Trichoderma spp. Improve growth of Arabidopsis seedlings under salt stress through enhanced root development, osmolite production, and Na⁺ elimination through root exudates

Analysis of Ginkgo biloba Root Exudates and Inhibition of Soil Fungi by Flavonoids and Terpene Lactones

Ginkgo biloba is abundant in secondary metabolites, including flavonoids and terpenoids. While the majority of research has focused on the role of these compounds in disease resistance, their specific contribution to pathogen defense has been rarely explored. In this study, we collected root exudates from hydroponically cultivated ginkgo seedlings and conducted a metabolomic analysis. We identified several primary metabolites mainly comprising amino acids and nucleotides, while secondary metabolites consisted of various compounds, including bioactive compounds such as flavonoids and terpenoids. Focusing on the secondary metabolites with relatively higher abundance in the exudates, we selected a mixture of flavonoids and terpenoids for in vitro inhibition experiments against two soil-borne fungal pathogens, Fusarium oxysporum f. sp. cucumerinum that causes cucumber wilt and Rhizoctonia solani AG-8 that causes wheat root rot. The results indicated that the growth rate of both fungus cells was significantly reduced with the increasing concentration of the flavonoid and terpenoid mixture extracted from ginkgo and was completely inhibited at a concentration of 5 mg/mL. Further experiments revealed that this mixture of flavonoids and terpenoids had a destructive effect on the cellular structure of both fungi, thereby reducing cell viability and achieving an antifungal effect. These findings provide a foundation for further research into the use of ginkgo extracts in biological control.

Identification of the potato (Solanum tuberosum L.) P-type ATPase gene family and investigating the role of PHA2 in response to Pep13

P-type ATPase family members play important roles in plant growth and development and are involved in plant resistance to various biotic and abiotic factors. Extensive studies have been conducted on the P-type ATPase gene families in Arabidopsis thaliana and rice but our understanding in potato remains relatively limited. Therefore, this study aimed to screen and analyze 48 P-type ATPase genes from the potato (Solanum tuberosum L.) genome database at the genome-wide level. Potato P-type ATPase genes were categorized into five subgroups based on the phylogenetic classification of the reported species. Additionally, several bioinformatic analyses, including gene structure analysis, chromosomal position analysis, and identification of conserved motifs and promoter cis-acting elements, were performed. Interestingly, the plasma membrane H+-ATPase (PM H+-ATPase) genes of one of the P3 subgroups showed differential expression in different tissues of potato. Specifically, PHA2, PHA3, and PHA7 were highly expressed in the roots, whereas PHA8 was expressed in potatoes only under stress. Furthermore, the small peptide Pep13 inhibited the expression of PHA1, PHA2, PHA3, and PHA7 in potato roots. Transgenic plants heterologously overexpressing PHA2 displayed a growth phenotype sensitive to Pep13 compared with wild-type plants. Further analysis revealed that reducing potato PM H+-ATPase enzyme activity enhanced resistance to Pep13, indicating the involvement of PM H+-ATPase in the physiological process of potato late blight and the enhancement of plant disease resistance. This study confirms the critical role of potato PHA2 in resistance to Pep13.

Recent advances in the use of Trichoderma-containing multicomponent microbial inoculants for pathogen control and plant growth promotion

Chemical pesticides and fertilizers are used in agricultural production worldwide to prevent damage from plant pathogenic microorganisms, insects, and nematodes, to minimize crop losses and to preserve crop quality. However, the use of chemical pesticides and fertilizers can severely pollute soil, water, and air, posing risks to the environment and human health. Consequently, developing new, alternative, environment-friendly microbial soil treatment interventions for plant protection and crop yield increase has become indispensable. Members of the filamentous fungal genus Trichoderma (Ascomycota, Sordariomycetes, Hypocreales) have long been known as efficient antagonists of plant pathogenic microorganisms based on various beneficial traits and abilities of these fungi. This minireview aims to discuss the advances in the field of Trichoderma-containing multicomponent microbiological inoculants based on recent experimental updates. Trichoderma strains can be combined with each other, with other fungi and/or with beneficial bacteria. The development and field performance of such inoculants will be addressed, focusing on the complementarity, synergy, and compatibility of their microbial components.

Mechanisms for plant growth promotion activated by Trichoderma in natural and managed terrestrial ecosystems

Trichoderma spp. are free-living fungi present in virtually all terrestrial ecosystems. These soil fungi can stimulate plant growth and increase plant nutrient acquisition of macro- and micronutrients and water uptake. Generally, plant growth promotion by Trichoderma is a consequence of the activity of potent fungal signaling metabolites diffused in soil with hormone-like activity, including indolic compounds as indole-3-acetic acid (IAA) produced at concentrations ranging from 14 to 234 μg l-1, and volatile organic compounds such as sesquiterpene isoprenoids (C15), 6-pentyl-2H-pyran-2-one (6-PP) and ethylene (ET) produced at levels from 10 to 120 ng over a period of six days, which in turn, might impact plant endogenous signaling mechanisms orchestrated by plant hormones. Plant growth stimulation occurs without the need of physical contact between both organisms and/or during root colonization. When associated with plants Trichoderma may cause significant biochemical changes in plant content of carbohydrates, amino acids, organic acids and lipids, as detected in Arabidopsis thaliana, maize (Zea mays), tomato (Lycopersicon esculentum) and barley (Hordeum vulgare), which may improve the plant health status during the complete life cycle. Trichoderma-induced plant beneficial effects such as mechanisms of defense and growth are likely to be inherited to the next generations. Depending on the environmental conditions perceived by the fungus during its interaction with plants, Trichoderma can reprogram and/or activate molecular mechanisms commonly modulated by IAA, ET and abscisic acid (ABA) to induce an adaptative physiological response to abiotic stress, including drought, salinity, or environmental pollution. This review, provides a state of the art overview focused on the canonical mechanisms of these beneficial fungi involved in plant growth promotion traits under different environmental scenarios and shows new insights on Trichoderma metabolites from different chemical classes that can modulate specific plant growth aspects. Also, we suggest new research directions on Trichoderma spp. and their secondary metabolites with biological activity on plant growth.

Wastewater irrigation and Trichoderma colonization in tomato plants: effects on plant traits, antioxidant activity, and performance of the insect pest Macrosiphum euphorbiae

The scarcity of freshwater for agriculture in many regions has led to the application of sewage and saline water for irrigation. Irrigation with non-conventional water sources could become a non-harmful process for plant cultivation, and the effects of their use on crops should be monitored in order to develop optimal management strategies. One possibility to overcome potential barriers is to use biostimulants such as Trichoderma spp. fungi. Tomato is a crop of great economic importance in the world. This study investigated the joint effects of Trichoderma afroharzianum T-22 on tomato plants irrigated with simulated unconventional waters. The experiment consisted of a control and three water treatments. In the control, the plants were watered with distilled water. The three water treatments were obtained by using an irrigation water added with nitrogen, a wastewater effluent, and a mixed groundwater-wastewater effluents. Potted tomato plants (variety Bobcat) were grown in a controlled growth chamber. Antioxidant activity, susceptibility to the aphids Macrosiphum euphorbiae, and tomato plant growth parameters were estimated. Trichoderma afroharzianum T-22 had a positive effect on plant growth and antioxidant defenses when plants were irrigated with distilled water. Instead, no significant morphological effects induced by T. afroharzianum T-22 on plants were observed when unconventional water was used for irrigation. However, inoculation with T. afroharzianum T-22 activated a stress response that made the colonized plants more susceptible to aphid development and increased their fecundity and longevity. Thanks to this study, it may be possible for the first time to open a new discussion on the practical possibility of using reclaimed wastewater for crop irrigation with the addition of a growth-promoting fungal symbiont.

A biostimulant yeast, Hanseniaspora opuntiae, modifies Arabidopsis thaliana root architecture and improves the plant defense response against Botrytis cinerea

MAIN CONCLUSION

The biostimulant Hanseniaspora opuntiae regulates Arabidopsis thaliana root development and resistance to Botrytis cinerea. Beneficial microbes can increase plant nutrient accessibility and uptake, promote abiotic stress tolerance, and enhance disease resistance, while pathogenic microorganisms cause plant disease, affecting cellular homeostasis and leading to cell death in the most critical cases. Commonly, plants use specialized pattern recognition receptors to perceive beneficial or pathogen microorganisms. Although bacteria have been the most studied plant-associated beneficial microbes, the analysis of yeasts is receiving less attention. This study assessed the role of Hanseniaspora opuntiae, a fermentative yeast isolated from cacao musts, during Arabidopsis thaliana growth, development, and defense response to fungal pathogens. We evaluated the A. thaliana-H. opuntiae interaction using direct and indirect in vitro systems. Arabidopsis growth was significantly increased seven days post-inoculation with H. opuntiae during indirect interaction. Moreover, we observed that H. opuntiae cells had a strong auxin-like effect in A. thaliana root development during in vitro interaction. We show that 3-methyl-1-butanol and ethanol are the main volatile compounds produced by H. opuntiae. Subsequently, it was determined that A. thaliana plants inoculated with H. opuntiae have a long-lasting and systemic effect against Botrytis cinerea infection, but independently of auxin, ethylene, salicylic acid, or jasmonic acid pathways. Our results demonstrate that H. opuntiae is an important biostimulant that acts by regulating plant development and pathogen resistance through different hormone-related responses.

Exploiting root exudates to manage soil-borne disease complexes in a changing climate

Ongoing climate change will both profoundly impact land-use (e.g., changes in crop species or cultivar and cropping practices) and abiotic factors (e.g., moisture and temperature), which will in turn alter plant-microorganism interactions in soils, including soil-borne pathogens (i.e., plant pathogenic bacteria, fungi, oomycetes, viruses, and nematodes). These pathogens often cause soil-borne disease complexes, which, due to their complexity, frequently remain undiagnosed and unmanaged, leading to chronic yield and quality losses. Root exudates are a complex group of organic substances released in the rhizosphere with potential to recruit, repel, stimulate, inhibit, or kill other organisms, including the detrimental ones. An improved understanding of how root exudates affect interspecies and/or interkingdom interactions in the rhizosphere under ongoing climate change is a prerequisite to effectively manage plant-associated microbes, including those causing diseases.

Enhancing photosynthesis and root development for better fruit quality, aroma, and lessening of radioactive materials in key lime (Citrus aurantifolia) using Trichoderma harzianum and Bacillus thuringiensis

The present study was conducted to investigate the effects of Trichoderma harzianum and Bacillus thuringiensis alone or with gradual levels of NPK on photosynthesis, growth, fruit quality, aroma improvement and reduced radionuclides of key lime fruits. The lemon seedlings were treated with (T0) without fertilizers as control, (T1) 100g of NPK at 100%, (T2) 5 g of Trichoderma. harzianum at 50% + 50 g of NPK at 50%, (T3) 5 g of Bacillus thuringiensis at 50% + 50 g of NPK at 50 %, (T4) 7.5 g of Trichoderma harzianum at 75% + 25 g of NPK at 25 %, (T5) 7.5 g of Bacillus thuringiensis at 75% + 25 g of NPK at 25 %, (T6) 10 g of Trichoderma harzianum at 100 % and (T7)10 g of Bacillus thuringiensis at 100 %. The results showed that T2 increased net photosynthetic rate, stomatal conductance, transpiration rate, internal CO2 concentration, fresh and dry root biomass by 209%, 74%, 56%, 376%, 69.4% and 71.6%, while, T5 increased root volume, root length, and root tip number by 27.1%, 167%, and 67%, respectively over the control trees. The microbial treatments developed cortex, vascular cylinder and tracheal elements of the root. Fruit number, length, diameter, weight, pulp thickness, pulp/peel ratio, juice, total soluble solids (TSS), pigment contents and antioxidant activity increased significantly in the T2 treatment. Vitamin C, total phenols, total flavonoids, and total sugar content increased by 1.59-, 1.66-, 1.44- and 2.07- fold in T5 treated fruits compared to the control. The two microbes increased volatile compounds and decreased radionucleotides in the fruit, moreover, 27 identified and 2 (two) unmatched volatile compounds were identified by GCMS analysis. It is concluded that T. harzianum and B. thuringiensis with 25-50 g NPK treatments improved photosynthesis, root structure, fruit growth, fruit quality, aroma and lessened radionuclides in key lime fruits.

Trichoderma harzianum inoculation promotes sweet sorghum growth in the saline soil by modulating rhizosphere available nutrients and bacterial community

As one of the major abiotic stresses, salinity can affect crop growth and plant productivity worldwide. The inoculation of rhizosphere or endophytic microorganisms can enhance plant tolerance to salt stresses, but the potential mechanism is not clear. In this study, Trichoderma harzianum ST02 was applied on sweet sorghum [Sorghum bicolor (L.) Moench] in a field trial to investigate the effects on microbiome community and physiochemical properties in the rhizosphere soil. Compared with the non-inoculated control, Trichoderma inoculation significantly increased the stem yield, plant height, stem diameter, and total sugar content in stem by 35.52%, 32.68%, 32.09%, and 36.82%, respectively. In addition, Trichoderma inoculation improved the nutrient availability (e.g., N, P, and K) and organic matter in the rhizosphere soil and changed the bacterial community structure and function in both bulk and rhizosphere soil by particularly increasing the relative abundance of Actinobacter and N-cycling genes (nifH, archaeal and bacterial amoA). We proposed that T. harzianum ST02 could promote sweet sorghum growth under saline conditions by regulating available nutrients and the bacterial community in the rhizosphere soil.

Partially substituting chemical NPK fertilizers and their impact on Eureka lemon trees (Citrus limon L. Burm) productivity and fruit quality

The main aim of this study is to improve productivity, physical and chemical properties of the fruits and fruit quality of Eureka Lemon trees while lowering production costs by investigating the use of different NPK alternative sources (slow release, and bio) to reduce the use of chemical NPK fertilizers. Ten treatments of NPK fertilizers were applied. The results indicate that the highest values of yield (111.0 and 114.0 kg/tree) were found with 100% chemical NPK (control) for both first and second seasons, respectively. The lemon fruit weight ranged from 131.3 to 152.4 and 131.4 to 153.5 g for first and second seasons, respectively, for all treatments under study. The highest values of fruit length and fruit diameter were found with 100% chemical NPK (control) for both two seasons. The highest values of juice quality parameters (TSS, juice acidity, TSS/acid ratio and vitamin C concentration) responded favorably to higher chemical NPK treatment rates. The highest values of TSS, juice acidity, TSS/Acid ratio, and vitamin C concentration were 9.45%, 6.25%, 1.524 and 4.27 mg/100 g, respectively, were found with 100% chemical NPK (control) for both two seasons. Meanwhile, the lowest value of total sugar was found with 100% chemical NPK (control) for both two seasons.

Organic Amendments Improved the Productivity and Bio-Fortification of Fine Rice by Improving Physiological Responses and Nutrient Homeostasis under Salinity Stress

Salinity stress (SS) is major abiotic stress that is seriously limiting crop production across the globe. The application of organic amendments (OA) mitigate the effects of salinity and improves soil health and crop production on a sustainable basis. However, limited studies are conducted to determine the impact of farmyard manure (FYM) and press mud (PM) on the performance of rice crop. Therefore, we performed this study to determine the impacts of FYM and PM on the growth, physiological and biochemical attributes, yield, and grain bio-fortification of rice crop under SS. The experiment was comprised of SS levels; control, 6 and 12 dS m^-1 SS and OA; control, FYM: 5%, press mud 5% and combination of FYM (5%) + PM (5%). Soil salinity imposed deleterious impacts on the growth, yield, and grain quality of rice, however, OA appreciably offset the deleterious impacts of SS and improved the growth, yield, and grain bio-fortification of rice crop. The combined application of FYM + PM improved the growth and yield of rice through an increase in chlorophyll contents, leaf water contents, anti-oxidant activities (ascorbate peroxidise: APX; catalase: CAT, peroxidise: POD and ascorbic acid: AsA), K⁺ accumulation and decrease in Na⁺/K⁺ ratio, electrolyte leakage, malondialdehyde (MDA), hydrogen peroxide (H₂O₂), Na⁺ accumulation. Moreover, the combined application of FYM + PM significantly improved the grain protein (5.84% and 12.90%), grain iron (40.95% and 42.37%), and grain zinc contents (36.81% and 50.93%) at 6 and 12 dS m^-1 SS. Therefore, this study suggested that the application of FYM and PM augmented the growth, yield, physiology, biochemistry, and grain bio-fortification of rice and proved to be a good practice for better rice production in salt-affected soils.

A Salt-Tolerant Strain of Trichoderma longibrachiatum HL167 Is Effective in Alleviating Salt Stress, Promoting Plant Growth, and Managing Fusarium Wilt Disease in Cowpea

Salt stress is a constraint factor in agricultural production and restricts crops yield and quality. In this study, a salt-tolerant strain of Trichoderma longibrachiatum HL167 was obtained from 64 isolates showing significant salt tolerance and antagonistic activity to Fusarium oxysporum. T. longibrachiatum HL167 inhibited F. oxysporum at a rate of 68.08% in 200 mM NaCl, penetrated F. oxysporum under 200 mM NaCl, and eventually induced F. oxysporum hyphae breaking, according to electron microscope observations. In the pot experiment, pretreatment of cowpea seedlings with T. longibrachiatum HL167 reduced the accumulation level of ROS in tissues and the damage caused by salt stress. Furthermore, in the field experiment, it was discovered that treating cowpea with T. longibrachiatum HL167 before root inoculation with F. oxysporum can successfully prevent and control the development of cowpea Fusarium wilt, with the best control effect reaching 61.54%. Moreover, the application of HL 167 also improved the K+/Na+ ratio of cowpea, alleviated the ion toxicity of salt stress on cowpea, and HL167 was found to effectively colonize the cowpea roots. T. longibrachiatum HL167, which normally survives in saline–alkali environments and has the functions of disease prevention and plant growth promotion capabilities, has important research implications for improving the saline–alkali soil environment and for the sustainable development of green agriculture.

Alleviation of the adverse effects of NaCl stress on tomato seedlings (Solanum lycopersicum L.) by Trichoderma viride through the antioxidative defense system

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.

Microplastics reduce nitrogen uptake in peanut plants by damaging root cells and impairing soil nitrogen cycling

Microplastic (MP) pollution severely impairs the sustainable development of modern agriculture. However, the mechanisms underlying the effects of MP contaminants on nutrient cycles in agroecosystems are poorly understood. In this study, we examined the impacts of two types of MPs, polypropylene (PP) and rubber crumb (RC), on nitrogen (N) transformation and N cycling in soil-peanut system. High concentrations of PP (1% w/w) and RC (1% w/w) inhibited vegetative growth and N uptake in peanut plants by damaging root cells and disturbing soil N cycling. These MPs damaged the plasma membranes of root cells and caused oxidative stress, as evidenced by the decreased number of xylem vessels, which in turn inhibited N uptake by roots. Integrated metagenomic and metabolomic analyses revealed that the differential soil metabolite levels in response to MP treatment affected the microbial community structure in the rhizosphere and the expression of key N cycling-related genes, resulting in altered N transformation and the decreased availability of N in rhizosphere soil. These findings provide the first evidence of the effects of MPs on N uptake in peanut plants and shed light on the importance of rational management of MPs for crop growth and yield in agroecosystems.

Trichoderma longibrachiatum TG1 increases endogenous salicylic acid content and antioxidants activity in wheat seedlings under salinity stress

Several studies have reported the deleterious effects of excessive salt stress on Triticum aestivum L. seedlings. Seed pretreatment with exogenous salicylic acid (SA) enhances plants to tolerate salt stress. Herein, the present study aims to investigate the potential of plant-growth-promoting fungus Trichoderma longibrachiatum (TG1) to increase the plant growth and enhance the salicylic acid (SA) contents and antioxidants activity in wheat seedlings under different concentrations of salt stress. Wheat seeds were pretreated in TG1 spore suspension before exposure to different salt stresses. Compared with 0, 50, 100, 150 salt stresses, the TG1 and NaCl increased the wheat seeds germination rate, germination potential and germination index significantly; the shoot height and root length were increased by an average of 39.45% and 29.73%, respectively. Compared to NaCl stress across the four concentrations (0, 50, 100, and 150 mM), the TG1 treated wheat seedlings increased SA concentration and phenylalanine ammonia-lyase activity (PAL) by an average of 55.87% and 24.10% respectively. In addition, the TG1+NaCl-treated seedlings increased superoxide dismutase (SOD), peroxidases (POD), and catalase (CAT) activities in the shoot by an average of 47.68%, 23.68%, and 38.65% respectively compared to NaCl-stressed seedlings. Significantly, the genes, SOD, CAT, and POD were relatively up-regulated in the salt-tolerant TG1-treated seedlings at all NaCl concentrations in comparison to the control. Wheat seedlings treated with TG1+NaCl increased the transcript levels of SOD, POD and CAT by 1.35, 1.85 and 1.04-fold at 50 mM NaCl concentration, respectively, compared with 0 mM NaCl concentration. Our results indicated that seeds pretreatment with TG1 could increase endogenous SA of plants and promote seedling growth under salt stress by improving enzymatic antioxidant activities and gene expression.

Trichoderma species from plant and soil: An excellent resource for biosynthesis of terpenoids with versatile bioactivities

BACKGROUND

Trichoderma species are rich source of bioactive secondary metabolites. In the past decades, a series of secondary metabolites were reported from different Trichoderma fungi, among which terpenoids possessing versatile structural diversities and extensive pharmacological activities are one of the particularly important categories.

AIM OF REVIEW

The review aims to summarize the terpenoids isolated from Trichoderma species regarding their structural diversities, biological activities, and promising biosynthetic potentials.

KEY SCIENTIFIC CONCEPTS OF REVIEW

So far, a total of 253 terpenoids, including 202 sesquiterpenes, 48 diterpenes, 2 monoterpenes and 1 meroterpenoid, were isolated and identified from Trichoderma species between 1948 and 2022. Pharmacological investigations of Trichoderma terpenoids mainly focused on their antibacterial activities, antifungal activities, inhibitory activities on marine plankton species and cytotoxic activities, indicating that Trichoderma species are important microbial agents for drug discovery and environmentally friendly agrochemicals development. Intriguing chemistry and enzymology involved in the biosynthesis of Trichoderma terpenoids were also presented to facilitate further precise genome mining-guided novel structure discovery. Taken together, the abundance of novel skeletons, bioactivities and biosynthetic potentials presents new opportunities for drug and agrochemicals discovery, genome mining and enzymology exploration from Trichoderma species. The work will provide references for the profound study of terpenoids derived from Trichoderma, and facilitate further studies on Trichoderma species in the areas of chemistry, medicine, agriculture and microbiology.

Fungal endophytes of Brassicaceae: Molecular interactions and crop benefits

Brassicaceae family includes an important group of plants of great scientific interest, e.g., the model plant Arabidopsis thaliana, and of economic interest, such as crops of the genus Brassica (Brassica oleracea, Brassica napus, Brassica rapa, etc.). This group of plants is characterized by the synthesis and accumulation in their tissues of secondary metabolites called glucosinolates (GSLs), sulfur-containing compounds mainly involved in plant defense against pathogens and pests. Brassicaceae plants are among the 30% of plant species that cannot establish optimal associations with mycorrhizal hosts (together with other plant families such as Proteaceae, Chenopodiaceae, and Caryophyllaceae), and GSLs could be involved in this evolutionary process of non-interaction. However, this group of plants can establish beneficial interactions with endophytic fungi, which requires a reduction of defensive responses by the host plant and/or an evasion, tolerance, or suppression of plant defenses by the fungus. Although much remains to be known about the mechanisms involved in the Brassicaceae-endophyte fungal interaction, several cases have been described, in which the fungi need to interfere with the GSL synthesis and hydrolysis in the host plant, or even directly degrade GSLs before they are hydrolyzed to antifungal isothiocyanates. Once the Brassicaceae-endophyte fungus symbiosis is formed, the host plant can obtain important benefits from an agricultural point of view, such as plant growth promotion and increase in yield and quality, increased tolerance to abiotic stresses, and direct and indirect control of plant pests and diseases. This review compiles the studies on the interaction between endophytic fungi and Brassicaceae plants, discussing the mechanisms involved in the success of the symbiosis, together with the benefits obtained by these plants. Due to their unique characteristics, the family Brassicaceae can be seen as a fruitful source of novel beneficial endophytes with applications to crops, as well as to generate new models of study that allow us to better understand the interactions of these amazing fungi with plants.

Biochemical Changes in Two Barley Genotypes Inoculated With a Beneficial Fungus Trichoderma harzianum Rifai T-22 Grown in Saline Soil

One of the most important environmental factors impacting crop plant productivity is soil salinity. Fungal endophytes have been characterised as biocontrol agents that help in plant productivity and induce resistance responses to several abiotic stresses, including salinity. In the salt-tolerant cereal crop barley (Hordeum vulgare L.), there is limited information about the metabolites and lipids that change in response to inoculation with fungal endophytes in saline conditions. In this study, gas chromatography coupled to mass spectrometry (GC-MS) and LC-electrospray ionisation (ESI)-quadrupole-quadrupole time of flight (QqTOF)-MS were used to determine the metabolite and lipid changes in two fungal inoculated barley genotypes with differing tolerance levels to saline conditions. The more salt-tolerant cultivar was Vlamingh and less salt tolerant was Gairdner. Trichoderma harzianum strain T-22 was used to treat these plants grown in soil under control and saline (200 mM NaCl) conditions. For both genotypes, fungus-colonised plants exposed to NaCl had greater root and shoot biomass, and better chlorophyll content than non-colonised plants, with colonised-Vlamingh performing better than uninoculated control plants. The metabolome dataset using GC-MS consisted of a total of 93 metabolites of which 74 were identified in roots of both barley genotypes as organic acids, sugars, sugar acids, sugar alcohols, amino acids, amines, and a small number of fatty acids. LC-QqTOF-MS analysis resulted in the detection of 186 lipid molecular species, classified into three major lipid classes-glycerophospholipids, glycerolipids, and sphingolipids, from roots of both genotypes. In Cultivar Vlamingh both metabolites and lipids increased with fungus and salt treatment while in Gairdner they decreased. The results from this study suggest that the metabolic pathways by which the fungus imparts salt tolerance is different for the different genotypes.

Physiological mechanisms of ABA-induced salinity tolerance in leaves and roots of rice

Abscisic acid (ABA) plays a crucial role in response to abiotic stress as important small molecules in regulating metabolism. This study aimed to evaluate the ability of foliar spraying ABA to regulate growth quality at rice seedling stage under salt stress. Results demonstrated that salt stress strongly reduced all the growth parameters of two rice seedlings ('Chaoyouqianhao' and 'Huanghuazhan'), caused prominent decrease in the levels of photosynthetic pigments (mainly in Huanghuazhan), photosynthesis and fluorescence parameters. Salinity treatment increased the concentration of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in roots, whereas significant decreased H2O2 was found in leaves of Huanghuazhan. Additionally, salinity triggered high Na+ content particularly in leaves and enhanced catalase (CAT) activities, ascorbate peroxidase (APX) and peroxidase (POD) activities of the two rice seedlings. Nevertheless, salinity-induced increased root ascorbic acid (AsA) and glutathione (GSH) levels while decreased in leaves, which depended on treatment time. Conversely, ABA application partially or completely mitigated salinity toxicity on the seedlings. ABA could reverse most of the changed physiological parameters triggered by salt stress. Specially, ABA treatment improved antioxidant enzyme levels and significantly reduced the Na+ content of two varieties as well as increased the K+, Mg2+ and Ca2+ content in leaves and roots. ABA treatment increased the hormone contents of 1-aminocclopropane carboxylic acid (ACC), trans-zeatin (TZ), N6-isopentyladenosine (IPA), Indole-3-acetic acid (IAA), and ABA in leaves of two rice varieties under salt stress. It is suggested that ABA was beneficial to protect membrane lipid peroxidation, the modulation of antioxidant defense systems and endogenous hormonal balance with imposition to salt stress.

Root Morphology, Allometric Relations and Rhizosheath of Ancient and Modern Tetraploid Wheats (Triticum durum Desf.) in Response to Inoculation with Trichoderma harzianum T-22

Early root traits and allometrics of wheat are important for competition and use of resources. They are under-utilized in research and un-explored in many ancient wheats. This is especially true for the rhizosheath emerging from root-soil interactions. We investigated root morphology, root/shoot relations and the amount of rhizosheath of four tetrapoid wheat seedlings (30 days after emergence): the italian landrace Saragolle Lucana and modern varieties Creso, Simeto and Ciclope, and tested the hypothesis that inoculation with Trichoderma harzianum T-22 (T-22) enhances rhizosheath formation and affects wheat varieties differently. Overall growth of non-inoculated plants showed different patterns in wheat varieties, with Saragolle and Ciclope at the two extremes: Saragolle invests in shoot rather than root mass, and in the occupation of space with highest (p < 0.05) shoot height to the uppermost internode (5.02 cm) and length-to-mass shoot (97.8 cm g^-1) and root (more than 140 m g^-1) ratios. This may be interpreted as maximizing competition for light but also as a compensation for low shoot efficiency due to the lowest (p < 0.05) recorded values of optically-measured chlorophyll content index (22.8). Ciclope invests in biomass with highest shoot (0.06 g) and root (0.04 g) mass and a thicker root system (average diameter 0.34 mm vs. 0.29 in Saragolle) as well as a highest root/shoot ratio (0.95 g g^-1 vs. 0.54 in Saragolle). Rhizosheath mass ranged between 22.14 times that of shoot mass in Ciclope and 43.40 in Saragolle (different for p < 0.05). Inoculation with Trichoderma increased the amount of rhizosheath from 9.4% in Ciclope to 36.1% in Simeto and modified root architecture in this variety more than in others. Ours are the first data on roots and seedling shoot traits of Saragolle Lucana and of Trichoderma inoculation effects on rhizosheath. This opens to new unreported interpretations of effects of Trichoderma inoculation on improving plant growth.

Influence of Trichoderma harzianum and Bacillus thuringiensis with reducing rates of NPK on growth, physiology, and fruit quality of Citrus aurantifolia

Abstract Continuous use of chemical fertilizers gradually shrinks the crop yield and quality, and these adverse effects can be reduced by adopting new sustainable practices such as the use of manure, biofertilizers, and nano fertilizers. Limited information is existed on the application of Trichoderma harzianum and Bacillus thuringiensis microbes to improve lemon seedlings growth, physiology, and fruit formation. Therefore, the current study is aimed to evaluate the effects of T. harzianum and B. thuringiensis microbes mixing with low levels of inorganic fertilizer (NPK) on the plant growth, development, and quality of limau nipis (key lemon) fruits. The lemon seedlings growing media were inoculated during transplanting with T. harzianum and B. thuringiensis at various NPK fertilizers under polybagged conditions. The seedlings were grown around eighteen (18) months after inoculation with biofertilizers followed by Randomized Complete Block Design (RCBD) with five (5) replications. The results showed that T. harzianum with 50 g of NPK treatment (T2) increased the seedling's height, branch number, leaf height, ground area, and absolute growth rate (AGR) plant height by 50.12%, 107.84%, 17.91%, 17.91%, 116.93%, and 56.02%, respectively, over the control treatment. The number of leaves (60.82%), leaf area (42.75%), stem diameter (27.34%), specific leaf area (SLA) (39.07%), leaf area index (LAI) (54.40%), and absolute growth rate for leaf number (73.86%), leaf area (306.85%) and stem diameter (46.8%) of lemon seedlings increased significantly with B. thuringiensis plus 50 g NPK treatment (T3). The applications of B. thuringiensis with 25 g NPK fertilizer treatment (T5) increased leaf fresh weight (LFW), leaf dry weight (LDW), leaf moisture content (LMC), specific leaf weight (SLW), leaf relative growth rate (RGR), and chlorophyll content by 96.45%, 56.78%, 13.60%, 24.76%, 45.45%, and 16.22%, respectively, over the control group. In addition, T5 treatment increased the fruits number, individual fruit weight, fruit diameter, fruit dimension, leaf total soluble solids (TSS), and fruit TSS content of lemon tress by 81.81%, 55.52%, 43.54%, 25.69%, 89.47%, and 70.78% compared to the control treatment. Furthermore, soil inoculation of B. thuringiensis significantly increased the pulp to peel ratio and juice content of lemon fruits. From this study, it can be concluded that soil inoculation of both T. harzianum and B. thuringiensis with 25-50% NPK during transplanting improved plant growth, physiology, and fruit quality of limau nipis trees.

Proton and calcium pumping P-type ATPases and their regulation of plant responses to the environment

Plant plasma membrane H+-ATPases and Ca2+-ATPases maintain low cytoplasmic concentrations of H+ and Ca2+, respectively, and are essential for plant growth and development. These low concentrations allow plasma membrane H+-ATPases to function as electrogenic voltage stats, and Ca2+-ATPases as "off" mechanisms in Ca2+-based signal transduction. Although these pumps are autoregulated by cytoplasmic concentrations of H+ and Ca2+, respectively, they are also subject to exquisite regulation in response to biotic and abiotic events in the environment. A common paradigm for both types of pumps is the presence of terminal regulatory (R) domains that function as autoinhibitors that can be neutralized by multiple means, including phosphorylation. A picture is emerging in which some of the phosphosites in these R domains appear to be highly, nearly constantly phosphorylated, whereas others seem to be subject to dynamic phosphorylation. Thus, some sites might function as major switches, whereas others might simply reduce activity. Here, we provide an overview of the relevant transport systems and discuss recent advances that address their relation to external stimuli and physiological adaptations.

Understanding the potential of root microbiome influencing salt-tolerance in plants and mechanisms involved at the transcriptional and translational level

Soil salinity severely affects plant growth and development and imparts inevitable losses to crop productivity. Increasing the concentration of salts in the vicinity of plant roots has severe consequences at the morphological, biochemical, and molecular levels. These include loss of chlorophyll, decrease in photosynthetic rate, reduction in cell division, ROS generation, inactivation of antioxidative enzymes, alterations in phytohormone biosynthesis and signaling, and so forth. The association of microorganisms, viz. plant growth-promoting rhizobacteria, endophytes, and mycorrhiza, with plant roots constituting the root microbiome can confer a greater degree of salinity tolerance in addition to their inherent ability to promote growth and induce defense mechanisms. The mechanisms involved in induced stress tolerance bestowed by these microorganisms involve the modulation of phytohormone biosynthesis and signaling pathways (including indole acetic acid, gibberellic acid, brassinosteroids, abscisic acid, and jasmonic acid), accumulation of osmoprotectants (proline, glycine betaine, and sugar alcohols), and regulation of ion transporters (SOS1, NHX, HKT1). Apart from this, salt-tolerant microorganisms are known to induce the expression of salt-responsive genes via the action of several transcription factors, as well as by posttranscriptional and posttranslational modifications. Moreover, the potential of these salt-tolerant microflora can be employed for sustainably improving crop performance in saline environments. Therefore, this review will briefly focus on the key responses of plants under salinity stress and elucidate the mechanisms employed by the salt-tolerant microorganisms in improving plant tolerance under saline environments.

Changes in Volatile Organic Compounds from Salt-Tolerant Trichoderma and the Biochemical Response and Growth Performance in Saline-Stressed Groundnut

Soil salinity is one of the major obstacles that is limiting the growth and yield of groundnut. This study aims to investigate the effect of growth-promoting fungi, Trichoderma, on groundnut plants that were cultivated in saline conditions. Five different Trichoderma isolates were grown in four different NaCl concentrations. Selected Trichoderma were then applied to the groundnut seeds and their growth and development were monitored during the study. Growth inhibition, volatile organic compounds, chlorophylls, carotenoids, total phenolics and flavonoids, and minerals were assessed between the Trichoderma treatments. Increasing the salt concentration from 0.25–0.75 M decreased the growth of the Trichoderma isolates. The amounts and profiles of the volatile organic compounds from the T. asperellum isolate were significantly different to those in the T. virens isolate. In the vegetative growth stage, increased chlorophyll content was recorded in both the T. asperellum and T. virens-treated groundnut. The leaves that were obtained from the groundnut that was treated with T. virens T.v4 contained significantly higher indole-3-acetic acid (420 µg IAA/g) than the same plants’ roots (113.3 µg IAA/g). Compared to the control groundnut, the T. asperellum T.a8-treated groundnut showed increased phenolics (31%) and flavonoids (43%) and increased shoots and biomass weight at the generative growth stage. This study demonstrates that Trichoderma, with their plant growth promotion ability, could potentially be used to improve the growth of groundnut growing under salinity stress. Importantly, salt-tolerant Trichoderma could be regarded as a beneficial and sustainable way to improve the survival of salt-sensitive crops.

Trichoderma longibrachiatum (TG1) Enhances Wheat Seedlings Tolerance to Salt Stress and Resistance to Fusarium pseudograminearum

Salinity is abiotic stress that inhibits seed germination and suppresses plant growth and root development in a dose-dependent manner. Fusarium pseudograminearum (Fg) is a plant pathogen that causes wheat crown rot. Chemical control methods against Fg are toxic to the environment and resistance has been observed in wheat crops. Therefore, an alternative approach is needed to manage this devastating disease and the effects of salinity. Our research focused on the mycoparasitic mechanisms of Trichoderma longibrachiatum (TG1) on Fg and the induction of defenses in wheat seedlings under salt and Fg stress at physiological, biochemical and molecular levels. The average inhibition rate of TG1 against Fg was 33.86%, 36.32%, 44.59%, and 46.62%, respectively, in the four NaCl treatments (0, 50, 100, and 150 mM). The mycoparasitic mechanisms of TG1 against Fg were coiling, penetration, and wrapping of Fg hyphae. In response to inoculation of TG1 with Fg, significant upregulation of cell wall degrading enzymes (CWDEs) was observed. The expression of β-1, 6-glucan synthase (PP4), endochitinase precursor (PH-1), and chitinase (chi18-15) increased by 1. 6, 1. 9, and 1.3-fold on day 14 compared with day 3. Wheat seedlings with combined TG1 + Fg treatments under different NaCl stress levels decreased disease index by an average of 51.89%; increased the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity by an average of 38%, 61%, and 24.96%, respectively; and decreased malondialdehyde (MDA) and hydrogen peroxide (H2O2) content by an average of 44.07% and 41.75% respectively, compared with Fg treated seedlings. The combined TG1 + Fg treatment induced the transcription level of plant defense-related genes resulting in an increase in tyrosin-protein kinase (PR2), chitinase class I (CHIA1), and pathogenesis-related protein (PR1-2) by an average of 1.15, 1.35, and 1.37-fold, respectively compared to Fg treatment. However, the expression levels of phenylalanine ammonia-lyase (PAL) increased 3.40-fold under various NaCl stresses. Our results suggest that TG1 enhances wheat seedling growth and controls wheat crown rot disease by strengthening the plant defense system and upregulating the expression of pathogenesis-related genes under both Fg and salt stress.

Bioformulation development via valorizing silica-rich spent mushroom substrate with Trichoderma asperellum for plant nutrient and disease management

The present investigation was performed to valorize paddy straw (PS) based silica (Si) rich Spent Mushroom Substrate (SMS) of Pleurotus ostreatus for Plant Nutrient and Disease Management in wilt (caused by F. oxysporum f. sp. lycopersici) susceptible tomato plant F1 Hybrid King 180. Raw PS and SMS generated by P. ostreatus cultivated on PS only, and PS amended with 5% soybean cake (SC) were bio-fortified with Trichoderma asperellum (TA). SMS (PS+ 5% SC) was found supporting the growth of T. asperellum to an extent of 12.37 × 10¹³ conidia/g substrate. GC-MS analysis of SMS detected several bioactive metabolites like Palmitic acid, Oleic acid, Methyl linoleate, Stigmasterol, etc., known for plant health management. Bioformulations were developed employing Press Mud (PM) and Talcum Powder (TP) as carrier materials. Among the different bioformulations tested in pots study; SMS (PS+ 5% SC) SiTAPM, collectively named as TF-I, provided improved levels of morpho-biochemical and nutritional parameters, i.e., Plant Biomass (2.27 folds), Root Volume (1.75 folds), Chlorophyll (2.66 folds), Carotenoids (2.42 folds), Number of Fruits (1.76 folds), Fruit Biomass (2.02 folds), Total Soluble Sugars (2.32 folds), Total Soluble Proteins (1.70 folds), and nutraceutical parameters as Lycopene (1.42 folds), β-carotene (2.65 folds) and Ascorbic Acid (1.54 folds), along with significant (p < 0.05) reduction in the Disease Severity Index (84.34%-21.23%), over the pathogen affected plant taken as control. The fruits and leaves garnered under TF-I displayed Total Polyphenol Content (TPC) of 74.5 and 126.9 mg g^-1 gallic acid, respectively, with 83.73% DPPH and 72.25% FRAP activity, indicating the elicitation of antioxidant properties in tomato fruits. EDS analyses showed 21.53% Si in SMS, and plant mapping investigation indicated a substantial accumulation of Si, which is well conceded to promote growth, disease resistance, and antioxidant parameters. The study also endorsed the use of PM over TP, as TF-I recorded an acceptable conidial count (2.22 × 10⁸ cfu/g) towards the end of six months storage period over other bioformulations. Overall, the study envisages the development and application of innovative methodology (TF-I), offering an eco-friendly alternative for producing quality crops and a sustainable solution to waste management, thus delivering a holistic contribution towards the circular economy.

Inoculation of barley with Trichoderma harzianum T-22 modifies lipids and metabolites to improve salt tolerance

Soil salinity has a serious impact on plant growth and agricultural yield. Inoculation of crop plants with fungal endophytes is a cost-effective way to improve salt tolerance. We used metabolomics to study how Trichoderma harzianum T-22 alleviates NaCl-induced stress in two barley (Hordeum vulgare L.) cultivars, Gairdner and Vlamingh, with contrasting salinity tolerance. GC-MS was used to analyse polar metabolites and LC-MS to analyse lipids in roots during the early stages of interaction with Trichoderma. Inoculation reversed the severe effects of salt on root length in sensitive cv. Gairdner and, to a lesser extent, improved root growth in more tolerance cv. Vlamingh. Biochemical changes showed a similar pattern in inoculated roots after salt treatment. Sugars increased in both cultivars, with ribulose, ribose, and rhamnose specifically increased by inoculation. Salt stress caused large changes in lipids in roots but inoculation with fungus greatly reduced the extent of these changes. Many of the metabolic changes in inoculated cv. Gairdner after salt treatment mirror the response of uninoculated cv. Vlamingh, but there are some metabolites that changed in both cultivars only after fungal inoculation. Further study is required to determine how these metabolic changes are induced by fungal inoculation.

An Endophytic Fungi-Based Biostimulant Modulates Volatile and Non-Volatile Secondary Metabolites and Yield of Greenhouse Basil (Ocimum basilicum L.) through Variable Mechanisms Dependent on Salinity Stress Level

Salinity in water and soil is one of the major environmental factors limiting the productivity of agronomic and horticultural crops. In basil (Ocimum basilicum L., Lamiaceae) and other Ocimum species, information on the plant response to mild salinity levels, often induced by the irrigation or fertigation systems, is scarce. In the present work, we tested the effectiveness of a microbial-based biostimulant containing two strains of arbuscular mycorrhiza fungi (AMF) and Trichoderma koningii in sustaining greenhouse basil yield traits, subjected to two mild salinity stresses (25 mM [low] and 50 mM [high] modulated by augmenting the fertigation osmotic potential with NaCl) compared to a non-stressed control. The impact of salinity stress was further appraised in terms of plant physiology, morphological ontogenesis and composition in polyphenols and volatile organic compounds (VOC). As expected, increasing the salinity of the solution strongly depressed the plant yield, nutrient uptake and concentration, reduced photosynthetic activity and leaf water potential, increased the Na and Cl and induced the accumulation of polyphenols. In addition, it decreased the concentration of Eucalyptol and β-Linalool, two of its main essential oil constituents. Irrespective of the salinity stress level, the multispecies inoculum strongly benefited plant growth, leaf number and area, and the accumulation of Ca, Mg, B, p-coumaric and chicoric acids, while it reduced nitrate and Cl concentrations in the shoots and affected the concentration of some minor VOC constituents. The benefits derived from the inoculum in term of yield and quality harnessed different mechanisms depending on the degree of stress. under low-stress conditions, the inoculum directly stimulated the photosynthetic activity after an increase of the Fe and Mn availability for the plants and induced the accumulation of caffeic and rosmarinic acids. under high stress conditions, the inoculum mostly acted directly on the sequestration of Na and the increase of P availability for the plant, moreover it stimulated the accumulation of polyphenols, especially of ferulic and chicoric acids and quercetin-rutinoside in the shoots. Notably, the inoculum did not affect the VOC composition, thus suggesting that its activity did not interact with the essential oil biosynthesis. These results clearly indicate that beneficial inocula constitute a valuable tool for sustaining yield and improving or sustaining quality under suboptimal water quality conditions imposing low salinity stress on horticultural crops.

Saline-alkaline stress in growing maize seedlings is alleviated by Trichoderma asperellum through regulation of the soil environment

A significant proportion of the land area of Heilongjiang Province, China, is composed of saline-alkaline soil, which severely inhibits maize growth. Although Trichoderma treatment is widely regarded as a promising strategy for improving the soil environment and promoting plant growth, the mechanism through which Trichoderma asperellum enhances maize resistance to saline-alkaline stress is not clear. In this study, we explored the effect of T. asperellum application at different concentrations to soil saline-alkaline environment on the seedlings of two maize cultivars, assessing the biochemical parameters related to oxidation resistance. Increasing spore densities of T. asperellum suspension effectively regulated the soil ion balance in the rhizosphere of maize seedlings, reduced the soil pH by 2.15-5.76% and sodium adsorption ratios by 22.70-54.13%, increased soil nutrient content and enzyme activity, and improved the soil environment for seedling growth. Additionally, T. asperellum treatment increased the maize seedling content of osmo-regulating substances and rate of glutathione:oxidised glutathione (43.86-88.25%) and ascorbate:oxidised ascorbate (25.26-222.32%) by affecting the antioxidant enzyme activity in the roots, increasing reactive oxygen species scavenging, and maintaining the osmotic balance and metabolic homeostasis under saline-alkaline stress. T. asperellum also improved the saline-alkaline tolerance of maize seedlings by improving the root growth characteristics. Moreover, results showed that Trichoderma applied at high concentration had the greatest effect. In conclusion, improvement in the saline-alkaline tolerance of maize seedlings by T. asperellum under saline-alkaline soil conditions may be achieved through diverse effects that vary among maize cultivars.

Methods for Root Exudate Collection and Analysis

Plant root exudation has long been recognized as a vital communication system between plants and microbial communities populating the rhizosphere. Due to the high complexity of the collection process and analysis, a variety of techniques have been developed to mimic natural exudation conditions. In addition, significant progress improving existing techniques and developing new methodologies of root exudate collection and analysis have been made. However, optimal standard methods that compare closely with environmental soil conditions are not yet available. In this review, we provide an overview of all those topics and provide suggestions for improvement.

An Endophytic Trichoderma Strain Promotes Growth of Its Hosts and Defends Against Pathogen Attack

Plants host numerous endophytic microbes which promote plant performance, in particular under stress. A new endophytic fungus was isolated from the leaves of a deciduous wood tree Leucas aspera. Morphological inspection and multilocus phylogeny identified the fungus as a new Trichoderma strain. If applied to Arabidopsis thaliana and Nicotiana attenuata, it mainly colonizes their roots and strongly promotes initial growth of the plants on soil. The fungus grows on high NaCl or mannitol concentrations, and shows predatory capability on the pathogenic fungus Alternaria brassicicola. Colonized Arabidopsis plants tolerate higher salt stress and show lower A. brassicicola spread in roots and shoots, while arbuscular mycorrhiza formation in N. attenuata is not affected by the Trichoderma strain. These beneficial features of the novel Trichoderma strain are important prerequisites for agricultural applications.

Trichoderma Enhances Net Photosynthesis, Water Use Efficiency, and Growth of Wheat (Triticum aestivum L.) under Salt Stress

Soil salinity is one of the most important abiotic stresses limiting plant growth and productivity. The breeding of salt-tolerant wheat cultivars has substantially relieved the adverse effects of salt stress. Complementing these cultivars with growth-promoting microbes has the potential to stimulate and further enhance their salt tolerance. In this study, two fungal isolates, Th4 and Th6, and one bacterial isolate, C7, were isolated. The phylogenetic analyses suggested that these isolates were closely related to Trichoderma yunnanense, Trichoderma afroharzianum, and Bacillus licheniformis, respectively. These isolates produced indole-3-acetic acid (IAA) under salt stress (200 mM). The abilities of these isolates to enhance salt tolerance were investigated by seed coatings on salt-sensitive and salt-tolerant wheat cultivars. Salt stress (S), cultivar (C), and microbial treatment (M) significantly affected water use efficiency. The interaction effect of M x S significantly correlated with all photosynthetic parameters investigated. Treatments with Trichoderma isolates enhanced net photosynthesis, water use efficiency and biomass production. Principal component analysis revealed that the influences of microbial isolates on the photosynthetic parameters of the different wheat cultivars differed substantially. This study illustrated that Trichoderma isolates enhance the growth of wheat under salt stress and demonstrated the potential of using these isolates as plant biostimulants.

The fungal NADPH oxidase is an essential element for the molecular dialog between Trichoderma and Arabidopsis

Members of the fungal genus Trichoderma stimulate growth and reinforce plant immunity. Nevertheless, how fungal signaling elements mediate the establishment of a successful Trichoderma-plant interaction is largely unknown. In this work, we analyzed growth, root architecture and defense in an Arabidopsis-Trichoderma co-cultivation system, including the wild-type (WT) strain of the fungus and mutants affected in NADPH oxidase. Global gene expression profiles were assessed in both the plant and the fungus during the establishment of the interaction. Trichoderma atroviride WT improved root branching and growth of seedling as previously reported. This effect diminished in co-cultivation with the ∆nox1, ∆nox2 and ∆noxR null mutants. The data gathered of the Arabidopsis interaction with the ∆noxR strain showed that the seedlings had a heightened immune response linked to jasmonic acid in roots and shoots. In the fungus, we observed repression of genes involved in complex carbohydrate degradation in the presence of the plant before contact. However, in the absence of NoxR, such repression was lost, apparently due to a poor ability to adequately utilize simple carbon sources such as sucrose, a typical plant exudate. Our results unveiled the critical role played by the Trichoderma NoxR in the establishment of a fine-tuned communication between the plant and the fungus even before physical contact. In this dialog, the fungus appears to respond to the plant by adjusting its metabolism, while in the plant, fungal perception determines a delicate growth-defense balance.

Substrate and Plant Genotype Strongly Influence the Growth and Gene Expression Response to Trichoderma afroharzianum T22 in Sugar Beet

Many strains of Trichoderma fungi have beneficial effects on plant growth and pathogen control, but little is known about the importance of plant genotype, nor the underlying mechanisms. We aimed to determine the effect of sugar beet genotypic variation on Trichoderma biostimulation. The effect of Trichoderma afroharzianum T22 on sugar beet inbred genotypes were investigated in soil and on sterile agar medium regarding plant growth, and by quantitative reverse transcriptase-linked polymerase chain reaction (qRT-PCR) analysis for gene expression. In soil, T22 application induced up to 30% increase or decrease in biomass, depending on plant genotype. In contrast, T22 treatment of sterile-grown seedlings resulted in a general decrease in fresh weight and root length across all sugar beet genotypes. Root colonization of T22 did not vary between the sugar beet genotypes. Sand- and sterile-grown roots were investigated by qRT-PCR for expression of marker genes for pathogen response pathways. Genotype-dependent effects of T22 on, especially, the jasmonic acid/ethylene expression marker PR3 were observed, and the effects were further dependent on the growth system used. Thus, both growth substrate and sugar beet genotype strongly affect the outcome of inoculation with T. afroharzianum T22.

The interactions of Trichoderma at multiple trophic levels: inter-kingdom communication

Trichoderma spp. are universal saprotrophic fungi in terrestrial ecosystems, and as rhizosphere inhabitants, they mediate interactions with other soil microorganisms, plants, and arthropods at multiple trophic levels. In the rhizosphere, Trichoderma can reduce the abundance of phytopathogenic microorganisms, which involves the action of potent inhibitory molecules, such as gliovirin and siderophores, whereas endophytic associations between Trichoderma and the seeds and roots of host plants can result in enhanced plant growth and crop productivity, as well as the alleviation of abiotic stress. Such beneficial effects are mediated via the activation of endogenous mechanisms controlled by phytohormones such as auxins and abscisic acid, as well as by alterations in host plant metabolism. During either root colonization or in the absence of physical contact, Trichoderma can trigger early defense responses mediated by Ca²⁺ and reactive oxygen species, and subsequently stimulate plant immunity by enhancing resistance mechanisms regulated by the phytohormones salicylic acid, jasmonic acid, and ethylene. In addition, Trichoderma release volatile organic compounds and nitrogen or oxygen heterocyclic compounds that serve as signaling molecules, which have effects on plant growth, phytopathogen levels, herbivorous insects, and at the third trophic level, play roles in attracting the natural enemies (predators and parasitoids) of herbivores. In this paper, we review some of the most recent advances in our understanding of the environmental influences of Trichoderma spp., with particular emphasis on their multiple interactions at different trophic levels.

Biological mechanisms of cadmium accumulation in edible Amaranth (Amaranthus mangostanus L.) cultivars promoted by salinity: A transcriptome analysis

Strategies to prevent cadmium (Cd) mobilization by crops under salinity conditions differs among distinct genotypes, but the biological mechanisms of Cd accumulation in different genotype crops promoted by salinity have remained scarce. In this study, we investigated the biological mechanisms of Cd accumulation in two quite different amaranth cultivars of low-Cd accumulator Quanhong (QH) and high-Cd accumulator Liuye (LY) in response to salt stress. Transcriptomes analysis was carried out on leaves and roots tissues of LY and QH grown with exchangeable Cd 0.27 mg kg^-1 and salinity 3.0 g kg^-1 treatment or control conditions, respectively. A total of 3224 differentially expressed genes (DEGs) in LY (1119 in roots, 2105 in leaves) and 848 in QH (207 in roots, 641 in leaves) were identified. Almost in each fold change category (2-2⁵, 2⁵-2¹⁰, >2¹⁰), the numbers of DEGs induced by salinity in LY treatments were much more than those in QH treatments, indicating that LY is more salt sensitive. Gene ontology (GO) analysis revealed that salinity stress promoted soil acidification and Cd mobilization in LY treatments through the enhancive expression of genes related to adenine metabolism (84-fold enrichment) and proton pumping ATPase (50-fold enrichment) in roots, and carbohydrate hydrolysis (2.5-fold enrichment) in leaves compared with that of whole genome, respectively. The genes expression of organic acid transporter (ALMT) was promoted by 2.71- to 3.94-fold in roots, facilitating the secretion of organic acids. Salt stress also inhibited the expression of key enzymes related to cell wall biosynthesis in roots, reducing the physical barriers for Cd uptake. All these processes altered in LY were more substantially compared with that of QH, suggesting that salt sensitive cultivars might accumulate more Cd and pose a higher health risk.

Antarctic root endophytes improve physiological performance and yield in crops under salt stress by enhanced energy production and Na+ sequestration

Climatic change is pointed as one of the major challenges for global food security. Based on current models of climate change, reduction in precipitations and in turn, increase in the soil salinity will be a sharp constraint for crops productivity worldwide. In this context, root fungi appear as a new strategy to improve plant ecophysiological performance and crop yield under abiotic stress. In this study, we evaluated the impact of the two fungal endophytes Penicillium brevicompactum and P. chrysogenum isolated from Antarctic plants on nutrients and Na+ contents, net photosynthesis, water use efficiency, yield and survival in tomato and lettuce, facing salinity stress conditions. Inoculation of plant roots with fungal endophytes resulted in greater fresh and dry biomass production, and an enhanced survival rate under salt conditions. Inoculation of plants with the fungal endophytes was related with a higher up/down-regulation of ion homeostasis by enhanced expression of the NHX1 gene. The two endophytes diminished the effects of salt stress in tomato and lettuce, provoked a higher efficiency in photosynthetic energy production and an improved sequestration of Na+ in vacuoles is suggested by the upregulating of the expression of vacuolar NHX1 Na+/H+ antiporters. Promoting plant-beneficial interactions with root symbionts appears to be an environmentally friendly strategy to mitigate the impact of climate change variables on crop production.

Carbon metabolic profiling of Trichoderma strains provides insight into potential ecological niches

Many Trichoderma species are cosmopolitan and widespread free-living fungi in various ecological environment, and many are economically important in the fields of agriculture and industry. However, carbon metabolism profiles of Trichoderma species have not been characterized in detail. In this study, Biolog FF MicroPlates were used to contrast carbon utilization and the differences among five Trichoderma species, each representing a unique phenotype. Their metabolic abilities varied greatly. Species producing cellulases and chitinases and with phosphate-solubilizing activities exhibited high efficiency of substrate utilization, whereas low efficiency was shown by saline-alkaline-tolerant species that metabolized simple carbon sources. Species producing cellulases at high levels may be specified to decompose and assimilate cellulose and hemicellulose in woody substrates, and those producing chitinases may have mycoparasitic roles. Species with plant growth-promoting traits are good at uptake of exudates from plant roots. Overall, metabolic models reflect nutritional adaptation of Trichoderma to diverse niches in nature.

Trichoderma parareesei Favors the Tolerance of Rapeseed (Brassica napus L.) to Salinity and Drought Due to a Chorismate Mutase

Both drought and salinity represent the greatest plant abiotic stresses in crops. Increasing plant tolerance against these environmental conditions must be a key strategy in the development of future agriculture. The genus of Trichoderma filament fungi includes several species widely used as biocontrol agents for plant diseases but also some with the ability to increase plant tolerance against abiotic stresses. In this sense, using the species T. parareesei and T. harzianum, we have verified the differences between the two after their application in rapeseed (Brassica napus) root inoculation, with T. parareesei being a more efficient alternative to increase rapeseed productivity under drought or salinity conditions. In addition, we have determined the role that T. parareesei chorismate mutase plays in its ability to promote tolerance to salinity and drought in plants by increasing the expression of genes related to the hormonal pathways of abscisic acid (ABA) under drought stress, and ethylene (ET) under salt stress.

Metabolites in the root exudates of groundnut change during interaction with plant growth promoting rhizobacteria in a strain-specific manner

Plant growth promoting rhizobacteria (PGPR) are extensively used as biofertilizers to improve the soil nutrition for a variety of crop plants. The plant-PGPR interaction, with special reference to chemical signalling molecules is not understood clearly, unlike other beneficial plant-microbe interactions. Chemo-attraction of a PGPR from soil microbial pool towards a plant could be dependent on some of the molecules in the plant root exudates (REs), similar to the beneficial association of legume-rhizobia. In this study, a few functional properties of PGPR like growth, chemotaxis, and biofilm formation by two PGPR strains viz., Bacillus sonorensis RS4 and Pseudomonas aeruginosa RP2 were assessed in the presence of groundnut REs. Functional properties of both the strains were significantly influenced by the REs in a strain-dependent manner. Metabolite profiling of the REs from PGPR-bacterized (RS4 or RP2) and non-bacterized seedlings was performed with GC-MS/MS after 12 and 24 days of growth. A total of 75 metabolites were detected in groundnut REs. Threonine and glyoxylic oxime acid were detected in RP2-bacterized REs, while serine, pentanoic acid, glucopyranoside, tartaric acid, and 2-pyrrolidinone were detected in REs of seedlings bacterized with RP2 and RS4. The results suggested that the PGPR induced distinct variations in the REs. Identification of the interaction-specific metabolites will be useful to develop effective PGPR based bio-formulations for better PGPR colonization and improving crop yields.

Towards the Biological Control of Devastating Forest Pathogens from the Genus Armillaria

Research Highlights: A large scale effort to screen, characterize, and select Trichoderma strains with the potential to antagonize Armillaria species revealed promising candidates for field applications. Background and Objectives: Armillaria species are among the economically most relevant soilborne tree pathogens causing devastating root diseases worldwide. Biocontrol agents are environment-friendly alternatives to chemicals in restraining the spread of Armillaria in forest soils. Trichoderma species may efficiently employ diverse antagonistic mechanisms against fungal plant pathogens. The aim of this paper is to isolate indigenous Trichoderma strains from healthy and Armillaria-damaged forests, characterize them, screen their biocontrol properties, and test selected strains under field conditions. Materials and Methods: Armillaria and Trichoderma isolates were collected from soil samples of a damaged Hungarian oak and healthy Austrian spruce forests and identified to the species level. In vitro antagonism experiments were performed to determine the potential of the Trichoderma isolates to control Armillaria species. Selected biocontrol candidates were screened for extracellular enzyme production and plant growth-promoting traits. A field experiment was carried out by applying two selected Trichoderma strains on two-year-old European Turkey oak seedlings planted in a forest area heavily overtaken by the rhizomorphs of numerous Armillaria colonies. Results: Although A. cepistipes and A. ostoyae were found in the Austrian spruce forests, A. mellea and A. gallica clones dominated the Hungarian oak stand. A total of 64 Trichoderma isolates belonging to 14 species were recovered. Several Trichoderma strains exhibited in vitro antagonistic abilities towards Armillaria species and produced siderophores and indole-3-acetic acid. Oak seedlings treated with T. virens and T. atrobrunneum displayed better survival under harsh soil conditions than the untreated controls. Conclusions: Selected native Trichoderma strains, associated with Armillaria rhizomorphs, which may also have plant growth promoting properties, are potential antagonists of Armillaria spp., and such abilities can be exploited in the biological control of Armillaria root rot.

Supplementation of Trichoderma improves the alteration of nutrient allocation and transporter genes expression in rice under nutrient deficiencies

Nutrients are the finite natural resources that are essential for productivity and development of rice and its deficiency causes compromised yield along with reduced immunity against several biotic and abiotic stresses. In this study, the potential of Trichoderma reesei has been investigated as a biofertilizer (BF) to ameliorate nutrient stress in different rice cultivars at physiological, biochemical and molecular levels. The results indicated that cultivar Heena is much more compatible with BF as compared to cultivar Kiran at 50% nutrient limiting condition. Enhancement in physiological attributes and photosynthetic pigments were observed in BF treated Heena seedlings. The localization of biofertilizer in treated roots was further validated by scanning electron micrographs. This result correlated well with the higher levels of Indole acetic acid and Gibberellic acid in biofertilizer treated rice. Similarly, the uptake of micro-nutrients such as Fe, Co, Cu and Mo was found to be 1.4-1.9 fold higher respectively in BF treated Heena seedlings under 50% nutrient deficient condition. Furthermore, different stress ameliorating enzymes Guaiacol peroxidase, Super oxide dismutase, Total Phenolic Content, Phenol Peroxidase, Phenylalanine ammonia lyase and Ascorbate peroxidase in Heena seedlings were also increased by 1.8, 1.4, 1.2, 2.4, 1.2, and 8.3-fold respectively, at 50% nutrient deficient condition. The up-regulation of different micro and macro-nutrients allocation and accumulation; metal tolerance related; auxin synthesis genes in BF treated Heena as compared to 50% nutrient deficient condition was further supported by our findings that the application of biofertilizer efficiently ameliorated the deficiency of nutrients in rice.

Effects of Two Trichoderma Strains on Plant Growth, Rhizosphere Soil Nutrients, and Fungal Community of Pinus sylvestris var. mongolica Annual Seedlings

Trichoderma spp. are proposed as major plant growth-promoting fungi that widely exist in the natural environment. These strains have the abilities of rapid growth and reproduction and efficient transformation of soil nutrients. Moreover, they can change the plant rhizosphere soil environment and promote plant growth. Pinus sylvestris var. mongolica has the characteristics of strong drought resistance and fast growth and plays an important role in ecological construction and environmental restoration. The effects on the growth of annual seedlings, root structure, rhizosphere soil nutrients, enzyme activity, and fungal community structure of P. sylvestris var. mongolica were studied after inoculation with Trichoderma harzianum E15 and Trichoderma virens ZT05, separately. The results showed that after inoculation with T. harzianum E15 and T. virens ZT05, seedling biomass, root structure index, soil nutrients, and soil enzyme activity were significantly increased compared with the control (p < 0.05). There were significant differences in the effects of T. harzianum E15 and T. virens ZT05 inoculation on the growth and rhizosphere soil nutrient of P. sylvestris var. mongolica (p < 0.05). For the E15 treatment, the seedling height, ground diameter, and total biomass of seedlings were higher than that those of the ZT05 treatment, and the rhizosphere soil nutrient content and enzyme activity of the ZT05 treatment were higher than that of the E15 treatment. The results of alpha and beta diversity analyses showed that the fungi community structure of rhizosphere soil was significantly different (p < 0.05) among the three treatments (inoculated with T. harzianum E15, T. virens ZT05, and not inoculated with Trichoderma). Overall, Trichoderma inoculation was correlated with the change of rhizosphere soil nutrient content.

Arbuscular Mycorrhiza Enhances Biomass Production and Salt Tolerance of Sweet Sorghum

Arbuscular mycorrhizal (AM) fungi (AMF) are widely known to form a symbiosis with most higher plants and enhance plant adaptation to a series of environmental stresses. Sweet sorghum (Sorghum bicolor (L.) Moench) is considered a promising alternative feedstock for bioalcohol production because of its sugar-rich stalk and high biomass. However, little is known of AMF benefit for biomass production and salt tolerance of sweet sorghum. Here, we investigated the effects of Acaulospora mellea ZZ on growth and salt tolerance in two sweet sorghum cultivars (Liaotian5 and Yajin2) under different NaCl addition levels (0, 0.5, 1, 2, and 3 g NaCl/kg soil). Results showed AMF colonized the two cultivars well under all NaCl addition levels. NaCl addition increased mycorrhizal colonization rates in Yajin2, but the effects on Liaotian5 ranged from stimulatory at 0.5 and 1 g/kg to insignificant at 2 g/kg, and even inhibitory at 3 g/kg. High NaCl addition levels produced negative effects on both AM and non-AM plants, leading to lower biomass production, poorer mineral nutrition (N, P, K), higher Na⁺ uptake, and lower soluble sugar content in leaves. Compared with non-AM plants, AM plants of both cultivars had improved plant biomass and mineral uptake, as well as higher K⁺/Na⁺ ratio, but only Yajin2 plants had a low shoot/root Na ratio. AM inoculation increased the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and soluble sugar content in leaves. Overall, both cultivars benefited from mycorrhization, and Yajin2 with less salt tolerance showed higher mycorrhizal response. In conclusion, AMF could help to alleviate the negative effects caused by salinity, and thus showed potential in biomass production of sweet sorghum in saline soil.