Monografias, Dissertações e Teses
URI permanente desta comunidadehttps://repositorioacademico.universidadebrasil.edu.br/handle/123456789/1
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Resultados da Pesquisa
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 de espécies de Metarhizium a estresse oxidativo induzido por Menadiona(Universidade Brasil, 2024) Dias, Elvira Marques da Luz; Soto, Carlos Alberto Tellez; Rangel, Drauzio Eduardo NarettoOxidative stress is caused by reactive oxygen species (ROS) such as superoxide ion, hydrogen peroxide and hydroxyl radicals. Various types of stress conditions including heat, UV-A radiation and chemicals such as diamide, paraquat, menadione, sodium chloride are potent inducers of ROS. Entomopathogenic fungi are predisposed to ROS induced by heat and UV-A radiation when outside the insect host and when inside the host, they are subject to phagocytic cells that generate ROS to eliminate invading pathogens. This work aimed to evaluate the tolerance levels of Metarhizium species to oxidative stress induced by menadione and to analyze the viability of Metarhizium species to oxidative stress in different concentrations of menadione. Conidial germination was evaluated 24 h after inoculation on potato dextrose agar (BDA) (control) or PDA supplemented with 0.05 menadione; 0.07; 0.09; 0.11; 0.13; 0.15 and 0.17 mM. The plates were kept at 26°C in the dark. The fungi most resistant to oxidative stress were M. anisopliae (ARSEF 4570) from Macquarie Island in Australia located in the Antarctic Circle and M. brunneum (ARSEF 5626) from Finland, probably because they evolved under intense ultraviolet radiation, cold and others. stresses, with M. album (ARSEF 2082) being the fungus most susceptible to oxidative stress, probably because of its lack of pigmentation. Our results contribute to the understanding of the responses to oxidative stress of the studied fungi, which are naturally.Item Tolerância à radiação UV-B do fungo entomopatogênico Metarhizium Rileyi para o desenvolvimento com o agente microbiano para o manejo das principais espécies lepidópteras nas culturas de soja e algodão(Universidade Brasil, 2022) Andrade, Eliezer Pereira de; Rangel, Drauzio Eduardo NarettoSoybean, corn and cotton crops are afflicted by several noctuid pests, therefore, the development of bioinsecticides can provide the control of these pests with the sustainability of the system. The fungus Metarhizium rileyi has the greatest potential since its epizootics decimate caterpillar populations in the absence of fungicide applications. The low survival of insect-pathogenic fungi when used for insect control in agriculture, however, is mainly due to the deleterious effects of ultraviolet radiation and heat from solar irradiation. 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, which sensitivity to UV-B radiation had been previously studied. Conidial suspensions were exposed at room temperature (ca. 26 °C) to 847.90 mWm2 of Quaite-weighted UV-B using two fluorescent lamps TL 20W12 RS (Philips, Eindhoven, Holland). The plates containing the conidial suspensions were irradiated for 1, 2, and 3 h, providing doses of 3.05, 6.10, 9.16, and 12.21 kJ m2 , respectively. Remarkable variability in conidial UV-B tolerance was found among 14 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 isolate. The least tolerant isolate was CNPSo-Mr 597 (germination below 5% after 2 h exposure). Nine isolates were similar with ARSEF 2575 (germination above 50% after 2 h exposure). Concluding, the majority of M. rileyi isolates can endure 1 or 2 h of UV B radiation exposure. However, after 3 h exposure caused great reduction of germination below 40% for all isolates, except for CNPSo-Mr 150 and ARSEF 324.