Search Results (428)

Napier grass (Cenchrus purpureus Schumach) is an important forage crop and livestock feed. However, its yield and quality in Kenya are often limited by Napier grass headsmut and stunt disease. Napier grass genetic improvements through mutation breeding and selection could avail cultivars with increased forage. This study investigated the response of embryogenic calli to different levels of colchicine in inducing polyploidy in the two germplasms of Napier grass; South africa and Bana grass. The experiments were carried out as a factorial experiment in a completely randomized design (CRD). The colchicine concentrations used were 0, 0.05, 0.1, and 0.2%, and the exposure durations were 24, 48, and 72 h. During the shoot regeneration stage, culturing explants on an MS medium (Murashige and Skoog) supplemented with 0.2 mg L⁻¹ Benzyl Adenine (BAP), 0.1 mg L⁻¹ dichlorophenoxyacetic acid (2, 4-D), and 0.1 mg L⁻¹ indole-3-butyric acid (IBA) was more suitable for shoot regeneration. Chromosome doubling was confirmed by genomic DNA and the stomata size and number. Culturing explants on an MS medium supplemented with 1 mg L⁻¹ IBA, 1 mg L⁻¹ 2, 4-D, and 0.5 mg L⁻¹ BAP was more suitable in inducing embryogenic calli in both genotypes. Polyploidy results revealed that a 0.1% concentration of colchicine with two days of treatment established the maximum number of octoploid plantlets induced in vitro, while a 0.2% concentration was very toxic. The stomata size and number of derived octoploid plantlets were bigger with a lower density, a shorter plant height, and a smaller stem diameter, and despite being the first to produce tillers, they were significantly higher than their progenitors. Induced mutants also had a significantly higher number of chromosomes and showed different band patterns and distances during gel electrophoresis. However, we recommend the use of flow cytometry to confirm the ploidy level. The superior mutant plantlets can be selected and recommended for characterization across representative agro-ecologies for large-scale production and used in Cenchrus purpureus breeding programs in Kenya and its environments. Full article

Climate change alters climatic factors, which in turn affect the suitability of crops to grow. Winter wheat is a major crop in the Beijing-Tianjin-Heibei region of China. To assess the climate factors on winter wheat production, the meteorological data (temperature, precipitation, sunshine, etc.) from 25 stations in the target region the Beijing-Tianjin-Hebei region of China from 1961 to 2010, the winter wheat yield data from 1978 to 2010, and the growth stages were used. A model of the suitability of light, temperature, and water was subsequently developed to quantitatively analyze the spatial and temporal variability of the suitability of the winter wheat to the climate of the region. Temperature suitability was high during the sowing and grouting periods (temperature suitability peaks at 0.941 during grouting) and lowest in the rejuvenation period. In terms of spatial distribution, it is strong in the south and low in the north, and it exhibits a gradual increase in interannual variation. Precipitation suitability fluctuates steadily, with a peak in the tillering stage and a trough in the jointing stage. In terms of spatial distribution, it is highest in the northeast and decreases in the west; in inter-annual changes, it fluctuates strongly with weak overall growth. Sunshine suitability is stable at 0.9 or above. In spatial distribution, it is high in the northwest and low in the southeast, and it decreases slowly in the interannual variations. The trend of climatic suitability is consistent with temperature and precipitation, showing a pattern of falling first and then rising. In terms of spatial distribution, the overall climate suitability is high in the south and low in the north. In inter-annual changes, climate suitability generally increases slowly. Temperature and precipitation are key factors. Moisture stress became the most important factor for winter wheat cultivation in the region. Sunshine conditions are typically sufficient. This study provides a theoretical basis for a rational layout of winter wheat growing areas in the Beijing-Tianjin-Hebei region and the full utilization of climatic resources. Full article

Micro-sprinkling fertigation, a novel irrigation and fertilization way, can improve the grain yield (GY) and nitrogen use efficiency (NUE) of winter wheat to meet sustainable agriculture requirements. In order to clarify the physiological basis behind the improvements, a field experiment with a split-plot design was conducted during the 2020–2021 and 2021–2022 growing seasons. The main plot encompassed two irrigation and fertilization modes, namely, conventional irrigation and fertilization (CIF) and micro-sprinkling fertigation (MSF), and the subplots included four nitrogen application rates (0, 120, 180, and 240 kg ha⁻¹, denoted as N0, N120, N180, and N240, respectively). Moreover, a ¹⁵N isotopic tracer experiment was performed to determine the distributions of nitrogen in the soil. Compared with those under CIF, the GY under MSF at N180 and N240 significantly increased by 9.09% and 9.72%, which was driven mainly by increases in the grain number (GN) and thousand-grain weight (TGW). The increase in the TGW under MSF was the result of the significantly increased net photosynthesis rate at the grain-filling stage. Notably, the number and dry weight of inefficient tillers and the number of ears with fewer than 10 grains were significantly lower under MSF than those under CIF. In addition, the ¹⁵N isotopic tracer experiment revealed that nitrogen was primarily concentrated in the 0–30 cm soil layers under MSF, which conforms well with the spatial distributions of the roots and water, and subsequently improved the NUE under N180 and N240. In conclusion, MSF enhanced both the GY and NUE at the N180 level by optimizing root–water–nitrogen spatiotemporal coordination and reducing redundant tillering. Full article

Global food security is increasingly challenged by climate change and the availability of arable land. This situation calls for improved crop monitoring and management strategies. Rice is a staple food for nearly half of the world’s population and a significant source of calories. Accurately identifying rice varieties is crucial for maintaining varietal purity, planning agricultural activities, and enhancing genetic improvement strategies. This study evaluates the effectiveness of machine learning algorithms to identify the most effective approach to predicting rice varieties, using multitemporal Sentinel-2 images in the Marismas del Guadalquivir of Sevilla, Spain. Spectral reflectance data were collected from ten Sentinel-2 bands, which include visible, red-edge, near-infrared, and shortwave infrared regions, at two key phenological stages: tillering and reproduction. The models were trained on pixel-level data from the growing seasons of 2021 and 2024, and they were evaluated using a test set from 2022. Four classifiers were compared: random forest, XGBoost, K-nearest neighbors, and logistic regression. Performance was assessed based on accuracy, precision, recall, specificity and F1 score. Non-linear models outperformed linear ones. The highest performance was achieved with the Random Forest classifier during the reproduction phase, reaching an exceptional accuracy of 0.94 using all bands or only the most informative subset (red edge, NIR, and SWIR). This classifier also maintained excellent accuracy (0.93 and 0.92) during the initial tillering phase. This fact demonstrates that it is possible to perform reliable varietal mapping in the early stages of the growing season. Full article

Potassium (K) is a critical macronutrient for sugarcane (Saccharum spp.), playing a vital role in metabolic processes, sucrose accumulation, and yield formation. Herein, this study systematically evaluated the effects of potassium oxide (K₂O) application on sugarcane (cultivar YZ1696) growth at the seedling and tillering stages. Hydroponic experiments demonstrated that 6 mmol/L K₂O optimally promoted seedling growth, whereas field trials revealed that 150 kg/ha K₂O maximized growth rate, yield, and sucrose content. Sugarcane growth exhibited a biphasic response—stimulation followed by inhibition—with increasing K₂O dosage at both developmental stages. Transcriptomic profiling of sugarcane roots under low-potassium (K-deficient), optimal potassium, and high-potassium conditions identified 10,266 differentially expressed genes (DEGs), with the most pronounced transcriptional shifts occurring under K deficiency. Functional enrichment analysis identified DEGs associated with potassium transport, calcium signaling, and carbohydrate metabolism. Notably, potassium uptake was mediated by distinct mechanisms: Shaker family channels (AKT1, AKT2, SPIKE) and the TPK family member KCO1 were induced under optimal K supply, whereas HAK/KUP/KT transporters (HAK1/5/10/21/25) exhibited broad activation across K concentrations, underscoring their key role in K homeostasis. Furthermore, calcium signaling genes (e.g., CIPK23) displayed K-dependent expression patterns. Weighted gene co-expression network analysis identified key gene modules that correlated strongly with agronomic traits, including plant height, yield, and sucrose content. Optimal K conditions favored the expression of yield- and sucrose-associated genes, suggesting a molecular basis for K-mediated productivity enhancement. Our findings revealed the genetic and physiological mechanisms underlying K-dependent sugarcane improvement, providing actionable insights for precise potassium fertilization to maximize the yield and sugar content. Full article

Nitrogen (N) availability significantly influences plant metabolism and productivity. The aim of this study was to assess the effects of low N stress and subsequent N supplementation on key enzymes of nitrogen metabolism, nitrogen metabolism-related substances, and chlorophyll a fluorescence kinetic parameters in rice genotypes with different nitrogen utilization efficiencies. We used the Jijing 88 (low-N tolerant) and Xinong 999 (low-N sensitive) as test materials. During the seedling, tillering, and booting stages, the 1/2N and 1/4N treatments were restored to the 1N treatment level. Nine treatments were used in this experiment: CK (1N), A1 (1/2N), A2 (1/2N restored to 1N during the seedling stage), A3 (1/2N restored to 1N during the tillering stage), A4 (1/2N restored to 1N during the booting stage), B1 (1/4N), B2 (1/4N restored to 1N during the seedling stage), B3 (1/4N restored to 1N during the tillering stage), and B4 (1/4N restored to 1N during the booting stage). Key physiological responses, nitrogen compounds, enzymes activities, and chlorophyll a fluorescence kinetics were analyzed. Under low nitrogen conditions, the growth and nitrogen assimilation of rice were inhibited. Compared to XN 999, JJ 88 maintains higher levels of dry matter, nitrate reductase activity (NR), glutamine synthetase activity (GS), glutamate oxaloacetate transaminase activity (GOT), glutamate pyruvate transaminase activity (GPT), as well as nitrate (NO₃⁻) and ammonium (NH₄⁺) nitrogen contents. After N supplementation during the early growth stage, both JJ 88 and XN 999 exhibit recovery capabilities. However, in the late growth stage, JJ 88 demonstrates superior recovery capabilities. In addition to enhancing nitrogen metabolism levels, there is also an increase in the content of osmotic regulation substances such as soluble sugars, free amino acids, and proline, along with responses in chlorophyll fluorescence kinetic parameters. This was primarily manifested in the enhancement of performance index (PI_ABS, PI_total), and quantum yield (φ_EO, φ_RO, ψ_EO), which maintain photosynthetic performance and electron transport efficiency. The research findings indicated that reducing N supply during the early growth stage and restoring N levels in the later stage are beneficial for the recovery of low-nitrogen-tolerant rice varieties. Therefore, in the context of sustainable agricultural production, the breeding of low-nitrogen-tolerant rice varieties and the optimization of N fertilizer management are crucial. Full article

Remote sensing is a widely used tool for crop monitoring to improve water management. Rice, a crop traditionally grown under flooded conditions, requires farmers to understand the relationship between crop reflectance, water depth and final yield. This study focused on seven commercial rice fields in 2022 and six in 2023, analyzing the correlations between water depth and Sentinel-2 reflectance over two growing seasons in Valencia, Spain. During the tillering stage across both seasons, water depth showed positive correlations with visible bands and negative correlations with NIR and SWIR bands. There were no correlations with the indices NDVI, GNDVI, NDRE and NDWI. The NIR band showed significant correlations across both seasons, with R² values of 0.69 and 0.71, respectively. In addition, the calculation of NIR anomalies for each field proved to be a good indicator of final yield anomalies. In 2022, anomalies above 10% corresponded to yield deviations above 500 kg·ha⁻¹, while in 2023, anomalies above 15% were associated with yield deviations above 1000 kg·ha⁻¹. The response of final yield to water level was positive up to average values of 9 cm. The use of the NIR band during the rice crop tillering stage can support farmers in improving irrigation management. Full article

This study investigated the impact of nitrogen (N) fertilization on the yield and grain filling (GF) characteristics of two conventional japonica rice varieties with distinct panicle types: Yangchan 3501 (large-panicle: spikelets per panicle $> 150$) and Nangeng 46 (medium-panicle: $100 <$ spikelets per panicle $< 150$). Field experiments were conducted over two growing seasons (2022–2023) with three N application rates (T1: 225 kg ha⁻¹, T2: 270 kg ha⁻¹, T3: 315 kg ha⁻¹). Key measurements included tiller dynamics, panicle composition, GF parameters modeled using the Richards equation, and enzyme activities related to nitrogen metabolism (Fd-GOGAT, NR) and carbohydrate transport (α-amylase, SPS). Results showed that the yield increased with higher N levels for both varieties, with Yangchan 3501 achieving higher yields primarily through increased grains per panicle (15.65% rise under T3 vs. T1), while Nangeng 46 relied on panicle number (8.83% increase under T3 vs. T1). Nitrogen application enhanced Fd-GOGAT and NR activities, prolonging photosynthesis and improving GF rates, particularly in the inferior grains of Yangchan 3501 during middle and late stages. However, a high N reduced seed-setting rates and 1000-grain weight, with larger panicle types exhibiting a greater sensitivity to N-induced changes in branch structure and assimilate allocation. This study highlights that optimizing N management can improve nitrogen-metabolism enzyme activity and GF efficiency, especially in large-panicle rice, while medium-panicle types require higher N inputs to maximize panicle number. These findings provide actionable insights for achieving high yields and efficient nutrient use in conventional rice cultivation. Full article

Accurately estimating leaves’ relative chlorophyll contents (widely represented by Soil and Plant Analysis Development (SPAD) values) across growth stages is crucial for assessing crop health, particularly in regions characterized by varying sowing dates. Unlike previous studies focusing on high-resolution UAV imagery or specific growth stages, this research incorporates satellite-derived texture indices (TIs) into a SPAD value estimation model applicable across multiple growth stages (from tillering to grain-filling). Field experiments were conducted in Jiangsu Province, China, where winter wheat sowing dates varied significantly from field to field. Sentinel-2 imagery was employed to extract vegetation indices (VIs) and TIs. Following a two-step variable selection method, Random Forest (RF)-LassoCV, five machine learning algorithms were applied to develop estimation models. The newly developed model (SVR-RBF_VIs+TIs) exhibited robust estimation performance (R² = 0.8131, RMSE = 3.2333, RRMSE = 0.0710, and RPD = 2.3424) when validated against independent SPAD value datasets collected from fields with varying sowing dates. Moreover, this optimal model also exhibited a notable level of transferability at another location with different sowing times, wheat varieties, and soil types from the modeling area. In addition, this research revealed that despite the lower resolution of satellite imagery compared to UAV imagery, the incorporation of TIs significantly improved estimation accuracies compared to the sole use of VIs typical in previous studies. Full article

The utilization of saline–alkali land for rice cultivation is critical for global food security. However, most existing studies on rice salt tolerance focus on the seedling stage, with limited insights into tolerance mechanisms during reproductive growth, particularly at the panicle initiation stage (PI). Leveraging precision salinity-control facilities, this study imposed four salt stress gradients (0, 3, 5, and 7‰) to dissect the differential response mechanisms of six rice varieties (YXYZ: Yuxiangyouzhan, JLY3261: Jingliangyou3261, SLY91: Shuangliangyou91, SLY138: Shuangliangyou138, HLYYHSM: Hualiangyouyuehesimiao, and SLY11:Shuangliangyou111) during PI. The results revealed that increasing salinity significantly reduced tiller number (13.14–68.04%), leaf area index (18.58–57.99%), canopy light interception rate (11.91–44.08%), and net photosynthetic rate (2.63–52.42%) (p < 0.001), accompanied by reactive oxygen species (ROS)-induced membrane lipid peroxidation. Integrative analysis of field phenotypic and physiological indices revealed distinct adaptation strategies: JLY3261 rapidly activated antioxidant enzymes under 3‰ salinity, alleviating lipid peroxidation (no significant difference in H₂O₂ or malondialdehyde content compared to 0‰ salinity) and maintaining tillering and aboveground biomass. SLY91 tolerated 7‰ salinity via CAT/POD-mediated lipid peroxide degradation, with H₂O₂ and malondialdehyde contents increasing initially but decreasing with escalating stress. These findings highlight genotype-specific antioxidant strategies underlying salt-tolerance mechanisms and the critical need for integrating phenomics–physiological assessments at reproductive stages into salt-tolerance breeding pipelines. Full article

Accurate phenological information on sugarcane is crucial for guiding precise cultivation management and enhancing sugar production. Remote sensing offers an efficient approach for large-scale phenology retrieval, but most studies have primarily focused on staple crops. The methods for retrieving the sugarcane phenology—the germination, tillering, elongation, and maturity stages—remain underexplored. This study addresses the challenge of accurately monitoring the sugarcane phenology in complex terrains by proposing an optimized strategy integrating spatiotemporal fusion data. Ground-based validation showed that the change detection method based on the Double-Logistic curve significantly outperformed the threshold-based approach, with the highest accuracy for the elongation and maturity stages achieved at the maximum slope points of the ascending and descending phases, respectively. For the germination and tillering stages with low canopy cover, a novel time-windowed change detection method was introduced, using the first local maximum of the third derivative curve (denoted as Point A) to establish a temporal buffer. The optimal retrieval models were identified as 25 days before and 20 days after Point A for germination and tillering, respectively. Among the six commonly used vegetation indices, the NDVI (normalized difference vegetation index) performed the best across all the phenological stages. Spatiotemporal fusion using the ESTARFM (Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model) significantly improved the monitoring accuracy in heterogeneous agricultural landscapes, reducing the RMSE (root-mean-squared error) by 21–46%, with retrieval errors decreasing from 18.25 to 12.97 days for germination, from 8.19 to 4.41 days for tillering, from 19.17 to 10.78 days for elongation, and from 19.02 to 15.04 days for maturity, highlighting its superior accuracy. The findings provide a reliable technical solution for precision sugarcane management in heterogeneous landscapes. Full article

Straw returning inhibits tillering at the early stage of rice growth and thus affects grain yield. Sulfur-coated urea (SCU) has been expected to increase nitrogen use efficiency (NUE) and yield, save labor input, and reduce environmental pollution in crop production. Nevertheless, the sulfur coatings of SCU are easy to break and then shorten the nutrient release cycle. Whether there was a complementary effect between straw returning and SCU in NUE and grain yield had remained elusive. To investigate the effects of straw returning combined with the application of SCU on NUE and rice yield, a two-year field experiment was conducted from 2022 to 2023 with three treatments (straw returning combined with conventional urea (SRU), no straw returning combined with SCU (NRS), straw returning combined with SCU (SRS)). We found that straw returning combined with the application of SCU increased rice yield and NUE significantly. Compared with SRU and NRS, SRS treatments significantly increased grain yield by 14.61–16.22%, and 4.14–7.35%, respectively. Higher effective panicle numbers per m² and grain numbers per panicle were recorded in NRS and SRS treatments than SRU. SRS treatment increased nitrogen recovery efficiency by 79.53% and 22.97%, nitrogen agronomic efficiency by 18.68% and 17.37%, and nitrogen partial factor productivity by 10.51% and 9.81% compared with SRU and NRS treatment, respectively. The enhanced NUE in SRS was driven by higher leaf area index, SPAD value, net photosynthetic rate, carbon metabolic enzyme (RuBP and SPS) activity, nitrogen metabolic enzyme (NR, GS, and GOGAT) activity, sucrose and nitrogen content in leaves, and nitrogen accumulation in plant during grain filling. Moreover, the improved yield in SRS was closely related to superior NUE. In conclusion, straw returning combined with application of SCU boosted grain yield and NUE via enhanced carbon–nitrogen metabolism during the late growth period in rice. Full article

Qingke (Hordeum vulgare L. var. nudum Hook. f.), a staple crop in the Tibetan Plateau, suffers from severe yield reduction under continuous cropping (by 38.67%), yet the underlying mechanisms remain unclear. This study systematically investigated the effects of 23-year continuous cropping (23y-CC) on the nutrient dynamics, carbohydrate metabolism, and enzymatic activities in Qingke leaves across five developmental stages (T1: seedling; T2: tillering; T3: jointing; T4: flowering; T5: filling). Compared to the control (first-year planting), 23y-CC significantly reduced leaf nitrogen (N), phosphorus (P), and potassium (K) contents by 60.94%, 47.96%, and 60.82%, respectively, at early growth stages. Key nitrogen-metabolizing enzymes, including glutamate synthase (GOGAT), glutamine synthase (GS), and nitrate reductase (NR), exhibited reduced activities under 23y-CC, indicating impaired nitrogen assimilation. Carbohydrate profiling revealed lower starch and glucose contents but higher sucrose accumulation in later stages (T4–T5) under 23y-CC, accompanied by the dysregulation of sucrose synthase (SS) and invertase activities. These findings elucidate how continuous cropping disrupts nutrient homeostasis and carbon allocation, ultimately compromising Qingke productivity. This study provides novel insights into agronomic strategies for mitigating continuous cropping obstacles in Qingke. Full article

Arsenic (As) and cadmium (Cd) in rice grains are major global food safety concerns. Iron (Fe) can help reduce both, but current Fe treatments suffer from poor stability, low leaf absorption, and fast soil immobilization, with unclear underlying mechanisms. To address these issues, an Fe-based metal–organic framework (MIL-88) was modified with sodium alginate (SA) to form MIL-88@SA. Its stability as a foliar inhibitor and its leaf absorption were tested, and its effects on As and Cd accumulation in rice were compared with those of soluble Fe (FeCl₃) and chelating Fe (HA + FeCl₃) in a field study on As–Cd co-contaminated rice paddies. Compared with the control, MIL-88@SA outperformed or matched the other Fe treatments. A single foliar spray during the tillering stage increased the rice yield by 19% and reduced the inorganic As and Cd content in the grains by 22.8% and 67.8%, respectively, while the other Fe treatments required two sprays. Its superior performance was attributed to better leaf affinity and thermal stability. Laser ablation inductively coupled plasma–mass spectrometry (LA–ICP–MS) and confocal laser scanning microscopy (CLSM) analyses revealed that Fe improved photosynthesis and alleviated As–Cd stress in leaves, MIL-88@SA promoted As and Cd redistribution, and Fe–Cd co-accumulation in leaf veins enhanced Cd retention in leaves. Full article

Belowground buds play a vital role in the clonal propagation and structural regulation of perennial herbaceous plants, especially in alpine environments, where vegetative renewal depends heavily on bud bank dynamics. However, the interactive effects of nitrogen addition and phenological stages on bud development and aboveground branching remain poorly understood. In this study, we examined the responses of rhizome buds, tiller buds, and aboveground tiller types of Kentucky bluegrass to six nitrogen levels (0, 6, 9, 12, 15, and 18 g/m²) across five growth stages on the Qinghai–Tibet Plateau. The results showed that moderate nitrogen input (N2, 9 g/m²) significantly enhanced total bud density, particularly at the heading and maturity stages, indicating a threshold response. Aboveground reproductive tiller density peaked at N2 (9 g/m²), while vegetative and total tiller densities plateaued beyond N3 (12 g/hm²), suggesting a diminishing marginal effect of nitrogen on aboveground tiller density. Furthermore, bud density showed stage-specific correlations with tiller types: vegetative tillers were primarily influenced at the heading stage, and reproductive tillers were mainly influenced at the mature stage, with weakened associations in senescence. These findings highlight the phenological specificity and non-linear response of clonal grass regeneration to nitrogen input and provide a theoretical basis for optimizing nutrient management in cold alpine grasslands. Full article