RESUMEN
Epizootics of the entomopathogenic fungus Metarhizium rileyi regulate lepidopteran populations in soybean, cotton, and peanut agroecosystems to the point that insecticide applications could be unnecessary. However, the contribution and how different strains operate during the epizootic are unknown. Several unanswered questions remain: 1. How many genotypes of M. rileyi are present during an epizootic? 2. Which genotype is the most common among them? 3. Are the genotypes involved in annual epizootics at the same location the same? Therefore, the development of molecular markers to accurately identify these genotypes is very important to answer these questions. SSR primers were designed by prospecting in silico to discriminate genotypes and infer the genetic diversity of M. rileyi isolates from the collection kept at Embrapa Soybean. We tested 13 SSR markers on 136 isolates to identify 43 clones and 12 different genetic clusters, with genetic diversity ranging from Hs = 0.15 (cluster I) to Hs = 0.41 (cluster IV) and an average diversity of 0.24. No clusters were categorically distinguished based on hosts or geographical origin using Bayesian clustering analysis. Nonetheless, some clusters comprised most of the isolates with a common geographic origin; for example, cluster VIII was mainly composed of isolates from Central-western Brazil, cluster II from Southern Brazil, and cluster XII from Quincy, Northern Florida, in the United States. Underrepresented regions (few isolates) from Pacific Island nations of Japan, the Philippines, and Indonesia (specifically from Java) were placed into clusters IX and X. Although the analyzed isolates displayed evidence of clonal structure, the genetic diversity indices suggest a potential for the species to adapt to different environmental conditions.
Asunto(s)
Variación Genética , Metarhizium , Repeticiones de Microsatélite , Metarhizium/genética , Animales , Genotipo , Control Biológico de VectoresRESUMEN
Metarhizium spp. is used as a biocontrol agent but is limited because of low tolerance to abiotic stress. Metarhizium robertsii is an excellent study model of fungal pathogenesis in insects, and its tolerance to different stress conditions has been extensively investigated. Priming is the time-limited pre-exposure of an organism to specific stress conditions that increases adaptive response to subsequent exposures. Congo red is a water-soluble azo dye extensively used in stress assays in fungi. It induces morphological changes and weakens the cell wall at sublethal concentrations. Therefore, this chemical agent has been proposed as a stressor to induce priming against other stress conditions in entomopathogenic fungi. This study aimed to evaluate the capacity of Congo red to induce priming in M. robertsii. Conidia were grown on potato dextrose agar with or without Congo red.The tolerance of conidia produced from mycelia grown in these three conditions was evaluated against stress conditions, including osmotic, oxidative, heat, and UV-B radiation. Conidia produced on medium supplemented with Congo red were significantly more tolerant to UV-B radiation but not to the other stress conditions assayed. Our results suggest that Congo red confers trans-priming to UV-B radiation but not for heat, oxidative, or osmotic stress.
Asunto(s)
Metarhizium , Metarhizium/fisiología , Rojo Congo , Rayos Ultravioleta , Esporas Fúngicas/fisiologíaRESUMEN
For the first time, the International Symposium on Fungal Stress was joined by the XIII International Fungal Biology Conference. The International Symposium on Fungal Stress (ISFUS), always held in Brazil, is now in its fourth edition, as an event of recognized quality in the international community of mycological research. The event held in São José dos Campos, SP, Brazil, in September 2022, featured 33 renowned speakers from 12 countries, including: Austria, Brazil, France, Germany, Ghana, Hungary, México, Pakistan, Spain, Slovenia, USA, and UK. In addition to the scientific contribution of the event in bringing together national and international researchers and their work in a strategic area, it helps maintain and strengthen international cooperation for scientific development in Brazil.
Asunto(s)
Biología , Brasil , Francia , España , MéxicoRESUMEN
Little is known about the impact of hypoxia and anoxia during mycelial growth on tolerance to different stress conditions of developing fungal conidia. Conidia of the insect-pathogenic fungus Metarhizium robertsii were produced on potato dextrose agar (PDA) medium under normoxia (control = normal oxygen concentrations), continuous hypoxia, and transient anoxia, as well as minimal medium under normoxia. The tolerance of the conidia produced under these different conditions was evaluated in relation to wet heat (heat stress), menadione (oxidative stress), potassium chloride (osmotic stress), UV radiation, and 4-nitroquinoline-1-oxide (=4-NQO genotoxic stress). Growth under hypoxic condition induced higher conidial tolerance of M. robertsii to menadione, KCl, and UV radiation. Transient anoxic condition induced higher conidial tolerance to KCl and UV radiation. Nutritional stress (i.e., minimal medium) induced higher conidial tolerance to heat, menadione, KCl, and UV radiation. However, neither of these treatments induced higher tolerance to 4-NQO. The gene hsp30 and hsp101 encoding a heat shock protein was upregulated under anoxic condition. In conclusion, growth under hypoxia and anoxia produced conidia with higher stress tolerances than conidia produced in normoxic condition. The nutritive stress generated by minimal medium, however, induced much higher stress tolerances. This condition also caused the highest level of gene expression in the hsp30 and hsp101 genes. Thus, the conidia produced under nutritive stress, hypoxia, and anoxia had greater adaptation to stress.
Asunto(s)
Metarhizium , Vitamina K 3 , Esporas Fúngicas , Vitamina K 3/metabolismo , Rayos Ultravioleta , Hipoxia/metabolismoRESUMEN
Soybean, corn, and cotton crops are afflicted by several noctuid pests and the development of bioinsecticides could help control these pests. The fungus Metarhizium rileyi has the greatest potential because its epizootics decimate caterpillar populations in the absence of insecticide applications. However, insect-pathogenic fungi when used for insect control in agriculture have low survival mainly due to the deleterious effects of ultraviolet radiation and heat from solar radiation. In this study, fourteen isolates of M. rileyi were studied and compared with isolates ARSEF 324 and ARSEF 2575 of Metarhizium acridum and Metarhizium robertsii, respectively, whose sensitivity to UV-B radiation had previously been studied. Conidia were exposed at room temperature (ca. 26 °C) to 847.90 mWm-2 of Quaite-weighted UV-B using two fluorescent lamps. The plates containing the conidial suspensions were irradiated for 1, 2, and 3 h, providing doses of 3.05, 6.10, and 9.16 kJ m2, respectively. A wide variability in conidial UV-B tolerance was found among the fourteen isolates of M. rileyi. Isolate CNPSo-Mr 150 was the most tolerant isolate (germination above 80% after 2 h exposure), which was comparable to ARSEF 324 (germination above 90% after 2 h exposure), the most tolerant Metarhizium species. The least tolerant isolates were CNPSo-Mr 141, CNPSo-Mr 142, CNPSo-Mr 156, and CNPSo-Mr 597. Nine M. rileyi isolates exhibited similar tolerance to UV-B radiation as ARSEF 2575 (germination above 50% after 2 h exposure). In conclusion, the majority of M. rileyi isolates studied can endure 1 or 2 h of UV-B radiation exposure. However, after 3 h of exposure, the germination of all studied isolates reduced below 40%, except for CNPSo-Mr 150 and ARSEF 324.
Asunto(s)
Metarhizium , Animales , Rayos Ultravioleta , Esporas Fúngicas , InsectosRESUMEN
White light during mycelial growth influences high conidial stress tolerance of the insect-pathogenic fungus Metarhizium robertsii, but little is known if low- or high-white light irradiances induce different stress tolerances. The fungus was grown either in the dark using two culture media: on minimal medium (Czapek medium without sucrose = MM) or on potato dextrose agar (PDA) or PDA medium under five different continuous white light irradiances. The stress tolerances of conidia produced on all treatments were evaluated by conidial germination on PDA supplemented with KCl for osmotic stress or on PDA supplemented with menadione for oxidative stress. Conidia produced on MM in the dark were more tolerant to osmotic and oxidative stress than conidia produced on PDA in the dark or under the light. For osmotic stress, growth under the lower to higher irradiances produced conidia with similar tolerances but more tolerant than conidia produced in the dark. For oxidative stress, conidia produced under the white light irradiances were generally more tolerant to menadione than conidia produced in the dark. Moreover, conidia produced in the dark germinated at the same speed when incubated in the dark or under lower irradiance treatment. However, at higher irradiance, conidial germination was delayed compared to germination in the dark, which germinated faster. Therefore, growth under light from low to high irradiances induces similar conidial higher stress tolerances; however, higher white light irradiances cause a delay in germination speed.
Asunto(s)
Luz , Metarhizium , Metarhizium/fisiología , Metarhizium/efectos de la radiación , Presión Osmótica , Estrés Oxidativo , Esporas Fúngicas/efectos de la radiaciónRESUMEN
Light is an important signal for fungi in the environment and induces many genes with roles in stress and virulence responses. Conidia of the entomopathogenic fungi Aschersonia aleyrodis, Beauveria bassiana, Cordyceps fumosorosea, Lecanicillium aphanocladii, Metarhizium anisopliae, Metarhizium brunneum, Metarhizium robertsii, Simplicillium lanosoniveum, Tolypocladium cylindrosporum, and Tolypocladium inflatum were produced on potato dextrose agar (PDA) medium under continuous white light, on PDA medium in the dark, or under nutritional stress (= Czapek medium without sucrose = MM) in the dark. The conidial tolerance of these species produced under these different conditions were evaluated in relation to heat stress, oxidative stress (menadione), osmotic stress (KCl), UV radiation, and genotoxic stress caused by 4-nitroquinoline 1-oxide (4-NQO). Several fungal species demonstrated greater stress tolerance when conidia were produced under white light than in the dark; for instance white light induced higher tolerance of A. aleyrodis to KCl and 4-NQO; B. bassiana to KCl and 4-NQO; C. fumosorosea to UV radiation; M. anisopliae to heat and menadione; M. brunneum to menadione, KCl, UV radiation, and 4-NQO; M. robertsii to heat, menadione, KCl, and UV radiation; and T. cylindrosporum to menadione and KCl. However, conidia of L. aphanocladii, S. lanosoniveum, and T. inflatum produced under white light exhibited similar tolerance as conidia produced in the dark. When conidia were produced on MM, a much stronger stress tolerance was found for B. bassiana to menadione, KCl, UV radiation, and 4-NQO; C. fumosorosea to KCl and 4-NQO; Metarhizium species to heat, menadione, KCl, and UV radiation; T. cylindrosporum to menadione and UV radiation; and T. inflatum to heat and UV radiation. Again, conidia of L. aphanocladii and S. lanosoniveum produced on MM had similar tolerance to conidia produced on PDA medium in the dark. Therefore, white light is an important factor that induces higher stress tolerance in some insect-pathogenic fungi, but growth in nutritional stress always provides in conidia with stronger stress tolerance than conidia produced under white light.
Asunto(s)
Beauveria , Metarhizium , Animales , Cordyceps , Hypocreales , Insectos , Iluminación , Esporas FúngicasRESUMEN
Differential sensitivities to the cell wall stress caused by Congo red (CR) have been observed in many fungal species. In this study, the tolerances and sensitivities to CR was studied with an assorted collection of fungal species from three phylogenetic classes: Sordariomycetes, Dothideomycetes, and Eurotiomycetes, three orders, and eight families. These grouped into different ecological niches, such as insect pathogens, plant pathogens, saprotrophs, and mycoparasitics. The saprotroph Aspergillus niger and the mycoparasite Trichoderma atroviride stood out as the most resistant species to cell wall stress caused by CR, followed by the plant pathogenic fungi, a mycoparasite, and other saprotrophs. The insect pathogens had low tolerance to CR. The insect pathogens Metarhizium acridum and Cordyceps fumosorosea were the most sensitive to CR. In conclusion, Congo red tolerance may reflect ecological niche, accordingly, the tolerances of the fungal species to Congo red were closely aligned with their ecology.
Asunto(s)
Pared Celular , Rojo Congo , Hongos , Pared Celular/efectos de los fármacos , Rojo Congo/farmacología , Cordyceps/efectos de los fármacos , Ecosistema , Hongos/efectos de los fármacos , Humanos , Hypocreales/efectos de los fármacos , Metarhizium/efectos de los fármacos , FilogeniaRESUMEN
Chagas disease is one of the most important insect-vectored diseases in Brazil. The entomopathogenic fungus Metarhizium anisopliae was evaluated against nymphs and adults of Panstrongylus megistus, Triatoma infestans, and T. sordida. Pathogenicity tests at saturated humidity demonstrated high susceptibility to fungal infection. The shortest estimates of 50% lethal time (LT50 ) for P. megistus varied from 4.6 (isolate E9) to 4.8 days (genetically modified strain 157p). For T. infestans, the shortest LT50 was 6.3 (E9) and 7.3 days (157p). For T. sordida, the shortest LT50 was 8.0 days (157p). The lethal concentration sufficient to kill 50% of T. infestans (LC50 ) was 1.9 × 107 conidia/ml for strain 157p. In three chicken coops that were sprayed with M. anisopliae, nymphs especially were well controlled, with a great population reduction of 38.5% after 17 days. Therefore M. anisopliae performed well, controlling Triatominae in both laboratory and field studies.
Asunto(s)
Metarhizium/patogenicidad , Panstrongylus/microbiología , Control Biológico de Vectores/métodos , Triatoma/microbiología , Animales , Brasil , Enfermedad de Chagas/prevención & control , Pollos , Vivienda para Animales , Humedad , Insectos Vectores/microbiología , Ninfa/microbiologíaRESUMEN
Fungi sense light and utilize it as a source of environmental information to prepare against many stressful conditions in nature. In this study, Metarhizium robertsii was grown on: 1) potato dextrose agar medium (PDA) in the dark (control); 2) under nutritive stress in the dark; and 3) PDA under continuous (A) white light; (B) blue light lower irradiance = LI; (C) blue light higher irradiance = HI; (D) green light; and (E) red light. Conidia produced under these treatments were tested against osmotic stress and UV radiation. In addition, a suite of genes usually involved in different stress responses were selected to study their expression patterns. Conidia produced under nutritive stress in the dark were the most tolerant to both osmotic stress and UV radiation, and the majority of their stress- and virulence-related genes were up-regulated. For osmotic stress tolerance, conidia produced under white, blue LI, and blue HI lights were the second most tolerant, followed by conidia produced under green light. Conidia produced under red light were the least tolerant to osmotic stress and less tolerant than conidia produced on PDA medium in the dark. For UV tolerance, conidia produced under blue light LI were the second most tolerant to UV radiation, followed by the UV tolerances of conidia produced under white light. Conidia produced under blue HI, green, and red lights were the least UV tolerant and less tolerant than conidia produced in the dark. The superoxide dismutases (sod1 and sod2), photolyases (6-4phr and CPDphr), trehalose-phosphate synthase (tps), and protease (pr1) genes were highly up-regulated under white light condition, suggesting a potential role of these proteins in stress protection as well as virulence after fungal exposure to visible spectrum components.
Asunto(s)
Desoxirribodipirimidina Fotoliasa , Regulación Fúngica de la Expresión Génica , Luz , Metarhizium , Esporas Fúngicas , Regulación Fúngica de la Expresión Génica/efectos de la radiación , Metarhizium/crecimiento & desarrollo , Metarhizium/efectos de la radiación , Presión Osmótica , Esporas Fúngicas/efectos de la radiación , Rayos UltravioletaRESUMEN
Osmotic stress induced by high solute concentration can prevent fungal metabolism and growth due to alterations in properties of the cytosol, changes in turgor, and the energy required to synthesize and retain compatible solutes. We used germination to quantify tolerance/sensitivity to the osmolyte KCl (0.1-4.5 M, in 0.1 M increments) for 71 strains (40 species) of ecologically diverse fungi. These include 11 saprotrophic species (17 strains, including two xerophilic species), five mycoparasitic species (five strains), six plant-pathogenic species (13 strains), and 19 entomopathogenic species (36 strains). A dendrogram obtained from cluster analyses, based on KCl inhibitory concentrations 50 % and 90 % calculated by Probit Analysis, revealed three groups of fungal isolates accordingly to their osmotolerance. The most-osmotolerant group (Group 3) contained the majority of saprotrophic fungi, and Aspergillus niger (F19) was the most tolerant. The highly xerophilic Aspergillus montevidense and Aspergillus pseudoglaucus were the second- and third-most tolerant species, respectively. All Aspergillus and Cladosporium species belonged to Group 3, followed by the entomopathogens Colletotrichum fioriniae, Simplicillium lanosoniveum, and Trichothecium roseum. Group 2 exhibited a moderate osmotolerance, and included plant-pathogens such as Colletotrichum and Fusarium, mycoparasites such as Clonostachys spp, some saprotrophs such as Mucor and Penicillium spp., and some entomopathogens such as Isaria, Lecanicillium, Mariannaea, Simplicillium, and Torrubiella. Group 1 contained the osmo-sensitive strains: the rest of the entomopathogens and the mycoparasitic Gliocladium and Trichoderma. Although stress tolerance did not correlate with their primary ecological niche, classification of these 71 fungal strains was more closely aligned with their ecology than with their phylogenetic relatedness. We discuss the implications for both microbial ecology and fungal taxonomy.
Asunto(s)
Ecosistema , Hongos , Tolerancia a la Sal , Hongos/clasificación , Hongos/fisiología , FilogeniaRESUMEN
Stress is a normal part of life for fungi, which can survive in environments considered inhospitable or hostile for other organisms. Due to the ability of fungi to respond to, survive in, and transform the environment, even under severe stresses, many researchers are exploring the mechanisms that enable fungi to adapt to stress. The International Symposium on Fungal Stress (ISFUS) brings together leading scientists from around the world who research fungal stress. This article discusses presentations given at the third ISFUS, held in São José dos Campos, São Paulo, Brazil in 2019, thereby summarizing the state-of-the-art knowledge on fungal stress, a field that includes microbiology, agriculture, ecology, biotechnology, medicine, and astrobiology.
Asunto(s)
Hongos , Estrés Fisiológico , Brasil , Hongos/fisiologíaRESUMEN
The fungal species Trichoderma is frequently found in soil antagonizing plant-pathogenic fungi as well as parasitizing plant-pathogenic nematodes. Metarhizium species are insect-pathogenic fungi that are used throughout the world to control agricultural insect pests. Here, we determine whether the antagonism (A) of Trichoderma atroviride to Metarhizium robertsii during growth and spore formation can impact the stress biology of M. robertsii conidia. Cultures of M. robertsii were either produced without exposure to T. atroviride (control) or in the presence of T. atroviride. M. robertsii was grown in dual culture with T. atroviride on potato dextrose agar (PDA) using the following treatments: 1) Trichoderma inoculated at the same time with Metarhizium (A0); 2) Trichoderma inoculated two days after the inoculation of Metarhizium (A2); 3) Trichoderma inoculated four days after Metarhizium (A4); 4) Trichoderma inoculated 6 d after Metarhizium (A6); 5) M. robertsii grown alone on PDA medium (control); and 6) M. robertsii grown alone on minimal medium (Czapek-Dox medium without sucrose) (MM). Germination of M. robertsii conidia from all six treatments was then assessed under osmotic, oxidative, UV-B, and thermal stress. M. robertsii conidia produced on MM were the most tolerant to all stress conditions. For all stress conditions, conidia from treatments A0 and A2 were not viable. For osmotic stress, conidia produced in treatment A4 were the most tolerant, followed by conidia from treatment A6, which were both more tolerant than the control. For oxidative stress, conidia produced in both A4 and A6 treatments were similarly tolerant and more tolerant than conidia produced in the control. For thermal stress, conidia produced in treatments A4, A6, and control (PDA) were similarly heat-tolerant. For UV-B stress, conidia produced in treatments A4 and A6 were equally tolerant and more tolerant than conidia produced in the control. The germination speed of conidia produced in all treatments, A0, A2, A4, and A6 was also tested. Conidia produced on MM germinated faster than the other treatments. Conidia produced in the A4 treatment were the second fastest, followed by conidia produced in treatment A6. Both A4 and A6 conidia germinated faster than conidia produced in the control treatment. Conidia produced in the treatments A0 and A2 did not germinate in 24 h. In summary, moderate levels of biotic stress from a fungal competitor or low-nutrient conditions can enhance the stress tolerance of M. robertsii conidia.
Asunto(s)
Hypocreales , Metarhizium , Interacciones Microbianas , Calor , Hypocreales/fisiología , Metarhizium/fisiología , Presión Osmótica , Esporas Fúngicas/fisiología , Factores de TiempoRESUMEN
The International Symposium on Fungal Stress (ISFUS) was born in a dream that Drauzio Eduardo Naretto Rangel had in 2013. This article reviews the first three ISFUSs and prospects for the future meetings. Although ISFUS was born as a small family organized meeting, since the first meeting, ISFUS has achieved great success, receiving very important research grants from FAPESP, FAPEG, and CAPES to bring international scientists to Brazil. Moreover, three special issues in leading journals have been published with articles relating to the talks presented at each ISFUS. For the first meeting, most speakers published in a special issue in Current Genetics. From the second and third meeting, articles from the speakers were published in special issues of the top mycology journal, Fungal Biology, published by Elsevier on behalf of the British Mycological Society. Here we show that following the dreams with a full heart and adding lots of love, passion, and hard work can achieve success.
Asunto(s)
Congresos como Asunto , Hongos , Micología , Brasil , Congresos como Asunto/historia , Hongos/fisiología , Historia del Siglo XXI , Internacionalidad , Estrés FisiológicoRESUMEN
The topic of 'fungal stress' is central to many important disciplines, including medical mycology, chronobiology, plant and insect pathology, industrial microbiology, material sciences, and astrobiology. The International Symposium on Fungal Stress (ISFUS) brought together researchers, who study fungal stress in a variety of fields. The second ISFUS was held in May 8-11 2017 in Goiania, Goiás, Brazil and hosted by the Instituto de Patologia Tropical e Saúde Pública at the Universidade Federal de Goiás. It was supported by grants from CAPES and FAPEG. Twenty-seven speakers from 15 countries presented their research related to fungal stress biology. The Symposium was divided into seven topics: 1. Fungal biology in extreme environments; 2. Stress mechanisms and responses in fungi: molecular biology, biochemistry, biophysics, and cellular biology; 3. Fungal photobiology in the context of stress; 4. Role of stress in fungal pathogenesis; 5. Fungal stress and bioremediation; 6. Fungal stress in agriculture and forestry; and 7. Fungal stress in industrial applications. This article provides an overview of the science presented and discussed at ISFUS-2017.
Asunto(s)
Hongos/fisiología , Hongos/patogenicidad , Estrés Fisiológico , Brasil , Microbiología Ambiental , Microbiología Industrial , MicologíaRESUMEN
Microorganisms are essential to the functionality of the soil, particularly in organic matter decomposition and nutrient cycling, which regulate plant productivity and shape the soil structure. However, biotic and abiotic stresses greatly disrupt soil fungal communities and, thereby, disturb the ecosystem. This study quantified seasonal tolerances to UV-B radiation and heat of fungal communities, which could be cultured, found in soil from two native Atlantic forest fragments called F1 and F2, five reforested areas (RA) planted in 1994, 1997, 2004, 2007, and 2009 with native species of the Atlantic forest, and one sand mining degraded soil (SMDS). The cold activity of the soil fungal communities (FC) from the eight different areas was also studied. Higher tolerance to UV-B radiation and heat was found in the FC from the SMDS and the 2009RA, where the incidence of heat and UV radiation from sun was more intense, which caused selection for fungal taxa that were more UV-B and heat tolerant in those areas. Conversely, the FC from the native forests and older reforested sites were very susceptible to heat and UV-B radiation. The cold activity of the soil FC from different areas of the study showed an erratic pattern of responses among the sampling sites. Little difference in tolerance to UV-B radiation and heat was found among the FC of soil samples collected in different seasons; in general soil FC collected in winter were less tolerant to UV-B radiation, but not for heat. In conclusion, FC from SMDS soil that receive intense heat and UV radiation, as well as with low nutrient availability, were more tolerant to both UV-B radiation and heat.
Asunto(s)
Restauración y Remediación Ambiental , Bosques , Respuesta al Choque Térmico , Micobioma/fisiología , Micobioma/efectos de la radiación , Tolerancia a Radiación , Microbiología del Suelo , Calor , Minería , Estaciones del Año , Rayos UltravioletaRESUMEN
Species of the Metarhizium anisopliae complex are globally ubiquitous soil-inhabiting and predominantly insect-pathogenic fungi. The Metarhizium genus contains species ranging from specialists, such as Metarhizium acridum that only infects acridids, to generalists, such as M. anisopliae, Metarhizium brunneum, and Metarhizium robertsii that infect a broad range of insects and can also colonize plant roots. There is little information available about the susceptibility of Metarhizium species to clinical and non-clinical antifungal agents. We determined the susceptibility of 16 isolates comprising four Metarhizium species with different ecological niches to seven clinical (amphotericin B, ciclopirox olamine, fluconazole, griseofulvin, itraconazole, tebinafine, and voriconazole) and one non-clinical (benomyl) antifungal agents. All isolates of the specialist M. acridum were clearly more susceptible to most antifungals than the isolates of the generalists M. anisopliae sensu lato, M. brunneum, and M. robertsii. All isolates of M. anisopliae, M. brunneum, and M. robertsii were resistant to fluconazole and some were also resistant to amphotericin B. The marked differences in susceptibility between the specialist M. acridum and the generalist Metarhizium species suggest that this characteristic is associated with their different ecological niches, and may assist in devising rational antifungal treatments for the rare cases of mycoses caused by Metarhizium species.
Asunto(s)
Antifúngicos/farmacología , Metarhizium/efectos de los fármacos , Micosis/microbiología , Animales , Farmacorresistencia Fúngica/genética , Ecosistema , Humanos , Insectos/microbiología , Metarhizium/clasificación , Metarhizium/genéticaRESUMEN
Light conditions during fungal growth are well known to cause several physiological adaptations in the conidia produced. In this study, conidia of the entomopathogenic fungi Metarhizium robertsii were produced on: 1) potato dextrose agar (PDA) medium in the dark; 2) PDA medium under white light (4.98 W m-2); 3) PDA medium under blue light (4.8 W m-2); 4) PDA medium under red light (2.8 W m-2); and 5) minimum medium (Czapek medium without sucrose) supplemented with 3 % lactose (MML) in the dark. The conidial production, the speed of conidial germination, and the virulence to the insect Tenebrio molitor (Coleoptera: Tenebrionidae) were evaluated. Conidia produced on MML or PDA medium under white or blue light germinated faster than conidia produced on PDA medium in the dark. Conidia produced under red light germinated slower than conidia produced on PDA medium in the dark. Conidia produced on MML were the most virulent, followed by conidia produced on PDA medium under white light. The fungus grown under blue light produced more conidia than the fungus grown in the dark. The quantity of conidia produced for the fungus grown in the dark, under white, and red light was similar. The MML afforded the least conidial production. In conclusion, white light produced conidia that germinated faster and killed the insects faster; in addition, blue light afforded the highest conidial production.
Asunto(s)
Metarhizium/crecimiento & desarrollo , Metarhizium/patogenicidad , Tenebrio/microbiología , Animales , Luz , Metarhizium/efectos de la radiación , VirulenciaRESUMEN
The low survival of insect-pathogenic fungi when used for insect control in agriculture is mainly due to the deleterious effects of ultraviolet radiation and heat from solar irradiation. In this study, conidia of 15 species of entomopathogenic fungi were exposed to simulated full-spectrum solar radiation emitted by a Xenon Test Chamber Q-SUN XE-3-HC 340S (Q-LAB® Corporation, Westlake, OH, USA), which very closely simulates full-spectrum solar radiation. A dendrogram obtained from cluster analyses, based on lethal time 50 % and 90 % calculated by Probit analyses, separated the fungi into three clusters: cluster 3 contains species with highest tolerance to simulated full-spectrum solar radiation, included Metarhizium acridum, Cladosporium herbarum, and Trichothecium roseum with LT50 > 200 min irradiation. Cluster 2 contains eight species with moderate UV tolerance: Aschersonia aleyrodis, Isaria fumosorosea, Mariannaea pruinosa, Metarhizium anisopliae, Metarhizium brunneum, Metarhizium robertsii, Simplicillium lanosoniveum, and Torrubiella homopterorum with LT50 between 120 and 150 min irradiation. The four species in cluster 1 had the lowest UV tolerance: Lecanicillium aphanocladii, Beauveria bassiana, Tolypocladium cylindrosporum, and Tolypocladium inflatum with LT50 < 120 min irradiation. The QSUN Xenon Test Chamber XE3 is often used by the pharmaceutical and automotive industry to test light stability and weathering, respectively, but it was never used to evaluate fungal tolerance to full-spectrum solar radiation before. We conclude that the equipment provided an excellent tool for testing realistic tolerances of fungi to full-spectrum solar radiation of microbial agents for insect biological control in agriculture.
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Entomophthorales/efectos de los fármacos , Entomophthorales/crecimiento & desarrollo , Tolerancia a Radiación , Energía Solar , Luz Solar , Rayos Ultravioleta , XenónRESUMEN
The Fungal Kingdom is responsible for many ecosystem services as well as many industrial and agricultural products. Nevertheless, how these fungal species function and carry out these services is dependent on their capacity to grow under different stress conditions caused by a variety of abiotic factors such as ionizing radiation, UV radiation, extremes of temperature, acidity and alkalinity, and environments of low nutritional status, low water activity, or polluted with, e.g. toxic metals or xenobiotics. This article reviews some natural or synthetic environments where fungi thrive under stress and have important impacts in agriculture and forestry.