Soilborne Phytopathogenic Fungi Research Articles

Antagonistic activity and mechanism of an isolated Streptomyces corchorusii stain AUH-1 against phytopathogenic fungi.

The various diseases that occur during the growth of plants usually cause a significant reduction in production and quality of agricultural products. Actinomycetes, especially Streptomyces spp., become a valuable biological control resource due to their preponderant abilities to produce various secondary metabolites with novel structure and remarkable biological activity. The present work aimed to isolate an effective antagonistic actinomycete against various soilborne phytopathogenic fungi. By dual culture with Fusarium oxysporum f. sp. niveum, an antagonistic actinomycete named Streptomyces corchorusii stain AUH-1 was screened out from 26 soil samples. The in vitro bioassay results showed that S. corchorusii stain AUH-1 had a broad-spectrum antagonistic activity against a range of fungal plant pathogens, such as F. oxysporum f. sp. niveum, Phytophthora parasitica var. nicotianae, Rhizoctonia solani, P. capsica, Botryosphaeria dothidea, F. oxysporum f. sp. vasinfectum, Verticillium dahliae, and F. oxysporum f. sp. cucumerinum. According to the morphological observations in scanning electron microscopy (SEM) and fluorescence microscope (FM), it was found that the cell membranes of F. oxysporum f. sp. niveum were damaged when treated with the antifungal metabolite form S. corchorusii stain AUH-1. Meanwhile, the dropped ergosterol formation and increased malondialdehyde levels further confirmed that S. corchorusii strain AUH-1 exerted its antagonistic activity against F. oxysporum f. sp. niveum via damaging the structure and function of cell membranes. In conclusion, S. corchorusii strain AUH-1 showed a promising prospect for the development of biological agent, especially due to its broad-spectrum and effective antagonist on various soil-borne plant pathogens.

Effect of aerated and non-aerated compost tea against some fungal phytopathogens

Suppressive effect of aerated and non-aerated compost tea against different fungal phytopathogens, namely Alternaria solani, Bipolaris sorokiniana, Fusarium oxysporum, Pestalotia palmarum and Sclerotium rolfsii was evaluated in Plant Protection Laboratory of Agrotechnology Discipline, Khulna University, Khulna, Bangladesh during 2016. Commercial compost, “Rastic Joibo Shar” was used to prepare aerated and non-aerated compost teas at 20% and 25% concentrations. All the treatments significantly inhibited the mycelial growth of tested five fungal phytopathogens. Among the five pathogens 25% concentration of non-aerated compost tea gave highest mycelial growth inhibition (76%) of Sclerotium rolfsii. Colony characteristics of five phytopathogens were significantly varied in all aspect by treating aerated and non-aerated compost teas at different concentrations. Finally it may be concluded that both aerated and non-aerated compost teas have suppressing effect on radial mycelial growth Thus compost tea may be used as alternatives to inorganic fertilizers/fungicides to suppress the pathogenic activity of the soil borne fungal phytopathogens. Thus based on the efficacy of in-vitro experiments, efficacy in field condition can be assessed against different diseases.
 J. Bangladesh Agril. Univ. 17(2): 142–147, June 2019

Nocardiopsis dassonvillei strain MB22 from the Algerian Sahara promotes wheat seedlings growth and potentially controls the common root rot pathogen Bipolaris sorokiniana

The biocontrol potential and plant-growth-promotion activities of seventeen actinobacteria, isolated from roots of native plants and soils harvested in the Algerian Sahara, were investigated. All strains were tested in vitro against five soil-borne phytopathogenic fungi. Six out of seventeen strains were tested in vivo for their biocontrol potential against Bipolaris sorokiniana strain LB12 as well as for their growth-promotion activities of durum wheat (cv. Vitron) seedlings via seed treatments in sterilized and non-sterilized soils. The root rot disease severity index (DSI) of wheat plants derived from seeds treated with actinobacteria (biological seed treatment) was significantly lower (p < 0.05) compared with those obtained from non-treated wheat seeds sown in inoculated pots (positive control). The strain Nocardiopsis dassonvillei MB22 showed the highest biocontrol activity with the DSI much lower than that of the positive control (27.7% versus 90.8% when non-treated seeds were sown in infested soil). No significant difference was observed between the DSI of plants obtained from biological seed treatments with the strain MB22 and those derived from seeds treated with the chemical fungicide Difeconazole®. Biological seed treatment with the spores of the strain MB22 resulted in greatest increases in the dry weight, the root and shoot length of seedlings. In in vitro tests, the strain MB22 was positive for the production of indole-3-acetic acid, siderophores, hydrogen cyanide, showed chitinolytic activity and solubilized inorganic phosphates which are commonly known features for the plant-growth-promotion and biocontrol activities of a given strain.

Application of Agriculturally Important Microorganisms for Biocontrol of Root Rot Infection of Sugar Beet

The roots rot of sugar beet caused by the soil-borne phytopathogenic fungi genera Fusarium and Alternaria are serious causes yield loss in the world. In this study, the antagonistic cellulolytic bacteria were isolated from the rhizosphere of sugar beet plants. The cellulase, antifungal, and growth-promoting activities of strains were examined, and one strain Bacillus cytaseus C-82 was selected. When C-82 was tested for its fungal inhibition and biological control activity under field conditions against root rot of sugar beet, it significantly reduced the disease and increased sugar beet yields by 30–34 c/ha relative to the untreated control plants.

Culture media to detect and criteria to evaluate and report the activity of extracellular enzymes produced by phytopathogenic fungi

ABSTRACT: Extracellular enzymes are involved in the fungal pathogenesis in plants. Currently, culture media, data analyses, and data report related to extracellular enzymes produced in vitro conditions are different and therefore, lack standardization. This work aimed to compare the culture media cited on the literature (normal) with the potato-dextrose-agar (PDA) medium combined with a specific compound to produce extracellular enzymes through three soilborne phytopathogenic fungi (F. solani f. sp. passiflorae, S. rolfsii, and R. solani AG-4 HGI), as well as to analyze and report enzyme data based on five different criteria. The assay was randomized, with three factors (culture media, isolates, and enzymes) and six repetitions. The studied enzymes were amylase (AM), carboxymethylcellulase (CMCase), lipase (LP), laccase (LC), catalase (CT), and gelatinase (GT). The normal media detected more enzymes and was more precise compared to the PDA medium plus specific compound. The criteria that calculated the area of the circular crown of AM, CMCase, LP, and LC and measured the intensity (0 = absence, up to 4 = intense) of CT and GT adopting note scale were the best to evaluate and report the results of the enzymes. We suggest the normal media culture to study enzyme production, as well as the criteria mentioned to assess and report the data related to enzyme activities.

MCherry-Labeled Verticillium dahliae Could Be Utilized to Investigate Its Pathogenicity Process in Nicotiana benthamiana.

Verticillium dahliae is a soil-borne phytopathogenic fungus that causes a destructive vascular wilt, but details of the molecular mechanism behind its pathogenicity are not very clear. Here, we generated a red fluorescent isolate of V. dahliae by protoplast transformation to explore its pathogenicity mechanism, including colonization, invasion, and extension in Nicotiana benthamiana, using confocal microscopy. The nucleotide sequences of mCherry were optimized for fungal expression and cloned into pCT-HM plasmid, which was inserted into V. dahliae protoplasts. The transformant (Vd-m) shows strong red fluorescence and its phenotype, growth rate, and pathogenicity did not differ significantly from the wild type V. dahliae (Vd-wt). Between one and three days post inoculation (dpi), the Vd-m successfully colonized and invaded epidermal cells of the roots. From four to six dpi, hyphae grew on root wounds and lateral root primordium and entered xylem vessels. From seven to nine dpi, hyphae extended along the surface of the cell wall and massively grew in the xylem vessel of roots. At ten dpi, the Vd-m was found in petioles and veins of leaves. Our results distinctly showed the pathway of V. dahliae infection and colonization in N. benthamiana, and the optimized expression can be used to deepen our understanding of the molecular mechanism of pathogenicity.

Biochemical and Molecular Study of Trichoderma harzianum Enriched Secretome Protein Profiles Using Lectin Affinity Chromatography.

Protein glycosylation is one of the most studied post-translational modifications and has received considerable attention for its critical role in the cell biology of eukaryotic cells. The genus Trichoderma has been extensively studied in the biocontrol of soil-borne fungal phytopathogens. The aim of this study was to identify the proteins secreted from Trichoderma harzianum after interacting with the cell walls of two phytopathogens, Sclerotinia sclerotiorum and Fusarium oxysporum. This study used N-glycoprotein enrichment with a concanavalin A (Con A) affinity column, staining detection differential SDS-PAGE, sequencing by mass spectrometric, and protein identification by comparison with the NCBI database to detect the protein expression of the two resulting secretome samples. The majority of the proteins found in both enriched secretomes belonged to a specific class of carbohydrate-active enzymes (CAZymes), within which glycosyl hydrolases (GHs), glycosyltransferases (GTs), and auxiliary activities (AAs) were identified. In this study was described two proteins that have not been previously reported in the secretomes of Trichoderma, a glycosyltransferase (six-harpin) and a galactose oxidase, belonging to the class of auxiliary activities (AA), classified as an AA subfamily AA5-2.The expression pattern of gene encoding to 17 identified proteins, evaluated by real-time quantitative PCR (RT-qPCR), showed significant difference of expression of some GHs and proteases, suggesting a specific gene expression regulation by T. harzianum in presence of different cell walls of two phytopathogens.

Sustainable management of soil borne pathogens of tomato

Tomato is the second most cultivated crop in world, which not only used in culinary but also has industrial and medicinal value. Tomato plants are susceptible to various soil borne diseases that severely affect its growth and fruit quality either grown in fields or cultivated in greenhouse under controlled conditions. The use of rhizospheric microorganisms as a biocontrol agent (BCA) against phytopathogens is considered as one of the most promising eco-friendly approach for sustainable management for tomato cultivation. The rhizopsheric microorganisms caters several mechanisms to control or suppress soil borne phytopathogenic fungi, bacteria and nematodes, via direct mechanism of mycoparasitism and/or indirect mechanisms such as antibiosis through production of secondary metabolites or antibiotics; and competition for nutrients and ecological niche. The present work outlines role of rhizospheric microbial isolates in management of phytopathogens affecting quantitative and qualitative production of tomato.

Effect of Temperatures and Culture Media on Sclerotium rolfsii Mycelial Growth, Sclerotial Formation and Germination

Sclerotium rolfsii is a serious soilborne phytopathogenic fungus causing serious yield loss in crops of high economic importance. In this study, the effects of temperatures and culture media were evaluated on S. rolfsii mycelial growth, sclerotial production and germination. The three isolates tested grew over a range of temperatures from 10°C to 35°C but not at 5°C and 40°C. Radial growth and dry mycelium production were highest at 30°C. Sclerotial initiation started on the 3rd day after incubation at 30°C and 35°C, and mature sclerotia were observed after 15 and 6 days of incubation, respectively. Optimal sclerotial production and the dry weight of 100 sclerotia varied depending on isolates and temperatures and occurred at 25°C-35°C. No mature sclerotia were produced at 5°C, 10°C, 15°C and 40°C. Sclerotial germination, noted after 24 h of incubation, was 96%-100% at 25°C-35°C, declined at 15°C-20°C, and was totally inhibited at 5°C, 10°C and 40°C even after 72 h of incubation. For all S. rolfsii isolates, optimal radial growth occurred on OAT medium followed by CZA, MYEA and PDA. When grown on PDA and OAT media, S. rolfsii developed cottony colonies with abundant mycelium whereas on WA and CZA pathogen growth was thin and scanty. Colonies formed on the other media developed sparse and flat mycelia. For sclerotial formation, WA and CZA were the most suitable culture media but no dark brown sclerotia were observed on NA and YDA. The highest sclerotial formation was observed on PDA and CZA. The highest sclerotium weight was produced by Sr3 isolate on PDA whereas for Sr1 and Sr2 isolates, sclerotial weights were significantly comparable on PDA, MYEA and CZA. Sclerotial germination was optimal on all tested media except NA. The significance of these findings on S. rolfsii biology is discussed.

Antagonistic Potential of Different Isolates of Trichoderma against Fusarium oxysporum, Rhizoctonia solani, and Botrytis cinerea

Trichoderma spp. are widely used as bio-fungicides in agriculture. Induction of plant defense and mycoparasitism (killing of one fungus by another) are considered to be the most important mechanisms of Trichoderma-mediated biological control. In the present study, 380 isolates of 21 Trichoderma species were isolated from Grassland forest soil of Iner Mongolia, China and screened for their antagonistic and antibiosis efficacy against Fusarium oxysporum, Rhizoctonia solani and Botrytis cinerea by dual culture. The result indicated that the antagonistic potential of 380 isolates of Trichoderma strains against Fusarium oxysporum, Rhizoctonia solani and Botrytis cinerea were varied which inhibited Fusarium oxysporum ranges 10.12-70.70%, Botrytis cinerea (44.18-82.98%) and Rhizoctonia solani (35.07-88.07). Among isolates of Trichoderma, 195 isolates showed strong antagonistic potential which inhibited >50% mycelial growth of F. oxysporum, 319 and 377 Trichoderma isolates inhibited >50% mycelial growth of R. solani and B. cinerea respectively. Furthermore, 47 Trichoderma strains have inhibited >50% mycelial growth and have >30 Mycoparasitism for the three tested pathogens. Moreover, one hundred eighty five (185) isolates were also showed inhibitory but their antagonistic potential <50% of the mycelial growth while 50 isolates showed <40% mycelial growth of F. oxysporum, 61 isolates showed <50% mycelial growth for R. solani and 3 isolates showed <50% mycelial growth for B. cinerea. These potential isolates of Trichoderma may be further exploited as a biocontrol agent against F. oxysporum, R. solani and B. cinerea as well as other soilborne phytopathogenic fungi.

Isolation of Chlorogenic Acid from Soil Borne Fungi Screlotium rolfsii, their Reversal of Multidrug Resistance and Anti-proliferative in Mouse Lymphoma Cells.

Fungi performing a wide range of function in soil by secreting low molecular weight compound known as secondary metabolites. S. rolfsii is a soil borne phytopathogenic fungi was used for the production of bioactive compounds. The present study belongs to evaluate the anticancer potentials of a secondary metabolites isolated from S. rolfsii, their multidrug resistance (MDR), and molecular docking study. (1S,3R,4R,5R,E)-3-(3-(3,4-Dihydroxyphenyl)acryloyloxy)-1,4,5 trihydroxycyclohexanecarboxylic acid (1), or best known as chlorogenic acid, was isolated from the ethyl acetate fraction of crude secondary metabolites produced by the soil borne Fungus Screlotium rolfsii. Structure of chlorogenic acid (1) was confirmed by means of FT-IR, 1H NMR, 13C NMR, and mass spectrometry as well as by melting point. Effect of compound 1 on the reversion of multidrug resistant (MDR) mediated by Pglycoprotein (P-gp) against cancer cells was evaluated with a rhodamine-123 exclusion screening test on human mdr1 gene transfected mouse gene transfected L5178 and L5178Y mouse T-cell lymphoma. Compound 1 was also evaluated for Anti-proliferative effect on the L5178 mouse Tcell lymphoma cell line. Results from the present investigation revealed that compound 1 exhibits excellent MDR reversing effect in a dose-dependent manner against mouse T-lymphoma cell line. Compound 1 also showed anti-proliferative effect on L5178Y mouse T-lymphoma cell line.

Synthesis, fungicidal activity and phloem mobility of phenazine-1-carboxylic acid-alanine conjugates

Phenazine-1-carboxylic acid (PCA) is a natural product that has been proven effective against a number of soil-borne fungal phytopathogens and registered for biofungicide against rice sheath blight in China. In order to improve the phloem mobility of phenazine-1-carboxylic acid (PCA), four PCA derivatives were designed and synthesized by conjugating PCA with l-alanine methyl ester, d-alanine methyl ester, l-alanine and d-alanine respectively. In vitro and planta bioassays results showed that conjugates L-PAM and D-PAM exhibited higher fungicidal activities against Rhizoctonia solani Kuhn than PCA while L-PA and D-PA were less active than PCA. The concentration of conjugates in Ricinus communis phloem sap was determined by HPLC. The results showed that only L-PA exhibited phloem mobility among these conjugates, and its concentration in Ricinus communis phloem sap increased with the increase of time (the maximum concentration was 12.69μM within 5h). However, the results of pot experiments showed that L-PA and other conjugates didn't exhibited the inhibition for the growth of Rhizoctonia solani Kuhn in the lower leaves after treatment in the upper leaves of rice seedlings. This may be due to the poor plant absorbility for them or their too little amount of accumulation in the lower leaves.

VdPKS1 is required for melanin formation and virulence in a cotton wilt pathogen Verticillium dahliae.

Verticillium dahliae is a soil-borne phytopathogenic fungus that causes vascular wilt disease in a broad range of hosts. This pathogen survives for many years in soil in the form of melanized microsclerotia. To investigate the melanin synthesis in V. dahliae, we identified a polyketide synthase gene in V. dahliae, namely VdPKS1. PKS1 is known to involve in the dihydroxynaphthalene melanin synthesis pathway in many fungi. We found that VdPKS1 was required for melanin formation but not for microsclerotial production in V. dahliae. The VdPKS1 gene-disruption mutant (vdpks1) formed melanin-deficient albino microsclerotia, which did not affect the fungal colonization in host tissues but significantly reduced the disease severity. Gene transcription analysis in the wild-type and the vdpks1 strains suggested that VdPKS1 gene-disruption influenced the expression of a series of genes involved in ethylene biosynthesis, microsclerotial formation and pathogenesis. Our results suggest that the VdPKS1-mediated melanin synthesis is important for virulence and developmental traits of V. dahliae.

Draft Genome Sequence of the Rhizobacterium Pseudomonas chlororaphis PCL1601, Displaying Biocontrol against Soilborne Phytopathogens.

ABSTRACTIn this study, we present the draft genome sequence of the bacterial strain Pseudomonas chlororaphis PCL1601. This bacterium was isolated from the rhizosphere of healthy avocado trees and displayed antagonistic and biological control activities against different soilborne phytopathogenic fungi and oomycetes.

Penetration Assays, Fungal Recovery and Pathogenicity Assays for Verticillium dahliae

Verticillium dahliae is a soil-borne phytopathogenic fungus that infects host roots and proliferates in vascular tissues. The great loss of economically important crop caused by V. dahliae has raised worldwide concern, however, little is known about the mechanism of its pathogenicity ( Klosterman et al., 2011 ; Yadeta and Thomma, 2013). Our recent work has shown that V. dahliae develops hyphopodium as an infection structure to breach plant root cell wall ( Zhao et al., 2016 ). Here, we provide a detailed protocol to analyze the penetration ability and the pathogenicity of V. dahliae as well as recover fungal hyphae from infected cotton stems developed from our previous studies ( Zhang et al., 2016a and 2016b; Zhao et al., 2016 ). Cellophane membrane has been used in inducing appressorium development of foliar pathogens but not root pathogens (Bourett and Howard, 1990). We adopted the method of using the cellophane membrane to induce and assess the development of hyphopodium. Hopefully, it will greatly promote the research of molecular events involved in recognition of the host that regulate infectious development. This protocol is also helpful to identify the key component controlling the pathogenicity of V. dahliae and widen our understanding of the mechanism of plant-microbe interaction.

Biocontrol Activities of Gamma Induced Mutants of Trichoderma harzianum against some Soilborne Fungal Pathogens and their DNA Fingerprinting.

Background Random induced mutation by gamma radiation is one of the genetic manipulation strategies to improve the antagonistic ability of biocontrol agents. Objectives This study aimed to induce mutants with more sporulation, colonization rate leading to enhanced antagonistic ability (in vitro assay) comparing to wild type (WT) and the assessment of genetic differences (in situ evaluation) using molecular markers. The superior mutants could be appropriate biocontrol agents against soil borne fungal diseases. Materials and Methods In this research sampling and isolation of Trichoderma isolates were performed from soils with low incidence of soil borne disease. T. harzianum 65 was selected and irradiation was conducted with gammacell at optimal dose 250 Gray/s. Mutants (115) were obtained from the WT. The antagonistic abilities of twenty-four mutants were evaluated using dual culture and culture filtrate tests. Results The results of in vitro assays revealed that Th15, Th11 and Th1 mutants exhibited stronger growth inhibition (GI) and colonization rate on Macrophomina phaseolina and Rhizoctonia solani AG4 compared to the wild type. Th15 and Th11 mutants exhibited stronger GI and colonization rate on Sclerotinia sclerotiorum in dual culture and culture filtrate tests and Th1 and Th11 mutants exhibited stronger GI on Fusarium grminearum in culture filtrate test. The DNA fingerprinting was carried out using RAPD and rep-PCR markers. Two (Th9 and Th17) out of the 24 mutants categorized distantly from the rest based on different polymorphism obtained by molecular markers. However, Th9 was different in GI% from Th17. RAPD analysis separated WT from mutants, Th9 from Th17 and also phenotypically superior mutants from other mutants. Meanwhile, rep-PCR analysis categorized WT isolate and mutants according to their antagonistic properties. Conclusions The latter marker (rep-PCR) appeared to be reproducible and simple to distinguish mutants from a single isolate of T. harzianum. Mutants (3 isolates) were phenotypically and genotypically distinct from WT. These mutants demonstrated a pronounced biocontrol activities against soilborne fungal phytopathogens.

Potential of endophytic Streptomyces spp. for biocontrol of Fusarium root rot disease and growth promotion of tomato seedlings

ABSTRACTSixteen endophytic actinobacteria isolated from roots of native plants were evaluated for their antagonistic potential against soil-borne phytopathogenic fungi. Among them, three strong antagonistic isolates were selected and characterised for in vitro plant-growth-promoting and biocontrol traits, including production of hydrogen cyanide, indole-3-acetic acid and siderophores, chitinase and β-1,3-glucanase activities, and inorganic phosphate solubilisation. In all trials, the strain Streptomyces sp. SNL2 revealed promising features. The selected actinobacteria were investigated for the biocontrol of Fusarium oxysporum f. sp. radicis lycopersici and for growth promotion of tomato (Solanum lycopersicum L. cv. Aïcha) seedlings in autoclaved and non-autoclaved soils. All seed-bacterisation treatments significantly reduced the root rot incidence compared to a positive control (with infested soil), and the isolate SNL2 exhibiting the highest protective activity. It reduced the disease incidence from 88.5% to 13.2%, whereas chemical seed treatment with Thiram® provided 14.6% disease incidence. Furthermore, isolate SNL2 resulted in significant increases in the dry weight, shoot and root length of seedlings. 16S rDNA sequence analysis showed that isolate SNL2 was related to Streptomyces asterosporus NRRL B-24328T (99.52% of similarity). Its interesting biocontrol potential and growth enhancement of tomato seedlings open up attractive uses of the strain SNL2 in crop improvement.

VdNUC-2, the Key Regulator of Phosphate Responsive Signaling Pathway, Is Required for Verticillium dahliae Infection.

In fungal cells, a phosphate (Pi) responsive signaling and metabolism (PHO) pathway regulates Pi-homeostasis. NUC-2/PHO81 and its homologs are one of the most important components in the regulation pathway. In soil-borne phytopathogenic fungus Verticillium dahliae, we identified a Neurospora crassa nuc-2 homolog gene VdNUC-2. VdNUC-2 is composed of 1,018 amino acids, and is highly conserved in tested filamentous fungi. Under conditions of Pi-starvation, compared with the wild-type strain and ectopic complementation strains, the VdNUC-2 knocked out mutants exhibited reduced radial growth, decreased production of conidia and microsclerotia, and were more sensitive to hydrogen peroxide stress. The virulence of VdNUC-2 defective mutants was significantly compromised, and that was unable to be restored by exogenous application of extra Pi. Additionally, the deletion mutants of VdNUC-1, a key transcription factor gene positively controlled by VdNUC-2 in the PHO pathway, showed the similar cultural phenotypes as VdNUC-2 mutants when both of them grew in Pi-limited conditions. However, the virulence of VdNUC-1 mutants was comparable to the wild-type strain. These evidences indicated that the virulence reduction in VdNUC-2 mutants is not due to the interruptions in the PHO pathway or the disturbance of Pi-homeostasis in V. dahliae cytoplasm. VdNUC-2 is not only a crucial gene in the PHO pathway in V. dahliae, but also is required for the full virulence during host-infection.

Produção in vitro de enzimas extracelulares por fungos e sua relação com os sintomas descritos em planta hospedeira

RESUMOOs fungos fitopatogênicos habitantes de solo causam perdas econômicas em muitas culturas e são difíceis de serem controlados. Esses fungos podem ser agrupados pelos sintomas comuns que causam nas plantas, bem como pelas enzimas extracelulares que podem produzir. O objetivo do trabalho foi verificar a produção in vitro de enzimas extracelulares por fungos de solo e tentar relacionar essas enzimas com os sintomas que cada fungo causa em planta hospedeira. O ensaio foi delineado em esquema inteiramente casualizado, com dois fatores, sete fungos (Cylindrocladium spathiphylli, Rhizoctonia solani, Sclerotium rolfsii, Ceratocystis fimbriata, Sclerotinia sclerotiorum, Fusarium oxysporum f. sp. dianthi e Verticillium dahliae) mais testemunha e seis enzimas (amilase, carboximetilcelulase, lipase, lacase, catalase e gelatinase) com 10 repetições. Catalase e gelatinase foram mensuradas por escala de notas, enquanto que as demais pelo cálculo da área da coroa circular. O ensaio foi repetido e a análise foi realizada com os dados de dois ensaios. Os fungos que causam podridão na raiz ou no colo da planta apresentaram maior produção de lacase, enquanto os que causam obstrução, fendas ou até a destruição do sistema vascular demonstraram a prevalência da lipase.

Natural infection of the soil-borne fungus Rosellinia necatrix with novel mycoviruses under greenhouse conditions

Fungi are an important component of the soil ecosystem. Mycoviruses have numerous potential impacts on soil fungi, including phytopathogenic fungal species. However, the diversity and ecology of mycoviruses in soil fungi is largely unexplored. Our previous work has shown that the soil-borne phytopathogenic fungus Rosellinia necatrix was infected with several novel mycoviruses after growing for 2–3 years in an apple orchard. In this study, we investigated whether natural infection of R. necatrix with mycoviruses occurs under limited conditions. Virus-free R. necatrix isolates were grown in a small bucket containing soil samples for a short time (1.5–4.5 months) under greenhouse conditions. Screening of dsRNA mycoviruses among 365 retrieved isolates showed that four, including 6–31, 6–33, 6–35, and 7–11, harbored virus-like dsRNAs. Molecular characterization of the dsRNAs revealed that three retrieved isolates, 6–31, 6–33, and 6–35 were infected with a novel endornavirus and isolate 7–11 is infected with a novel partitivirus belonging to the genus Alphapartitivirus. These novel mycoviruses had no overt biological impact on R. necatrix. Overall, this study indicates that natural infections of R. necatrix with new mycoviruses can occur under experimental soil conditions.