The fungus Ophiostoma fimbriatum (E & H) Nann, though exceptionally rare in northern climates, is fairly widespread in tropical and sub-tropical areas of the world causing diseases on many species of plants. The disease producing capabilities of the fungus have become a major economic problem in the growth and storage of sweet potatoes (Ipomoea batatas (L.) Lam) in the southern parts of the United States. The organism is interesting from the point of view that it produces, very readily on sweet potato dextrose agar, two types of asexual or vegetative spores and the perfect stage with the perithecia containing ascospores. Several strains of the fungi have been isolated from natural habitats. This work deals, in general, with a study of the gross morphology of this ascomycete and some observations on the nuclear apparatus of the resting and germinating conidia. More specifically, this study treats with certain factors in nutrition which affect the physiology in such a way that the growth and sporulation characteristics of the organism are altered. Since several strains of 0. fimbriatum have been isolated naturally it is thought that these must have been derived from mutant changes occurring in an original "wild" form which was propagated to more susceptible varietal hosts. As a result, studies are undertaken in an attempt to induce changes in an original culture by adopting artificial mutagenic methods. A pathogenicity experiment is done on sweet potato blocks in the laboratory to ascertain the relative degree of virulence between the new-formed strains. This work shows that the cultural characteristics and reproductive behaviour of this fungus could be modified by specific variations in the culture medium. It is shown among other things, that copper, in the role of a micro-nutrient, plays a definite part in the manifestation of sexuality and in the development of pigmentation in the organism. "Mutations" are produced by using X-irridiation and ultra-violet rays as inductive agents. Many of the new-formed "mutants" are unstable and back mutation to the original "wild" type is common. / Science, Faculty of / Botany, Department of / Graduate

Cultural studies were carried out with haploid strains of Tremella mesenterica Fr., T. encephala Pers. and T. subanomala Coker to determine the conditions and course of conjugation. Under the conditions of the experiments, the optimum pH for growth was 4.7 for all three species and so also was the optimum for conjugation in mixed isolates of T. encephala and T. mesenterica. A time lapse sequence was photographed to follow the course of conjugation in mixed isolates of T. mesenterica. Conjugation hormones such as those reported for T. mesenterica by Bandoni (1965) were demonstrated for the other two species. These hormones passed through dialysis membrane into agar. Extremely dilute suspensions of T. mesenterica haplonts were pulse exposed to semipurified hormone extracts. These suspensions were filtered and the cells were observed on the dried filter cleared with glacial acetic acid. Conjugation tube production terminated with removal of the hormone. Growth and conjugation in T. mesenterica were unaffected by the antibiotic cycloheximide. / Science, Faculty of / Botany, Department of / Graduate

No description available.

Phytophthora parasitica, P. citrophthora, and other plant pathogenic fungi were isolated from re-cycled water used to irrigate citrus and other crops. The several propogules of P. parasitica were then studied to determine their survival capabilities in soil and irrigation water. Chlamydospores of P. parasitica were present in field soils from foot-rot infested citrus groves and persisted for at least 60 days in air-dried or moist soils. They germinated in irrigation water or moist soil and formed sporangia within 16 hr. Sporangia were also present in these field soils and survived for at least 60 days in moist soil. They germinated, releasing zoospores into irrigation water 5 min after being inundated. Zoospores were not present in water flooded on air-dried field soil until after 20 hr incubation. Citrus leaves became infected by zoospores within 15 min when placed in zoospore infested water. Although they remained motile in irrigation water for up to 20 hr at 20 C, zoospores encysted when agitated or upon the addition of nutrients, orange peel, or citrus leaves. At low nutrient levels (< 5 mg glucose/liter of sterile distilled water) zoospores germinated and upon cessation of growth the protoplasm contracted within the hyphae and pseudo-septa were formed. Empty cysts or hyphae often lysed; remaining hyphal fragments containing protoplasm survived for at least 40 days at 25 C in untreated waste water and resumed growth upon addition of nutrients. At higher nutrient levels (10-1,000 mg glucose/liter of sterile distilled water) the hyphal tips often produced appressorium-like structures when in contact with the container surface. Exudates from orange peel or citrus leaves stimulated similar activity. The appressorium-like structures usually germinated to produce microsporangia when the nutrients were replaced with untreated irrigation waste water. Some microsporangia persisted in untreated waste water at 25 C for 60 days but most germinated sooner, producing only a single zoospore. Mycelial inoculum from these zoospores was pathogenic to roots of citrus seedlings. Results indicate that P. parasitica is spread by re-cycled irrigation water and that zoospores, or structures produced by them, can play a significant role as survival or dispersal units in re-cycled water.

by Wong Yuk Hang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 110-114). / Abstract --- p.i / Acknowledgement --- p.iv / Dedication --- p.v / Table of Contents --- p.vi / List of Tables --- p.xi / List of Figures --- p.xii / Chapter Chapter 1 --- Introduction and literature review / Chapter 1.1 --- Introduction --- p.2 / Chapter 1.2 --- Literature review --- p.5 / Chapter 1.2.1 --- General considerations --- p.5 / Chapter 1.2.2 --- Nature of glucosinolate --- p.6 / Chapter 1.2.3 --- Degradation of glucosinolates by myrosinase --- p.7 / Chapter 1.2.4 --- Toxicology of glucosinolate and hydrolysis products --- p.8 / Chapter 1.2.5 --- Plant myrosinase --- p.9 / Chapter 1.2.6 --- Fungal myrosinase --- p.11 / Chapter 1.2.7 --- Purification and properties of fungal myrosinase --- p.11 / Chapter Chapter 2 --- Screening of fungi with myrosinase activity and physiological studies of myrosinase production in Aspergillus oryzae / Chapter 2.1 --- Introduction --- p.15 / Chapter 2.2 --- Materials and methods --- p.16 / Chapter 2.2.1 --- Fungal strains --- p.16 / Chapter 2.2.2 --- Media --- p.16 / Chapter 2.2.3 --- Screening --- p.17 / Chapter 2.2.4 --- Enzyme assay and protein determination --- p.18 / Chapter 2.2.4.1 --- Myrosinase assay --- p.18 / Chapter 2.2.4.2 --- Definition of myrosinase unit and specific activity --- p.19 / Chapter 2.2.4.3 --- Protein determination --- p.19 / Chapter 2.2.5 --- Physiological studies of myrosinase production in Aspergillus oryzae --- p.19 / Chapter 2.2.5.1 --- Incubation time --- p.20 / Chapter 2.2.5.2 --- Inducer concentration --- p.20 / Chapter 2.3 --- Results --- p.21 / Chapter 2.3.1 --- Screening --- p.21 / Chapter 2.3.1.1 --- Degradation of sinigrin in culture medium --- p.21 / Chapter 2.3.1.2 --- Confirmation of myrosinase activity --- p.21 / Chapter 2.3.2 --- Physiological studies of myrosinase production in Aspergillus oryzae --- p.21 / Chapter 2.3.2.1 --- Incubation time --- p.21 / Chapter 2.3.2.2 --- Inducer concentration --- p.22 / Chapter 2.4 --- Discussion --- p.23 / Chapter 2.4.1 --- Fungi selection in screening programme --- p.23 / Chapter 2.4.2 --- Medium composition --- p.23 / Chapter 2.4.3 --- Screening --- p.24 / Chapter 2.4.4 --- Physiological studies of myrosinase production in Aspergillus oryzae --- p.25 / Chapter 2.4.4.1 --- Incubation time --- p.25 / Chapter 2.4.4.2 --- Inducer concentration --- p.25 / Chapter Chapter 3 --- Purification and characterization of myrosinase in Aspergillus oryzae / Chapter 3.1 --- Introduction --- p.33 / Chapter 3.2 --- Materials and methods --- p.35 / Chapter 3.2.1 --- Reagents --- p.35 / Chapter 3.2.2 --- Fungal propagation --- p.35 / Chapter 3.2.3 --- Purification of the fungal myrosinase --- p.36 / Chapter 3.2.3.1 --- Preparation of crude extract --- p.36 / Chapter 3.2.3.2 --- Dialysis --- p.37 / Chapter 3.2.3.3 --- DEAE-Sepharose CL-6B ion-exchange chromatography --- p.37 / Chapter 3.2.3.4 --- Sephacryl S-200 molecular sieving chromatography --- p.37 / Chapter 3.2.3.5 --- FPLC Phenyl Superose hydrophobic interaction chromatography --- p.38 / Chapter 3.2.3.6 --- FPLC Mono P chromatofocusing --- p.38 / Chapter 3.2.4 --- Myrosinase assay and protein concentration determination --- p.39 / Chapter 3.2.4.1 --- Spot test for myrosinase activity --- p.39 / Chapter 3.2.4.2 --- Standard end-point assay --- p.40 / Chapter 3.2.4.3 --- Determination of protein concentration --- p.42 / Chapter 3.2.5 --- Physicochemical characterization of the myrosinase isozymes --- p.42 / Chapter 3.2.5.1 --- Sodium dodecyl sulfate polyacrylamide gel electrophoresis --- p.42 / Chapter 3.2.5.2 --- Protein staining and glycoprotein detection --- p.43 / Chapter 3.2.5.3 --- Chromatofocusing --- p.43 / Chapter 3.2.5.4 --- Gel filtration with FPLC Superose 6 --- p.44 / Chapter 3.2.6 --- Enzymatic properties --- p.44 / Chapter 3.2.6.1 --- Effect of pH on crude enzyme stability --- p.44 / Chapter 3.2.6.2 --- Effect of substrate concentration on enzyme activity --- p.45 / Chapter 3.2.6.3 --- Effect of pH on enzyme activity --- p.45 / Chapter 3.2.6.4 --- Effect of temperature on enzyme activity --- p.46 / Chapter 3.2.6.5 --- Effects of metallic ions on enzyme activity --- p.46 / Chapter 3.2.6.6 --- Effects of various compounds on enzyme activity --- p.46 / Chapter 3.2.6.7 --- Effects of various buffers on enzyme activity --- p.47 / Chapter 3.3 --- Results --- p.48 / Chapter 3.3.1 --- Fungal propagation --- p.48 / Chapter 3.3.2 --- Purification of fungal myrosinase in Aspergillus oryzae --- p.48 / Chapter 3.3.2.1 --- Extraction of the enzyme --- p.48 / Chapter 3.3.2.2 --- Dialysis --- p.49 / Chapter 3.3.2.3 --- DEAE-Sepharose ion-exchange chromatography --- p.49 / Chapter 3.3.2.4 --- Sephacryl S-200 molecular sieving chromatography --- p.50 / Chapter 3.3.2.5 --- FPLC Phenyl Superose hydrophobic interaction chromatography --- p.50 / Chapter 3.3.2.6 --- FPLC Mono P chromatofocusing --- p.51 / Chapter 3.3.3 --- Physicochemical characterization --- p.52 / Chapter 3.3.3.1 --- Sodium dodecyl sulfate polyacrylamide gel electrophoresis --- p.52 / Chapter 3.3.3.2 --- Chromatofocusing --- p.53 / Chapter 3.3.3.3 --- Gel filtration --- p.53 / Chapter 3.3.4 --- Enzymatic properties --- p.53 / Chapter 3.3.4.1 --- Effect of pH on the crude enzyme stability --- p.53 / Chapter 3.3.4.2 --- Effect of substrate concentration on enzyme activity --- p.54 / Chapter 3.3.4.3 --- Effect of pH on enzyme activity --- p.54 / Chapter 3.3.4.4 --- Effect of temperature on enzyme activity --- p.55 / Chapter 3.3.4.5 --- Effects of metallic ions on enzyme activity --- p.55 / Chapter 3.3.4.6 --- Effects of various compounds on enzyme activity --- p.56 / Chapter 3.3.4.7 --- Effects of various buffers on enzyme activity --- p.57 / Chapter 3.4 --- Discussion --- p.58 / Chapter 3.4.1 --- Purification of Aspergillus oryzae myrosinase --- p.58 / Chapter 3.4.1.1 --- Dialysis --- p.58 / Chapter 3.4.1.2 --- Enzyme purification --- p.58 / Chapter 3.4.2 --- Physicochemical properties --- p.60 / Chapter 3.4.2.1 --- Glycoprotein --- p.60 / Chapter 3.4.2.2 --- Molecular weights --- p.60 / Chapter 3.4.2.3 --- Isoelectric points --- p.61 / Chapter 3.4.3 --- Enzymatic properties --- p.61 / Chapter 3.4.3.1 --- pH and temperature optima --- p.61 / Chapter 3.4.3.2 --- Substrate affinity --- p.62 / Chapter 3.4.3.3 --- Inhibitions by various compounds and metallic ions --- p.63 / Chapter 3.4.3.4 --- Inhibitions by various buffer systems --- p.64 / Chapter Chapter 4 --- Summary --- p.106 / References --- p.110

Previous studies of fungal decay have mainly examined long term effects of wood decay. In contrast, the present work, was designed to quantify fungal degradation of wood during incipient decay. Three facultatively anaerobic, dimorphic fungi were isolated from the rumen of sheep. These fungi were identified as Mucor racemosus, Candida tropicalis and Geotrichum capitatum. Scanning electron microscopy showed that these fungi colonised Pinus patula and Eucalyptus grandis extensively but did not appear to degrade the wood. The obligate anaerobe Neocallimastix frontalis colonised wood very sparsely, whereas the white rot bas id iomycetes Cori 01 us versicolor, and Phanaerochaete chrysosporium, and the brown rotters Coniophora puteana and Lentinus lepideus, colonised wood under both aerobic and anaerobic conditions. The extents of colonisation were greater under aerobic conditions. The work then quantified the effects of the basidiomycetes C. versicolor, P. chrysosporium, C. puteana and L .lepideus, and the non-decay mould, M. racemosus in individual and coculture experiments. Wood colonisation was quantified by Kjeldahl nitrogen determinations converted to biomass assays, and degradation was quantified by weight losses, and Klason lignin determinations. Furthermore, the degraded wood samples were also analysed by HPLC analysis of hydrolysates and their sugar contents were determined to establish whether the glucose of cellulose and xylose + mannose of hemicellulose had been utilised by the respective fungi. The extent and nature of sugar utilisation by monocultures and cocultures in wood were then compared with the biomass and degradation data. statistical analyses of' these comparisons correlated the extents of colonisation, degradation, and the patterns of wood sugars predominantly utilised by each fungus. The results of the corresponding glucose, xylose and 'lignin analyses confirmed the brown rot physiological capacity of C.puteana in both'woods. The white rot fungi behaved as simultaneous rotters and,<M·~<.racemosus was shown to be ligninolytic in P .patula. The white rot physiological capacity of C.versicolor was confirmed in 'E.grandis and that of P.chrysosporium in P.patula. Antagonism and synergism in wood was detected between individuals 'within cocultures during incipient decay. The significance of these findings becomes apparent when decayed wood of unknown history is analysed as described here. Such findings may be interpreted to provide valuable information describing the physiological nature of the responsible fungi, even if these are no longer viable or culturable. / Thesis (M.Sc.)-University of Durban-Westville, 1992

No description available.

Thesis (MScAgric)--Stellenbosch University, 1948. / NO ABSTRACT AVAILABLE

O efeito da exposição à luz visível e a limitação de oxigênio durante o crescimento micelial foi investigado na tolerância de conídios de dez fungos entomopatogênicos a: (A) radiação UV; (B) estresse osmótico causado pelo cloreto de potássio (KCl) e (C) estresse genotóxico provocado por 4-nitroquinoline-1-óxido (4-NQO). No primeiro experimento, foi avaliado o limiar de fotoativação de Metarhizium robertsii. Foram estudadas quatro intensidades de luz com 1, 3, 4 e 5 lumens, nas quais, foi avaliada a germinação e o aumento de tolerância ao estresse osmótico. No segundo experimento, foi analisada a influência da luz branca no aumento da tolerância à radiação UV, KCl, e 4-NQO em dez espécies de fungos entomopatogênicos. No terceiro experimento, foi avaliado a influência da luz branca, azul, verde e vermelha no aumento de tolerância à radiação UV e estresse osmótico em M. robertsii. No quarto experimento, foi avaliada a influência da limitação de oxigênio no aumento de tolerância à radiação UV, KCl, e 4-NQO em dez espécies de fungos entomopatogênicos. No quinto experimento, foi utilizado o isolado M. robertsii (ARSEF 2575), foi analisado a expressão dos genes provavelmente envolvidos na indução da tolerância ao estresse quando conídios são produzidos sob luz visível e limitação de oxigênio. No primeiro experimento, conídios produzidos sob a luz branca apresentaram maior tolerância ao estresse osmótico em comparação com os conídios produzidos no escuro. Não houve grande diferença de tolerância entre as intensitdades de luz testadas. No segundo experimento, a luz branca induziu o aumento de tolerância aos estresses em B. bassiana (KCl e 4NQO), M. brunneum (KCl e 4NQO), M. robertsii (UV e KCl), T. cylindrosporum (KCl), I. fumosorosea (UV), L. aphanocladii (KCl) e A. aleyrodis (KCl e 4NQO). No terceiro experimento, conídios produzidos sob a luz branca e azul, foram mais tolerantes à radiação UV e ao estresse osmótico, conídios crescidos sob a luz vermelha foram menos tolerantes. No quarto experimento, a hipoxia induziu o aumento de tolerância aos estresses em B. bassiana (UV, KCl e 4NQO), M. brunneum (UV, KCl e 4NQO), M. robertsii (UV, KCl), M. anisopliae (UV e KCl), T. inflatum (KCl) e A. aleyrodis (KCl e 4NQO). A anoxia induziu o aumento de tolerância ao estresse em seis isolados, B. bassiana (UV e 4NQO), M. brunneum (KCl), M. anisopliae (KCl e 4NQO), M. robertsii (UV e KCl), T. inflatum (KCl), A. aleyrodis (4NQO). O estresse nutritivo (MM) induziu o aumento de tolerância aos estresses em B. bassiana (UV, KCl e 4NQO), M. brunneum (UV e KCl), M. robertsii (UV e KCl) e M. anisopliae (UV e KCl), T. cylindrosporum (UV), I. fumosorosea (KCl), T. inflatum (UV) e S. lanosoniveum (KCl). No quinto experimento, os genes superexpressos foram: Mrhsp30 (MM, luz branca, luz azul, vermelha, luz verde, anoxia), Mrhsp101 (luz vermelh, a luz verde e hipoxia), Mr6-4 phr (MM, luz branca, luz azul), Mrsod2 (MM, luz vermelha), Mrtps (luz azul, vermelha, verde e hipóxia), Mrpr1 (luz verde). Neste estudo, a luz branca e limitação de oxigênio foram determinantes no aumento de tolerância aos estresses. / The effect of exposure of visible light and oxygen limitation during mycelial growth was investigated in the tolerance of conidia of ten entomopathogenic fungi to: (A) UV radiation; (B) osmotic stress caused by potassium chloride (KCl) and (C) genotoxic stress caused by 4-nitroquinoline 1-oxide (4NQO). In the first experiment, the photoactivation threshold of Metarhizium robertsii was evaluated. Four light intensities with 1, 3, 4 and 5 lumens were studied, where germination and increased tolerance to osmotic stress were evaluated. In the second experiment, the influence of white light without increasing the tolerance to UV, KCl, and 4-NQO in ten species of entomopathogenic fungi was analyzed. In the third experiment, the influence of white, blue, green and red light on the increase of tolerance to UV radiation and osmotic stress in M. robertsii was evaluated. In the fourth experiment, the influence of oxygen limitation on the increase of tolerance to UV, KCl, and 4-NQO in tem entomopathogenic fungi species were evaluated. In the fifth experiment, the M. robertsii isolate (ARSEF 2575) was used; an expression of the genes involved in the induction of stress tolerance was analyzed when conidia are produced under visible light and oxygen limitation. In the first experiment, conidia produced under white light presented greater tolerance to osmotic aesthetics in comparative eaters. There were no major differences in tolerance between tested light intensities. In the second experiment, white light induced increased stress tolerance in B. bassiana (KCl e 4NQO), M. brunneum (KCl e 4NQO), M. robertsii (UV e KCl), T. cylindrosporum (KCl), I. fumosorosea (UV), L. aphanocladii (KCl) e A. aleyrodis (KCl e 4NQO). In the third experiment, conidia produced under white and blue light were more tolerant to UV radiation and osmotic stress, conidia grown under the red light so tolerant. In the fourth experiment, hypoxia induced increased stress tolerance in B. bassiana (for UV, KCl e 4NQO), M. brunneum (UV, KCl e 4NQO), M. robertsii (UV, KCl), M. anisopliae (UV e KCl), T. inflatum (KCl) e A. aleyrodis (KCl e 4NQO). Anoxia induced higher tolerance in B. bassiana (for UV e 4NQO), M. brunneum (KCl), M. anisopliae (KCl e 4NQO), M. robertsii (UV e KCl), T. inflatum (KCl), A. aleyrodis (4NQO). The nutritive stress (MM) induced increased stress tolerance in B. bassiana (UV, KCl e 4NQO), M. brunneum (UV e KCl), M. robertsii (UV e KCl) e M. anisopliae (UV e KCl), T. cylindrosporum (UV), I. fumosorosea (KCl), T. inflatum (UV) e S. lanosoniveum (KCl). In the fifth experiment, the over-expressed genes were Mrhsp30 (MM, white light, blue light, red, green light, anoxia), Mrhsp101 (red light, green light and hypoxia), Mr6-4 phr (MM, white light, blue light), Mrsod2 (MM, red light), Mrtps (blue, red, green and hypoxia light), Mrpr1 (green light). In this study, white light and oxygen limitation were determinants of increased stress tolerance.

O efeito da exposição à luz visível e a limitação de oxigênio durante o crescimento micelial foi investigado na tolerância de conídios de dez fungos entomopatogênicos a: (A) radiação UV; (B) estresse osmótico causado pelo cloreto de potássio (KCl) e (C) estresse genotóxico provocado por 4-nitroquinoline-1-óxido (4-NQO). No primeiro experimento, foi avaliado o limiar de fotoativação de Metarhizium robertsii. Foram estudadas quatro intensidades de luz com 1, 3, 4 e 5 lumens, nas quais, foi avaliada a germinação e o aumento de tolerância ao estresse osmótico. No segundo experimento, foi analisada a influência da luz branca no aumento da tolerância à radiação UV, KCl, e 4-NQO em dez espécies de fungos entomopatogênicos. No terceiro experimento, foi avaliado a influência da luz branca, azul, verde e vermelha no aumento de tolerância à radiação UV e estresse osmótico em M. robertsii. No quarto experimento, foi avaliada a influência da limitação de oxigênio no aumento de tolerância à radiação UV, KCl, e 4-NQO em dez espécies de fungos entomopatogênicos. No quinto experimento, foi utilizado o isolado M. robertsii (ARSEF 2575), foi analisado a expressão dos genes provavelmente envolvidos na indução da tolerância ao estresse quando conídios são produzidos sob luz visível e limitação de oxigênio. No primeiro experimento, conídios produzidos sob a luz branca apresentaram maior tolerância ao estresse osmótico em comparação com os conídios produzidos no escuro. Não houve grande diferença de tolerância entre as intensitdades de luz testadas. No segundo experimento, a luz branca induziu o aumento de tolerância aos estresses em B. bassiana (KCl e 4NQO), M. brunneum (KCl e 4NQO), M. robertsii (UV e KCl), T. cylindrosporum (KCl), I. fumosorosea (UV), L. aphanocladii (KCl) e A. aleyrodis (KCl e 4NQO). No terceiro experimento, conídios produzidos sob a luz branca e azul, foram mais tolerantes à radiação UV e ao estresse osmótico, conídios crescidos sob a luz vermelha foram menos tolerantes. No quarto experimento, a hipoxia induziu o aumento de tolerância aos estresses em B. bassiana (UV, KCl e 4NQO), M. brunneum (UV, KCl e 4NQO), M. robertsii (UV, KCl), M. anisopliae (UV e KCl), T. inflatum (KCl) e A. aleyrodis (KCl e 4NQO). A anoxia induziu o aumento de tolerância ao estresse em seis isolados, B. bassiana (UV e 4NQO), M. brunneum (KCl), M. anisopliae (KCl e 4NQO), M. robertsii (UV e KCl), T. inflatum (KCl), A. aleyrodis (4NQO). O estresse nutritivo (MM) induziu o aumento de tolerância aos estresses em B. bassiana (UV, KCl e 4NQO), M. brunneum (UV e KCl), M. robertsii (UV e KCl) e M. anisopliae (UV e KCl), T. cylindrosporum (UV), I. fumosorosea (KCl), T. inflatum (UV) e S. lanosoniveum (KCl). No quinto experimento, os genes superexpressos foram: Mrhsp30 (MM, luz branca, luz azul, vermelha, luz verde, anoxia), Mrhsp101 (luz vermelh, a luz verde e hipoxia), Mr6-4 phr (MM, luz branca, luz azul), Mrsod2 (MM, luz vermelha), Mrtps (luz azul, vermelha, verde e hipóxia), Mrpr1 (luz verde). Neste estudo, a luz branca e limitação de oxigênio foram determinantes no aumento de tolerância aos estresses. / The effect of exposure of visible light and oxygen limitation during mycelial growth was investigated in the tolerance of conidia of ten entomopathogenic fungi to: (A) UV radiation; (B) osmotic stress caused by potassium chloride (KCl) and (C) genotoxic stress caused by 4-nitroquinoline 1-oxide (4NQO). In the first experiment, the photoactivation threshold of Metarhizium robertsii was evaluated. Four light intensities with 1, 3, 4 and 5 lumens were studied, where germination and increased tolerance to osmotic stress were evaluated. In the second experiment, the influence of white light without increasing the tolerance to UV, KCl, and 4-NQO in ten species of entomopathogenic fungi was analyzed. In the third experiment, the influence of white, blue, green and red light on the increase of tolerance to UV radiation and osmotic stress in M. robertsii was evaluated. In the fourth experiment, the influence of oxygen limitation on the increase of tolerance to UV, KCl, and 4-NQO in tem entomopathogenic fungi species were evaluated. In the fifth experiment, the M. robertsii isolate (ARSEF 2575) was used; an expression of the genes involved in the induction of stress tolerance was analyzed when conidia are produced under visible light and oxygen limitation. In the first experiment, conidia produced under white light presented greater tolerance to osmotic aesthetics in comparative eaters. There were no major differences in tolerance between tested light intensities. In the second experiment, white light induced increased stress tolerance in B. bassiana (KCl e 4NQO), M. brunneum (KCl e 4NQO), M. robertsii (UV e KCl), T. cylindrosporum (KCl), I. fumosorosea (UV), L. aphanocladii (KCl) e A. aleyrodis (KCl e 4NQO). In the third experiment, conidia produced under white and blue light were more tolerant to UV radiation and osmotic stress, conidia grown under the red light so tolerant. In the fourth experiment, hypoxia induced increased stress tolerance in B. bassiana (for UV, KCl e 4NQO), M. brunneum (UV, KCl e 4NQO), M. robertsii (UV, KCl), M. anisopliae (UV e KCl), T. inflatum (KCl) e A. aleyrodis (KCl e 4NQO). Anoxia induced higher tolerance in B. bassiana (for UV e 4NQO), M. brunneum (KCl), M. anisopliae (KCl e 4NQO), M. robertsii (UV e KCl), T. inflatum (KCl), A. aleyrodis (4NQO). The nutritive stress (MM) induced increased stress tolerance in B. bassiana (UV, KCl e 4NQO), M. brunneum (UV e KCl), M. robertsii (UV e KCl) e M. anisopliae (UV e KCl), T. cylindrosporum (UV), I. fumosorosea (KCl), T. inflatum (UV) e S. lanosoniveum (KCl). In the fifth experiment, the over-expressed genes were Mrhsp30 (MM, white light, blue light, red, green light, anoxia), Mrhsp101 (red light, green light and hypoxia), Mr6-4 phr (MM, white light, blue light), Mrsod2 (MM, red light), Mrtps (blue, red, green and hypoxia light), Mrpr1 (green light). In this study, white light and oxygen limitation were determinants of increased stress tolerance.