Myco-ecological warfare with Meloidogyne species

The experiment was carried out in Department of Plant Pathology, Dr Yashwant Singh Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh, India during cropping season of May to August in year 2018–2019 to study the efficacy of fungal and bacterial bio-control agents in managing the Fusarium wilt of cucumber. Different fungal and bacterial bio-control agents were thus tested under laboratory conditions for their efficacy in inhibiting the mycelial growth of Fusarium oxysporum by using dual culture technique and streak plate method, respectively. Among fungal bio-control agents, Trichoderma harzianum was found most effective with 61.08% inhibition of mycelial growth of F. oxysporum followed by Trichoderma virens with 57.51% mycelial inhibition whereas, among bacterial bio-control agents, maximum mycelial inhibition of 45.69% was observed in Pseudomonas fluorescens. During the cropping season, seed, and soil treatment with effective fungal and bacterial bioagents was carried out under field conditions. Seed treatment and soil application of Trichoderma harzianum was found effective with disease control of 48.25% followed by Trichoderma virens which is proved to be efficacious with 42% disease control against Fusarium wilt of cucumber.

The root-knot nematode (Meloidogyne spp.) is an obligate plant parasite and is one of the largest threats to the Australian sweetpotato industry, causing crop losses of up to 57% of marketable yield. In this study, two potential fungal biocontrol agents were encapsulated in alginate granules and their nematophagous activity was assessed in a laboratory-based microcosm experiment. Both species of fungi significantly reduced numbers of root-knot nematodes in red ferrosol soil. A greater reduction was observed in untreated field soil prior to introduction of root-knot nematodes and fungal biocontrol agents compared to soil that had been heat-sterilised. In a ten-week glasshouse experiment, no significant difference in the root-knot nematode populations in sweetpotato roots and soil was found between fungal biocontrol agent and control treatments. There was a trend towards an increase in the sweetpotato storage root weight and reduction in storage root damage in fungal biocontrol agent compared to control treatments, and both yield and damage levels were similar to those achieved from the use of chemical nematicide treatments. These results demonstrate the need for greater understanding of the interactions between soil biological populations and introduced nematophagous fungi if effective biocontrol is to be consistently achieved with these bioagents under field conditions.

An experiment was conducted to study the compatibility of copper hydroxide (Kocide 3000) with bacterial and fungal biocontrol agents under in vitro conditions.Bacterial biocontrol agents viz., Pseudomonas fluorescens and Bacillus subtilis were compatible with copper hydroxide (Kocide 3000) even at a high concentration of 300 ppm.Fungal biocontrol agent, Trichoderma viride was inhibited by copper hydroxide at a concentration above 2500 ppm.The fungal biocontrol agent was highly compatible with the fungicide than the bacterial biocontrol agents.

Fungal biocontrol agents (BCAs), whose identity has been clearly established and their biocontrol potential has been assessed simultaneously, are investigated for their mechanism(s) of biocontrol activities against microbial pathogens causing various plant diseases. They may act on the target pathogens through one or more mechanisms resulting in the inhibition of growth, sporulation and spread within the infected plants. The fungal BCAs may exhibit parasitism, antibiosis, competition for nutrients and /space, ability for prevention of colonization of specific tissues of the host by the pathogen and induction of resistance in plants against disease(s) as their primary and secondary mechanisms of biocontrol activity against the target pathogen(s). Different methods have been developed to study the mechanism(s) of activity of the selected BCAs. Some of the BCAs that were believed to restrict pathogen development by mycoparasitism or production of antibiotics were later demonstrated to induce systemic resistance in plants against pathogens. In addition to providing protection to plants against pathogens, some fungal BCAs are able to promote growth of plants, resulting in higher plant biomass and yield. The fungal BCA, Muscodor albus has the potential, as the biofumigant for the control of diseases occurring in the field and as well as in storage. Determination of the modes of action of fungal BCAs will be useful to develop appropriate application methods for effective management of crop diseases.

Fungal biocontrol agents (BCAs) have arisen as an ecologically sustainable agricultural substitute for conventional pesticides. This method provides valuable control over pests and plant diseases by utilizing fungi's naturally predatory and competitive characteristics, thereby minimizing the use of harmful synthetic chemicals. The mode of action is reviewed, and fungal BCAs are discussed, including Trichoderma spp., Beauveria bassiana, and Metarhizium anisopliae, whose pathogenicity, outcompeting ability, and production of secondary metabolites are known to inhibit pathogens. Employed as bio-controls, fungal BCAs also bring many environmental and health benefits by lowering pesticide resistance potential, minimizing ecological impact, and increasing soil health. In addition, compared to broad-spectrum chemical pesticides, fungal biocontrol agents are more specific and do not disturb beneficial organisms. These BCAs hold great promise, but their widespread use is limited by environmental sensitivity, high production costs, and limited shelf life of the formulation. Formulation and genetic engineering innovations are overcoming these challenges by improving the efficiency and scalability of fungal biocontrol products, including the multiple applications of synergistic compounds. In the face of climate change and the urgent need for sustainable agricultural methods, these fungal biological control agents (BCAs) will play an integral role in IPM, enabling sustainable, diverse, and resilient ecosystems that contribute to agricultural sustainability for the future. This review highlights the potential of fungal biocontrol as an effective tool for ensuring food security in the post-antibiotic era, with further development necessary to harness its complete potential on a global scale.

Aim: To evaluate the selected native isolates of Trichoderma spp. of Kasaragod district for abiotic stress tolerance and compatibility assessment with other biocontrol agents. Study Design: CRD. Place and Duration of Study: Department of Plant Pathology, College of Agriculture, Padannakkad, between November 2023 and November 2024. Methodology: The selected Trichoderma isolates Tr-5, Tr-12, Tr-41, Tr-43 (Trichoderma asperellum) and Tr-40 (Trichoderma lixii) were subjected to various abiotic stresses, namely low (4°C, 10°C and 15°C) and high (30°C, 45°C and 55°C) temperatures, salinity (0.5M, 1.5M and 2.5 M NaCl) and drought (10%, 30% and 40% PEG). The PDA was embedded with different NaCl and PEG concentrations to test the salinity and drought tolerance. After 4 days of inoculation (DAI), radial growth of Trichoderma isolates in treatments and controls was recorded. The compatibility of these Trichoderma isolates was checked with the other bio-control agents viz., Pseudomonas fluorescens, Metarhizium anisopliae, Lecanicillium lecanii and Beauveria bassiana using the dual culture technique. Results: In the temperature tolerance study, the selected isolates did not show any radial growth at 4°C, 10°C, 45°C, and 55°C.At 15°C, slight mycelial growth was observed, and the optimal range was found to be 30°C for good mycelial growth. The tolerance to salinity was up to 0.5M NaCl, but only in Tr-5 (0.83cm), Tr-12 (0.91), and Tr-40 (0.8) isolates; the mycelial growth was observed at 1.5M NaCl. At 10% PEG, the radial growth of isolates was on par with the control. Upon increasing concentration, radial growth of Trichoderma isolates was decreased/ absent along with sporulation. In the compatibility study, Trichoderma isolates were found to be compatible with P. fluorescens, M. anisopliae, L. lecanii and B. bassiana. But with fungal biocontrol agents, only Tr-40 showed incompatibility with M. anisopliae (66.67%), L. lecanii (33.58%), but was compatible with B. bassiana. Conclusion: In this study, all five native Trichoderma isolates, Tr-5, Tr-12, Tr-40, Tr-41 and 43 showed high tolerance to abiotic stresses at an optimum range of temperature (30oC), NaCl (0.5M), and PEG (10%). The isolates of Trichoderma spp. were compatible with bacterial and fungal bio-control agents except Tr-40.

Fungi are an extremely diverse group of organisms, with about 230,000 species distributed widely essentially in every ecosystem. Among them, only limited species are considered to be effective biocontrol agents. The fungal antagonists restrict the growth of plant pathogens by the three suggested mechanisms: antibiosis, competition and parasitism. Besides, they also induce the defense responses in host plants, termed “induced systemic resistance” (van Loon et al. 1998). Among the abovementioned mechanisms, antibiosis is considered the most important, in which the antagonists produce an array of secondary metabolites such as antibiotics and toxin, which contribute to the antagonistic activity of fungal biocontrol agents against plant pathogens. Antagonistic strains belonging to the Trichoderma and Fusarium genera were able to produce various secondary metabolites which can play a role in the mechanism of their biological activity ( http://www.item.ba.cnr.it/biopesti.htm ). Production of antimicrobial secondary metabolites has been reported in many fungal biocontrol agents (Gottlieb and Shaw 1970; Fries 1973; Hutchinson 1973; Sivasithamparam and Ghisalberti 1998; Vyas and Mathur 2002). In this review, we highlight the secondary metabolites of selected fungal biocontrol agents and their involvement in the control of plant pathogens.

Evaluation of different biological test systems to assess the toxicity of metabolites from fungal biocontrol agents

In recent decades, soybean production has increased tremendously due to high demand of its oil- and protein-rich seeds. Despite its high economic importance, soybean crop is threatened by a wide range of biotic agents affecting the yield. Plant pathogenic fungi are a significant group of organisms that endanger the health of soybeans. Fungal diseases, which include pod blight, charcoal rot, Rhizoctonia aerial blight, Phytophthora and Pythium seed rot, and rust, are seasonal threats that are heavily influenced by environmental factors. In this aspect, fungal biocontrol agents have a high potential to replace synthetic chemicals, which have raised serious detrimental public concerns. Some of the most widely used biocontrol agents against plant pathogenic fungi belong to the genus Trichoderma that have been used extensively against soil- and seed-borne diseases, storage rots, and diseases in the phyllosphere. This chapter discusses some major fungal biocontrol agents (BCAs) that have been identified to be useful in the eco-friendly management of soybean fungal infections. The fungal biocontrol agents are expected to provide great potential in addressing some of the major pest problems in near future.

Advances in fundamental and applied studies in China of fungal biocontrol agents for use against arthropod pests

Plant pathogens challenge our efforts to maximize crop production due to their ability to rapidly develop resistance to pesticides. Fungal biocontrol agents have become an important alternative to chemical fungicides, due to environmental concerns related to the latter. Here we review the complex modes of action of biocontrol agents in general and epiphytic yeasts belonging to the genus Pseudozyma specifically and P. aphidis in particular. Biocontrol agents act through multiple direct and indirect mechanisms, which are mainly based on their secretions. We discuss the direct modes of action, such as antibiosis, reactive oxygen species-producing, and cell wall-degrading enzyme secretions which can also play a role in mycoparasitism. In addition, we discuss indirect modes of action, such as hyperbiotrophy, induced resistance and growth promotion based on the secretion of effectors and elicitors from the biocontrol agent. Due to their unique characteristics, epiphytic yeasts hold great potential for use as biocontrol agents, which may be more environmentally friendly than conventional pesticides and provide a way to reduce our dependency on fungicides based on increasingly expensive fossil fuels. No less important, the complex mode of action of Pseudozyma-based biocontrol agents can also reduce the frequency of resistance developed by pathogens to these agents.

The increasing incidence and prevalence of the pathogen Aphanomyces euteiches in various pulse-growing regions worldwide necessitates the development of effective management strategies, including biological control agents. Numerous labs have undertaken research examining biological control methods to evaluate aphanomyces root rot suppression in multistep processes that include isolation of inhibitory organisms, lab assays, growth chamber assays, and field trials. Given the emergence of various biocontrol agents and the need to mitigate aphanomyces yield losses, we have undertaken a meta-analysis approach to analyze the effectiveness of biocontrol agents in relation to application method, biocontrol agent richness, biocontrol agent type, the type of study, and reporting system-oriented moderator variables. An effect size, calculated as a natural log response ratio, resulted in a summary weighted mean of −0.411, suggesting the overall effectiveness of biocontrol agents (p < .001). Aphanomyces root rot suppression using biological treatments showed significant heterogeneity for all moderator variables, confirming that the studies do not share a common effect size and the use of a random effect model was appropriate. Across studies, meta-analyses revealed that soil amendments, biocontrol agent application as a seed coating and suspension, bacterial and fungal biocontrol agents, mixed applications, growth chamber and field studies, and qualitative and quantitative reporting systems were all associated with significantly positive outcomes for aphanomyces root rot suppression. Our findings suggest that there is potential promise for biological control of aphanomyces root rot, and more field trials need to be conducted to demonstrate the efficacy level observed under growth chamber conditions. Moreover, we identified a lack of detailed understanding of the mechanism(s) of biological control of aphanomyces root rot as a research priority.

The pathogen Sclerotinia sclerotiorum is the source of cabbage head rot disease, which causes significant economic loss in the Nilgiris district, Tamil Nadu. To manage the disease, biocontrol agents were isolated from the rhizosphere region of cabbage and the antagonistic properties were assessed for their capacity to control cabbage head rot under in vitro conditions. Trichoderma viride (Tv3) recorded 86% inhibition and Pseudomonas fluorescens (PfC5) inhibited 80% reduction of mycelial growth of Sclerotinia sclerotiorum. During storage, the effectiveness of different carrier materials in maintaining the population of these biocontrol agents was evaluated. In glasshouse studies, the use of biocontrol agents in combination (Seed treatment + Soil application with (PfC5 + Tv3) + Foliar spray with PfC5) significantly recorded maximum (72.50) per cent disease reduction. Upregulation of defense genes triggered the enzymes viz., polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia lyase (PAL) and phenol were accumulated in cabbage treated with fungal and bacterial biocontrol agents and reduced the head rot disease incidence in cabbage and increase the yield.

This review deals with the mechanism of antagonistic action of bacterial and fungal biocontrol agents such as the production of antibiotics, siderophores, enzyme secretion, competition for nutrition, plant growth promotion by rhizosphere microorganism. The utilisation of synthetic pesticides has been the predominant control processor for diseases brought about by phytopathogenic microorganisms. Notwithstanding, their open and improper application in intensive agriculture has realised issues that have prompted ecological contamination, considerable residues in agricultural products and phytopathogen resistance. They are likewise disrupting the quantity of beneficial microorganism which is available in the soil and capable of expanding soil fertility. Along these lines, there is a need to look through the option of synthetic pesticides that are safe, environmental and monetarily feasible to confront this problem. Biocontrol agent’s utilisation is the best alternative method to control the different kinds of diseases, such as nematode infestation, fungal pathogen and bacterial pathogen. Nowadays, biocontrol agents assume a significant role in the field of agriculture. It is a financially savvy, environment-friendly and inhibits the advancement of pathogenic microorganism sustainably. This review emphasises the role of biocontrol agents against different pathogenic microorganisms and their significance potentiality to improve plant growth and enhance defence system of plants.

India is the largest producer of banana in the world. Nendran, a French plantain, is the most important banana cultivar in Kerala. It is mainly affected by many diseases both in the field and after harvest. Being a freshly consumed fruit crop there are a lot of limitations in using chemicals for its disease control. Keeping this view, a study was conducted at the Department of Plant Pathology, College of Agriculture, Vellayani, to control anthracnose, a serious post harvest disease under tropical conditions. In this study comparative evaluation of three fungal biocontrol agents namely [Trichoderma sp. (KAU), Trichoderma sp. (TRPN-3), Trichoderma sp. (TRKR-2)] and bacterial biocontrol agents [Pseudomonas fluorescens (PN026), Bacillus sp. (B15), Bacillus sp. (B17)] were tested against Colletotrichum musae. Among the fungal biocontrol agents maximum mycelial growth inhibition was recorded with Trichoderma sp. (KAU) (77.44%) followed by Trichoderma sp. (TRKR-2) (77.11%). Minimum mycelial growth inhibition was recorded in P.fluorescens (PN026) (55.33%). Based on the results reveals that Trichoderma sp. (KAU) is a highly promising biocontrol agent for managing anthracnose of banana.