Soil salinity is one of the most challenging environmental factors affecting rice productivity, particularly in regions with high saline soils such as Egypt. The ability of rice to maintain high yield and quality under saline stress is often limited, leading to significant reductions in productivity. With the increasing salinization of agricultural lands, finding effective agronomic practices and treatments to mitigate salt-induced damage in rice crops is critical for ensuring food security. This study investigates the potential of exogenous glycine betaine (GB) and proline (Pro) applications to mitigate the adverse effects of salt stress on rice (cv. Sakha 108) over two consecutive growing seasons (2021-2022). Treatments of 30 mM GB and 30 mM Pro significantly enhanced dry weight (162.2 and 169.7 g in 2021 and 2022, respectively), plant height (88.94 and 99.00 cm), tiller number (10.58 and 10.33), and grain yield (4.22 and 4.30 t/ha) compared to control groups. Combined treatments of 30 mM GB and 30 mM Pro exhibited the greatest improvements across both years, with maximum dry weight (193.44 and 186.56 g), plant height (112.00 and 112.33 cm), tiller number (15.33 and 16.28), spikelet number per meter (264.00 and 264.05), thousand-kernel weight (70.00 and 73.2 g), and grain yield (6.17 and 6.64 t/ha). Additionally, the combined treatments resulted in the highest harvest index (53.22% in 2021 and 48.94% in 2022), amylose content (24.24% and 20.09%), and protein content (12.33% and 12.00%). Correlation analysis highlighted strong positive relationships among traits, such as plant height with grain yield (r = 0.94), biomass yield (r = 0.92), and harvest index (r = 0.90). Path analysis further demonstrated that thousand-kernel weight and biomass yield had the most significant direct effects on grain yield, with values of 0.43 and 0.42, respectively. Heatmap clustering and principal component analysis (PCA) confirmed the synergistic effects of combined GB and Pro treatments, with the 30P_30GB treatment consistently clustering with high-yield traits, enhancing nitrogen use efficiency and stress resilience. In conclusion, the combined application of glycine betaine and proline significantly enhances the agronomic and chemical traits of rice under salt stress. This study demonstrates that these osmoprotectants improve vegetative growth, grain yield, and quality, with synergistic effects observed at optimal concentrations. The findings highlight the potential of glycine betaine and proline as effective tools for improving salt tolerance in rice, offering practical solutions to address challenges in saline-affected agricultural regions.

Salt stress has become a major limiting factor of rice (Oryza sativa L.) yield worldwide. Appropriate nitrogen application contributes to improvement in the salt tolerance of rice. Here, we show that improvement in nitrogen-use efficiency increases salt stress tolerance in rice. Rice varieties with different nitrogen-use efficiencies were subjected to salt stress; they were stimulated with 50, 100, and 150 mmol/L of NaCl solution at the seedling stage and subjected to salinities of 0.2, 0.4%, and 0.6% at the reproductive growth stage. Compared with nitrogen-inefficient rice varieties, the nitrogen-efficient rice varieties showed significant increases in the expression levels of nitrogen-use-efficiency-related genes (TOND1 and OsNPF6.1), nitrogen content (5.1-12.1%), and nitrogen-use enzyme activities (11.7-36.4%) when under salt stress conditions. The nitrogen-efficient rice varieties showed a better adaptation to salt stress, as shown by the decrease in leaf-withering rate (4.7-10.3%), the higher chlorophyll (3.8-9.7%) and water contents (1.1-9.2%), and the better root status (7.3-9.1%) found in the rice seedlings under salt stress conditions. Analysis of physiological indexes revealed that the nitrogen-efficient rice varieties accumulated higher osmotic adjustment substances (9.7-79.9%), lower ROS (23.1-190.8%) and Na+ (15.9-97.5%) contents, higher expression levels of salt stress-related genes in rice seedlings under salt stress conditions. Furthermore, the nitrogen-efficient rice varieties showed higher yield under salt stress, as shown by a lower salt-induced decrease in 1000-grain weight (2.1-6.2%), harvest index (1.4-4.9%), and grain yield (2.8-4.1%) at the reproductive growth stage in salinized soil. Conversely, the nitrogen-efficient rice varieties showed better growth and physiological metabolism statuses under severe salt stress conditions. Our results suggest that nitrogen-efficient rice varieties could improve nitrogen-use and transport efficiency; accordingly, their use can improve the gene expression network, alleviating salt damage and improving grain yield under severe salt stress conditions.

Soil salinization has resulted in a significant decrease in crop yields, particularly affecting the production of crops like rice (Oryza sativa L.). Prohexadione calcium (Pro-Ca) can enhance crop resilience against failure by managing plant height. However, its impact on various tiller positions during the tillering phase of rice under salt stress remains unknown. This study explores the distinct effects of salt stress on the physiological traits of the main stem and different tiller segments of rice plants, along with the role of Pro-Ca in mitigating salt stress. The findings revealed that under salt stress conditions, the number of tillers and leaves on the main stem decreased significantly in rice. Moreover, the levels of malondialdehyde (MDA) and H2O2 in the leaves and stems of each tiller position notably increased. The percentage of tillers experiencing reduction or elevation was higher than that of the main stem compared to the respective control. Application of Pro-Ca through foliar spraying under NaCl stress effectively alleviated the impact of salt stress on the tiller growth of rice during the tillering phase. It also boosted the activities of antioxidant enzymes like superoxide dismutase (SOD) and peroxidase (POD) in the leaves and stems of the tillers. Furthermore, it successfully mitigated the damage inflicted by salt stress on the cell membrane of rice tillers during the tillering phase. The regulatory effect of calcium on cyclic acid was particularly pronounced in alleviating the impact on the tillers under salt stress conditions.

In recent years, the effects of fluoride (F) pollution in numerous ecosystems such as groundwater, soil, etc. Have become a major issue worldwide. This increase in F pollution is a direct consequence of the unbridled use of fertilizers in agricultural and several other human activities that require immediate and appropriate action. Therefore, this manuscript reveals important findings on the efficacy of bacteria isolated from agricultural fields in central Chhattisgarh in manifesting resistance to F and in reversing the F-induced oxidative damage in susceptible Oryza sativa L, (Var. MTU1010). Chronic exposure of Oryza sativa L. to sodium fluoride (NaF) (50 mg L- 1) severely impeded growth and various physiological parameters such as germination percentage, biomass and root and shoot length and stimulated the formation of reactive oxygen species (ROS), which enhanced electrolyte leakage and formation of cytotoxic products like malondialdehyde. To this end, potential bacterial strains, namely MT2A, MT3A, MT4A, and Du3A were isolated, screened for various plant growth promoting (PGP) traits and used to explore their efficiency to mitigate F toxicity in Oryza sativa L. in vivo. The seedlings inoculated with the bacterial strains showed significant development as evidenced by an increase in root and shoot length, biomass and chlorophyll content. Additionally, inoculation of these strains in combination with F stress significantly decreased oxidative stress by increasing the expression of protective genes encoding antioxidant enzymes and boosted agronomic traits remarkably. Overall, the manuscript demonstrates the pivotal role played by the isolated bacteria in abating ill effects of F in the Oryza sativa L. seedlings and proves their potential as protective bioagents against F stress.

Spikelet degeneration is a critical physiological issue that limits grain yield in rice (Oryza sativa L.), influenced by soil moisture conditions during meiosis. The study aimed to investigate the role and mechanism of moderate soil drying in spikelet degeneration and grain yield, as well as to establish a strategy and irrigation regime for suppressing spikelet degeneration to increase grain yield in rice. Field experiments were conducted involving two irrigation regimes: conventional well-watered (C-WW) and moderate soil drying (M-SD) during meiosis. Transgenic rice lines and chemical regulators were employed to elucidate the underlying partial biological mechanisms of this process. The results showed that M-SD regime effectively reduced spikelet degeneration rate and increased grain yield compared to C-WW. This improvement under M-SD regime was primarily attributed to the enhanced proline and aquaporin-mediated osmotic balance and redox homeostasis in young rice panicles, as well as the increased root activity during meiosis. The increased levels of brassinosteroids (BRs) and decreased levels of ethylene (ETH) in young panicles under the M-SD were closely associated with the enhanced proline and aquaporin-mediated osmotic balance and redox homeostasis, decreased oxidative damage, and reduced spikelet degeneration rate. The intrinsic relationship among key aquaporin genes expression and proline levels, osmotic balance and redox homeostasis, spikelet degeneration rate, as well as BRs and ETH levels, was further confirmed through the use of transgenic rice lines and chemical regulators. Collectively, an M-SD regime during meiosis can effectively suppress spikelet degeneration and thereby enhance grain yield, primarily through well-maintained osmotic balance and redox homeostasis in rice.

The adversities of cadmium (Cd) contamination are quite distinguished among other heavy metals (HMs), and so is the efficacy of zinc (Zn) nutrition in mitigating Cd toxicity. Rice ( Oryza sativa ) crop, known for its ability to absorb HMs, inadvertently facilitates the bioaccumulation of Cd, posing a significant risk to both the plant itself and to humans consuming its edible parts, and damaging the environment as well. The use of nanoparticles, such as nano-zinc oxide (nZnO), to improve the nutritional quality of crops and combat the harmful effects of HMs, have gained substantial attention among scientists and farmers. While previous studies have explored the individual effects of nZnO or Serendipita indica (referred to as S.i ) on Cd toxicity, the synergistic action of these two agents has not been thoroughly investigated. Therefore, the gift of nature, i.e., S. indica , was incorporated alongside nZnO (50 mg L -1 ) against Cd stress (15 mu M L -1 ) and their alliance manifested as phenotypic level modifications in two rice genotypes (Heizhan43; Hz43 and Yinni801; Yi801). Antioxidant activities were enhanced, specifically peroxidase (61.5 and 122.5% in Yi801 and Hz43 roots, respectively), leading to a significant decrease in oxidative burst; moreover, Cd translocation was reduced (85% for Yi801 and 65.5% for Hz43 compared to Cd alone treatment). Microstructural study showed a decrease in number of vacuoles and starch granules with ameliorative treatments. Overall, plants treated with nZnO displayed gene expression pattern (particularly of ZIP genes), different from the ones with alone or combined S.i and Cd. Inferentially, the integration of nZnO and S.i holds great promise as an effective strategy for alleviating Cd toxicity in rice plants. By immobilizing Cd ions in the soil and promoting their detoxification, this novel approach contributes to environmental restoration and ensures food safety worldwide.

Key message Serendipita indica induced metabolic reprogramming in colonized plants complements phosphorus-management in improving their tolerance to arsenic stress on multifaceted biological fronts. Restoration of the anthropic damage done to our environment is inextricably linked to devising strategies that are not only economically sound but are self-renewing and ecologically conscious. The dilemma of heavy metal (HM) dietary ingestion, especially arsenic (As), faced by humans and animals alike, necessitates the exploitation of such technologies and the cultivation of healthy and abundant crops. The remarkable symbiotic alliance between plants and 'mycorrhizas' has evolved across eons, benefiting growth/yield aspects as well as imparting abiotic/biotic stress tolerance. The intricate interdependence of Serendipita indica (S. indica) and rice plant reportedly reduce As accumulation, accentuating the interest of microbiologists, agriculturists, and ecotoxicological scientists apropos of the remediation mechanisms of As in the soil-AMF-rice system. Nutrient management, particularly of phosphorus (P), is also praised for mitigating As phytotoxicity by deterring the uptake of As molecules due to the rhizospheric cationic competition. Taking into consideration the reasonable prospects of success in minimizing As acquisition by rice plants, this review focuses on the physiological, metabolic, and transcriptional alterations underlying S. indica symbiosis, recuperation of As stress together with nutritional management of P by gathering case studies and presenting successful paradigms. Weaving together a volume of literature, we assess the chemical forms of As and related transport pathways, discuss As-P-rice interaction and the significance of fungi in As toxicity mitigation, predominantly the role of mycorrhiza, as well as survey of the multifaceted impacts of S. indica on plants. A potential strategy for simultaneous S. indica + P administration in paddy fields is proposed, followed by future research orientation to expand theoretic comprehension and encourage field-based implementation.

High soil salinity has an unfavorable consequence on the growth and productivity of rice crop. However, some salt-tolerant plant growth-promoting bacteria (ST-PGPB) regulate specific physiological, biochemical, and molecular properties to promote crop growth while minimizing the detrimental effects of salt stress. In this regard, we isolated ST-PGPB from rhizospheric soil and examined it to mitigate the salinity stress in rice seedlings. The growth of the bacterium at 3 M NaCl demonstrated its halotolerance, and 16S rRNA sequencing identified it as Bacillus siamensis, and the isolated strain was named BW. Further study indicated that biopriming with BW strain helps plant growth promotion-related phenotype and significantly mitigates salinity stress in rice seedlings. Treatment of rice seeds with BW resulted in significantly improved germination of seedlings at 75 mM to 150 mM NaCl, along with better physiology and biochemical parameters than the untreated ones. Furthermore, Bacillus sp. BW efficiently colonizes rice roots and produces auxin and siderophore, via forming biofilm under different salt concentrations. Under 100-200 mM NaCl treatment conditions, the extracellular metabolite profile from BW showed a substantial abundance in specific metabolites, such as osmoprotective chemicals, suggesting the likely protective mechanism against salinity stress damage. This study demonstrates the role and potential of a halotolerant- BW strain in supporting the growth of rice plants under salinity conditions.

Spikelet degeneration in rice (Oryza sativa L.) is a serious physiological defect, and can be regulated by soil moisture status and phytohormones. This study investigated the possibility that brassinosteroids (BRs) in collaboration with abscisic acid (ABA) are involved in mediating the effect of soil drying during meiosis on spikelet degeneration in rice. Three rice cultivars were field grown and three irrigation regimes including well watered (WW), moderate soil drying (MD), and severe soil drying (SD) were imposed during meiosis. MD significantly decreased spikelet degeneration in comparison with WW, due mainly to the alleviation in oxidative damage via enhancing ascorbate-glutathione (AsA-GSH) cycle activity in young panicles, and SD exhibited the opposite effects. Enhanced AsA-GSH cycle strength, decreased oxidative stress, and spikelet degeneration rate were closely associated with the synergistically elevated BR and ABA levels in young panicles in MD. In contrast, low BR and excessive ABA levels led to an increase in spikelet degeneration in SD. The three cultivars exhibited the same tendencies. The intrinsic link among AsA-GSH cycle, oxidative stress, spikelet degeneration rate, and BR and ABA levels was further verified by using transgenic rice lines and chemical regulators. BRs or ABA play a unique role in regulating spikelet degeneration. Synergistically increased BR and ABA levels in MD could work together to strengthen AsA-GSH cycle activity, leading to a reduction in oxidative damage and spikelet degeneration. On the other hand, a severe imbalance between low BR and excessive ABA levels may have contributed to the opposite effects in SD. Enhanced brassinosteroid (BR) and abscisic acid (ABA) levels in a moderate soil-drying regime during meiosis can synergistically suppress spikelet degeneration in rice, whereas a severe imbalance between low BR and excessive ABA levels in a severe soil-drying regime leads to an increase in spikelet degeneration.