O projeto teve por finalidade isolar e identificar fungos, avaliar o potencial toxigênico dos isolados de Aspergillus spp. e Fusarium spp., detectar e quantificar aflatoxinas B1, B2, G1, G2 e fumonisinas B1 e B2 em amostras de misturas de cereais. Foram analisadas 15 marcas de misturas de cereais, prontas para o consumo, adquiridas de supermercados e de empresas que comercializam o produto nacionalmente via internet. Foram adquiridas amostras por sete meses, totalizando 105 amostras ao final do experimento. A contagem de bolores nas amostras variou de 1,0 x 101 a 2 x 105 unidades formadoras de colônias (UFC)/g, com isolamento de sete cepas de Aspergillus flavus. As aflatoxinas B1 e G1 foram detectadas em poucas amostras e em baixos níveis, sendo que estes resultados podem ser devidos à baixa atividade de água nos produtos avaliados, a qual foi inferior a 0,63. A fumonisina B1 foi detectada em 84,8% das amostras, no entanto, a ingestão diária provável calculada para as fumonisinas esteve abaixo da recomendação do JECFA. Apenas uma amostra apresentou níveis de fumonisinas acima do limite esperado para 2016. Adicionalmente, foi observado que 21% das amostras apresentaram mais de um tipo de micotoxina, o que poderia conduzir à potencialização de efeitos tóxicos. / The project aimed to isolate and identify fungi, evaluate the toxigenic potential of isolates of Aspergillus spp. and Fusarium spp. detect and quantify aflatoxins B1, B2, G1, G2 and fumonisins B1 and B2 in samples of cereal mixtures. We analyzed 15 brands of cereal mixtures ready to eat adding up to 105 samples at the end of the experiment. Samples were acquired in supermarkets and from companies that market the product nationally by internet. The mold count in the samples ranged from 1.0 x 101 to 2 × 105 colonies forming units (CFU)/ g, with isolation of seven strains of Aspergillus flavus. Aflatoxin B1 and G1 were detected in a few samples and at low levels, what might be due to the low water activity in the product reviews, which was less than 0.63. Fumonisin B1 was detected in 84.8% of the samples, however, the probable daily intake calculated for fumonisin was bellow the JECFA recommendation. Only one sample showed fumonisin levels above the expected limit for 2016. Additionally, it was observed that 21% of the samples presented more than one type of mycotoxin, which could lead to enhancement of toxic effects.

Fusarium root rot is one of the most important diseases of pulse crops, with numerous Fusarium spp. comprising the disease complex. Fusarium solani and F. avenaceum have been reported to be major pathogens in the pea root rot complex, and all commonly grown varieties are susceptible. Greenhouse methods to evaluate peas for resistance to Fusarium root rot resulted in inconsistent disease severity across varieties. In 2015, F. avenaceum infested field plots were more heavily damaged based on emergence and yield than F. solani infested plots, and opposite trends were observed in 2016. Differences in root rot severity between years could be due to F. solani infestation causing more damage under warmer temperatures, while plots infested with F. avenaceum caused more damage under cooler temperatures. These results highlight the difficulties observed when screening for soil-borne pathogens, and the increased difficulties when a pathogen complex and changing environmental conditions are involved.

Submitted diploma thesis deals with laboratory diagnostics of filamentous micromycetes (moulds) genus Fusarium in the laboratories of medical mycology. In the first part of the diploma thesis is dedicated space for general familiarization with filamentous microscopic fungi. Next separate chapter describes the genus Fusarium, especially in relation to human medicine. The final part of the diploma thesis summarizes current possibilities of laboratory diagnostics of filamentous micromycetes, focusing on the genus Fusarium. Invasive infections caused by filamentous fungi are increasingly common complication, especially in immunocompromised patients. In most cases they affect the patients with hematologic malignity and patients after hematopoietic stem cell transplantation or solid organ transplantation. The most common etiological agent of such infections is unambiguously the Aspergillus genus. However, in recent years, increasingly cases of infections due to less common filamentous fungi, including Fusarium spp. are described. Invasion fungal infections are associated with very high mortality. The basic requirement thus becomes the speed and accuracy of diagnosis. The most important methods for the laboratory diagnostics of invasive infections caused by filamentous fungi are conventional methods -...

Spontaneous mutagenesis can be divided into three main steps: the introduction of DNA damage and lesions, damage recognition and DNA repair. All sources of spontaneous mutagenesis originate from within the cell itself, e.g., polymerase errors cause DNA mismatches and reactive oxygen species alter the chemical composition of DNA bases. The combined effects of all these processes influence spontaneous genomic mutation rates, which are thought to be a characteristic of individual species and/or groups of species. Although much is known about different mutagens and how they cause mutations the sequence context of these mutations are less well understood. The results of this MSc study on mutation in the filamentous fungus Fusarium circinatum showed that the 5ʹ and 3ʹ neighbouring bases of a single nucleotide polymorphism can significantly influence the type of substitution that occurred leading to the formation of mutational motifs. This was the case for both sets of genes examined (core housekeeping and non-ribosomal protein synthetase genes), whose evolution is known to differ. The fact that none of the identified motifs are shared between the two sets of genes could indicate that the cellular mutagens and/or repair machinery function differently for the two gene groups. Furthermore, none of the mutable motifs that have been identified for the well-known mutagens in model organisms could be detected in the fungus, which suggests that mutagens and/or DNA repair mechanisms of this fungus are unique. Although limited information is available for non-model eukaryotes, an estimate for the rate at which mutations arise across the genome of F. circinatum could be a good starting point for comparisons of its evolutionary rate to those of its close relatives. This was accomplished using a fluctuation analysis involving nitrate non-utilizing mutation reversion. Although mutation rate determined in this study is probably not precisely accurate, it represents a good starting point for future comparative studies on the evolutionary rate of Fusarium species. As a whole this study laid the foundation for a better understanding of spontaneous mutagenesis at specific sites in certain groups of genes as well as across the genome of the economically important plant pathogen F. circinatum. Restricted until August 2017 / Dissertation (MSc)--University of Pretoria, 2013. / gm2013 / Microbiology and Plant Pathology / Unrestricted

No description available.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

No description available.

Master of Science / Department of Agronomy / Ramasamy Perumal / Tesfaye Tesso / Grain mold (GM) is an important biotic constraint limiting yield and market value of sorghum grains. It results in kernel discoloration and deterioration. Such kernels have reduced seed viability, low food and feed quality. Breeding for grain mold resistance is challenging because of the complex nature of host-pathogen-environment interactions. This complex task could be made simpler by utilizing molecular markers. Utilization of marker resources may help to find genomic regions associated with grain mold resistance. In this study, three sets of field and laboratory based experiments were performed which will help in finding potential grain mold pathogens responsible for kernel deterioration in the studied environment and search for genotypes with better kernel quality and grain mold resistance. In the first part of the study, in vitro screening of 44 grain mold resistant sorghum genotypes developed and released by Texas A & M AgriLife Research. This study was aimed at identifying sources resistance to grain mold infection through laboratory screening. The result revealed that genotypes Tx3371, Tx3373, Tx3374, Tx3376, Tx3407, Tx3400, and Tx3402 were have high level of resistance and were identified as potential sources of grain mold resistance as each showed minimal fungal infection and higher grain quality traits. The second experiment was performed to optimize surface sterilization protocol for the extraction of fungal pathogens from the kernel surface (pericarp) and to study the effect of bleach percentage and time period on pathogen extraction. Seven treatments using sterilized double distilled water (0 % bleach (v/v)) and different bleach (NaOCl) concentrations (2.5, 5, 7.5, 10, 12.5 and 15 %) were used with a time interval of 2.5, 5, 7.5 and 10 min. Optimized surface sterilization in the range of 7.5 to 15 % bleach (v/v) for 7.5 to 10 min resulted least contamination and fungal genera isolation from the surface of the kernel. The third study was aimed at characterizing genotypes (sorghum association panel) for grain mold pathogen F. thapsinum and by using genome wide association (GWA) tool in order to find genomic regions associated with grain mold resistance. We studied the effect of different agronomic and panicle architecture traits on grain mold incidence and severity. Effects of grain mold on kernel quality traits were also studied. We reported two loci associated with grain mold resistance. Based on first year field screening results, 46 genotypes having grain mold ratings 1-5 (1 = < 1% panicle kernel molded; 5 = > 50% panicle kernel molded) were selected for a detailed study aimed at understanding grain mold x fungal pathogen interactions to physical and chemical kernel traits. Seed germination test, vigor index, and tetrazolium viability test were performed to study effect of grain mold infection on kernel viability and vigor. Alternaria, Fusarium thapsinum, F. verticillioides and F. proliferatum were the main fungal genera isolated from bisected kernels. Based on two year screening, SC623, SC67, SC621, SC947 and SC1494 were most resistant based on both PGMR and TGMR rating while SC370, SC833, SC1484, and SC1077 showed the most susceptible reaction and this was consistent for individual location analysis. SC309, SC213, SC833, SC971 and SC1047 are genotypes having identified loci for grain mold resistance.

Fusarium Ear Blight is a devastating fungal disease of cereals and due to the contamination of the harvested grain with a range of trichothecene mycotoxins presents a risk to human and animal health. The re-emergence of Fusarium graminearum on wheat and maize, the evolution of more aggressive fungal strains and the lack of an effective control strategy, has increased the need for a greater understanding of the disease aetiology. This project aimed to enhance the understanding of the interaction between F. graminearum and wheat (Triticum aestivum), through the utilisation of microscopy and molecular pathogenomics. A detailed investigation of the infection process revealed a prolonged latent period of intercellular infection that preceded host cell death, intracellular colonisation and the onset of disease symptoms. Phenotypic differences in colonisation and mycotoxin gene expression implied that hyphae within the two phases of infection were transcriptionally distinct, while a bioinformatic analysis described the fungal secretome. The two fungal gene-deficient strains assessed, top1 and tri5, were unable to establish symptomless infection or spread throughout the wheat ear, in the presence or absence of mycotoxin production, suggesting the existence of additional virulence factors. Subsequently, a genome wide transcriptome investigation of the two phases of infection, using both Affymetrix and RNA-sequencing technologies, revealed the unique expression profile, and secretome, of the advancing hyphal front of the symptomless infections. This greater understanding of the biphasic interaction will provide a benchmark for comparison with the single gene deficient strains. Finally, a laser capture microdissection procedure was developed to enable future cell-type specific transcriptome experiments. Collectively, I have discovered and developed a model of how F. graminearum establishes symptomless and symptomatic infection. In doing so, this study has enhanced the understanding of this non-biotrophic pathosystem, providing many new lines of investigation, which could greatly improve crop protection strategies.

<p>During the last ten years the cultivation of maize in Sweden has increased and is expected to grow further. Most of the maize in Sweden becomes silage which is used to feed animals at farms. Maize has in other countries been shown to be a substrate for growth of mould and especially <em>Aspergillus </em>spp., <em>Fusarium </em>spp. and <em>Pencillium </em>spp. has been reported. Members of all three of these species can, during favorable conditions, produce mycotoxins which can cause a number of different health problems in both animals and man. The aim of this study was to investigate the occurrence of mould and mycotoxins to increase our knowledge of the hygienic quality of Swedish maize silage. Microbiological analyses were made to study the growth of fungi. To analyze for fumonisin B₁, B₂and zearalenone, HPLC with fluorescence detection was made. The mycotoxins mycophenolic acid, roquefortine C, gliotoxin, penicillic acid, penitrem A, fumitremorgen C and verrucologen were analyzed with LC-MS/MS. The results showed that 47 % of the samples were contaminated with <em>Penicillium </em>spp. and 6 % had growth of <em>Aspergillus fumigatus</em>. A small amount of zearalenone was found in one sample and 0.01ppm of roquefortine C was detected in one sample. The data obtained indicate that Swedish maize silage has a moderate growth of fungi with a very low production of mycotoxins. More studies have to be performed to make more decisive conclusions.</p>