Halotolerant bacterial endophyte Bacillus velezensis CBE mediates abiotic stress tolerance with minimal transcriptional modifications in Brachypodium distachyon

Nitrogen and water are the primary resources limiting agricultural production worldwide. We have demonstrated the ability of a novel halotolerant bacterial endophyte, Bacillus velezensis CBE, to induce osmotic stress tolerance in Brachypodium distachyon under nitrogen-deprived conditions. Additionally, we aimed to identify the molecular factors in plants that contribute to the beneficial effects induced by B. velezensis CBE in B. distachyon. To achieve this, we conducted transcriptomic profiling using RNA-seq on 18-day-old B. distachyon seedlings treated with B. velezensis CBE in the presence or absence of available nitrogen, with and without osmotic stress. These profiles were then compared to those obtained from B. distachyon treated with known plant growth-promoting bacterial strains, Azospirillum brasilense Cd and Azoarcus olearius DQS4, under the same growth conditions. We identified differentially expressed genes (DEGs) in response to the combinations of bacterial strains and stress treatments. Interestingly, only 73 transcripts showed significant differential expression in B. velezensis CBE-treated plants under stress conditions, compared to 1,078 DEGs in plants treated with A. brasilense Cd and 2,015 DEGs in A. olearius DQS4. Our findings suggest that the novel endophyte B. velezensis CBE mediates osmotic stress tolerance in B. distachyon through the fine-tuning of molecular mechanisms with minimal transcriptional modifications.

Molecular Communication of Microbial Plant Biostimulants in the Rhizosphere Under Abiotic Stress Conditions

Microbial plant biostimulants offer a promising, sustainable solution for enhancing plant growth and resilience, particularly under abiotic stress conditions such as drought, salinity, extreme temperatures, and heavy metal toxicity. These biostimulants, including plant growth-promoting rhizobacteria, mycorrhizal fungi, and nitrogen-fixing bacteria, enhance plant tolerance through mechanisms such as phytohormone production, nutrient solubilization, osmotic adjustment, and antioxidant enzyme activation. Advances in genomics, metagenomics, transcriptomics, and proteomics have significantly expanded our understanding of plant-microbe molecular communication in the rhizosphere, revealing mechanisms underlying these interactions that promote stress resilience. However, challenges such as inconsistent field performance, knowledge gaps in stress-related molecular signaling, and regulatory hurdles continue to limit broader biostimulant adoption. Despite these challenges, microbial biostimulants hold significant potential for advancing agricultural sustainability, particularly amid climate change-induced stresses. Future studies and innovation, including Clustered Regularly Interspaced Short Palindromic Repeats and other molecular editing tools, should optimize biostimulant formulations and their application for diverse agro-ecological systems. This review aims to underscore current advances, challenges, and future directions in the field, advocating for a multidisciplinary approach to fully harness the potential of biostimulants in modern agriculture.

Impacts of Climate Change and Mitigation Strategies for Some Abiotic and Biotic Constraints Influencing Fruit Growth and Quality

Factors such as extreme temperatures, light radiation, and nutritional condition influence the physiological, biochemical, and molecular processes associated with fruit development and its quality. Besides abiotic stresses, biotic constraints can also affect fruit growth and quality. Moreover, there can be interactions between stressful conditions. However, it is challenging to predict and generalize the risks of climate change scenarios on seasonal patterns of growth, development, yield, and quality of fruit species because their responses are often highly complex and involve changes at multiple levels. Advancements in genetic editing technologies hold great potential for the agricultural sector, particularly in enhancing fruit crop traits. These improvements can be tailored to meet consumer preferences, which is crucial for commercial success. Canopy management and innovative training systems are also key factors that contribute to maximizing yield efficiency and improving fruit quality, which are essential for the competitiveness of orchards. Moreover, the creation of habitats that support pollinators is a critical aspect of sustainable agriculture, as they play a significant role in the production of many crops, including fruits. Incorporating these strategies allows fruit growers to adapt to changing climate conditions, which is increasingly important for the stability of food production. By investing in these areas, fruit growers can stay ahead of challenges and opportunities in the industry, ultimately leading to increased success and profitability. In this review, we aim to provide an updated overview of the current knowledge on this important topic. We also provide recommendations for future research.

Facing climate change: plant stress mitigation strategies in agriculture

Climate change poses significant challenges to global agriculture, with rising temperatures, altered precipitation patterns, and increased frequency of extreme weather events threatening crop yields. These changes exceed the adaptability thresholds of many crops, decreasing their yield and threatening food security. At plant physiological levels, climate change-induced stressors disrupt photosynthesis, growth, and reproductive processes, contributing to a reduced productivity. Furthermore, the negative impacts of climate change on agriculture are exacerbated by anthropogenic factors, with agriculture itself contributing significantly to greenhouse gas emissions. To mitigate these challenges, various approaches have been explored. This work reviews the most important physical, chemical, and biological strategies most commonly used in a broad range of agricultural crops. Among physical strategies, increasing water use efficiency without yield reduction through different irrigation strategies, and the use of foliar treatments with reflective properties to mitigate the negative effects of different stresses have been proven to be effective. Concerning chemical approaches, the exogenous treatment of plants with chemicals induces existing molecular and physiological plant defense mechanisms, enhancing abiotic stress tolerance. Regarding biological treatments, plant inoculation with mycorrhiza and plant growth-promoting rhizobacteria (PGPR) can improve enzymatic antioxidant capacity and mineral solubilization, favoring root and plant growth and enhance plant performance under stressful conditions. While these strategies provide valuable short- to medium-term solutions, there is a pressing need for new biotechnological approaches aimed at developing genotypes resistant to stressful conditions. Collaborative efforts among researchers, policymakers, and agricultural stakeholders are essential to ensure global food security in the face of ongoing climate challenges.

Carrabiitol®, a Novel Oligosaccharide Polyol Composition, Mitigates the Impact of Flooding, Drought, Salinity, and High Temperature in Tomato

Abiotic stress results in various physiological and biochemical changes in plants. Osmolytes play a pivotal role in improving the tolerance to abiotic stress in plants. This study evaluated the effectiveness of a commercial formulation, Carrabiitol®, an oligosaccharide polyol composition, in alleviating adverse impacts of abiotic stress in tomato (Solanum lycopersicum L. var. Arka Rakshak) plants. Plants were raised from seed and treated with 1 mL/L, 2 mL/L, and 3 mL/L of Carrabiitol®. The foliage of developing plants was treated at the 2-3 leaf stage (T2, T3, and T4) and at pre-flowering stage (T5, T6, and T7). Growth conditions were compared with those of plants developed from untreated seed (T1). Developing tomato plants were then exposed to flooding, salinity (50 mM NaCl), high temperature (41.1 °C), or drought at the flowering stage. Plants were evaluated for their dry weight, leaf water potential, stomatal conductance, transpiration rate, antioxidant potential, chlorophyll, carotenoid, glucose, sucrose, malondialdehyde, and proline contents. Pre-treated seed, which received a booster treatment at the 2-3 leaf stage (T4 = seed treatment and booster at the 2-3 leaf stage with 3 mL/L Carrabiitol®) and pre-flowering stages (T5, T6, and T7 = seed treatment and booster doses at the pre-flowering stage with 1, 2, and 3 mL/L Carrabiitol®, respectively), was effective in mitigating negative impacts on various growth parameters of stressed tomato plants (p < 0.05). Carrabiitol® may be an effective, sustainable, and bio-rational organic osmolyte formulation for reducing the effects of abiotic stress on plant growth and productivity.

CRF transcription factors in the trade-off between abiotic stress response and plant developmental processes

Climate change-induced environmental stress significantly affects crop yield and quality. In response to environmental stressors, plants use defence mechanisms and growth suppression, creating a resource trade-off between the stress response and development. Although stress-responsive genes have been widely engineered to enhance crop stress tolerance, there is still limited understanding of the interplay between stress signalling and plant growth, a research topic that can provide promising targets for crop genetic improvement. This review focuses on Cytokinin Response Factors (CRFs) transcription factor's role in the balance between abiotic stress adaptation and sustained growth. CRFs, known for their involvement in cytokinin signalling and abiotic stress responses, emerge as potential targets for delaying senescence and mitigating yield penalties under abiotic stress conditions. Understanding the molecular mechanisms regulated by CRFs paves the way for decoupling stress responses from growth inhibition, thus allowing the development of crops that can adapt to abiotic stress without compromising development. This review highlights the importance of unravelling CRF-mediated pathways to address the growing need for resilient crops in the face of evolving climatic conditions.

Ascophyllum nodosum SWE enhances root anatomy, but not POD activity in both a salt-tolerant and salt-sensitive soybean ( Glycine max) variety exposed to salt stress

There is growing evidence that seaweed extracts (SWE) may be a solution for mitigating the negative effects of salt stress on crop yield and quality, as they introduce bioactive ingredients able to regulate the expression of growth-inducing and stress-responsive genes. We demonstrate that SWE slightly ameliorated the negative physical growth effects of salt stress, especially in the root anatomy of the salt-sensitive (Clark) variety. The SWE did not stimulate or enhance peroxidase (POD) activity in either the salt-sensitive (Clark) or salt-tolerant variety (Manokin). However, a complete assessment of other antioxidant enzymes (SOD, CAT, APX) involved in the ROS detoxification process is further required.

Potential of Plant-Based Extracts to Alleviate Sorbitol-Induced Osmotic Stress in Cabbage Seedlings

In light of expected climate change, it is important to seek nature-based solutions that can contribute to the protection of our planet as well as to help overcome the emerging adverse changes. In an agricultural context, increasing plant resistance to abiotic stress seems to be crucial. Therefore, the scope of the presented research was focused on the application of botanical extracts that exerted positive effects on model plants growing under controlled laboratory conditions, as well as plants subjected to sorbitol-induced osmotic stress. Foliar spraying increased the length and fresh mass of the shoots (e.g., extracts from Taraxacum officinale, Trifolium pratense, and Pisum sativum) and the roots (e.g., Solidago gigantea, Hypericum perforatum, and Pisum sativum) of cabbage seedlings grown under stressful conditions, as well as their content of photosynthetic pigments (Pisum sativum, Lens culinaris, and Hypericum perforatum) along with total phenolic compounds (Hypericum perforatum, Taraxacum officinale, and Urtica dioica). The antioxidant activity of the shoots measured with the use of DDPH (Pisum sativum, Taraxacum officinale, Urtica dioica, and Hypericum perforatum), ABTS (Trifolium pratense, Symphytum officinale, Valeriana officinalis, Pisum sativum, and Lens culinaris), and FRAP (Symphytum officinale, Valeriana officinalis, Urtica dioica, Hypericum perforatum, and Taraxacum officinale) assays was also enhanced in plants exposed to osmotic stress. Based on these findings, the most promising formulation based on Symphytum officinale was selected and subjected to transcriptomic analysis. The modification of the expression of the following genes was noted: Bol029651 (glutathione S-transferase), Bol027348 (chlorophyll A-B binding protein), Bol015841 (S-adenosylmethionine-dependent methyltransferases), Bol009860 (chlorophyll A-B binding protein), Bol022819 (GDSL lipase/esterase), Bol036512 (heat shock protein 70 family), Bol005916 (DnaJ Chaperone), Bol028754 (pre-mRNA splicing Prp18-interacting factor), Bol009568 (heat shock protein Hsp90 family), Bol039362 (gibberellin regulated protein), Bol007693 (B-box-type zinc finger), Bol034610 (RmlC-like cupin domain superfamily), Bol019811 (myb_SHAQKYF: myb-like DNA-binding domain, SHAQKYF class), Bol028965 (DA1-like Protein). Gene Ontology functional analysis indicated that the application of the extract led to a decrease in the expression of many genes related to the response to stress and photosynthetic systems, which may confirm a reduction in the level of oxidative stress in plants treated with biostimulants. The conducted studies showed that the use of innovative plant-based products exerted positive effects on crops and can be used to supplement current cultivation practices.

Abiotic Stress Tolerance in Crop and Medicinal Plants

Climate change and the increased need for crop production highlight the urgent importance of introducing crops with increased tolerance to adverse environmental conditions [...].

Review on Pesticide Abiotic Stress over Crop Health and Intervention by Various Biostimulants

Plants are essential for life on earth, and agricultural crops are a primary food source for humans. For the One Health future, crop health is crucial for safe, high-quality agricultural products and the development of future green commodities. However, the overuse of pesticides in modern agriculture raises concerns about their adverse effects on crop resistance and product quality. Recently, biostimulants, including microecological bacteria agents and nanoparticles, have garnered worldwide interest for their ability to sustain plant health and enhance crop resistance. This review analyzed the effects and mechanisms of pesticide stress on crop health. It also investigated the regulation of biostimulants on crop health and the multiomics mechanism, combining research on nanoselenium activating various crop health aspects conducted by the authors' research group. The paper helps readers understand the impact of pesticides on crop health and the positive influence of various biostimulants, especially nanomaterials and small molecules, on crop health.

Trichoderma spp.-mediated mitigation of heat, drought, and their combination on the Arabidopsis thaliana holobiont: a metabolomics and metabarcoding approach

Introduction

The use of substances to increase productivity and resource use efficiency is now essential to face the challenge of feeding the rising global population with the less environmental impact on the ecosystems. Trichoderma-based products have been used as biopesticides, to inhibit pathogenic microorganisms, and as biostimulants for crop growth, nutrient uptake promotion, and resistance to abiotic stresses.

Methods

In this work, plant metabolomics combined with roots and rhizosphere bacterial metabarcoding were exploited to inspect the performance of Trichoderma spp. biostimulants on Arabidopsis thaliana under drought, heat and their combination and its impact on plant holobiont.

Results and discussion

An overall modulation of N-containing compounds, phenylpropanoids, terpenes and hormones could be pointed out by metabolomics. Moreover, metabarcoding outlined an impact on alpha and beta-diversity with an abundance of Proteobacteria, Pseudomonadales, Burkholderiales, Enterobacteriales and Azospirillales. A holobiont approach was applied as an integrated analytical strategy to resolve the coordinated and complex dynamic interactions between the plant and its rhizosphere bacteria using Arabidopsis thaliana as a model host species.

Alleviating Drought Stress in Brassica juncea (L.) Czern & Coss. by Foliar Application of Biostimulants-Orthosilicic Acid and Seaweed Extract

Agricultural productivity is negatively impacted by drought stress. Brassica is an important oilseed crop, and its productivity is often limited by drought. Biostimulants are known for their role in plant growth promotion, increased yields, and tolerance to environmental stresses. Silicon in its soluble form of orthosilicic acid (OSA) has been established to alleviate deteriorative effects of drought. Seaweed extract (SWE) also positively influence plant survival and provide dehydration tolerance under stressed environments. The present study was conducted to evaluate the efficacy of OSA and SWE on mitigating adverse effects of drought stress on Brassica genotype RH-725. Foliar application of OSA (2 ml/L and 4 ml/L) and SWE of Ascophyllum nodosum (3 ml/L and 4 ml/L) in vegetative stages in Brassica variety RH 725 under irrigated and rainfed condition revealed an increase in photosynthetic rate, stomatal conductance, transpirational rate, relative water content, water potential, osmotic potential, chlorophyll fluorescence, chlorophyll stability index, total soluble sugars, total protein content, and antioxidant enzyme activity; and a decrease in canopy temperature depression, proline, glycine-betaine, H₂O₂, and MDA content. Application of 2 ml/L OSA and 3 ml/L SWE at vegetative stage presented superior morpho-physiological and biochemical characteristics and higher yields. The findings of the present study will contribute to developing a sustainable cropping system by harnessing the benefits of OSA and seaweed extract as stress mitigators.

Preparation of Seaweed Nanopowder Particles Using Planetary Ball Milling and Their Effects on Some Secondary Metabolites in Date Palm (Phoenix dactylifera L.) Seedlings

Due to their distinctive physicochemical characteristics, nanoparticles have recently emerged as pioneering materials in agricultural research. In this work, nanopowders (NP) of seaweed (Turbinaria triquetra) were prepared using the planetary ball milling procedure. The prepared nanopowders from marine seaweed were characterized by particle size, zeta potential, UV-vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). When the seaweed nanopowder of Turbinaria triquetra was subjected to FT-IR analysis, it revealed the presence of different functional groups, including alkane, carboxylic acids, alcohol, alkenes and aromatics. Moreover, the methanol extract was used to identify the polyphenolic components in seaweed (NP) using high performance liquid chromatography (HPLC) and the extract revealed the presence of a number of important compounds such as daidzein and quercetin. Moreover, the pot experiment was carried out in order to evaluate the effects of prepared seaweed (NP) as an enhancer for the growth of date palm (Phoenix dactylifera L.). The date palm seedlings received four NP doses, bi-distilled water was applied as the control and doses of 25, 50 or 100 mg L^-1 of seaweed liquid NP were used (referred to as T1, T2, T3 and T4, respectively). Foliar application of liquid NP was applied two times per week within a period of 30 days. Leaf area, number of branches, dry weight, chlorophylls, total soluble sugars and some other secondary metabolites were determined. Our results indicated that the foliar application of liquid NP at T3 enhanced the growth parameters of the date palm seedlings. Additionally, liquid NP at T3 and T4 significantly increased the photosynthetic pigments. The total phenolic, flavonoid and antioxidant activities were stimulated by NP foliar application. Moreover, the data showed that the T3 and T4 doses enhanced the activity of the antioxidant enzymes (CAT, POX or PPO) compared to other treatments. Therefore, the preparation of seaweed NP using the planetary ball milling method could produce an eco-friendly and cost- effective material for sustainable agriculture and could be an interesting way to create a nanofertilizer that mitigates plant growth.

A Seaweed Extract-Based Biostimulant Mitigates Drought Stress in Sugarcane

Drought is one of the most important abiotic stresses responsible for reduced crop yields. Drought stress induces morphological and physiological changes in plants and severely impacts plant metabolism due to cellular oxidative stress, even in C4 crops, such as sugarcane. Seaweed extract-based biostimulants can mitigate negative plant responses caused by drought stress. However, the effects of foliar application of such biostimulants on sugarcane exposed to drought stress, particularly on plant metabolism, stalk and sugar yields, juice purity, and sugarcane technological quality, have received little attention. Accordingly, this study aimed to evaluate the effects of foliar application of a seaweed extract-based biostimulant on late-harvest sugarcane during the driest period of the year. Three experiments were implemented in commercial sugarcane fields in Brazil in the 2018 (site 1), 2019 (site 2), and 2020 (site 3) harvest seasons. The treatments consisted of the application and no application of seaweed extract (SWE) as a foliar biostimulant in June (sites 2 and 3) or July (site 1). The treatments were applied to the fourth ratoon of sugarcane variety RB855536 at site 1 and the fifth and third ratoons of sugarcane variety SP803290 at sites 2 and 3, respectively. SWE was applied at a dose of 500 ml a.i. ha-1 in a water volume of 100 L ha-1. SWE mitigated the negative effects of drought stress and increased stalk yield per hectare by up to 3.08 Mg ha-1. In addition, SWE increased stalk sucrose accumulation, resulting in an increase in sugar yield of 3.4 kg Mg-1 per hectare and higher industrial quality of the raw material. In SWE-treated plants, Trolox-equivalent antioxidant capacity and antioxidant enzyme activity increased, while malondialdehyde (MDA) levels decreased. Leaf analysis showed that SWE application efficiently improved metabolic activity, as evidenced by a decrease in carbohydrate reserve levels in leaves and an increase in total sugars. By positively stabilizing the plant's cellular redox balance, SWE increased biomass production, resulting in an increase in energy generation. Thus, foliar SWE application can alleviate drought stress while enhancing sugarcane development, stalk yield, sugar production, and plant physiological and enzymatic processes.

Strategies and prospects for biostimulants to alleviate abiotic stress in plants

Global climate change-induced abiotic stresses (e.g., drought, salinity, extreme temperatures, heavy metals, and UV radiation) have destabilized the fragile agroecosystems and impaired plant performance and thereby reducing crop productivity and quality. Biostimulants, as a promising and eco-friendly approach, are widely used to address environmental concerns and fulfill the need for developing sustainable/modern agriculture. Current knowledge revealed that plant and animal derived stimulants (e.g., seaweeds and phytoextracts, humic substances, and protein hydrolysate) as well as microbial stimulants (e.g., plant beneficial bacteria or fungi) have great potential to elicit plant tolerance to various abiotic stresses and thus enhancing plant growth and performance-related parameters (such as root growth/diameter, flowering, nutrient use efficiency/translocation, soil water holding capacity, and microbial activity). However, to successfully implement biostimulant-based agriculture in the field under changing climate, the understanding of agricultural functions and action mechanism of biostimulants coping with various abiotic stresses at physicochemical, metabolic, and molecular levels is needed. Therefore, this review attempts to unravel the underlying mechanisms of action mediated by diverse biostimulants in relation to abiotic stress alleviation as well as to discuss the current challenges in their commercialization and implementation in agriculture under changing climate conditions.