Trichoderma asperellum (T42) and Pseudomonas fluorescens (OKC)-Enhances Resistance of Pea against Erysiphe pisi through Enhanced ROS Generation and Lignifications

Role of methylglyoxal and redox homeostasis in microbe-mediated stress mitigation in plants

One of the general consequences of stress in plants is the accumulation of reactive oxygen (ROS) and carbonyl species (like methylglyoxal) to levels that are detrimental for plant growth. These reactive species are inherently produced in all organisms and serve different physiological functions but their excessive accumulation results in cellular toxicity. It is, therefore, essential to restore equilibrium between their synthesis and breakdown to ensure normal cellular functioning. Detoxification mechanisms that scavenge these reactive species are considered important for stress mitigation as they maintain redox balance by restricting the levels of ROS, methylglyoxal and other reactive species in the cellular milieu. Stress tolerance imparted to plants by root-associated microbes involves a multitude of mechanisms, including maintenance of redox homeostasis. By improving the overall antioxidant response in plants, microbes can strengthen defense pathways and hence, the adaptive abilities of plants to sustain growth under stress. Hence, through this review we wish to highlight the contribution of root microbiota in modulating the levels of reactive species and thereby, maintaining redox homeostasis in plants as one of the important mechanisms of stress alleviation. Further, we also examine the microbial mechanisms of resistance to oxidative stress and their role in combating plant stress.

Soil bio-solarization and Trichoderma asperellum suppress black root rot disease and increase strawberry yield.. [DOI: 10.21203/rs.3.rs-3096529/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Trichoderma asperellum applied as pellets, disks, or spore suspension against the causal agents of strawberry-black root rot disease represented by three fungal species was tested. The pellets/disks could significantly reduce the growth area of the pathogenic fungi Rhizoctonia solani, Fusarium solani, and Macrophomina phaseolina in vitro. Solarization via mulching soil with transparent polyethylene sheets could affect these pathogens. It reduced the counts of the fungi buried in cloth bags at 1–10 cm of soil surface by 70, 65, and 65% for R. solani, F. solani, and M. phaseolina, respectively relative to unmulched soil. Yet, the more depths of bags in soil, the less the mulching affects the three pathogens. In two field experiments, the disease incidence and severity were more reduced when T. asperellum pellets/suspension was integrated with bio-solarization (mulching soon after bio-fumigation with Al-Abour Compost®)) than any single treatment. The highest reductions obtained by T. asperellum pellets combined with bio-solarization averaged 75 and 73.8%, respectively. Bio-solarization with Actamyl affected the disease incidence/severity to a lesser extent. All tested treatments significantly boosted yield of strawberry plants. Strawberry yield and activities of the pathogenesis-related proteins peroxidase and chitinase showed favorable responses almost parallel to the extent of reduction in the disease incidence and severity caused by all treatments. The highest yield increase achieved via combining T. asperellum pellets with bio-solarization was 160.8%. Our results support hypothetical biocontrol potential that T. asperellum and bio-solarization together with adequate phytosanitary measures can reliably control strawberry-black root rot disease and enhance strawberry yield.

A Plant Biostimulant from Ascophyllum nodosum Potentiates Plant Growth Promotion and Stress Protection Activity of Pseudomonas protegens CHA0

Abiotic stresses, including salinity stress, affect numerous crops, causing yield reduction, and, as a result, important economic losses. Extracts from the brown alga Ascophyllum nodosum (ANE), and compounds secreted by the Pseudomonas protegens strain, CHA0, can mitigate these effects by inducing tolerance against salt stress. However, the influence of ANE on P. protegens CHA0 secretion, and the combined effects of these two biostimulants on plant growth, are not known. Fucoidan, alginate, and mannitol are abundant components of brown algae and of ANE. Reported here are the effects of a commercial formulation of ANE, fucoidan, alginate, and mannitol, on pea (Pisum sativum), and on the plant growth-promoting activity of P. protegens CHA0. In most situations, ANE and fucoidan increased indole-3-acetic acid (IAA) and siderophore production, phosphate solubilization, and hydrogen cyanide (HCN) production by P. protegens CHA0. Colonization of pea roots by P. protegens CHA0 was found to be increased mostly by ANE and fucoidan in normal conditions and under salt stress. Applications of P. protegens CHA0 combined with ANE, or with fucoidan, alginate, and mannitol, generally augmented root and shoot growth in normal and salinity stress conditions. Real-time quantitative PCR analyses of P. protegens revealed that, in many instances, ANE and fucoidan enhanced the expression of several genes involved in chemotaxis (cheW and WspR), pyoverdine production (pvdS), and HCN production (hcnA), but gene expression patterns overlapped only occasionally those of growth-promoting parameters. Overall, the increased colonization and the enhanced activities of P. protegens CHA0 in the presence of ANE and its components mitigated salinity stress in pea. Among treatments, ANE and fucoidan were found responsible for most of the increased activities of P. protegens CHA0 and the improved plant growth.

Plant growth promotion and differential expression of defense genes in chilli pepper against Colletotrichum truncatum induced by Trichoderma asperellum and T. harzianum

BACKGROUND

Trichoderma asperellum and T. harzianum were assessed in this study as a potential biological control against Colletotrichum truncatum. C. truncatum is a hemibiotrophic fungus that causes anthracnose disease in chilli thereby affecting plant growth and fruit yield. Scanning electron microscope (SEM) technique showed the beneficial interaction between chilli root-Trichoderma spp. inducing the plant growth promotion, mechanical barrier, and defense network under C. truncatum challenged conditions.

METHODS

Seeds bio-primed with T. asperellum, T. harzianum, and T. asperellum + T. harzianum promoted the plant growth parameters and strengthening of physical barrier via lignification on the wall of vascular tissues. Seed primed with bioagents were used for exploring the molecular mechanism of defense response in pepper against anthracnose to assess the temporal expression of six defense genes in the Surajmukhi variety of Capsicum annuum. QRT-PCR demonstrated induction of defense responsive genes in chilli pepper bioprimed with Trichoderma spp. such as plant defensin 1.2 (CaPDF1.2), superoxide dismutase (SOD), ascorbate peroxidase (APx), guaiacol peroxidase (GPx), pathogenesis related proteins PR-2 and PR-5.

RESULTS

The results showed that bioprimed seeds were assessed for T. asperellum, T. harzianum, and T. asperellum + T. harzianum-chilli root colonization interaction under in vivo conditions. The results of the scanning electron microscope revealed that T. asperellum, T. harzianum and T. asperellum + T. harzianum interact with chilli roots directly via the development of plant-Trichoderma interaction system. Seeds bio-primed with bioagents promoted the plant growth parameters, fresh and dry weight of shoot and root, plant height, leaf area index, number of leaves, stem diameter and strengthening of physical barrier via lignification on the wall of vascular tissues and expression of six defense related genes in pepper against anthracnose.

CONCLUSIONS

Application of T. asperellum and T. harzianum and in combination of treatments enhanced the plant growth. Further, as seeds bioprimed with T. asperellum, T. harzianum and in combination with treatment of T. asperellum + T. harzianum induced the strengthening of the cell wall by lignification and expression of six defense related genes CaPDF1.2, SOD, APx, GPx, PR-2 and PR-5 in pepper against C. truncatum. Our study contributed for better disease management through biopriming with T. asperellum, T. harzianum and T. asperellum + T. harzianum. The biopriming possess enormous potential to promote plant growth, modulate the physical barrier, and induced the defense related genes in chilli pepper against anthracnose.

Root cell wall remodeling: A way for exopolysaccharides to mitigate cadmium toxicity in rice seedling

Exopolysaccharides (EPS) are macromolecules with environment beneficial properties. Currently, numerous studies focus on the absorption of heavy metals by EPS, but less attention has been paid to the effects of EPS on the plants. This study explored the effects of EPS from Lactobacillus plantarum LPC-1 on the structure and function of cell walls in rice seedling roots under cadmium (Cd) stress. The results showed that EPS could regulate the remodeling process of the cell walls of rice roots. EPS affects the synthesis efficiency and the content of the substances that made up the cell wall, and thus plays an essential role in limiting the uptake and transport of Cd in rice root. Furthermore, EPS could induce plant resistance to heavy metals by regulating the lignin biosynthesis pathway in rice roots. Finally, the cell wall remodeling induced by EPS likely contributes to plant stress responses by activating the reactive oxygen species (ROS) signaling.

Trichoderma Species: Our Best Fungal Allies in the Biocontrol of Plant Diseases-A Review

Biocontrol agents (BCA) have been an important tool in agriculture to prevent crop losses due to plant pathogens infections and to increase plant food production globally, diminishing the necessity for chemical pesticides and fertilizers and offering a more sustainable and environmentally friendly option. Fungi from the genus Trichoderma are among the most used and studied microorganisms as BCA due to the variety of biocontrol traits, such as parasitism, antibiosis, secondary metabolites (SM) production, and plant defense system induction. Several Trichoderma species are well-known mycoparasites. However, some of those species can antagonize other organisms such as nematodes and plant pests, making this fungus a very versatile BCA. Trichoderma has been used in agriculture as part of innovative bioformulations, either just Trichoderma species or in combination with other plant-beneficial microbes, such as plant growth-promoting bacteria (PGPB). Here, we review the most recent literature regarding the biocontrol studies about six of the most used Trichoderma species, T. atroviride, T. harzianum, T. asperellum, T. virens, T. longibrachiatum, and T. viride, highlighting their biocontrol traits and the use of these fungal genera in Trichoderma-based formulations to control or prevent plant diseases, and their importance as a substitute for chemical pesticides and fertilizers.

The Role of Endophytes in Combating Fungal- and Bacterial-Induced Stress in Plants

Plants are subjected to multifaceted stresses that significantly jeopardize crop production. Pathogenic microbes influence biotic stress in plants, which ultimately causes annual crop loss worldwide. Although the use of pesticides and fungicides can curb the proliferation of pathogens in plants and enhance crop production, they pollute the environment and cause several health issues in humans and animals. Hence, there is a need for alternative biocontrol agents that offer an eco-friendly mode of controlling plant diseases. This review discusses fungal- and bacterial-induced stress in plants, which causes various plant diseases, and the role of biocontrol defense mechanisms, for example, the production of hydrolytic enzymes, secondary metabolites, and siderophores by stress-tolerant fungi and bacteria to combat plant pathogens. It is observed that beneficial endophytes could sustain crop production and resolve the issues regarding crop yield caused by bacterial and fungal pathogens. The collated literature review indicates that future research is necessary to identify potential biocontrol agents that can minimize the utility of synthetic pesticides and increase the tenable agricultural production.

Effect of copper stress on Phaseolus coccineus in the presence of exogenous methyl jasmonate and/or Serratia plymuthica from the Spitsbergen soil

Copper stress in the presence of exogenous methyl jasmonate and Serratia plymuthica in a complete trifactorial design with copper (0, 50 µM), methyl jasmonate (0, 1, 10 µM) and Serratia plymuthica (without and with inoculation) was studied on the physiological parameters of Phaseolus coccineus. Copper application reduced biomass and allantoin content, but increased chlorophyll and carotenoids contents as well as catalase and peroxidases activities. Jasmonate did not modify biomass and organic acids levels under copper treatment, but additional inoculation elevated biomass and content of tartrate, malate and succinate. Jasmonate used alone or in combination with bacteria increased superoxide dismutase activity in copper application. With copper, allantoin content elevated at lower jasmonate concentration, but with additional inoculation - at higher jasmonate concentration. Under copper stress, inoculation resulted in higher accumulation of tartrate, malate and citrate contents in roots, which corresponded with lower allantoin concentration in roots. Combined with copper, inoculation reduced catalase and guaiacol peroxidase activities, whereas organic acids content was higher. Under metal stress, with bacteria, jasmonate reduced phenolics content, elevated superoxide dismutase and guaiacol peroxidase activities. The data indicate that jasmonate and S. plymuthica affected most physiological parameters of P. coccineus grown with copper and revealed some effect on biomass.

Synergism of endophytic Bacillus subtilis and Klebsiella aerogenes modulates plant growth and bacoside biosynthesis in Bacopa monnieri

Bacopa monnieri is the main source of pharmaceutically important bacosides; however, the low content of these molecules in planta remains a limiting factor for fulfilling the industrial requirement. The accumulation of secondary metabolites can be enhanced in plants upon inoculation with endophytes. In this study, we isolated and analyzed the culturable endophytes associated with different plant parts. By analyzing their impact on plant growth parameters (in vitro and in vivo) and Bacoside A content, we found few candidates which increased bacoside accumulation significantly. Finally, two promising endophytes namely Bacillus subtilis (OK070745) and Klebsiella aerogenes (OK070774) were co-cultivated with B. monnieri cuttings singly and in combination mode to clarify their effect on bacoside biosynthesis and their accumulation in B. monnieri shoot. Consortium-inoculated plants significantly enhanced the plant biomass and Bacoside A content with respect to single inoculation. The results of real-time quantitative (RT-PCR) revealed significant accumulation of bacoside biosynthetic pathway transcripts (HMGCR, PMVK, FDPS, SQS, and β-AS) in the case of plants inoculated with microbial combination, while the single inoculation of B. subtilis diverted the plant's machinery toward the synthesis of phenylpropanoid genes like CCR, CAD, CHS, and HST. In addition, higher expression of MYB 2 and WRKY 1 transcription factors in combinational treatment points out their probable role in better physiological and developmental processes. Altogether, this is the first study on B. monnieri-endophyte interaction showing improvement in the accumulation of bacoside A by modulating various genes of metabolic pathway and thus suggests an effective "green approach" for augmenting in planta production of pharmaceutically important bacosides.

Bacillus subtilis- and Pseudomonas fluorescens-Mediated Systemic Resistance in Tomato Against Sclerotium rolfsii and Study of Physio-Chemical Alterations

The present study is a comparative study between Reactive Oxygen Species (ROS) signaling and antioxidative enzymatic signaling and deals with induced systemic resistance (ISR) in enhancing the disease resistance in typical tomato plant (Solanum lycopersicum L.) infected by the collar rot fungus, Sclerotium rolfsii (Teleomorph: Athelia rolfsii) by priming with Bacillus subtilis, Pseudomonas fluorescens, and their microbial consortia by a single strain of Bacillus subtilis, and P. fluorescens as well as by developed microbial consortium with both bacteria. Leaf samples were collected after different durations of pathogen inoculation, i.e., 1, 2, 3, and 4 days, and the systemic level of oxidative stress parameters, such as hydrogen peroxide (H2O2), photosynthetic apparatus, superoxide radicals, and enzymatic antioxidants, were studied. Plant mortality under various treatments in two different seasons was calculated. The highest H2O2 was scavenged by the microbial consortium-treated plants (B1P1) and the lowest in pathogen-challenged plants (PC) compared to the untreated control. Cellular damage and reduction in the chlorophyll pigments were the highest at 48 h, and the photosynthetic efficiency (Fv/Fm) was evaluated from 24 to 96 h; the lowest values were observed for pathogen-challenged plants and the highest for B1P1. Enzymatic antioxidants showed the maximum value for B1P1 and the minimum for PC compared to the unchallenged control. Furthermore, an analysis of variance and principal component analysis (PCA) were conducted to examine the effect of the evaluation time (ET) and inoculation conditions (ICs) alone and in combination (ET × IC) on the physiological and biochemical parameters; accordingly, the score and the loading plots were constructed. Tomato root sections inoculated with different treatments were observed through scanning electron microscopy (SEM) to validate the potentiality of primed biocontrol agents in controlling the invasion of the pathogen. Further studies on the potential of this isolate to enhance the plant growth at the field level would strengthen the possibility of using the isolate as an alternative for organic fertilizers and pesticides.

Peduncle Necking in Rosa hybrida Induces Stress-Related Transcription Factors, Upregulates Galactose Metabolism, and Downregulates Phenylpropanoid Biosynthesis Genes

Roses are highly valued as cut flowers worldwide but have limited vase life. Peduncle bending "bent neck" or "necking" is a major cause of reduced vase life, especially in some cultivars. Necking is thought to be caused by either an air embolism or accumulation of microorganisms at or within the stem end, blocking the xylem vessels and preventing water uptake. However, the underlying mechanisms of necking are poorly understood. Here, RNAseq analysis was applied to compare gene expression across three stages of peduncle necking (straight, <90°, and >90°), in the necking-susceptible Rosa hybrida cultivar H30. Most gene expression change was later in bending and there was, overall, more downregulation than upregulation of gene expression during necking. Photosynthetic, starch, and lignin biosynthesis genes were all downregulated, while genes associated with galactose metabolism, producing raffinose and trehalose that are both related to osmoprotection, were upregulated. Genes associated with starch breakdown, autophagy, and senescence were also upregulated, as were most of the NAC and WRKY transcription factors, involved in stress and senescence regulation. Microscopy showed a cellular collapse in the peduncle. These data support a possible mechanism, whereby a reduction in water transport leads to a cellular collapse in the peduncle, accompanied by upregulation of senescence and drought responses.

Prospects for Abiotic Stress Tolerance in Crops Utilizing Phyto- and Bio-Stimulants

Environmental stressors such as salinity, drought, high temperature, high rainfall, etc. have already demonstrated the negative impacts on plant growth and development and thereby limiting productivity of the crops. Therefore, in the time to come, more sustainable efforts are required in agricultural practices to ensure food production and security under such adverse environmental conditions. A most promising and eco-friendly way to achieve this goal would be to apply biostimulants to address the environmental concerns. Non-microbial biostimulants such as humic substances (HA), protein hydrolysate, plant-based products and seaweed extracts (SWE), etc. and/or microbial inoculants comprising of plant growth-promoting microbes such as arbuscular mycorrhizal fungi (AMF), fluorescent and non-fluorescent Pseudomonas, Trichoderma spp., Bacillus spp. etc. have tremendous potentiality to enhance plant growth, flowering, crop productivity, nutrient use efficiency (NUE) and translocation, as well as enhancing tolerance to a wide range of abiotic stresses by modifying physiological, biological and biochemical processes of the crop-plants. Similarly, application techniques and timing are also important to achieve the desired results. In this article we discussed the prospects of using seaweed, microbial, and plant-based biostimulants either individually or in combination for managing environmental stresses to achieve food security in a sustainable way. Particular attention was given to the modifications that take place in plant's physiology under adverse environmental conditions and how different biostimulants re-program the host's physiology to withstand such stresses. Additionally, we also discussed how application of biostimulants can overcome the issue of nutrient deficiency in agricultural lands and improve their use efficiency by crop plants.

Legume Crops and Biotrophic Pathogen Interactions: A Continuous Cross-Talk of a Multilayered Array of Defense Mechanisms

Legume species are recognized for their nutritional benefits and contribution to the sustainability of agricultural systems. However, their production is threatened by biotic constraints with devastating impacts on crop yield. A deep understanding of the molecular and genetic architecture of resistance sources culminating in immunity is critical to assist new biotechnological approaches for plant protection. In this review, the current knowledge regarding the major plant immune system components of grain and forage legumes challenged with obligate airborne biotrophic fungi will be comprehensively evaluated and discussed while identifying future directions of research. To achieve this, we will address the multi-layered defense strategies deployed by legume crops at the biochemical, molecular, and physiological levels, leading to rapid pathogen recognition and carrying the necessary information to sub-cellular components, on-setting a dynamic and organized defense. Emphasis will be given to recent approaches such as the identification of critical components of host decentralized immune response negatively regulated by pathogens while targeting the loss-of-function of susceptibility genes. We conclude that advances in gene expression analysis in both host and pathogen, protocols for effectoromics pipelines, and high-throughput disease phenomics platforms are rapidly leading to a deeper understanding of the intricate host-pathogen interaction, crucial for efficient disease resistance breeding initiatives.

Combined application of Ascophyllum nodosum extract and chitosan synergistically activates host-defense of peas against powdery mildew

BACKGROUND

Powdery mildew (PM) is an important disease of pea that reduce yield. Ascophyllum nodosum extract (ANE) and chitosan (CHT) are biostimulants used to improve plant health. Efficacy of ANE and CHT was assessed individually and in combination against pea powdery mildew.

RESULTS

Combined applications of ANE and CHT had a significant inhibitory effect on pathogen development and it reduced disease severity to 35%, as compared to control (90.5%). The combination of ANE and CHT enhanced the activity of plant defense enzymes; phenylalanine ammonia lyases (PAL), peroxidase (PO) and production of reactive oxygen species (ROS) and hydrogen peroxide (H2O2). Further, the treatment increased the expression of a number of plant defense genes in jasmonic acid (JA) signaling pathway such as LOX1 and COI and salicylic acid (SA)-mediated signaling pathway such as NPR1 and PR1. Other genes involved in defense mechanisms like NADPH oxidase and C4H were also upregulated by the combination treatment.

CONCLUSION

The combination of ANE and CHT suppresses pea powdery mildew largely by modulating JA and SA-mediated signaling pathways.

Bacterial Isolate Inhabiting Spitsbergen Soil Modifies the Physiological Response of Phaseolus coccineus in Control Conditions and under Exogenous Application of Methyl Jasmonate and Copper Excess

The aim of the study was to demonstrate the potential of the promotion and regulation of plant physiology and growth under control and copper stress conditions, and the impact of the exogenous application of methyl jasmonate on this potential. Runner bean plants were treated with methyl jasmonate (1 or 10 µM) (J; J1 or J10) and Cu (50 µM), and inoculated with a bacterial isolate (S17) originating from Spitsbergen soil, and identified as Pseudomonas luteola using the analytical profile index (API) test. Above- and under-ground plant parts were analyzed. The growth parameters; the concentration of the photosynthetic pigments, elements, flavonoids (FLAVO), phenolics (TPC), allantoin (ALLA), and low molecular weight organic acids (LMWOAs); the activity of antioxidant enzymes and enzymes of resistance induction pathways (e.g., superoxide dismutase (SOD), catalase (CAT), ascorbate (APX) and guaiacol (GPX) peroxidase, glucanase (GLU), and phenylalanine (PAL) and tyrosine ammonia-lyase (TAL)), and the antioxidant capacity (AC) were studied. The leaves exhibited substantially higher ALLA and LMWOA concentrations as well as PAL and TAL activities, whereas the roots mostly had higher activities for a majority of the enzymes tested (i.e., SOD, CAT, APX, GPX, and GLU). The inoculation with S17 mitigated the effect of the Cu stress. Under the Cu stress and in the presence of J10, isolate S17 caused an elevation of the shoot fresh weight, K concentration, and TAL activity in the leaves, and APX and GPX (also at J1) activities in the roots. In the absence of Cu, isolate S17 increased the root length and the shoot-to-root ratio, but without statistical significance. In these conditions, S17 contributed to a 236% and 34% enhancement of P and Mn, respectively, in the roots, and a 19% rise of N in the leaves. Under the Cu stress, S17 caused a significant increase in FLAVO and TPC in the leaves. Similarly, the levels of FLAVO, TPC, and AC were enhanced after inoculation with Cu and J1. Regardless of the presence of J, inoculation at Cu excess caused a reduction of SOD and CAT activities, and an elevation of GPX. The effects of inoculation were associated with the application of Cu and J, which modified plant response mainly in a concentration-dependent manner (e.g., PAL, TAL, and LMWOA levels). The conducted studies demonstrated the potential for isolate S17 in the promotion of plant growth.

Mutual interplay between phytopathogenic powdery mildew fungi and other microorganisms

Powdery mildew is a common and widespread plant disease of considerable agronomic relevance. It is caused by obligate biotrophic fungal pathogens which, in most cases, epiphytically colonize aboveground plant tissues. The disease has been typically studied as a binary interaction of the fungal pathogen with its plant hosts, neglecting, for the most part, the mutual interplay with the wealth of other microorganisms residing in the phyllo- and/or rhizosphere and roots. However, the establishment of powdery mildew disease can be impacted by the presence/absence of host-associated microbiota (epi- and endophytes) and, conversely, plant colonization by powdery mildew fungi might disturb indigenous microbial community structures. In addition, other (foliar) phytopathogens could interact with powdery mildews, and mycoparasites may affect the outcome of plant-powdery mildew interactions. In this review, we discuss the current knowledge regarding the intricate and multifaceted interplay of powdery mildew fungi, host plants and other microorganisms, and outline current gaps in our knowledge, thereby setting the basis for potential future research directions.

A novel function of N-signaling in plants with special reference to Trichoderma interaction influencing plant growth, nitrogen use efficiency, and cross talk with plant hormones

Trichoderma spp. is considered as a plant growth promoter and biocontrol fungal agents. They colonize on the surface of root in most of the agriculture crops. They secrete different secondary metabolites and enzymes which promote different physiological processes as well as protect plants from various environmental stresses. This is part of their vital functions. They are widely exploited as a biocontrol agent and plant growth promoter in agricultural fields. Colonization of Trichoderma with roots can enhance nutrient acquisition from surrounding soil to root and can substantially increase nitrogen use efficiency (NUE) in crops and linked with activation of plant signaling cascade. Among Trichoderma species, only some Trichoderma species were well characterized which help in the uptake of nitrogen-containing compound (especially nitrate form) and induced nitric oxide (NO) in plants. Both nitrate and NO are known as a signaling agent, involved in plant growth and development and disease resistance. Activation of these signaling molecules may crosstalk with other signaling molecule (Ca²⁺) and phytohormone (auxin, gibberellins, cytokinin and ethylene). This ability of Trichoderma is important to agriculture not only for increased plant growth but also to control plant diseases. Recently, Trichoderma strains have been shown to encompass the ability to regulate transcripts level of high-affinity nitrate transporters and probably it was positively regulated by NO. This review aims to focus the usage of Trichoderma strains on crops by their abilities to regulate transcript levels, probably through activation of plant N signaling transduction that improve plant health.

Trichoderma erinaceum Bio-Priming Modulates the WRKYs Defense Programming in Tomato Against the Fusarium oxysporum f. sp. lycopersici (Fol) Challenged Condition

The beneficial association and interaction of rhizocompetent microorganisms are widely used for plant biofertilization and amelioration of stress-induced damage in plants. To explore the regulatory mechanism involved in plant defense while associating with beneficial microbial species, and their interplay when co-inoculated with pathogens, we evaluated the response of tomato defense-related WRKY gene transcripts. The present study was carried out to examine the qRT-PCR-based relative quantification of differentially expressed defense-related genes in tomato (Solanum lycopersicum L.; variety S-22) primed with Trichoderma erinaceum against the vascular wilt pathogen (Fusarium oxysporum f. sp. lycopersici). The tissue-specific and time-bound expression profile changes under the four different treatments "(unprimed, Fol challenged, T. erinaceum primed and Fol+ T. erinaceum)" revealed that the highest upregulation was observed in the transcript profile of SlWRKY31 (root) and SlWRKY37 (leaf) in T. erinaceum bioprimed treated plants at 24 h with 16.51- and 14.07-fold increase, respectively. In contrast, SlWRKY4 showed downregulation with the highest repression in T. erinaceum bioprimed root (24 h) and leaf (48 h) tissue samples with 0.03 and 0.08 fold decrease, respectively. Qualitative expression of PR proteins (chitinases and glucanases) was found elicited in T. erinaceum primed plants. However, the antioxidative activity of tomato superoxide dismutase and catalase increased with the highest upregulation of SOD and SlGPX1 in Fol + T. erinaceum treatments. We observed that these expression changes were accompanied by 32.06% lesser H₂O₂ production in T. erinaceum bioprimed samples. The aggravated defense response in all the treated conditions was also reflected by an increased lignified stem tissues. Overall, we conclude that T. erinaceum bio-priming modulated the defense transcriptome of tomato after the Fol challenged conditions, and were accompanied by enhanced accumulation of defense-related WRKY transcripts, increased antioxidative enzyme activities, and the reinforcements through a higher number of lignified cell layers.

Trichoderma mediate early and enhanced lignifications in chickpea during Fusarium oxysporum f. sp. ciceris infection

Lignifications in secondary cell walls play a significant role in defense mechanisms of plants against the invading pathogens. In the present study, we investigated Trichoderma strain specific lignifications in chickpea plants pre-treated with 10 potential Trichoderma strains and subsequently challenged with the wilt pathogen Fusarium oxysporum f. sp. ciceris (Foc). Trichoderma-induced lignifications in chickpea were observed through histochemical staining and expression of some genes of the lignin biosynthetic pathway. Lignifications were observed in transverse sections of shoots near the soil line through histochemical staining and expression pattern of the target genes was observed in root tissues through semi quantitative RT-PCR at different time intervals after inoculation of F. oxysporum f. sp. ciceris. Lignin deposition and expression pattern of the target genes were variable in each treatment. Lignifications were enhanced in all 10 Trichoderma strain treated and F. oxysporum f. sp. ciceris challenged chickpea plants. However, four Trichoderma strains viz., T-42, MV-41, DFL, and RO, triggered significantly high lignifications compared to the other six strains. Time course studies showed that effective Trichoderma isolates induced lignifications very early compared to the other strains and the process of lignifications nearly completes within 6 days of pathogen challenge. Thus, from the results it can be concluded that effective Trichoderma strains trigger lignifications very early in chickpea under Foc challenge and provide better protection to chickpea plants.

Compatible Rhizosphere-Competent Microbial Consortium Adds Value to the Nutritional Quality in Edible Parts of Chickpea

Chickpea is used as a high-energy and protein source in diets of humans and livestock. Moreover, chickpea straw can be used as alternative of forage in ruminant diets. The present study evaluates the effect of beneficial microbial inoculation on enhancing the nutritional values in edible parts of chickpea. Two rhizosphere-competent compatible microbes (Pseudomonas fluorescens OKC and Trichoderma asperellum T42) were selected and applied to seeds either individually or in consortium before sowing. Chickpea seeds treated with the microbes showed enhanced plant growth [88.93% shoot length at 60 days after sowing (DAS)] and biomass accumulation (21.37% at 120 DAS). Notably, the uptake of mineral nutrients, viz., N (90.27, 91.45, and 142.64%), P (14.13, 58.73, and 56.84%), K (20.5, 9.23, and 35.98%), Na (91.98, 101.66, and 36.46%), Ca (16.61, 29.46, and 16%), and organic carbon (28.54, 17.09, and 18.54%), was found in the seed, foliage, and pericarp of the chickpea plants, respectively. Additionally, nutritional quality, viz., total phenolic (59.7, 2.8, and 17.25%), protein (9.78, 18.53, and 7.68%), carbohydrate content (26.22, 30.21, and 26.63%), total flavonoid content (3.11, 9.15, and 7.81%), and reducing power (112.98, 75.42, and 111.75%), was also found in the seed, foliage, and pericarp of the chickpea plants. Most importantly, the microbial-consortium-treated plants showed the maximum increase of nutrient accumulation and enhancement in nutritional quality in all edible parts of chickpea. Nutritional partitioning in different edible parts of chickpea was also evident in the microbial treatments compared to their uninoculated ones. The results thus clearly demonstrated microbe-mediated enhancement in the dietary value of the edible parts of chickpea because seeds are consumed by humans, whereas pericarp and foliage (straw) are used as an alternative of forage and roughage in ruminant diets.