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URI permanente desta comunidadehttps://repositorioacademico.universidadebrasil.edu.br/handle/123456789/914
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Item Tolerância de fungos entomopatogênicos e fitopatogênicos a diferentes agentes estressores(Universidade Brasil, 2020) Costa, Tacyana Pires de Carvalho; Rangel, Drauzio Eduardo NarettoIn the first chapter, germination, mycelial growth, and conidia production of the entomopathogenic fungi Trichothecium roseum, Metarhizium robertsii, and Metarhizium acridum were studied under conditions of osmotic stress induced by KCl, UV radiation, 4-nitroquinoline-1-oxide (4-NQO), heat, and Congo red. T. roseum is more tolerant than the others when confronting osmotic stress due to KCL, stress due to the 4-NQO, and stress due to Congo Red. However, under UV radiation conditions, Metarhizium species were more tolerant. In summary, we conclude that the fungus T. roseum is a promising agent in the biological control of insects. In the second chapter, the effects of visible light wavelengths on germination, mycelial radial growth, and conidia production of the phytopathogens Colletotrichum acutatum and Fusarium fujikuroi were studied. No differences were found for germination and growth for both fungi under different light and dark regimes; however, significant differences occurred in both conidial production and UV radiation. In the third chapter, differential sensitivities to cell wall stress caused by Congo red were studied in several species of fungi. The saprotrophic fungus Aspergillus niger and the mycoparasitic fungus Trichoderma atroviride stood out as the species most resistant to cell wall stress caused by Congo red, followed by phytopathogenic and other saprotrophic fungi. The insect pathogens exhibited low or moderate tolerance. The insect pathogens Metarhizium acridum and Isaria fumosorosea were the most sensitive.Item Tolerância ao estresse de conídios de Metarhizium Robertsii produzidos em meio suplementado com Sulfato de zinco(Universidade Brasil, 2023) Feitosa, Valéria de Albuquerque Sousa; Rangel, Drauzio Eduardo Naretto; Soto, Cláudio Alberto TellezFungi for industrial and agricultural uses are subject to a variety of physical and chemical insults, collectively referred to as stresses. The fungal response to stress conditions may be due to growth and metabolism impairments and it is important to understand the physiology of stress responses to alleviate detrimental influences when applying the fungus in the field for insect control. The present study aims to evaluate the physiological and morphological effects of zinc sulfate on the entomopathogenic fungi Metarhizium robertsii, as well as the mycelial growth of this fungus, and its tolerance to the stresses of conidia produced in media supplemented with zinc under UV radiation, stress osmotic (potassium chloride) and heat. Mycelium radial growth showed that this salt does not influence the growth of the studied fungus. With regard to tolerance to UV radiation, it was observed that the germination of conidia produced at a concentration of 1.5 g/l obtained similar tolerance to conidia produced under normal conditions, thus being more tolerant than those produced at concentrations 0.5, 1.0 and 2.0g /l. This finding is similarly observed with regard to tolerance to the Osmotic Stress condition. Germination of M. robertsii conidia supplemented with zinc sulfate induced greater heat tolerance when compared to other treatments.Item Estudo dos efeitos da hipóxia e anóxia durante o crescimento micelial de Metarhizium Robertsii na tolerância a estresses de conídios e regulação de genes(Universidade Brasil, 2022) Martins e Silva, Albery; Rangel, Drauzio Eduardo NarettoLittle is known about the impact of hypoxia and anoxia during mycelial growth on tolerance to different stress conditions of fungal conidia development. Metarhizium robertsii conidia were produced on potato dextrose agar (PDA) medium under normoxic (control = normal oxygen concentrations), continuous hypoxia and transient anoxia, as well as minimal medium. The tolerance of conidia produced under these different conditions was evaluated in relation to moist heat (thermal stress), menadione (oxidative stress), potassium chloride (osmotic stress), UV radiation and 4-nitroquinoline-1-oxide (genotoxic stress 4-NQO ). Growth under hypoxic conditions induced greater tolerance of M. robertsii conidia to menadione, KCl and UV radiation. The transient anoxic condition induced greater tolerance of conidia to KCl and UV radiation. Nutritional stress (ie, minimal medium) induced greater tolerance of conidia to heat, menadione, KCl and UV radiation. The hsp30 and hsp101 gene encoding a heat shock protein was overexpressed in molecular analysis under anoxic condition. In conclusion, growth under hypoxia and anoxia produced conidia with greater stress tolerance than conidia produced under normoxic conditions. The nutritional stress generated by the minimal medium, however, induced a much higher stress tolerance. This condition also caused the highest level of gene expression in the hsp30 and hsp101 genes. Allowing concluding that there was a greater adaptation to the stress of the conidia produced under nutritional stress, hypoxia and anoxia.