Rice Growth Stages Research Articles

Methane emission mitigation of Paenibacillus yonginensis DCY84T incorporated with silicate on paddy rice (Oryzae sativa L.) plantation revealed in soil microbiome profiling.

Anthropogenic methane emissions from paddy cultivation contribute to greenhouse gas levels owing to the anaerobic conditions in flooded rice fields, which promotes the activity of methanogenic bacteria. This study explored bioremediation strategies to mitigate methane release through the application of plant growth-promoting rhizobacteria combined with silicate in rice cultivation. Rice seeds were coated with Paenibacillus yonginensis DCY84T, with and without the addition of silicate, prior to sowing. Results revealed notable reduction in methane flux during the peak growth stage of rice in seeds treated with DCY84T (27.215±1.975mgm-2h-1), with a further reduction observed when silicate was also applied (23.592±3.112mgm-2h-1), compared to untreated seeds (37.305±2.990mgm-2h-1). Additionally, treatment with DCY84T (28.24±0.55g) resulted in an increase in rice yield (p<0.05), as evidenced by a greater 1000-grain weight compared to both the control group (26.91±0.09g) and the application of silicate (27.37±0.57g). The beta diversity of the soil microbial community highlighted distinct differences between the treated and control groups, indicating DCY84T inoculation with or without silicate altered the soil microbial structure. Particularly, the treated groups showed dominance of the phylum Proteobacteria, especially the classes Alphaproteobacteria and Deltaproteobacteria. Furthermore, the addition of silicate to DCY84T-coated rice seeds resulted in a higher abundance of bacterial families, such as Anaerolinaceae, Clostridiceae, and Nitrospirae which compete with methanogens for organic substrates, thereby reducing their methane production. Notably, the DCY84T-silicate treatment group showed higher levels of methane metabolism biomarkers such as formate dehydrogenase within the soil microbiome, which correlated with the observed reduction in methane emissions. These findings suggest that coating rice seeds with DCY84T and silicate prior to sowing effectively mediates methane production and release during rice cultivation by promoting beneficial soil bacterial communities.

Integrating Climatic Factors and Agronomic Management for Optimal Hybrid Rice Yield and Quality

ABSTRACT Rice is a staple food crop, and optimizing its yield and quality is crucial for food security. This study investigated the influence of weather variables and nitrogen (N) management practices on hybrid rice yield and processing quality in Eastern India. Two field experiments were conducted wxith three planting dates (15 June, 15 July, and 15 August) and four N management practices: fixed-time N management (FTCF) with recommended chemical fertilizer (CF), real-time N management (RT) based on SPAD (Soil Plant Analysis Development) value of rice leaf with only CF, integration of CF and organic fertilizer (OF) with RT management (RTCF+OF), and no fertilization as control during the wet seasons of 2013 and 2014. The statistical relationship between weather and crop yield variables was established to determine the impact of optimum weather variables at critical growth stages of hybrid rice. Results showed that the planting date of 15 July recorded significantly higher grain yield and improved post-harvest processing qualities compared to the other planting dates. Additionally, SPAD-based N management was comparable to fixed-time N management for grain yield production. During the pre- and post-anthesis period, minimum temperature (Tmin) had a significant negative effect, and solar radiation (SRAD) had a significant positive impact on processed yield and grain quality. Increasing the maximum temperature (Tmax) during the post-anthesis period negatively affected the yield and quality significantly. This study suggests that real-time N management through a SPAD meter can effectively reduce nitrogen loss and increase grain quality without affecting yield.

Stage-Specific Effects of Silver Nanoparticles on Physiology During the Early Growth Stages of Rice.

Silver nanoparticles (AgNPs), widely utilized nanomaterials, can negatively affect crop growth and development. However, it remains unclear whether crops exhibit similar responses to AgNPs stress at seed germination and seedling stages. In this study, rice seeds and seedlings were exposed to AgNPs, and their growth, photosynthetic efficiency, and antioxidant systems were recorded. demonstrated significant AgNPs accumulation in rice tissues, with notable higher accumulation in seedlings exposed to AgNPs after germination compared to AgNPs exposure during germination. The roots exhibited greater AgNPs accumulation than shoots across both stages. Exposure to AgNPs during the seed germination stage, even at concentrations up to 2 mg/L, did not significantly affect growth, physiological indices, or oxidative stress. In contrast, seedlings exposed to 1 and 2 mg/L AgNPs showed significant reductions in shoot length, biomass, nutrient content, and photosynthetic efficiency. At low AgNPs concentrations, the maximum relative electron transport rate (rETRmax) was significantly reduced, while the higher concentrations caused pronounced declines in the chlorophyll a fluorescence transient curves (OJIP) compared to the control group. Antioxidant enzyme activities increased in both leaves and roots in a dose-dependent manner, with roots exhibiting significantly higher activity, suggesting that roots are the primary site of AgNPs stress responses. In conclusion, rice responds differently to AgNPs exposure at distinct developmental stages, with the seedling stage being more susceptible to AgNPs-induced stress than the seed germination stage. These findings underscore the importance of considering growth stages when assessing the food safety and environmental risks associated with AgNPs exposure.

Agro-morphological and yield-related traits of selected Malaysian high yielding rice cultivars under silicon supplementation

Abstract The objective of the present study was to assess the potential of silicon application on the agro-morphological and yield-related traits of selected Malaysian high yielding rice cultivars. A pot study was set up in the Greenhouse No. 5 at the Faculty Plantation &amp; Agrotechnology, University Teknologi MARA Malacca Branch, Jasin Campus between March to August 2024. A total of 32 pots were laid out as a factorial experiment with four replications and arranged in a randomized complete block design. There were four level silicon treatments used in this study; T1 (control), T2 (250kg Si/ha), T3 (500kg Si/ha), and T4 (750 kg Si/ha). Remarkably, silicon nutrition application does not differ significantly influence rice growth attributes for IS21 and MR297 at the rice growth stages of 40 DAT, 60 DAT and 75 DAT. In term of yield related traits, panicle number, panicle length and grain yield showed an optimum at 250 kg Si/ha when compared to control and other treatments for IS21 variety. Meanwhile, silicon supplementation level at T4 (750 kg Si/ha) recorded the higher value than other treatments on panicle number, panicle length and grain yield for MR297 rice variety when compared to control and other treatments observed in this study respectively.

Topological organization for hybrid rice growth stages Phenotype based on Contrastive clustering

Hybrid-rice seed production technology is a significant contributor to the high yield. The way to improve seed production’s yield and quality is purification. With the functional requirements of the intelligent Undesired-rice removal process, the environmental elements of field operation and the morphological parameters of Desired-rice and Undesired-rice are collected and measured. This study presents a comprehensive analysis of the topological organization of hybrid rice growth stages using a deep clustering algorithm, t-SimCLR. The algorithm was rigorously tested and compared with existing methods, demonstrating superior performance in clustering accuracy and the ability to capture semantic relationships within the dataset. It elucidated expert prior knowledge of abnormal mature varieties for hybrid rice and explored the growth stages of hybrid rice and panicles. Expert knowledge on identifying abnormal mature varieties within hybrid rice was incorporated to ensure accuracy in variety purification. The study utilized three different datasets to reveal underlying structures and patterns, providing insights into the growth dynamics of hybrid rice. The t-SimCLR algorithm, which employs Contrastive Learning and neighbor embeddings, outperformed traditional methods such as UMAP, t-SNE, and SimCLR, particularly in maintaining the local structure of data and offering more meaningful two-dimensional embeddings. The parametric mapping is trained from the high-dimensional pixel space into two dimensions and achieves classification accuracy by the t-SimCLR algorithm. This study contributes to the advancement of hybrid rice purification techniques and sets the stage for developing more sophisticated intelligent systems for agricultural applications.

Accurate Prediction of 327 Rice Variety Growth Period Based on Unmanned Aerial Vehicle Multispectral Remote Sensing

Most rice growth stage predictions are currently based on a few rice varieties for prediction method studies, primarily using linear regression, machine learning, and other methods to build growth stage prediction models that tend to have poor generalization ability, low accuracy, and face various challenges. In this study, multispectral images of rice at various growth stages were captured using an unmanned aerial vehicle, and single-plant rice silhouettes were identified for 327 rice varieties by establishing a deep-learning algorithm. A growth stage prediction method was established for the 327 rice varieties based on the normalized vegetation index combined with cubic polynomial regression equations to simulate their growth changes, and it was first proposed that the growth stages of different rice varieties were inferred by analyzing the normalized difference vegetation index growth rate. Overall, the single-plant rice contour recognition model showed good contour recognition ability for different rice varieties, with most of the prediction accuracies in the range of 0.75–0.93. The accuracy of the rice growth stage prediction model in recognizing different rice varieties also showed some variation, with the root mean square error between 0.506 and 3.373 days, the relative root mean square error between 2.555% and 14.660%, the Bias between1.126 and 2.358 days, and the relative Bias between 0.787% and 9.397%; therefore, the growth stage prediction model of rice varieties can be used to effectively improve the prediction accuracy of the growth stage periods of rice.

Soil metabolic processes influenced by rice roots co-regulates the environmental evolution of antibiotic resistome

Plant root activities lead to significant differences in metabolites between the rhizosphere and non-rhizosphere soil, profoundly affecting microbial distribution. However, how this process drives the migration and propagation of manure-derived antibiotic resistance genes (ARGs) in farmland ecosystems remains unclear. Herein, we used a rice pot microcosm experiment to explore the characteristics of antibiotic resistome and bacterial communities in rhizosphere and non-rhizosphere soils and the driving effects of rhizosphere metabolites on ARG propagation. The results showed significant differences in some ARGs and bacterial diversity in rhizosphere and non-rhizosphere soils with varied differential ARGs between different growth stages of rice (P < 0.05). The biosynthesis of secondary metabolites and glutathione metabolism were found to be the main pathways affecting ARG differences in rhizosphere and non-rhizosphere soils under manure application. Structural equation modeling (SEM) analysis further indicated that ARG distribution differences between rhizosphere and non-rhizosphere soils were mainly regulated by differential metabolites, which influenced the ARG distribution by altering the succession of soil microbial communities. These results demonstrate the role of differential metabolites resulting from rice root activities in co-regulating ARG distribution, providing new insights into the regulatory mechanisms of soil ARG dynamics in paddy fields.

Effects of nutritional stress on soil fertility and antioxidant enzymes of rice in different growth periods.

Stress in plants denotes the detrimental impact of alterations in external environmental conditions on regular plant growth and development. Plants employ diverse mechanisms to mitigate or evade nutritional stress-induced damage. In order to investigate the physiological response mechanism of plants to nutritional stress and assess its impact on soil nutrient content and antioxidant enzyme activity in rice, a field experiment was conducted applying five treatments: control, nitrogen (N) deficiency, phosphorus (P) deficiency, potassium (K) deficiency, and full fertilization. Rice leaf and soil samples were concurrently gathered during both the vegetative and reproductive growth stages of rice. Analysis was conducted on soil N, P, and K levels, as well as leaf antioxidant enzyme activities, to investigate the impact of nutrient stress on rice antioxidant enzymes and soil fertility. The research findings indicate that full fertilization treatment enhanced the agronomic properties of the soil compared to the control treatment. In the N-deficiency treatment, reactive oxygen species (ROS) levels increased by 16.53-33.89% during the reproductive growth period compared to the vegetative growth period. The peroxidase (POD) activity decreased by 41.39% and superoxide dismutase (SOD) activity increased by 36.22% under K-deficiency treatment during the reproductive growth period compared to the vegetative growth period. Consequently, applying N and P fertilizer during the vegetative growth period can decrease membrane lipid peroxidation levels by 7.34-72.53%. The full fertilization treatment markedly enhanced rice yield compared to other treatments and increased the Nitrogen activation coefficient (NAC) and Phosphorus activation coefficient (PAC) in the soil, while decreasing the PAC. Elevating NAC levels can stimulate the activity or content of PRO, MDA, and RPS during the vegetative growth stage, whereas in the reproductive growth stage, it will decrease the content of ROS, PRO, and MDA. This data offers valuable insights and theoretical support for nutritional stress research.

Nano-sized ZnO enhances photosynthetic parameters, yield and Zn content in rice (Oryza sativa)

A pot culture experiment was conducted during rainy (kharif) season of 2021 at ICAR-Indian Institute of Rice Research, Hyderabad, Telangana to study the influence of the foliar application of various Zn sources such as nano ZnO, bulk ZnO, and ZnSO4 on rice crop. The experiment was laid out in a completely randomized design (CRD) with the following treatments, containing 3 concentrations of bulk ZnO (500 mg/litre, 1000 mg/litre, and 1500 mg/ litre), 3 concentrations of nano ZnO (50 mg/litre, 100 mg/ litre, and 150 mg/litre), 0.5% ZnSO4 and control with 3 replications. The findings revealed that ZnO nanoparticles (NPs) positively impacted rice grain yield, dry matter accumulation, and Zn content. Compared to the control (no zinc), ZnO NPs (150 mg/litre) and standard ZnSO4 treatments exhibited the highest plant height (83.3 cm and 73.7 cm, respectively), grain yield (5.97 g/pot and 6.03 g/pot), and straw yield (7.82 g/pot and 7.94 g/pot). The increased photosynthetic substances and higher dry matter accumulation throughout the rice growth stage contributed to the enhanced grain yield. Furthermore, supplementing Zn via nano ZnO (150 mg/litre) and 0.5% ZnSO4 resulted in significant Zn enrichment: 33,35; 77,87 and 21, 28% in straw, grain and soil, respectively over control plants. This study effectively demonstrates that ZnO nanoparticles have the potential to serve as high-performance fertilizers, benefiting both rice yield and quality.

Yield Loss Quantification Due to Stalk-Eyed Fly (Diopsidae) Infestations on Rice Crops (Oryza Sativa) in Fogera Plain

Stalk-Eyed Flies (Diopsidae) pose a significant threat to rice crops (Oryza sativa), causing yield loss and affecting crop development. This study aims to quantify yield loss due to Stalk-Eyed Fly infestations and identify susceptible growth stages of rice crops to this insect. Field experiments were conducted to assess the yield loss of rice due to stalk eyed fly at Fogera, in 2021 and 2022. With the treatments Both Thiamethoxam seed treatment and Chlorpyrifos systemic foliar insecticide were applied to combat the infestation, with untreated varieties serving as controls. And the pot experiment was conducted to assess susceptibility of rice growth stage to the stalk eye fly artistically analyses, were employed to evaluate treatment impacts. With the treatments of different crop stages, Seedling Stage, Tillering Stage, Stem Elongation Stage, Panicle Initiation Stage, Booting, Heading, Flowering. The effect of rice growth stage on stalk eyed fly infestation showed that there is statistically significant difference among the different growth stage, tillering stage appears to be the most susceptible to Stalk-Eyed Fly infestations in terms of the impact on tiller growth in rice crops. During this stage, the mean percentage change of tillers is the highest at 59.3%, indicating a substantial impact of infestations on tiller growth. This suggests that rice crops are particularly vulnerable to stalked fly infestations during the tillering stage, highlighting the importance of effective pest management strategies during this critical growth phase to mitigate potential yield losses. In the field experiment, significant variations in yield loss were observed across treatments. The presence of dead hearts, indicative of infestation, varied notably between treated and untreated rice. Rice varieties incorporating pesticide applications demonstrated lower dead heart percentages, suggesting there is rice yield loss if the stalk-eyed fly is not controlled. Notably, treatments influenced grain yield, with insect protection measures resulting in higher yields and lower yield loss compared to controls. In conclusion, stalk-eyed fly infestation impacts rice crop productivity, particularly during vulnerable growth stages. Pesticide applications show promise in reducing infestation severity and mitigating yield loss. We recommend implementing targeted treatment strategies, focusing on susceptible growth stages, to effectively manage infestations and optimize rice crop yields.

A phenological-knowledge-independent method for automatic paddy rice mapping with time series of polarimetric SAR images

Paddy rice, which sustains more than half of the global population, requires accurate and efficient mapping to ensure food security. Synthetic aperture radar (SAR) has become indispensable in this process due to its remarkable ability to operate effectively in adverse weather conditions and its sensitivity to paddy rice growth. Phenological-knowledge-based (PKB) methods have been commonly employed in conjunction with time series of SAR images for paddy rice mapping, primarily because they eliminate the need for training datasets. However, PKB methods possess inherent limitations, primarily stemming from their reliance on precise phenological information regarding paddy rice growth. This information varies across regions and paddy rice varieties, making it challenging to use PKB methods effectively on a large spatial scale, such as the national or global scale, where collecting comprehensive phenological data becomes impractical. Moreover, variations in farming practices and field conditions can lead to differences in paddy rice growth stages even within the same region. Using a generalized set of phenological knowledge in PKB methods may not be suitable for all paddy fields, potentially resulting in errors in paddy rice extraction. To address the challenges posed by PKB methods, this study proposed an innovative approach known as the phenological-knowledge-independent (PKI) method for mapping paddy rice using time series of Sentinel-1 SAR images. The central innovation of the PKI method lies in its capability to map paddy rice without relying on specific knowledge of paddy rice phenology or the need for a training dataset. This was made possible by the incorporation of three novel metrics: VH and VV normalized maximum temporal changes (NMTC) and VH temporal mean, derived from the distinctions between paddy rice and other land cover types in time series of SAR images. The PKI method was rigorously evaluated across three regions in China, each featuring different paddy rice varieties. Additionally, the PKI method was compared with two prevalent phenological-knowledge-based techniques: the automated paddy rice mapping method using SAR flooding signals (ARM-SARFS) and the manual interpretation of unsupervised clustering results (MI-UCR). The PKI method achieved an average overall accuracy of 97.99%, surpassing the ARM-SARFS, which recorded an accuracy of 89.65% due to errors stemming from phenological disparities among different paddy fields. Furthermore, the PKI method delivered results on par with the MI-UCR, which relied on the fusion of SAR and optical image time series, achieving an accuracy of 97.71%. As demonstrated by these findings, the PKI method proves highly effective in mapping paddy rice across diverse regions, all without the need for phenological knowledge or a training dataset. Consequently, it holds substantial promise for efficiently mapping paddy rice on a large spatial scale. The source code used in this study is available at https://code.earthengine.google.com/f82cf10cad64fa3f971ae99027001a6e.

Fe (hydr)oxides and organic colloids mediate colloid-bound chromium mobilization in Cr(VI) contaminated paddy soil

The association of chromium (Cr) with colloidal particles transport in contaminated sites can affect hexavalent chromium (Cr(VI)) migration and transformation, which is an important mechanism for Cr pollutants in soil and groundwater systems. Here, we investigated colloid and particle-bound Cr migration and transformation effects on rice Cr accumulation during different rice growth stages and different redox conditions in Cr(VI) contaminated soil by pot experiment. Results showed that 13–29% of soil Cr was water dispersible colloid-bound (100–1000 nm) form during rice growth. Using transmission electron microscopy - energy dispersion spectroscopy and asymmetric flow field - flow separation, we identified colloid-bound organic matter (OM) and iron (Fe), most likely in the form of Fe (hydr)oxides - clay composites, as the primary Cr carrier. Specifically, colloid-bound Cr was mainly associated with 125–350 nm soil particle size. Under different redox conditions, colloid- and nanoparticle-bound Cr concentration decreased with increasing nanoparticles zero-valent iron (nZVI) dose. Soil reoxidation promoted the colloid- and nanoparticle-bound Cr release due to the weakly crystalline Fe-(hydr)oxides reprecipitation. Further quantitative analysis showed that colloid-bound Cr concentrations were positively correlated with colloid-bound Mn concentrations during the whole rice growth soils. Most important of all, Cr content in rice grain was positively correlated with colloid-bound Cr significantly. This study provides a quantitative and size-resolved understanding of particle-bound Cr in paddy soils, highlighting the importance of colloid-bound Cr and Fe interactions in Cr geochemical cycle of paddy soil.

Effect of Rice–Carp Coculture on Phytoplankton and Microzooplankton Community Composition in Paddy Water during Different Rice Growth Stages

Integrated rice–fish farming, an agricultural practice that combines cultivating rice and breeding fish in the same field, has attracted widespread attention. However, there is limited research on how the rice–carp coculture impacts the community structure of phytoplankton and microzooplankton in paddy water. This study employed eDNA metabarcoding sequencing to analyze the composition of phytoplankton and microzooplankton in a rice monoculture system (RM) and a rice–carp coculture system (RF). Following annotation, we identified 9 phyla, 89 families, 275 genera, and 249 species of phytoplankton, along with 20 phyla (or subphyla and classes), 85 families, 222 genera, and 179 species of microzooplankton. The alpha diversity indices revealed significantly higher richness, diversity, and evenness in the RF group compared to the RM group during grain-filling stage. Principal coordinates analysis (PCoA) demonstrated notable differences in the phytoplankton and microzooplankton compositions between the two groups across various rice growth stages. Composition analysis showed that rice–carp coculture increased the relative abundance of dominant phytoplankton phyla such as Bacillariophyta, Chrysophyta, and Euglenophyta while decreasing that of Cryptophyta. In microzooplankton, the coculture resulted in an increased abundance of Intramacronucleata (subphylum) and a decrease in Conoidasida (class). In conclusion, the rice–carp coculture enhances the diversity of plankton, particularly during the grain-filling stage, and simultaneously alters the composition and abundance of dominant plankton species in the paddy water. These findings enhance understanding of the broader impacts of integrated rice–carp farming on agricultural ecosystems, emphasizing alterations in the diversity and composition of aquatic microorganisms

Morphological variation in bulliform phytoliths at different rice growth stages

Studying morphological changes in bulliform phytoliths in rice during different growth periods can provide essential information for understanding phytolith formation mechanisms and rice domestication processes. In this study, we analysed changes in the size and fish-scale decorations of rice bulliform phytoliths during a complete growth and development cycle. We then explored the underlying plant physiology, agricultural practices, and other factors that influence rice bulliform phytolith formation. From the transplanting stage to the ripening stage, the fan width (HL) and fan length (VL) of bulliform phytoliths tended to increase, decrease, and increase, reaching a maximum at the ripening stage (HL = 40.1 ± 6.1 μm, VL = 39.7 ± 5.3 μm). From the transplanting stage to ripening, the proportion of the long-stalked phenotype decreased significantly, and that of the short-stalked phenotype increased significantly. The proportion of rice bulliform phytoliths with ≥ 9 fish-scale decorations was 0 % at the transplanting and tillering stages and then increased from 42 % to 74 % from the elongation to ripening stage, with an average of 57 % for the four periods (elongation to ripening). The results of this study enhance the existing data on rice phytolith morphology, providing valuable insights into the morphological changes associated with rice domestication.

Effects of different phosphorus and potassium supply on the root architecture, phosphorus and potassium uptake, and utilization efficiency of hydroponic rice

Phosphorus (P) and potassium (K) affect seedling growth, root configuration, and nutrient uptake in hydroponic rice, but there are few studies on all growth stages of rice. The purpose of this experiment was to determine the response characteristics of root morphology, plant physiology, and P and K uptake and utilization efficiency to different supplies of P and K. Two local conventional rice varieties (Shennong 265 and Liaojing 294) were used as experimental materials across four treatments, including HPHK (sufficient P and K supply), HPLK (sufficient P supply under low K levels), LPHK (sufficient K supply under low P levels) and LPLK (low P and K levels) in a hydroponic setting. The results showed that HPHK and HPLK significantly decreased the acid phosphatase activity of leaves and roots from full heading to filling stages when compared to LPHK and LPLK. Sufficient supply of P or K significantly increased the accumulation of P and K (aboveground, leaves, stem sheath, and whole plant) and root morphological parameters (root length, root surface area, total root volume, and tips) during major growth stages when compared to LP or LK levels. HPHK was significantly higher than other treatments in terms of dry weight and the root activity at the main growth stage, P and K uptake rates in nutrient solutions at various stages, related P and K efficiency at the maturity stage, yield, effective panicle number, and grain number per panicle. In addition, the effect of HPHK on the above indexes were significantly greater than those of single sufficient supply of P or K. In conclusion, HPHK can improve plant configuration, increase plant P and K absorption and root activity, and increase rice yield and related P and K utilization efficiency.

Spatial and Temporal Variations of Climate Resources during the Growing Season of Early-Season Rice in Hunan Province

The rising temperatures and changes in precipitation due to climate change have significantly impacted agricultural production. Evaluating the effects of climate change on rice production is crucial for improving rice cultivation techniques and ensuring food security. It is essential to comprehensively examine the climatic, spatial, and temporal variations during the duration of crop production. Previous research has mainly focused on different rice planting areas, rice types, and various growth stages of rice. However, more research is needed on the climatic changes during the crop-growing season in specific regions. Therefore, this study compiled complete daily meteorological data from 37 meteorological stations in Hunan Province from 1961 to 2020. The period from 1961 to 2020 was divided into three segments: 1961–1980 (a), 1981–2000 (b), and 2001–2020 (c), to analyze the characteristics of agricultural climate resource changes during different growth stages of early-season rice in Hunan Province. Results show that the heat resources were significantly increased (accumulated temperature growth rate of 43.36 °C/10a), the sunshine resources were decreased by −14.60 h/10a, and the precipitation resources were slightly increased by 6.85 mm/10a. The increase in heat resources mainly occurs during the vegetative growth stage of early-season rice. Additionally, the high-value regions of heat resources and precipitation in period c are 97.8% and 34.2% higher than the average values of periods a and b, respectively. In contrast, the regions with high sunshine hours significantly decreased in period c compared to periods a and b. In summary, the heat, sunshine, and water resources in the central and eastern regions of Hunan Province increase simultaneously, and appropriate cultivation measures should be adopted in the future to improve the yield and resource utilization efficiency of early-season rice in a double-cropping system.

Improvement of Flowering Stage in Japonica Rice Variety Jiahe212 by Using CRISPR/Cas9 System.

The flowering period of rice significantly impacts variety adaptability and yield formation. Properly shortening the reproductive period of rice varieties can expand their ecological range without significant yield reduction. Targeted genome editing, like CRISPR/Cas9, is an ideal tool to fine-tune rice growth stages and boost yield synergistically. In this study, we developed a CRISPR/Cas9-mediated multiplex genome-editing vector containing five genes related to three traits, Hd2, Ghd7, and DTH8 (flowering-stage genes), along with the recessive rice blast resistance gene Pi21 and the aromatic gene BADH2. This vector was introduced into the high-quality japonica rice variety in Zhejiang province, Jiahe212 (JH212), resulting in 34 T0 plants with various effective mutations. Among the 17 mutant T1 lines, several displayed diverse flowering dates, but most exhibited undesirable agronomic traits. Notably, three homozygous mutant lines (JH-C15, JH-C18, and JH-C31) showed slightly earlier flowering dates without significant differences in yield-related traits compared to JH212. Through special Hyg and Cas marker selection of T2 plants, we identified seven, six, and two fragrant glutinous plants devoid of transgenic components. These single plants will serve as sib lines of JH212 and potential resources for breeding applications, including maintenance lines for indica-japonica interspecific three-line hybrid rice. In summary, our research lays the foundation for the creation of short-growth-period CMS (cytoplasmic male sterility, CMS) lines, and also provides materials and a theoretical basis for indica-japonica interspecific hybrid rice breeding with wider adaptability.

The heading stage: A critical period for schwertmannite in reducing arsenic accumulation in rice (Oryza sativa L.)

Schwertmannite, a common iron-derived mineral, is known for its high efficiency in adsorbing As from water and reducing the mobility and availability of As in soils. However, few studies have examined the critical period for the effectiveness of schwertmannite in hindering As uptake by rice plants, particularly its impact on the uptake and transport of As across different growth stages of rice. In this study, hydroponic experiments were performed to explore the absorption and translocation of As (500 µg/L As(III) or As(V)), when combined with schwertmannite, in rice during all growth stages. The results showed that As concentration in roots, stems and leaves increased with rice growth, while the addition of schwertmannite reduced the As concentration in all parts of rice, compared to the control without schwertmannite. Besides, schwertmannite application mitigated the harmful impact of As on rice yield, and reduced As levels in grains by 66 %-90 % compared to treatments with only As(III) or As(V). The heading stage is identified as a critical period for applying schwertmannite to reduce As uptake in rice. Specifically, during the heading stages, the plants uptake 85 %-91 % of the As contents in the absence of schwertmannite. However, adding schwertmannite retained about 84 %-90 % of As content, significantly reducing its absorption by rice plants at this stage. Therefore, maintaining As adsorption by schwertmannite up to the heading stage is beneficial to effectively reduce As uptake in rice and lower As concentration in rice grains.

Foliar spray of glycine-chelated zinc (Zn) and iron (Fe) lowered the effect of macronutrient deficiencies and enhanced rice yield components, yield, and grain biofortification

The current investigation amid the alleviating of the macronutrient [Nitrogen (N), Phosphorus (P), and Potassium (K)] deficiency effects on rice yield, yield components, and grain biofortification by foliar spraying of Zn and Fe chelated by glycine amino acid (ZFCG) on the flooded rice conditions. Three-factor factorial experiment was conducted based on a randomized complete block design with three replications. The experimental factors were: macronutrients [Nitrogen (N), Phosphorous (P), and Potassium (K)] soil application at two levels (100 and 50% of the recommended dose) and foliar application of ZFCG during the booting and ripening stages at three levels (0, 1, and 1.5 kg ha−1). The results clearly showed that the foliar spraying of 1.5 kg ha−1 ZFCG significantly increased the growth characters, yield attributes, yields, and white rice nutritional quality of Hashemi cultivar both at the application of 100% (normal condition) and 50% (nutrient stresses condition) of the recommended rate of NPK. The foliar application of 1.5 kg ha−1 ZFCG increased the rice grain, straw, biological yield, head rice yield, and harvest index of the plots that received 50% of the recommended rate by about 14.6, 10.12, 50, 7.5, and 6.7% compared to the values of the control plots (no adding the NPK), respectively and 49.25, 31.21, 31.60, and 16.67% at the plots that received 100% of recommended NPK, respectively. Moreover, the foliar application of glycine amino acid-Fe and Zn chelate at two vital rice growth stages increased the value of the Zn, Fe and protein content of white rice at the plots that received 1/2 of the recommended dose of NPK by about 52.37%, 2 times, and 8.64% compared to control plots, respectively, and also 20.77%, 2 times, and 12% at the plots that received 100% of recommended NPK, respectively. The observed values are close to their values in those plots that have received 100% of recommended rate of NPK without foliar application. Therefore, it can be concluded that the foliar co-application of 1.5 kg ha−1 ZFCG during the two important rice growth stages (booting and ripening) might both alleviate the improper and imbalanced macronutrient deficiency stresses and enhance the rice grain yield and biofortification at flooded rice cultivation.

Comparative Field Evaluation and Transcriptome Analysis Reveals that Chromosome Doubling Enhances Sheath Blight Resistance in Rice

Rice sheath blight, caused by Rhizoctonia solani Kihn (R. solani), poses a significant threat to rice production and quality. Autotetraploid rice, developed through chromosome doubling of diploid rice, holds great potential for enhancing biological and yield traits. However, its resistance to sheath blight in the field has remained unclear. In this study, the field resistance of 35 autotetraploid genotypes and corresponding diploids was evaluated across three environments from 2020 to 2021. The booting stage was optimal for inoculating period based on the inoculation and analysis of R. solani at five rice growth stages. We found autotetraploids generally exhibited lower disease scores than diploids, indicating enhanced resistance after chromosome doubling. Among the 35 genotypes, 16 (45.71%) displayed increased resistance, 2 (5.71%) showed decreased resistance, and 17 (48.57%) displayed unstable resistance in different sowing dates. All combinations of the genotype, environment and ploidy, including the genotype-environment-ploidy interaction, contributed significantly to field resistance. Chromosome doubling increased sheath blight resistance in most genotypes, but was also dependent on the genotype-environment interaction. To elucidate the enhanced resistance mechanism, RNA-seq revealed autotetraploid recruited more down-regulated differentially expressed genes (DEGs), additionally, more resistance-related DEGs, were down-regulated at 24 h post inoculation in autotetraploid versus diploid. The ubiquinone/terpenoid quinone and diterpenoid biosynthesis pathways may play key roles in ploidy-specific resistance mechanisms. In summary, our findings shed light on the understanding of sheath blight resistance mechanisms in autotetraploid rice.