Trichoderma atroviride as a promising biocontrol agent in seed coating for reducing Fusarium damping-off on maize

Polyphasic Characterization of the Biocontrol Potential of a Novel Strain of Trichoderma atroviride Isolated from Central Mexico

This work describes the characterization of Trichoderma atroviride strain CMU-08, isolated from Michoacán, Mexico. CMU-08 demonstrated robust growth and conidiation across a temperature range from 16 to 32 °C and a pH range from 4 to 9 on potato dextrose agar (PDA) and malt extract agar (MEA) media. The strain is an efficient antagonist of six species of phytopathogenic fungi and oomycetes in PDA, MEA, and Vogel minimal medium (VMM). Antagonist mechanisms of CMU-08 included direct mycoparasitism observed in dual-culture assays, as well as antibiosis attributed to growth inhibition via both volatile and non-volatile metabolites, with the effectiveness varying depending on the test phytopathogen and culture medium. Extracellular filtrates (ECFs) recovered from liquid cultures of CMU-08 under basal and induced conditions using Botrytis cinerea cell walls significantly inhibited their growth at a concentration of 750 µg/mL. Moreover, in detached tomato leaf assays, these ECFs reduced foliar damage caused by B. cinerea by 24-34%. The volatile organic compounds (VOCs) produced by CMU-08 also exhibited substantial efficacy, reducing foliar damage by up to 50% in similar tests. Despite showing no basal extracellular chitinase enzymatic activity, CMU-08 demonstrated significant induction of this activity in cultures supplemented with B. cinerea and Fusarium sp. cell walls. Four genes encoding extracellular chitinases (chit33, chit36, ech42, and locus 217415) showed different dynamics of transcriptional regulation during the dual-culture confrontation of strain CMU-08 with B. cinerea and Fusarium sp., varying according to the phytopathogen and the interaction stage. The CMU-08 strain shows physiological versatility and employs a variety of antagonist mechanisms toward different species of phytopathogenic microorganisms, making it a good candidate for developing a biocontrol product for field application.

Bio-control efficacy of selected indigenous nematophagous fungi against Meloidogyne enterolobii in vitro and on dry bean (Phaseolus vulgaris L.)

Dry bean (Phaseolus vulgaris L.) is an important commercialized field crop in South Africa for aiding in food security as a cheap protein source. However, it is highly susceptible to root-knot nematodes (RKN), Meloidogyne species. Use of indigenous nematophagous fungi as bio-control agents (BCA) of Meloidogyne nematodes is a promising research focus area. This is because indigenous fungal species are naturally part of the ecosystem and therefore compatible with other biological processes unlike most synthetic chemicals. The objective of the study was to identify indigenous nematophagous fungal BCA and establish their potential efficacy in reducing M. enterolobii population densities on dry bean with and without incorporation of compost. Screened indigenous fungal species included Aspergillus terreus, Talaromyces minioluteus, T. sayulitensis, Trichoderma ghanense, and T. viride. There were observed significant parasitism differences (P ≤ 0.05) among the BCA, with T. ghanense showing the highest egg parasitism (86%), followed by T. minioluteus (72%) and T. sayulitensis (70%). On the other hand, the highest J2 parasitism was observed on T. minioluteus (95%), followed by A. terreus and T. viride (63%). A similar trend was observed under in vivo conditions, with higher efficacy with compost incorporation. This provides a highly encouraging alternative and ecologically complementary Meloidogyne management in dry bean production.

Decrease in beneficial bacteria and increase in harmful bacteria in Gastrodia seedlings and their surrounding soil are mainly responsible for degradation of Gastrodia asexual propagation

Introduction

Asexual reproduction of Gastrodia elata Bl. f. glauca S. chow (GeB) produces degeneration with increasing number of GeB. Therefore, we analyzed the microorganisms of GeB seedlings and surrounding soil by Illumina Miseq high-throughput sequencing technology.

Methods

In this study, Illumina Miseq high-throughput sequencing technology was applied to analyze the types and quantities of GeB seedlings and surrounding soil microorganisms in the first to third generations of asexual reproduction, isolated and identified the dominant strains of GeB in the first to third generations and screened the antagonistic bacteria of its pathogenic fungi, and evaluated the effects of beneficial bacteria on the production performance of seedlings planted with GeB.

Results

With an increase in the number of asexual reproductive generations, the number of pathogenic fungi and bacteria in GeB seedlings and the surrounding soil increased, and the number of beneficial fungi and bacteria decreased. Pseudomonas sp., Agrobacterium rhizomes, and Herbaspirillum hiltneri were isolated and identified in the first generation, and Trichoderma harzianum, Penicillium viridiatum, Fusarium oxysporum, and Novosphingobium sp. Were isolated and identified in the third generation. Antagonistic strains of the three pathogenic bacterial strains were screened. In conclusion, beneficial bacteria significantly improved the production performance of asexual reproductive seedlings planted with GeB.

Discussion

In conclusion, our findings suggested that the microorganisms of GeB seedlings and the surrounding soil change as the number of generations of GeB reproduction increases, disrupts the microecological balance of surrounding soil and endophytic microbiomes.This study provides a theoretical basis for the degradation of asexual reproduction in GeB.

In Vitro Assessment of Eight Selected Indigenous Fungal Isolates Tolerance to Various Abiotic Stresses and their Effects on Seed Germination

Fungal bio-control agents (BCA) can minimize use of agro-chemicals while increasing plant productivity and tolerance to biotic-abiotic stressors. Ideally, BCA should tolerate varying environmental conditions they are introduced into, to successfully dominate and protect plants from stressors. However, BCA are living micro-organisms, their survival and efficacy can be impeded by extreme conditions. The current study aimed at evaluating whether indigenous fungal isolates, viz, Aspergillus flavus, A. terreus, Penicillium sp. AL-38 IRH-2012b, Talaromyces minioluteus, T. purpureogenus, T. sayulitensis, Trichoderma ghanense and T. viride can tolerate different levels of salinity, pH, nutrient and temperature. Certain fungal species are pests with potential of destroying many crops; the pathogenic effects of the aforementioned fungal isolates were further assessed on different crops' seeds. The results showed that, although being indigenous, Aspergillus, T. sayulitensis and T. ghanense failed to thrive in high salinity and pH. While Penicillium sp. AL-38 IRH-2012b failed to thrive under reduced nutrient level and all fungal isolates failed to grow at 10-20 °C. Furthermore, it was noted species within the same genus could affect crops in both favorable and unfavorable ways. The study demonstrated that the selected indigenous fungal isolates can tolerate different abiotic conditions and have potential to improve seed germination and seedling growth.

Light-Induced Changes in Secondary Metabolite Production of Trichoderma atroviride

Many studies aim at maximizing fungal secondary metabolite production but the influence of light during cultivation has often been neglected. Here, we combined an untargeted isotope-assisted liquid chromatography-high-resolution mass spectrometry-based metabolomics approach with standardized cultivation of Trichoderma atroviride under three defined light regimes (darkness (PD), reduced light (RL) exposure, and 12/12 h light/dark cycle (LD)) to systematically determine the effect of light on secondary metabolite production. Comparative analyses revealed a similar metabolite profile upon cultivation in PD and RL, whereas LD treatment had an inhibiting effect on both the number and abundance of metabolites. Additionally, the spatial distribution of the detected metabolites for PD and RL was analyzed. From the more than 500 detected metabolites, only 25 were exclusively produced upon fungal growth in darkness and 85 were significantly more abundant in darkness. The majority were detected under both cultivation conditions and annotation revealed a cluster of substances whose production followed the pattern observed for the well-known T. atroviride metabolite 6-pentyl-alpha-pyrone. We conclude that cultivation of T. atroviride under RL can be used to maximize secondary metabolite production.

Biochemical and Biotechnological Insights into Fungus-Plant Interactions for Enhanced Sustainable Agricultural and Industrial Processes

The literature is full of studies reporting environmental and health issues related to using traditional pesticides in food production and storage. Fortunately, alternatives have arisen in the last few decades, showing that organic agriculture is possible and economically feasible. And in this scenario, fungi may be helpful. In the natural environment, when associated with plants, these microorganisms offer plant-growth-promoting molecules, facilitate plant nutrient uptake, and antagonize phytopathogens. It is true that fungi can also be phytopathogenic, but even they can benefit agriculture in some way-since pathogenicity is species-specific, these fungi are shown to be useful against weeds (as bioherbicides). Finally, plant-associated yeasts and molds are natural biofactories, and the metabolites they produce while dwelling in leaves, flowers, roots, or the rhizosphere have the potential to be employed in different industrial activities. By addressing all these subjects, this manuscript comprehensively reviews the biotechnological uses of plant-associated fungi and, in addition, aims to sensitize academics, researchers, and investors to new alternatives for healthier and more environmentally friendly production processes.

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.

Microbial seed coating: An attractive tool for sustainable agriculture

Seed coating is considered one of the best methods to promote sustainable agriculture where the physical and physiological properties of seeds can be improved to facilitate planting, increase growth indices and alleviate abiotic and biotic stresses. Several methods of seed coating are used to attain good application uniformity and adherence in the seed coating process. Seed coating has been tested in seeds of various plant species with different dimensions, forms, textures, and germination types. Plant beneficial microorganisms (PBM), such as rhizobia, bacteria, and fungi inoculated via seed inoculation can increase seed germination, plant performance and tolerance across biotic (e.g., pathogens and pests) and abiotic stress (e.g., salt, drought, and heavy metals) while reducing the use of agrochemical inputs. In this review, the microbial seed coating process and their ability to increase seed performance and protect plants from biotic and abiotic stresses are well discussed and highlighted in sustainable agricultural systems.

Trichoderma atroviride LZ42 releases volatile organic compounds promoting plant growth and suppressing Fusarium wilt disease in tomato seedlings

Background

The promotion of plant growth and suppression of plant disease using beneficial microorganisms is considered an alternative to the application of chemical fertilizers or pesticides in the field.

Results

A coconut-scented antagonistic Trichoderma strain LZ42, previously isolated from Ganoderma lucidum-cultivated soil, was investigated for biostimulatory and biocontrol functions in tomato seedlings. Morphological and phylogenetic analyses suggested that strain LZ42 is closely related to T. atroviride. Tomato seedlings showed increased aerial and root dry weights in greenhouse trials after treatment with T. atroviride LZ42 formulated in talc, indicating the biostimulatory function of this fungus. T. atroviride LZ42 effectively suppressed Fusarium wilt disease in tomato seedlings, with an 82.69% control efficiency, which is similar to that of the carbendazim treatment. The volatile organic compounds (VOCs) emitted by T. atroviride LZ42 were found to affect the primary root growth direction and promote the root growth of tomato seedlings in root Y-tube olfactometer assays. The fungal VOCs from T. atroviride LZ42 were observed to significantly inhibit F. oxysporum in a sandwiched Petri dish assay. SPME–GC–MS analysis revealed several VOCs emitted by T. atroviride LZ42; the dominant compound was tentatively identified as 6-pentyl-2H-pyran-2-one (6-PP). The VOC 6-PP exhibited a stronger ability to influence the direction of the primary roots of tomato seedlings but not the length of the primary roots. The inhibitory effect of 6-PP on F. oxysporum was the highest among the tested pure VOCs, showing a 50% effective concentration (EC₅₀) of 5.76 μL mL⁻¹ headspace.

Conclusions

Trichoderma atroviride LZ42, which emits VOCs with multiple functions, is a promising agent for the biostimulation of vegetable plants and integrated management of Fusarium wilt disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02511-3.

Metabolic Footprints of Burkholderia Sensu Lato Rhizosphere Bacteria Active against Maize Fusarium Pathogens

Consistent with their reported abundance in soils, several Burkholderia sensu lato strains were isolated from the rhizosphere of maize plants cultivated at different sites in central México. Comparative analysis of their 16S rRNA gene sequences permitted their separation into three distinctive clades, which were further subdivided into six other clusters by their close resemblance to (1) Trinickia dinghuensis; (2) Paraburkholderia kirstenboschensis, P. graminis, P. dilworthii and P. rhynchosiae; (3) B. gladioli; (4) B. arboris; (5) B. contaminans, or (6) B. metallica representative species. Direct confrontation assays revealed that these strains inhibited the growth of pathogenic Fusarium oxysporum f. sp. radicis-lycopersici, and F. verticillioides within a roughly 3-55% inhibition range. The use of a DIESI-based non-targeted mass spectroscopy experimental strategy further indicated that this method is an option for rapid determination of the pathogen inhibitory capacity of Burkholderia sensu lato strains based solely on the analysis of their exometabolome. Furthermore, it showed that the highest anti-fungal activity observed in B. contaminans and B. arboris was associated with a distinctive abundance of certain m/z ions, some of which were identified as components of the ornbactin and pyochelin siderophores. These results highlight the chemical diversity of Burkholderia sensu lato bacteria and suggest that their capacity to inhibit the Fusarium-related infection of maize in suppressive soils is associated with siderophore synthesis.

Tracking pesticide exposure to operating workers for risk assessment in seed coating with tebuconazole and carbofuran

BACKGROUND

Coating seed with pesticides is an effective way to control plant pests, however, factory-based coating processes may carry a potential risk to operational workers of chemical exposure. To study the risk, carbofuran and tebuconazole were used to coat corn seed and their subsequent distribution on the bodies of workers was measured at manufacturers XFS and LS (Shanxi, China). Clothing was collected from workers during operations and analyzed using high-performance liquid chromatography.

RESULTS

At XFS, dermal exposure to carbofuran was 4.83, 3.31 and 1.48 mg kg^-1 , and exposure to tebuconazole was 6.88, 5.16 and 1.72 mg kg^-1 for coating, packing and transport workers, respectively. At LS, dermal exposure to carbofuran was 2.32, 0.46 and 0.55 mg kg^-1 , and exposure to tebuconazole was 1.69, 0.46 and 0.70 mg kg^-1 , for coating, packing and transport workers, respectively. The level of pesticide exposure was significantly higher for seed-coating workers than for packing and transport workers. The main area of exposure was the hands for all workers and the lower limbs for packers; exposure was relatively uniform for pesticide handlers. Occupational risk was assessed based on margin of exposure (MOE). In seed-coating, the MOE was greater than 100 for tebuconazole, indicating no potential risk, but ranged from 0.25 to 2.88 for carbofuran, indicating the risk of a health impact.

CONCLUSION

The level of exposure varied depending on type of operation undertaken and body parts of workers' body, but the risk of a health impact was highly associated with pesticide toxicity. This provides a guideline for workers in pesticide manufacturing to ensure safe operation of the seed-coating process. © 2021 Society of Chemical Industry.

Characterization of a novel dsRNA mycovirus of Trichoderma atroviride NFCF377 reveals a member of "Fusagraviridae" with changes in antifungal activity of the host fungus

Trichoderma atroviride is a common fungus found in various ecosystems that shows mycoparasitic ability on other fungi. A novel dsRNA virus was isolated from T. atroviride NFCF377 strain and its molecular features were analyzed. The viral genome consists of a single segmented double-stranded RNA and is 9,584 bp in length, with two discontinuous open reading frames (ORF1 and ORF2). A mycoviral structural protein and an RNA-dependent RNA polymerase (RdRp) are encoded by ORF1 and ORF2, respectively, between which is found a canonical shifty heptameric signal motif (AAAAAAC) followed by an RNA pseudoknot. Analysis of sequence similarity and phylogeny showed that it is closely related to members of the proposed family "Fusagraviridae", with a highest similarity to the Trichoderma atroviride mycovirus 1 (TaMV1). Although the sequence similarity of deduced amino acid to TaMV1 was evident, sequence deviations were distinctive at untranslated regions (UTRs) due to the extended size. Thus, we inferred this dsRNA to be a different strain of Trichoderma atroviride mycovirus 1 (TaMV1-NFCF377). Electron microscopy image exhibited an icosahedral viral particle of 40 nm diameter. Virus-cured isogenic isolates were generated and no differences in growth rate, colony morphology, or conidia production were observed between virus-infected and virus-cured strains. However, culture filtrates of TaMV1-NFCF377-infected strain showed enhanced antifungal activity against the plant pathogen Rhizoctonia solani but not to edible mushroom Pleurotus ostreatus. These results suggested that TaMV1-NFCF377 affected the metabolism of the fungal host to potentiate antifungal compounds against a plant pahogen, but this enhanced antifungal activity appeared to be species-specific.