Raj Kishan Agrahari

Ascorbate, a vital water-soluble antioxidant, plays a central role in scavenging reactive oxygen species (ROS) in plants under stress conditions, including iron (Fe) toxicity. Iron toxicity, primarily caused by excess ferrous ions (Fe²⁺) in flooded paddy fields, significantly limits rice (Oryza sativa L.) productivity, a staple crop for nearly two-thirds of the global population. This study explores the role of ascorbic acid in regulating iron stress responses in two contrasting rice genotypes—IR64 (sensitive) and Lachit (tolerant). Integrated physiological, biochemical, histochemical, metabolomic, and molecular analyses revealed that Lachit showed reduced Fe accumulation, lower lipid peroxidation, and enhanced ROS scavenging under Fe excess. Notably, the upregulation of key ascorbate biosynthesis genes (VTC1-3, VTC4, VTC2-like) in Lachit suggests a positive correlation between ascorbic acid production and Fe stress tolerance. Histochemical staining demonstrated higher hydrogen peroxide (H₂O₂) scavenging in Lachit, confirming better ROS detoxification. Metabolomic profiling showed elevated ascorbate levels and a suite of antioxidant metabolites contributing to improved stress resilience. Additionally, higher accumulation of secondary metabolites such as polyphenols and flavonoids across both genotypes suggests a synergistic role with ascorbate in mitigating Fe-induced oxidative stress. Collectively, these findings highlight ascorbate as a key regulator in iron stress mitigation and underscore its interaction with secondary metabolites in strengthening antioxidative defense. This study provides novel insights into ascorbate-centered mechanisms and identifies promising molecular targets for improving iron excess tolerance and productivity in rice through genetic engineering or genome editing approaches.

Abiotic stress is a major cause of the declining crop yield worldwide, especially in tropical agricultural areas. Meeting the global food demand has become a serious challenge, especially in tropical areas, because of soil acidity, Al and Fe toxicity, drought and heat stress, and climate change. In this article, we reviewed several research and review papers from Google Scholar to list the different solutions available for the mitigation of abiotic stress, especially in tropical regions where several major crops, such as maize, sorghum, wheat, rice, soybean, and millet, are affected by abiotic stress and fertilizer input. In particular, Sub-Saharan Africa (SSA) has been affected by the low use of fertilizers owing to their high cost. Therefore, soil and plant researchers and farmers have developed many techniques to mitigate the effects of stress and improve the crop yield based on the agroecological zone and crop type. Nutrient management using chemical fertilizers alone or in combination with organic crops is a strategy recommended to cope with abiotic stress and increase the crop yield, particularly in developing countries. Notably, integrated soil fertility management has been effective in semi-arid areas under drought and heat stress and in subhumid and humid areas with high soil acidity and Fe toxicity in Africa. Recent advances in the molecular physiology of various crops considered a staple food in SSA have facilitated the breeding of transgenic tolerant plants with high yield. However, the feasibility and implementation of this technique in the African continent and most tropical developing countries are major issues that can be solved via adequate subsidies and support to farmers. This review can aid in the development of novel strategies to decrease hunger and food insecurity in SSA.

Precise use of fertilizers has been a focal point in world agriculture for years because it increases crop production and reduces the negative impact of over-fertilization. Smart fertilizer management using information/data, sensors, and smart tools allows correct fertilization in precision agriculture, smart agriculture, and integrated nutrient management. Recent progress in prediction methods, such as hyperspectral imaging with machine learning, supports accurate N fertilization. In contrast, damage caused by the deficiency of several nutrients, such as Fe, K, and N, can be accurately identified by red, green, and blue (RGB) images. Current imaging technologies cannot cover all nutrients, but it has been proposed that nutrient biomarkers could be able to quantitatively predict the status of a particular nutrient with high specificity. This review presents an overview of the current approaches to plant phenotyping by imaging/sensor- and plant biomarker-technologies, and to soil analysis by imaging/sensor technologies for smart fertilizer management.

Aluminum (Al) toxicity in acidic soils is a global agricultural problem that limits crop productivity through the inhibition of root growth. However, poor management associated with the application of soil acidity amendments such as lime (CaCO₃) in certain crop types can pose a threat to low-input farming practices. Accordingly, it is important to develop appropriate techniques for the management of crop production in acidic soils. In this study, we identified ALS3 (ALUMINUM SENSITIVE 3) in soybeans (Glycine max, cultivar Toyomasari), which is highly expressed in the shoot under Al stress. GmALS3 (Glyma.10G047100) expression was found to be Al-specific under various stress conditions. We analyzed GmALS3 expression in the shoots of soybean plants grown in two different types of acidic soils (artificial and natural acidic soil) with different levels of liming and found that GmALS3 expression was suppressed with levels of liming that have been shown to eliminate soil Al³⁺ toxicity. Using soybeans as a model, we identified a potential biomarker that could indicate Al toxicity and appropriate liming levels for soybeans cultivated in acidic soils.

Plant-microbe interactions are both symbiotic and antagonistic, and the knowledge of both these interactions is equally important for the progress of agricultural practice and produce. This review gives an insight into the recent advances that have been made in the plant-microbe interaction study in the post-genomic era and the application of those for enhancing agricultural production. Adoption of next-generation sequencing (NGS) and marker assisted selection of resistant genes in plants, equipped with cloning and recombination techniques, has progressed the techniques for the development of resistant plant varieties by leaps and bounds. Genome-wide association studies (GWAS) of both plants and microbes have made the selection of desirable traits in plants and manipulation of the genomes of both plants and microbes effortless and less time-consuming. Stress tolerance in plants has been shown to be accentuated by association of certain microorganisms with the plant, the study and application of the same have helped develop stress-resistant varieties of crops. Beneficial microbes associated with plants are being extensively used for the development of microbial consortia that can be applied directly to the plants or the soil. Next-generation sequencing approaches have made it possible to identify the function of microbes associated in the plant microbiome that are both culturable and non-culturable, thus opening up new doors and possibilities for the use of these huge resources of microbes that can have a potential impact on agriculture.

To identify the upstream signaling of aluminum-induced malate secretion through aluminum-activated malate transporter 1 (AtALMT1), a pharmacological assay using inhibitors of human signal transduction pathways was performed. Early aluminum-induced transcription of AtALMT1 and other aluminum-responsive genes was significantly suppressed by phosphatidylinositol 4-kinase (PI4K) and phospholipase C (PLC) inhibitors, indicating that the PI4K-PLC metabolic pathway activates early aluminum-signaling. Inhibitors of phosphatidylinositol 3-kinase (PI3K) and PI4K reduced aluminum-activated malate transport by AtALMT1, suggesting that both the PI3K and PI4K metabolic pathways regulate this process. These results were validated using T-DNA insertion mutants of PI4K and PI3K-RNAi lines. A human protein kinase inhibitor, putatively inhibiting homologous calcineurin B-like protein (CBL)-interacting protein kinase (CIPK) and/or Ca-dependent protein kinase (CDPK) in Arabidopsis, suppressed late-phase aluminum-induced expression of AtALMT1, which was concomitant with the induction of AtALMT1 repressor, WRKY46 and suppression of AtALMT1 activator, Calmodulin-binding transcription activator 2 (CAMTA2). In addition, a human deubiquitinase inhibitor suppressed aluminum-activated malate transport, suggesting that deubiquitinases can regulate this process. We also found a reduction of aluminum-induced citrate secretion in tobacco by applying inhibitors of PI3K and PI4K. Taken all, our results indicated that phosphatidylinositol metabolism regulates organic acid secretion in plants under aluminum stress.