big grain growers' rice production mode; Micro cooperatives' rice production mode). Compared with SHM, the scale rice production modes increased the net energy by 425.02 MJ ha−1–13148.29 MJ ha−1, increased the energy use efficiency by 16.85%–22.89%, increased the net economic return by 15.67 USD ha−1–531.31 USD ha−1, increased the net profit-to-labor use ratio by 26.02%–393.87%, decreased the global warming potential (GWP) by 19.48%–27.23%, and decreased the yield-scaled GWP by 19.93%–29.50%. These results demonstrate that the scale rice production modes can satisfy the needs of reduced labor inputs, energy conservation, emission reduction, and increased profitability of rice production, thereby promoting sustainable and low-carbon development of the agricultural industry in China. Based on these findings, it is recommended that the government increase its support for developing scale rice production modes and encourage farmers to take equity in their lands or lease them to micro cooperatives for more efficient production. [Display omitted] • The performance of scale rice production modes in China is unknown. • To evaluate the performance of three rice production modes. • Scale rice production modes reduce energy input and greenhouse gas emissions. • Scale rice production modes ensure rice yield and increase the economic income. • It is recommended that government and farmers develop scale rice production modes. [ABSTRACT FROM AUTHOR]

Background: Seed dormancy, a quality characteristic that plays a role in seed germination, seedling establishment and grain yield, is affected by multiple genes and environmental factors. The genetic and molecular mechanisms underlying seed dormancy in rice remain largely unknown. Results: Quantitative trait loci (QTLs) for seed dormancy were identified in two different mapping populations, a chromosome segment substitution line (CSSL) and backcross inbred line (BIL) population, both derived from the same parents Nipponbare, a japonica cultivar with seed dormancy, and 9311, an indica cultivar lacking seed dormancy. A total of 12 and 27 QTL regions for seed dormancy were detected in the CSSLs and BILs, respectively. Among these regions, four major loci (qSD3.1, qSD3.2, qSD5.2 and qSD11.2) were commonly identified for multiple germination parameters associated with seed dormancy in both populations, with Nipponbare alleles delaying the seed germination percentage and decreasing germination uniformity. Two loci (qSD3.1 and qSD3.2) were individually validated in the near-isogenic lines containing the QTL of interest. The effect of qSD3.2 was further confirmed in a CSSL-derived F2 population. Furthermore, both qSD3.1 and qSD3.2 were sensitive to abscisic acid and exhibited a significant epistatic interaction to increase seed dormancy. Conclusions: Our results indicate that the integration of the developed CSSLs and BILs with high-density markers can provide a powerful tool for dissecting the genetic basis of seed dormancy in rice. Our findings regarding the major loci and their interactions with several promising candidate genes that are induced by abscisic acid and specifically expressed in the seeds will facilitate further gene discovery and a better understanding of the genetic and molecular mechanisms of seed dormancy for improving seed quality in rice breeding programs. [ABSTRACT FROM AUTHOR]

To investigate the development direction of mechanized rice production in China, we compared the differences between two production modes, namely, unmanned aerial vehicle direct seeding (UDS) and integrated mechanical transplanting (IMT) in energy use efficiency (EUE) and economic benefits from 2017 to 2019. Fertilizer, fuel, and water account for the top three largest proportions of total energy input under both production modes. The energy inputs in fuel, irrigation water, and plastic film under UDS were 4611.34 MJ ha−1, 1355.21 MJ ha−1, and 3913.02 MJ∙ha−1 lower than those under IMT, respectively. The application of transplanting and fertilizer-pesticide spraying integration machine under IMT contributed to its energy-saving advantages in electricity, fertilizer and pesticide; however, the energy inputs in these three aspects were only reduced by 30.74 MJ ha−1, 355.98 MJ ha−1 and 69.34 MJ ha−1, respectively. The total energy input under IMT from 2017 to 2019 was 45.11%–45.69% higher than that under UDS. There was no significant difference in rice grain yield and straw yield. The EUE, energy productivity and energy profitability under UDS were 41.03%, 41.87%, and 46.69% higher than those under IMT, respectively. The cost under UDS was 13.8% lower than that under IMT. In addition, under UDS, the net return was 7.5% higher, and the benefit-to-cost ratio was 24.7% higher. Energy input and cost under UDS were reduced compared with those under IMT on the premise of stable yield. It can be concluded that IMT is a more promising mechanized rice production mode in China. • Performances of IMT and UDS were analyzed in a three-year field experiment. • Grain yield and rice straw via UDS was similar to that in IMT. • Energy input under UDS was 31.19% (10061.38 MJ ha−1) lower than that under IMT. • UDS had significant lower cost with net return of US $2253.81 ha–1 • UDS is a high-yield and high-profitability production mode. [ABSTRACT FROM AUTHOR]

Environmental factors and plant hormones are major players in seed germination. Abscisic acid (ABA) not only delays seed germination but also acts as a central regulator in plant growth, development and response to stress conditions. In this study, a rice C2H2-type zinc finger protein, OsZFP15, was screened by microarray and characterized. RT-qPCR and GUS staining assays revealed that OsZFP15 was significantly induced by ABA and multiple abiotic stresses. Subcellular localization assay indicated that OsZFP15 protein was located in the nucleus of rice protoplast. Overexpression of OsZFP15 reduced the sensitivity to ABA and down-regulated transcript levels of ABA-responsive genes including LEA3 and LIP9 , but increased transcript level of OsABA8ox2 , suggesting that OsZFP15 is a positive regulator of ABA catabolism. Additionally, overexpression of OsZFP15 in rice enhanced ABA catabolism and thus accelerated seed germination. We further investigated the role of OsZFP15 in abiotic stress response. Overexpression of OsZFP15 promoted reactive oxygen species (ROS) production and accordingly reduced the tolerance to oxidative stress. Conversely, improvements in salinity and drought tolerance were observed in OsZFP15 overexpression plants. • Overexpression of OsZFP15 decreases the height of rice, but increases the seed setting rate and grain number per panicle. • Overexpression of OsZFP15 improves rice tolerance to drought and salt stress. • OsZFP15 enhances ABA catabolism through OsABA8ox2 to promote seed germination [ABSTRACT FROM AUTHOR]

This study performed energy analyses of fully mechanized rice production mode (FM) and semi-mechanized rice production mode (SM) in China. Fertilizer, fuel, and water were the three largest inputs, accounting for 92.02% of the total energy input. FM adopted side-deep fertilization with machine transplanting and implemented intermittent irrigation regime to improve water and fertilizer use efficiency. Compared with SM, FM reduced fertilizer and water energy inputs by 1252.62 MJ ha−1 and 2187.87 MJ ha−1, respectively. Because of the lower degree of mechanization, the fuel energy input of SM was 691.19 MJ ha−1 less than that of FM. The total average energy input of FM was 23,610 MJ ha−1, which was 10.80% lower than SM (26,470.01 MJ ha−1), whereas the rice and straw yields of FM were not significantly different from SM. The energy use efficiency, energy productivity, and energy profitability of FM were 11.10, 0.41 kg MJ−1, and 10.10, respectively, corresponding to increases of 8.56%, 8.61%, and 9.49% compared to SM. With appropriate agronomic measures in rice production, a higher degree of mechanization would not necessarily lead to an increase in energy input in Southwest China. [Display omitted] • Fully mechanized (FM) and semi-mechanized (SM) rice production modes were compared. • The energy consumption of SM increased by 12.11% on average compared to that of FM. • Fertilizer, fuel, and water accounted for about 92% of the total energy input. • Energy use efficiency and energy productivity of FM were higher than that of SM. • FM has more advantages than the SM. [ABSTRACT FROM AUTHOR]

This investigation aims to provide theoretical and practical evidence for the efficient utilization of nitrogen (N) in paddy-upland rapeseed-rice rotation systems because a lack of previous research on such rotation systems leads to inefficient management practices. The effects of the N application rates and the N fertilizer management strategies for rapeseed and rice were examined, respectively, in relation to the photosynthetic productivity and yields of hybrid rice. The results indicated that the leaf area, Pn, with 40% as basal fertilizer, 40% as tillering fertilize, and 20% as panicle fertilizer and a reduced N rate (30 kg/ha) during the rape season, were higher than other nitrogen management strategies trialed, with conventional N rates in the rape season. The average rice grain yield (9545.15 kg/ha) over the two years with 40% as basal fertilizer, 40% as tillering fertilizer, and 20% as panicle fertilizer was higher than other N treatments with the reduced N rates during the rape season. The reduced N rate during the rapeseed season and 40% as basal fertilizer, 40% as tillering fertilizer, and 20% as panicle fertilizer management during the rice season for the rape-rice rotation system exhibited the highest rice yields. Our findings indicated that the N fertilizer management model was a high-yielding, N-saving, and environmentally friendly measure for rape–rice rotation systems in southern China. [ABSTRACT FROM AUTHOR]

• Methodical nitrogen–water distribution management (MNWD) couples nitrogen and water application in rice production. • MNWD stabilized rice yield and reduced nitrogen and water input in rice production simultaneously. • Larger amount of root in soil layers deeper than 10 cm of MNWD was the key for higher water and nitrogen use efficiencies. Methodical nitrogen–water (N–W) distribution management (MNWD) is a comprehensive N–W management technique designed to meet the requirements of rice production in China and specifically, the stabilization of grain yield and reduction of input resources. In this study, four split plot field experiments were conducted in two locations to examine the impact of MNWD on N use efficiency (NUE) and water use efficiency (WUE). We used high N efficiency rice varieties, Dexiang 4103 and Fyou 498, and low N efficiency varieties, Yixiang 3724 and Chuanyou 6203, and three N–W management techniques were established as subplot treatments, including farmers' usual management (FU), N–W coupling management (NWC), and MNWD. Under MNWD, N application rates were 20% lower than those under NWC and FU, whereas the amounts of irrigation water were reduced by 20%–25% and 42%–48%, respectively. Yields under MNWD were similar to those under NWC (–2.51–0.45%), and there was an average yield increase of 8.13%–13.95% over FU. Rice plants under MNWD had larger amounts of roots, particularly in soil depth > 10 cm There were significant positive correlations between root dry mass in the various soil depths and WUE and irrigation WUE (IWUE), with the impact of roots in soil depth > 10 cm on rice plant WUE (IWUE) pronounced. MNWD's IWUE was higher than that of NWC and FU by 22.95%–38.79% and 86.49%–126.69%, respectively, and its WUE was higher by 6.75%–20.74% and 37.05%–71.80%, respectively. Correlation analysis showed that the N absorption and accumulation capacities of rice plants under MNWD increased along with increases in soil fertility. The MNWD's NUE advantage was apparent in soil depth > 10 cm where its root dry mass was especially large, with an average biomass productivity of N higher than that of NWC and FU by 4.16%–10.78% and 7.49%–18.01%, respectively and an N internal efficiency higher by 0.33%–8.29% and 5.32%–10.04%, respectively. Overall, MNWD effectively improved WUE and NUE of rice without significant grain yield reduction. [ABSTRACT FROM AUTHOR]