Seed priming with Beauveria bassiana improves growth and salt stress response in rice

Islam S.M., Chowdhury M.Z., Mim M.F., Momtaz M.B., Islam T.

AbstractThe entomopathogenic fungus (EPF), Beauveria bassiana, is reported as the most potent biological control agent against a wide range of insect families. This study aimed to isolate and characterize the native B. bassiana from various soil habitats in Bangladesh and to evaluate the bio-efficacy of these isolates against an important vegetable insect pest, Spodoptera litura. Seven isolates from Bangladeshi soils were characterized as B. bassiana using genomic analysis. Among the isolates, TGS2.3 showed the highest mortality rate (82%) against the 2nd instar larvae of S. litura at 7 days after treatment (DAT). This isolate was further bioassayed against different stages of S. litura and found that TGS2.3 induced 81, 57, 94, 84, 75, 65, and 57% overall mortality at egg, neonatal 1st, 2nd, 3rd, 4th, and 5th instar larvae, respectively, over 7 DAT. Interestingly, treatment with B. bassiana isolate TGS2.3 resulted in pupal and adult deformities as well as decreased adult emergence of S. litura. Taken together, our results suggest that a native isolate of B. bassiana TGS2.3 is a potential biocontrol agent against the destructive insect pest S. litura. However, further studies are needed to evaluate the bio-efficacy of this promising native isolate in planta and field conditions.

Metwally R.A., Soliman S.A.

Abstract Background Trichoderma viride are well known for their biocontrol capabilities, but little is known about how they stimulate plant development and increase their resistance to salt stress. One of the main abiotic factors limiting crop development and yield is salt stress. Therefore, the purpose of this work was to ascertain how NaCl effects on T. viride growth as well as on the seedlings morphological and physio-biochemical parameters of tomato (Solanum lycopersicum L.) under plate culture conditions. Additionally, a pot experiment was conducted to determine how T. viride affected the development characteristics of tomato plants subjected to various salt concentrations (50 and 100 mM NaCl). T. viride's contribution to tomato seedling stress tolerance was also closely examined. Results Results showed that 100 mM NaCl decreased the colony diameter of T. viride by 13.4% compared to the control. Under plate and greenhouse conditions, tomato seedlings exposed to salt exposure exhibited an overall decline in growth. Also, a reduction in relative water content (RWC) and protein contents occurred under salt stress. At the same time, increases were found in proline, total phenolics, flavonoids, H2O2 content, malondialdehyde, likewise the activities of peroxidase (POD), catalase (CAT), polyphenol oxidase (PPO), and ascorbate peroxidase (APX) enzymes. Even though, with T. viride application, the salt negative effects on both morphological and physio-biochemical parameters were mitigated to a greater extent. T. viride increased proline and total antioxidant capacity (TAC) in tomato seedlings at 100 mM NaCl by an average of 20.66 and 43.82% compared to their comparable control. T. viride increased the activities of CAT, PPO, and APX enzymes by 74.6, 58.48, and 61.61% at 50 mM NaCl compared to non-saline control seedlings. As well, T. viride decreased MDA and H2O2 contents by an average of 14 and 24.8% in tomato seedlings at 50 mM NaCl compared to their comparable control. Also, under 100 mM NaCl, the T. viride-treated tomato seedlings showed increased total phenolics (17.85%) and flavonoids (33.17%) compared to non- treated one. Conclusion Hence, our research sheds new insight on the pathways by which T. viride can boost tomato seedling tolerance to salt stress at morphological and physio-biochemical levels by activating both enzymatic and non-enzymatic antioxidant defense systems.

Mostofa M.G., Rahman M.M., Ghosh T.K., Kabir A.H., Abdelrahman M., Rahman Khan M.A., Mochida K., Tran L.P.

Potassium (K) is an integral part of plant nutrition , playing essential roles in plant growth and development . Despite its abundance in soils, the limitedly available form of K ion (K + ) for plant uptake is a critical factor for agricultural production. Plants have evolved complex transport systems to maintain appropriate K + levels in tissues under changing environmental conditions. Adequate stimulation and coordinated actions of multiple K + -channels and K + -transporters are required for nutrient homeostasis , reproductive growth, cellular signaling and stress adaptation responses in plants. Various contemporary studies revealed that K + -homeostasis plays a substantial role in plant responses and tolerance to abiotic stresses. The beneficial effects of K + in plant responses to abiotic stresses include its roles in physiological and biochemical mechanisms involved in photosynthesis , osmoprotection, stomatal regulation, water-nutrient absorption, nutrient translocation and enzyme activation . Over the last decade, we have seen considerable breakthroughs in K research, owing to the advances in omics technologies. In this aspect, omics investigations (e.g., transcriptomics , metabolomics , and proteomics) in systems biology manner have broadened our understanding of how K + signals are perceived, conveyed, and integrated for improving plant physiological resilience to abiotic stresses. Here, we update on how K + -uptake and K + -distribution are regulated under various types of abiotic stress. We discuss the effects of K + on several physiological functions and the interaction of K + with other nutrients to improve plant potential against abiotic stress-induced adverse consequences. Understanding of how K + orchestrates physiological mechanisms and contributes to abiotic stress tolerance in plants is essential for practicing sustainable agriculture amidst the climate crisis in global agriculture. • Potassium ion (K + ) is the most abundant cation required for plant growth and survival. • K + -transport and -signaling play crucial roles in plant abiotic stress responses. • K + controls multiple physiological processes, such as stomatal regulation and osmoprotection. • K + interacts with phytohormones and other nutrients for plant adaptation to abiotic stresses. • K + -use-efficiency is requisite to enhance crop performance under stressful conditions.

Singh D.

• Respiratory burst oxidase homologues (RBOHs) through localized ROS bursts regulate multitude of signal transduction pathways. • ROS level is attuned by specific mechanisms enabling reduction in the oxidative burst and ROS-scavenging systems. • ROS signaling network induces salinity tolerance at the cellular and whole-plant levels. • ROS and NO are involved in enhancement of antioxidant systems and interaction with other signaling molecules, such as MAPK, plant hormones, and calcium. • RNAi-mediated gene regulation and CRISPR/Cas9 system for gene editing provide efficient targeted modification for resistance to different stresses in many crops. Even under optimal conditions many metabolic processes produce ROS like superoxide anion (O 2 . - ), hydrogen peroxide (H 2 O 2 ) and hydroxyl radicals (OH ⋅ ), particularly in chloroplast and mitochondria. The overproduction of ROS (O 2 . - , H 2 O 2, OH . , RCO etc.) results from the exposure to various environmental conditions like dehydration, heat, salinity and biotic stresses. All biomolecules like lipids, proteins and DNA are extensively damaged by the reactive oxygen species which disrupts the cell integrity further leading to its death. Plants possess both enzymic and non-enzymatic mechanism for scavenging ROS. The enzymic mechanisms are designed to minimize the concentration of O 2 and H 2 O 2 . The overproduced enzymes are superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), glutathione reductase (GR) and glutathione-synthesizing enzymes. Several evidences have shown that although oxidative stress is a lethal situation for cell by ROS (especially H 2 O 2 and O 2 ⋅ - , it may be involved in cellular signaling procedure as second messenger to induce a large number of genes and produce proteins and osmoprotectant involved in salt stress defenses. This review gives an insight into the recent advancements on how antioxidant defense machinery, the antioxidant enzymes and the non-antioxidant metabolites work together to alleviate the negative effects of ROS and cross-talk with reactive sulfur nitrogen and carbomyl species which also act as an important signal molecule. This comprehensive knowledge about ROS action, their regulation through antioxidant machinery, interactions with RNS, RSS and RCS and in signal transduction will empower us in the development of salinity tolerant plants.

Jamil F., Mukhtar H., Fouillaud M., Dufossé L.

Rhizospheric plant–microbe interactions have dynamic importance in sustainable agriculture systems that have a reduced reliance on agrochemicals. Rhizosphere signaling focuses on the interactions between plants and the surrounding symbiotic microorganisms that facilitate the development of rhizobiome diversity, which is beneficial for plant productivity. Plant–microbe communication comprises intricate systems that modulate local and systemic defense mechanisms to mitigate environmental stresses. This review deciphers insights into how the exudation of plant secondary metabolites can shape the functions and diversity of the root microbiome. It also elaborates on how rhizosphere interactions influence plant growth, regulate plant immunity against phytopathogens, and prime the plant for protection against biotic and abiotic stresses, along with some recent well-reported examples. A holistic understanding of these interactions can help in the development of tailored microbial inoculants for enhanced plant growth and targeted disease suppression.

Huchzermeyer B., Menghani E., Khardia P., Shilu A.

Based on the origin, we can classify different types of stress. Environmental factors, such as high light intensity, adverse temperature, drought, or soil salinity, are summarized as abiotic stresses and discriminated from biotic stresses that are exerted by pathogens and herbivores, for instance. It was an unexpected observation that overproduction of reactive oxygen species (ROS) is a common response to all kinds of stress investigated so far. With respect to applied aspects in agriculture and crop breeding, this observation allows using ROS production as a measure to rank the stress perception of individual plants. ROS are important messengers in cell signaling, but exceeding a concentration threshold causes damage. This requires fine-tuning of ROS production and degradation rates. In general, there are two options to control cellular ROS levels, (I) ROS scavenging at the expense of antioxidant consumption and (II) enzyme-controlled degradation of ROS. As antioxidants are limited in quantity, the first strategy only allows temporarily buffering of a certain cellular ROS level. This way, it prevents spells of eventually damaging ROS concentrations. In this review, we focus on the second strategy. We discuss how enzyme-controlled degradation of ROS integrates into plant metabolism. Enzyme activities can be continuously operative. Cellular homeostasis can be achieved by regulation of respective gene expression and subsequent regulation of the enzyme activities. A better understanding of this interplay allows for identifying traits for stress tolerance breeding of crops. As a side effect, the result also may be used to identify cultivation methods modifying crop metabolism, thus resulting in special crop quality.

Ghabooli M., Kaboosi E.

Beneficial interaction of plants with fungi is one strategy for adapting to environmental stresses like drought. Serendipita indica , an endophytic root fungus, promotes plant growth and enhances tolerance to abiotic stresses. The present study aimed to investigate the amelioration of drought stress in tomato ( Solanum lycopersicum L.) upon S. indica and glucose application through morpho-physiological analysis. A completely randomized design was applied with two types of fungal inoculation (non-inoculated and S. indica ), two glucose concentrations (0 and 20 mM), and three levels of drought stress (0, 10%, and 20% polyethylene glycol) with three replications per treatment. The plants were collected to analyze various growth and physiological parameters 6 weeks after inoculation. The results showed that S. indica enhances root and shoot biomass and also root volume of inoculated plants in all treatments. An increase in carbohydrate (76%), proline (3.77-fold), potassium (21%), phosphorous (2.62-fold), antioxidant enzymes (peroxidase, ascorbate peroxidase , catalase and superoxide dismutase), total chlorophyll (33%), and carotenoid (16%) content were also observed with S. indica treated plants over untreated plants under drought stress. Additionally, the endophyte decreased hydrogen peroxide (H 2 O 2 ), malondialdehyde (MDA), and electrolyte leakage (EL) by 20, 10 and 22%, respectively. The results showed that the level of carbohydrate (90%), proline (35%), potassium (7%), plant water status (3%), chlorophyll (11%) and carotenoid (6%), as well as the activities of antioxidant enzymes, were increased in glucose-treated plants. Moreover, glucose application decreases the levels of MDA, hydrogen peroxide (H 2 O 2 ), and EL by 4, 7 and 13%, respectively. Overall, the interaction effect between fungal inoculation and glucose treatment with drought stress was significant in nearly all measured traits, which means both fungus and glucose promotes plant growth and can enhance drought stress tolerance. Hence, these indicate that S. indica and glucose co-application should be further investigated with field trials. • Serendipita indica colonization increases morpho-physiological parameters to enhance adapt to drought stress. • Glucose treatment mitigate the adverse effect of drought stress. • Serendipita indica colonization and glucose treatment help the tomato plants to tolerate the drought stress.

Ali R., Gul H., Hamayun M., Rauf M., Iqbal A., Hussain A., Lee I.

Ghosh U.K., Islam M.N., Siddiqui M.N., Cao X., Khan M.A.

Abiotic stresses have a detrimental impact on plant growth and productivity and are a major threat to sustainable crop production in rapidly changing environments. Proline, an important amino acid, plays an important role in maintaining the metabolism and growth of plants under abiotic stress conditions. Many insights indicate a positive relationship between proline accumulation and tolerance of plants to various abiotic stresses. Because of its metal chelator properties, it acts as a molecular chaperone, an antioxidative defence molecule that scavenges reactive oxygen species (ROS), as well as having signalling behaviour to activate specific gene functions that are crucial for plant recovery from stresses. It also acts as an osmoprotectant, a potential source to acquire nitrogen as well as carbon, and plays a significant role in the flowering and development of plants. Overproduction of proline in plant cells contributes to maintaining cellular homeostasis, water uptake, osmotic adjustment and redox balance to restore the cell structures and mitigate oxidative damage. Many reports reveal that transgenic plants, particularly those overexpressing genes tailored for proline accumulation, exhibit better adaptation to abiotic stresses. Therefore, this review aims to provide a comprehensive update on proline biosynthesis and accumulation in plants and its putative regulatory roles in mediating plant defence against abiotic stresses. Additionally, the current and future directions in research concerning manipulation of proline to induce gene functions that appear promising in genetics and genomics approaches to improve plant adaptive responses under changing climate conditions are also highlighted.

Chauhan A., Saini R., Sharma J.C.

Chourasia K.N., Lal M.K., Tiwari R.K., Dev D., Kardile H.B., Patil V.U., Kumar A., Vanishree G., Kumar D., Bhardwaj V., Meena J.K., Mangal V., Shelake R.M., Kim J., Pramanik D.

Among abiotic stresses, salinity is a major global threat to agriculture, causing severe damage to crop production and productivity. Potato (Solanum tuberosum) is regarded as a future food crop by FAO to ensure food security, which is severely affected by salinity. The growth of the potato plant is inhibited under salt stress due to osmotic stress-induced ion toxicity. Salinity-mediated osmotic stress leads to physiological changes in the plant, including nutrient imbalance, impairment in detoxifying reactive oxygen species (ROS), membrane damage, and reduced photosynthetic activities. Several physiological and biochemical phenomena, such as the maintenance of plant water status, transpiration, respiration, water use efficiency, hormonal balance, leaf area, germination, and antioxidants production are adversely affected. The ROS under salinity stress leads to the increased plasma membrane permeability and extravasations of substances, which causes water imbalance and plasmolysis. However, potato plants cope with salinity mediated oxidative stress conditions by enhancing both enzymatic and non-enzymatic antioxidant activities. The osmoprotectants, such as proline, polyols (sorbitol, mannitol, xylitol, lactitol, and maltitol), and quaternary ammonium compound (glycine betaine) are synthesized to overcome the adverse effect of salinity. The salinity response and tolerance include complex and multifaceted mechanisms that are controlled by multiple proteins and their interactions. This review aims to redraw the attention of researchers to explore the current physiological, biochemical and molecular responses and subsequently develop potential mitigation strategies against salt stress in potatoes.

Macuphe N., Oguntibeju O.O., Nchu F.

Endophytic entomopathogens have growth promoting, nutrient fortifying, and anti-insect properties that could improve the yield and quality of lettuce (Lactuca sativa L.). Lactuca sativa is a vegetable crop with high demand; however, it is susceptible to aphid infestations. This study’s objectives were to assess the pathogenicity of Beauveria bassiana (strain: SM3) (Bals.) Vuil. (Hypocreales) against Myzus persicae Sulzer, tissue colonization of lettuce by conidia of B. bassiana, as well as the effects of fungal inoculation on growth, tissue nutrient content, and proximate composition of the lettuce plants. Furthermore, the involvement of tissue nutrients in mediating the influence of endophytic fungus on the plant traits was examined. Insects and plants were exposed to four fungal conidial concentrations: 0, 1 × 106, 1 × 107 and 1 × 108 conidia mL−1 in an anti-insect bioassay and a greenhouse experiment, respectively. The B. bassiana strain was pathogenic against M. persicae, inducing mean insect mortality of 78% at the highest concentration (1 × 108 conidia mL−1). The B. bassiana endophytically colonized up to 76% of plants exposed to 1 × 108 conidia mL−1. Crown size and plant height varied significantly among treatments. However, the plant fresh and dry weights and nutrient elements N, P, K, Ca, and Mg did not vary significantly among treatments. Among the plant macronutrients assessed, only tissue carbon content was significantly (p < 0.01) affected by conidial treatments. The tissue C and Cu contents significantly correlated with the antioxidant capacity of the lettuce plants. Most of the micronutrients, viz. Mn, Fe, Cu, and B were remarkably higher (p < 0.05) in the fungus-treated plants than in the control plants. The antioxidant capacity (FRAP and TEAC) of plant extracts varied significantly (p < 0.001) among treatments, with the highest conidial treatment yielding the most increased antioxidant activity. In conclusion, the B. bassiana strain was endophytic to lettuce, pathogenic against M. persicae, and induced increased micro-nutrient tissue contents and antioxidant activities. This study demonstrated that B. bassiana could be potentially used in the biofortification of nutritive and medicinal qualities of plants.

Hafez E.M., Osman H.S., Gowayed S.M., Okasha S.A., Omara A.E., Sami R., Abd El-Monem A.M., Abd El-Razek U.A.

The development of new approaches for sustaining soil quality, leaf health, and maize productivity are imperative in light of water deficit and soil salinity. Plant growth-promoting rhizobacteria (PGPR) and silica nanoparticles (SiNP) are expected to improve soil chemistry leading to improved plant performance and productivity. In this field experiment, water deficit is imposed by three irrigation intervals—12 (I1), 15 (I2), and 18 (I3) days. Plants are also treated with foliar and soil applications (control, PGPR, SiNP, and PGPR + SiNP) to assess soil enzymatic activity, soil physicochemical properties, plant physiological traits, biochemical analysis, nutrient uptake, and productivity of maize (Zea mays L.) plants grown under salt-affected soil during the 2019 and 2020 seasons. With longer irrigation intervals, soil application of PGPR relieves the deleterious impacts of water shortage and improves yield-related traits and maize productivity. This is attributed to the improvement in soil enzymatic activity (dehydrogenase and alkaline phosphatase) and soil physicochemical characteristics, which enhances the plants’ health and growth under longer irrigation intervals (i.e., I2 and I3). Foliar spraying of SiNP shows an improvement in the physiological traits in maize plants grown under water shortage. This is mainly owing to the decline in oxidative stress by improving the enzymatic activity (CAT, SOD, and POD) and ion balance (K+/Na+), resulting in higher photosynthetic rate, relative water content, photosynthetic pigments, and stomatal conductance, alongside reduced proline content, electrolyte leakage, lipid peroxidase, and sodium content under salt-affected soil. The co-treatment of SiNP with PGPR confirms greater improvement in yield-related traits, maize productivity, as well as nutrient uptake (N, P, and K). Accordingly, their combination is a good strategy for relieving the detrimental impacts of water shortage and soil salinity on maize production.

Ozturk M., Turkyilmaz Unal B., García‐Caparrós P., Khursheed A., Gul A., Hasanuzzaman M.

Drought stress, which causes a decline in quality and quantity of crop yields, has become more accentuated these days due to climatic change. Serious measures need to be taken to increase the tolerance of crop plants to acute drought conditions likely to occur due to global warming. Drought stress causes many physiological and biochemical changes in plants, rendering the maintenance of osmotic adjustment highly crucial. The degree of plant resistance to drought varies with plant species and cultivars, phenological stages of the plant, and the duration of plant exposure to the stress. Osmoregulation in plants under low water potential relies on synthesis and accumulation of osmoprotectants or osmolytes such as soluble proteins, sugars, and sugar alcohols, quaternary ammonium compounds, and amino acids, like proline. This review highlights the role of osmolytes in water-stressed plants and of enzymes entailed in their metabolism. It will be useful, especially for researchers working on the development of drought-resistant crops by using the metabolic-engineering techniques.

Hafez E.M., Omara A.E., Alhumaydhi F.A., El‐Esawi M.A.

Soil water and nutrient status are two of the most important factors for plant development and crop yield. Vermicompost and biochar are supposed to amend soil attributes and increase the productivity. However, little is known about their mixture application on soil quality and nutrient uptake under natural conditions. The aim of this investigation was to understand the impact of soil amendments (control, vermicompost, biochar, and vermicompost + biochar) on yield, soil quality, physiological and biochemical attributes, as well as nutrient uptake of wheat plants grown at different irrigation water treatments (50%, 75%, and 100% of field capacity [FC]) in saline sodic soil. Vermicompost improved wheat growth and yield. Biochar-treated plants had higher growth performance and yield than control plants in all traits and than vermicompost in some cases, thus confirming its potential for enhancing soil quality and increasing nutrient uptake, which stimulates soil chemical properties. When vermicompost was added in combination with biochar, further enhancement in the growth and yield was recorded, highlighting the beneficial effect of vermicompost on plant yield. Vermicompost-biochar mixture application followed by biochar as a singular application caused significant improvements in relative water content, chlorophyll content, stomatal conductance, cytotoxicity, leaf K+ content with respect to nutrient uptake (N, P, and K), while reducing oxidative stress (i.e., activities of catalase [CAT] and ascorbate peroxidase [APX], and expression levels of CAT, APX, and Mn-SOD genes), leaf Na+ content, and proline content. This resulted in increases in yield-related traits and productivity owing to the enhancement in soil chemical characteristics and soil moisture content. Grain yield and nutrient uptake attained the highest values at 75% FC in wheat plants treated by the combination of vermicompost and biochar. In summary, this investigation revealed that the synergistic effect of vermicompost and biochar can not only enhance crop production but also eliminates the detrimental effects of soil salinity and water stress.

Jayanthi B., Ravi M.S., Jothi G., Hariharan M., Dixit S., Singh S., Palanisamy R., Sivakumar P.M., Raja R.K.

Biswas C., Dey P., R T., Babu V.R., Alam N.M.

Fourteen isolates of the entomopathogenic fungus Beauveria bassiana could be introduced as an endophyte into jute plant (Corchorus capsularis) through seed inoculation. Only four endophytic isolates induced the activation of salt stress-tolerant gene pathways in the jute plants that were treated. RNA Sequencing identified 1017 differentially expressed genes between the ‘endophyte colonized plant’ and the ‘untreated plant’. A total of 1117 genes exhibited upregulation, while 279 genes showed downregulation in the treated plant. The expression of salinity stress resistant genes (SLT1, GDSL, KAT3) were significantly up regulated. Furthermore, the analysis revealed the presence of genes encoding transcription factors MYB, bHLH, NAC, bZIP, WRKY, and zinc finger among the 1017 differentially expressed genes. Beauveria bassiana, an entomopathogenic fungus was introduced as an endophyte into jute plant (C. capsularis) through seed inoculation to investigate whether it could confer salinity tolerance. Four endophytic isolates provided salinity tolerance by up-regulating salinity tolerant genes (SLT1, GDSL, KAT3). This is the first report of endophytic B. bassiana providing salinity tolerance in jute.

Naz A., Rohman M.M., Haque M.A., Mim M.F., Chowdhury M.Z., Sultana R., Islam S.M.

Mim M.F., Hasan Chowdhury M.Z., Rohman M.M., Naz A., Bhuiyan A., Mohi-Ud-Din M., Haque M.A., Islam S.M.

Papantzikos V., Mantzoukas S., Koutsompina A., Karali E.M., Eliopoulos P.A., Servis D., Bitivanos S., Patakioutas G.

There are many challenges in cotton cultivation, which are mainly linked to management practices and market demands. The textile commerce requirements are increasing but the effects of climate change on cotton cultivation are becoming an issue, as its commercial development depends significantly on the availability of favorable climatic parameters and the absence of insect pests. In this research, it was studied whether the use of two commercial strains as cotton seed coatings could effectively contribute to the previous obstacles. The experiment was carried out in semi-field conditions at the University of Ioannina. It used a completely randomized design and lasted for 150 days. The following treatments were tested: (a) coated seeds with a commercial strain of Beauveria bassiana (Velifer®); (b) coated seeds with a combination of Velifer® and a commercial strain of Beauveria bassiana (Selifer®); and (c) uncoated cotton seeds (control). The biostimulant effect of the two seed coatings was assessed against the growth characteristics of cotton, and the total chlorophyll and proline content. The bioinsecticidal effect was evaluated by measuring the population of Aphis gossypii on the cotton leaves. The proline effect increased by 15% in the treated plants, whereas the total chlorophyll was higher in the use of both Velifer® and Velifer®–Selifer® treatments by 32% and 19%, respectively. Aphid populations also decreased in the treated plants compared to the control plants (29.9% in Velifer® and 22.4% in Velifer®–Selifer®). Based on an assessment of the above parameters, it follows that the two seed coatings can significantly enhance the growth performance of cotton and reduce the abundance of A. gossypii.

Bhuiyan A., Chowdhury M.Z., Mim M.F., Siddique S.S., Haque M.A., Rahman M.S., Islam S.M.

Microorganisms offer a sustainable way to increase crop production and promote eco-friendly farming. The endophytic fungus

Abdelhameed R.E., Soliman E.R., Gahin H., Metwally R.A.

Abstract Background Enhancing crops’ drought resilience is necessary to maintain productivity levels. Plants interact synergistically with microorganisms like Beauveria bassiana to improve drought tolerance. Therefore, the current study investigates the effects of biopriming with B. bassiana on drought tolerance in Malva parviflora plants grown under regular irrigation (90% water holding capacity (WHC)), mild (60% WHC), and severe drought stress (30% WHC). Results The results showed that drought stress reduced the growth and physiological attributes of M. parviflora. However, those bioprimed with B. bassiana showed higher drought tolerance and enhanced growth, physiological, and biochemical parameters: drought stress enriched malondialdehyde and H2O2 contents. Conversely, exposure to B. bassiana reduced stress markers and significantly increased proline and ascorbic acid content under severe drought stress; it enhanced gibberellic acid and reduced ethylene. Bioprimed M. parviflora, under drought conditions, improved antioxidant enzymatic activity and the plant’s nutritional status. Besides, ten Inter-Simple Sequence Repeat primers detected a 25% genetic variation between treatments. Genomic DNA template stability (GTS) decreased slightly and was more noticeable in response to drought stress; however, for drought-stressed plants, biopriming with B. bassiana retained the GTS. Conclusion Under drought conditions, biopriming with B. bassiana enhanced Malva’s growth and nutritional value. This could attenuate photosynthetic alterations, up-regulate secondary metabolites, activate the antioxidant system, and maintain genome integrity.

Papantzikos V., Mantzoukas S., Eliopoulos P.A., Servis D., Bitivanos S., Patakioutas G.

In this study, the bioinsecticidal action of a commercial formulation with Beauveria bassiana was evaluated on the new sucking pest in Greece: Halyomorpha halys, of the kiwifruit. Additionally, the biostimulant potential of the same formulation was studied on kiwi growth. The application was performed in three different ways in a commercial field of kiwi crop A. deliciosa “Hayward” field in Arta, Greece: (i) trunk spray, (ii) root injection, and (iii) trunk inoculation. During the 2 years seasons of the experiment, weekly measurements of the H. halys population were determined. The insect is sucking plants nutrients; therefore, the total chlorophyll content in the leaves of the treatments was recorded weekly. In addition, the percentage of infested kiwifruits was estimated at the end of the experiment. Moreover, to study the biostimulant potential of the formulation, growth measurements on stems and leaves were performed during the experiment. Finally, at the kiwi harvest point, the fruit biomass, dimensions, and weight were obtained, and the leaves’ proline content was evaluated. The results encourage us to further study this EPF formulation as the bioinsecticidal effect was noted by the reduction in H. halys population, and biostimulant action was perceived by the higher plant biomass.

Meng F., Guo J., Feng N., Zheng D., Chen X., Chen Z., Jiang H., Jiang X.

Salt stress has become one of the most widespread abiotic stresses globally, negatively affecting crop growth, development, and yield. Rice is an important economic crop affected by salt stress. This study used Huanghuazhan (‘HHZ’) as the test material to investigate the mitigating effect of spraying Hemin (alone) or with Hb and ZnPP (in combination) on the oxidative damage induced by 100 mM NaCl solution. The results showed that Hemin treatment maintained the growth of rice seedlings under NaCl stress and improved shoot (plant height, stem base width, leaf area) and root (root length, root surface area, root volume, average root diameter and number of root tips) morphological parameters. In addition, exogenous Hemin increased root activity, raised the content of various photosynthetic pigments, improved leaf structure, and increased the area of vascular bundles, which sustained photosynthesis and promoted the accumulation of biomass. Furthermore, Hemin reduced the accumulation of malondialdehyde (MDA) and hydrogen peroxide (H2O2), by activating the activities of various antioxidant enzymes and increasing the content of non-enzymatic antioxidants. While ZnPP (a specific inhibitor of heme oxygenase-1 (HO-1)) and Hb (CO scavenger) reversed the positive regulation of Hemin, and the indexes (biomass of rice seedlings, root activity, and the activity of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)) somewhat decreased. In conclusion, this study demonstrated that Hemin reduced ROS accumulation, maintained leaf structure and photosynthetic pigment content, and mitigated the adverse effects of oxidative damage caused by NaCl stress in rice through improving the antioxidant capacity of leaves and roots. This research provides a theoretical basis for Hemin to regulate salt tolerance in other crops. However, the molecular mechanisms involved in Hemin regulation need to be further explored.

Li N., Shao T., Xu L., Long X., Rengel Z., Zhang Y.

AbstractMelia azedarach demonstrates strong salt tolerance and thrives in harsh saline soil conditions, but the underlying mechanisms are poorly understood. In this study, we analyzed gene expression under low, medium, and high salinity conditions to gain a deeper understanding of adaptation mechanisms of M. azedarach under salt stress. The GO (gene ontology) analysis unveiled a prominent trend: as salt stress intensified, a greater number of differentially expressed genes (DEGs) became enriched in categories related to metabolic processes, catalytic activities, and membrane components. Through the analysis of the category GO:0009651 (response to salt stress), we identified four key candidate genes (CBL7, SAPK10, EDL3, and AKT1) that play a pivotal role in salt stress responses. Furthermore, the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis revealed that DEGs were significantly enriched in the plant hormone signaling pathways and starch and sucrose metabolism under both medium and high salt exposure in comparison to low salt conditions. Notably, genes involved in JAZ and MYC2 in the jasmonic acid (JA) metabolic pathway were markedly upregulated in response to high salt stress. This study offers valuable insights into the molecular mechanisms underlying M. azedarach salt tolerance and identifies potential candidate genes for enhancing salt tolerance in M. azedarach.

Mehrabi S.S., Sabokdast M., Bihamta M.R., Dedičová B.

Salt stress has detrimental effects on wheat plants at several physiological, biochemical, and molecular levels. This stress leads to suppressed growth, reduced grain yield, and poor quality of harvested grains. However, two approaches have shown promise for improving wheat salt tolerance: using a synthetic strigolactone analog called GR24 and applying plant growth-promoting rhizobacteria (PGPR). GR24 plays a vital role in regulating plant growth and development and in defense against various stresses. Conversely, PGPR are beneficial bacteria that colonize the rhizosphere of plants and promote their growth through multiple mechanisms. In our study, we investigated the effects of salinity on the growth and yield traits of two different wheat cultivars and explored the combined role of PGPR and GR24 in mitigating the impact of salt stress. We created three different salinity levels using NaCl in pots (original, 5 dS m−1, and 10 dS m−1) and inoculated wheat seeds with a salt-tolerant Bacillus velezensis UTB96 strain. In addition, we applied 10 μM GR24 via foliar application during the pollination stage. Our observations showed that salt stress negatively affected wheat’s growth, yield, and phytochemical properties compared to the control. However, both single and combined applications of PGPR and GR24 mitigated the adverse effects of salinity. The combined treatment had a more substantial impact than either alone in inducing and improving biochemical and ionic characteristics. These included decreasing Na+ content in both leaves and roots, and EL, H2O2, and MDA content in leaves while increasing K+ content in both leaves and roots, growth and yield-related traits, RWC, chlorophyll pigments, total protein, soluble sugar, starch, proline, GB, and antioxidant enzyme activity (APX, POX, and CAT) of leaves. In conclusion, integrating PGPR and GR24 can efficiently induce salt tolerance and improve plant growth under stressed conditions. This combined approach has the potential for broad applicability in supporting plant growth in the presence of salt stress.

Peng X., Jia T., Bai Q., Lang D., Zhang X.

Plant growth is enhanced by microbiological agents. In order to develop environment friendly composite microbial agent that can also improve the salt and drought tolerance of plants, the orthogonal experiment and response surface methodology were used to screen nutrients and fermentation conditions of composite microbial agent, and pot experiment was conducted to validate the application effect of optimized and complex microbial agent. Compatibility test showed that G2 (Bacillus cereus) and G5 (Bacillus pumilus) did not show any inhibitory effect on each other's growth in nutrient agar, moreover, in both the growth promotion characteristics and the seed germination tests, G2+G5 showed a synergistic effect. The process optimization results showed that the optimal carbon and nitrogen sources for the medium nutrients was maltose and yeast extract, and the optimal carbon-nitrogen ratio was 5:1; the optimal fermentation conditions included initial pH at 5.17, inoculation amount of 2.28%, liquid volume of 105.96 mL(250 mL)−1, and incubation temperature at 30.06℃. Pot experiment showed that application with composite microbial agent was able to increase antioxidant enzyme activities, ascorbat, proline content, and reduce reactive oxygen species accumulation and membrane peroxidation of G. uralensis seedlings under salt-drought stress. In conclusion, the composite G2+G5 agent possessed remarkable synergistic effect for improve plant tolerance to drought combined with salt stress, suggesting a noticeble practical potential in agricultural practice, and it can be used to develop newtype environment friendly microbial fertilizer.

Chowdhury M.Z., Mostofa M.G., Mim M.F., Haque M.A., Karim M.A., Sultana R., Rohman M.M., Bhuiyan A., Rupok M.R., Islam S.M.

The implementation of salt stress mitigation strategies aided by microorganisms has the potential to improve crop growth and yield. The endophytic fungus Metarhizium anisopliae shows the ability to enhance plant growth and mitigate diverse forms of abiotic stress. We examined the functions of M. anisopliae isolate MetA1 (MA) in promoting salinity resistance by investigating several morphological, physiological, biochemical, and yield features in rice plants. In vitro evaluation demonstrated that rice seeds primed with MA enhanced the growth features of rice plants exposed to 4, 8, and 12 dS/m of salinity for 15 days in an agar medium. A pot experiment was carried out to evaluate the growth and development of MA-primed rice seeds after exposing them to similar levels of salinity. Results indicated MA priming in rice improved shoot and root biomass, photosynthetic pigment contents, leaf succulence, and leaf relative water content. It also significantly decreased Na+/K+ ratios in both shoots and roots and the levels of electrolyte leakage, malondialdehyde, and hydrogen peroxide, while significantly increasing proline content in the leaves. The antioxidant enzymes catalase, glutathione S-transferase, ascorbate peroxidase, and peroxidase, as well as the non-enzymatic antioxidants phenol and flavonoids, were significantly enhanced in MA-colonized plants when compared with MA-unprimed plants under salt stress. The MA-mediated restriction of salt accumulation and improvement in physiological and biochemical mechanisms ultimately contributed to the yield improvement in salt-exposed rice plants. Our findings suggest the potential use of the MA seed priming strategy to improve salt tolerance in rice and perhaps in other crop plants.

Tomilova O.G., Kryukova N.A., Efimova M.V., Kolomeichuk L.V., Kovtun I.S., Glupov V.V.

The considerable decrease in crop productivity associated with the expansion of saline soils is an acute problem in agriculture. Endophytic fungi positively affect plant fitness under salinity conditions. The effects of potato inoculation with the conidia of the Beauveria bassiana strain Sar-31 on growth (the weight of fresh and dry biomass, shoot and root length, numbers of stolons and leaves, and the leaf surface) and physiological indices (the concentration of pigments, free proline and malondialdehyde, and antioxidant enzymes’ activity) were evaluated under moderate chloride salinity (100 mM). The results indicated that the plant’s association with the fungus mitigated the negative impact of salinity probably because of the activation of antioxidant enzymes and accumulation of free proline in potato tissues. Moreover, under the influence of B. bassiana Sar-31, the number of stolons significantly increased, which is one of the main characteristics of potato as an agricultural crop. Thus, Sar-31 may be a promising candidate for further investigation of its ability to stimulate growth and increase the stress tolerance of potato plants.

Du Y., Liu L., Feng N., Zheng D., Liu M., Zhou H., Deng P., Wang Y., Zhao H.

Abstract Background Salt stress is one of the key factors limiting rice production. Alginate oligosaccharides (AOS) enhance plant stress resistance. However, the molecular mechanism underlying salt tolerance in rice induced by AOS remains unclear. FL478, which is a salt-tolerant indica recombinant inbred line and IR29, a salt-sensitive rice cultivar, were used to comprehensively analyze the effects of AOS sprayed on leaves in terms of transcriptomic and metabolite profiles of rice seedlings under salt stress. Results In this experiment, exogenous application of AOS increased SOD, CAT and APX activities, as well as GSH and ASA levels to reduce the damage to leaf membrane, increased rice stem diameter, the number of root tips, aboveground and subterranean biomass, and improved rice salt tolerance. Comparative transcriptomic analyses showed that the regulation of AOS combined with salt treatment induced the differential expression of 305 and 1030 genes in FL478 and IR29. The expressed genes enriched in KEGG pathway analysis were associated with antioxidant levels, photosynthesis, cell wall synthesis, and signal transduction. The genes associated with light-trapping proteins and RLCK receptor cytoplasmic kinases, including CBA, LHCB, and Lhcp genes, were fregulated in response to salt stress. Treatment with AOS combined with salt induced the differential expression of 22 and 50 metabolites in FL478 and IR29. These metabolites were mainly related to the metabolism of amino and nucleotide sugars, tryptophan, histidine, and β -alanine. The abundance of metabolites associated with antioxidant activity, such as 6-hydroxymelatonin, wedelolactone and L-histidine increased significantly. Combined transcriptomic and metabolomic analyses revealed that dehydroascorbic acid in the glutathione and ascorbic acid cycles plays a vital role in salt tolerance mediated by AOS. Conclusion AOS activate signal transduction, regulate photosynthesis, cell wall formation, and multiple antioxidant pathways in response to salt stress. This study provides a molecular basis for the alleviation of salt stress-induced damage by AOS in rice.