Insights into the molecular mechanism of Trichoderma stimulating plant growth and immunity against phytopathogens.

Trichoderma species have received significant interest as beneficial fungi for boosting plant growth and immunity against phytopathogens. By establishing a mutualistic relationship with plants, Trichoderma causes a series of intricate signaling events that eventually promote plant growth and improve disease resistance. The mechanisms contain the indirect or direct involvement of Trichoderma in enhancing plant growth by modulating phytohormones signaling pathways, improving uptake and accumulation of nutrients, and increasing soil bioavailability of nutrients. They contribute to plant resistance by stimulating systemic acquired resistance through salicylic acid, jasmonic acid, and ethylene signaling. A cascade of signal transduction processes initiated by the interaction of Trichoderma and plants regulate the expression of defense-related genes, resulting in the synthesis of defense hormones and pathogenesis-related proteins (PRPs), which collectively improve plant resistance. Additionally, advancements in omics technologies has led to the identification of key pathways, their regulating genes, and molecular interactions in the plant defense and growth promotion responses induced by Trichoderma. Deciphering the molecular mechanism behind Trichoderma's induction of plant defense and immunity is essential for harnessing the full plant beneficial potential of Trichoderma. This review article sheds light on the molecular mechanisms that underlie the positive effects of Trichoderma-induced plant immunity and growth and opens new opportunities for developing environmentally friendly and innovative approaches to improve plant immunity and growth.

Methylorubrum rhodesianum M520 as a biocontrol agent against Meloidogyne incognita (Tylenchida: Heteroderidae) J2s infecting cucumber roots.

AIMS: Root-knot nematodes (RKNs) are plant pathogens that cause huge economic losses worldwide. The biological management of RKNs may be a sustainable alternative to chemical control methods. Here, the biocontrol potential of Methylorubrum rhodesianum M520 against the RKN Meloidogyne incognita was investigated to theoretically support its application as a biocontrol agent in field production. METHODS AND RESULTS: In-vitro assays showed 91.9% mortality of M. incognita second-stage juveniles in the presence of strain M520 and that the hatching rate of M. incognita eggs was 21.7% lower than that of eggs treated with sterile water. In pot experiments, the M520 treatment caused 70.8% reduction in root-knots and increased plant shoot length and stem and root fresh weights, compared to control plant values. In split-root experiments, cucumber roots treated with M520 showed 25.6% decrease in root gall number, compared to that in control roots. CONCLUSION: M520 has multiple mechanisms against RKNs and might be used as a biocontrol agent against M. incognita in cucumber, laying a foundation for further studying M520 biocontrol against RKNs.

Management of Ralstonia solanacearum in Tomato Using ZnO Nanoparticles Synthesized Through Matricaria chamomilla.

Matricaria chamomilla flower extract was used as a biocompatible material for synthesis of zinc oxide nanoparticles (ZnONPs). The synthesized NPs were evaluated for their antibacterial potential in vitro and in vivo against the Gram-negative bacterium Ralstonia solanacearum, which causes devastating bacterial wilt disease in tomato and other crops. Synthesized ZnONPs were further analyzed by UV-visible spectroscopy, Fourier transform infrared spectroscopy, x-ray diffraction, transmission electron microscopy, and scanning electron microscopy with energy-dispersive spectroscopy. The synthesized polydisperse ZnONPs were found to be in the size range of 8.9 to 32.6 nm, and at 18.0 µg ml-1 exhibited maximum in vitro growth inhibition of the pathogen R. solanacearum. Scanning electron microscopy analysis of affected bacterial cells showed morphological deformation such as disruption of the cell membrane and wall, and the leakage of cell contents. Results of in vivo studies also showed that application of ZnONPs to the artificially inoculated tomato plants with the pathogen R. solanacearum significantly enhanced the plant growth by reducing bacterial soil population and disease severity as compared with the untreated control. Biosynthesized ZnONPs could be an effective approach to control the bacterium R. solanacearum.

Parthenium hysterophorus alleviates wilt stress in tomato plants caused by Ralstonia solanacearum through direct antibacterial effect and indirect upregulation of host resistance.

Heavy damage to tomato crops due to wilt stress caused by the pathogenic bacterium Ralstonia solanacearum and the insufficient availability of management strategies with desired control levels urged the researchers to investigate more reliable control methods to manage this issue in tomato and other horticultural crops. In this study, Parthenium hysterophorus, a locally and freely available herbaceous plant, was successfully used to manage bacterial wilt of tomatoes. The significant growth reduction ability of P. hysterophorus leaf extract was recorded in an agar well diffusion test and its ability to severally damage the bacterial cells was confirmed in SEM analysis. In both greenhouse and field trials, soil amended with P. hysterophorus leaf powder at 25 g/kg soil was found to effectively suppress the pathogen population in soil and significantly reduce the wilt severity on tomato plants, resulting in increased growth and yield of tomato plants. P. hysterophorus leaf powder at concentrations greater than 25 g/kg soil caused phytotoxicity in tomato plants. The results showed that P. hysterophorus powder applied through the mixing of soil for a longer period of time before transplanting tomato plants was more effective than mulching application and a shorter period of transplantation. Finally, the indirect effect of P. hysterophorus powder in managing bacterial wilt stress was evaluated using expression analysis of two resistance-related genes, PR2 and TPX. The upregulation of these two resistance-related genes was recorded by the soil application of P. hysterophorus powder. The findings of this study revealed the direct and indirect action mechanisms of P. hysterophorus powder applied to the soil for the management of bacterial wilting stress in tomato plants and provided the basis for including this technique as a safe and effective management strategy in an integrated disease management package.

Mitigating Cd and bacterial wilt stress in tomato plants through trico-synthesized silicon nanoparticles and Trichoderma metabolites.

There has been a growing apprehension in recent years about the harmful effects of environmental pollutants on agricultural output, encompassing both living organisms and non-living factors that cause stress. In this study, the soil application of bulk silicon (Si), silicon nanoparticles (SiNPs) and Trichoderma metabolites (TM) were investigated alone or in combination for the management of an important abiotic stress i.e. Cd toxicity and biotic stress i.e. bacterial wilt (BW) in tomato plants. SiNPs were synthesized by Trichoderma and confirmed through XRD, FTIR, and Ranman spectrum analysis. Results showed that Si, SiNPs and TM were all effective treatments. The combine treatment of SiNPs and TM followed by SiNPs alone were superior over other treatments in mitigating Cd toxicity and reducing BW disease on tomato plants. The soil application of these treatments reduced the Cd toxicity by enhancing Cd-tolerance index, decreasing bioavailability of soil Cd, reducing Cd contents and translocation in plants, improving gaseous exchange, photosynthesis, and increasing the antioxidant enzyme activities and their transcriptions. These treatments significantly suppressed BW pathogen leading to the significant decrease in disease index and severity on plants. In vitro evaluation and scanning electron microscopic (SEM) analysis revealed that SiNPs and TM significantly disrupted the cellular morphology of BW pathogen Ralstonia solanacearum. Findings of this study proposes the possible use of SiNPs and TM in mitigating the Cd and BW stress in tomato plants and possibly in other crops.

Bioactive Secondary Metabolites from Trichoderma spp. against Phytopathogenic Fungi.

Phytopathogenic fungi, causing significant economic and production losses, are becoming a serious threat to global food security. Due to an increase in fungal resistance and the hazardous effects of chemical fungicides to human and environmental health, scientists are now engaged to explore alternate non-chemical and ecofriendly management strategies. The use of biocontrol agents and their secondary metabolites (SMs) is one of the potential approaches used today. Trichoderma spp. are well known biocontrol agents used globally. Many Trichoderma species are the most prominent producers of SMs with antimicrobial activity against phytopathogenic fungi. Detailed information about these secondary metabolites, when grouped together, enhances the understanding of their efficient utilization and further exploration of new bioactive compounds for the management of plant pathogenic fungi. The current literature provides the information about SMs of Trichoderma spp. in a different context. In this review, we summarize and group different antifungal SMs of Trichoderma spp. against phytopathogenic fungi along with a comprehensive overview of some aspects related to their chemistry and biosynthesis. Moreover, a brief overview of the biosynthesis pathway, action mechanism, and different approaches for the analysis of SMs and the factors affecting the regulation of SMs in Trichoderma is also discussed.

Bioactive Secondary Metabolites from Trichoderma spp. against Phytopathogenic Bacteria and Root-Knot Nematode.

Losses in crops caused by plant pathogenic bacteria and parasitic nematode are increasing because of a decrease in efficacy of traditional management measures. There is an urgent need to develop nonchemical and ecofriendly based management to control plant diseases. A potential approach of controlling plant disease in the crops is the use of biocontrol agents and their secondary metabolites (SMs). Luckily fungi and especially the genus Trichoderma comprise a great number of fungal strains that are the potential producer of bioactive secondary metabolites. In this study secondary metabolites from ten Trichoderma spp. were evaluated for their antibacterial and nematicidal potential against phytopathogenic bacteria Ralstonia solanacearum, Xanthomonas compestris and plant parasitic nematode Meloidogyne incognita. Five different growth media were evaluated for the production of SMs. It was shown that SMs of different Trichoderma spp. obtained on different growth media were different in the degree of their bioactivity. Comparison of five growth media showed that SMs produced on solid wheat and STP media gave higher antibacterial activity. SMs of T. pseudoharzianum (T113) obtained on solid wheat media were more effective against the studied bacteria followed by SMs from T. asperelloides (T136), T. pseudoharzianum (T129) and T. pseudoharzianum (T160). Scanning electron microscopy (SEM) was further conducted to observe the effect of SMs on bacterial cell morphology. As evident from the SEM, SMs produced severe morphological changes, such as rupturing of the bacterial cell walls, disintegration of cell membrane and cell content leaking out. SMs from T. viridae obtained on liquid STP and solid wheat media showed the highest percent of M. incognita juveniles (J2s) mortality and inhibition in egg hatching of M. incognita. The results of our study suggest that T. pseudoharzianum (T113) and T. viridae could be selected as an effective candidate for SMs source against phytopathogenic bacteria and M. incognita respectively.