<p>Neural tube defects (NTDs) are a common class of human birth defects with a complex, multifactorial etiology. Although many contributing factors have been identified, an estimated 60% of human population risk remains unexplained. A portion of that risk is likely attributable to gene-gene and gene-environment interactions which have yet to be fully elucidated. In one project, we used whole-exome sequencing to identify candidate genetic factors in a multiplex anencephaly family, revealing an aggregation of rare and common variants in planar cell polarity genes among the affecteds. In the second project, we profiled the methylomes of a pair of monozygotic twins discordant for anencephaly and identified several differentially methylated sites which could contribute to NTD risk, particularly the <italic>mir-886</italic> locus. Finally, we performed whole-exome and whole-methylome sequencing of mouse strains with differential susceptibility to fumonisin-induced NTDs, in combination with a human SNP association study. We identified epigenetic changes and variant associations which implicate Wnt and Hippo signaling genes as modifiers of the metabolic impacts of fumonisin exposure. These findings underscore the complexity of NTD pathogenesis and highlight the need to elucidate gene-gene and gene-environment interactions contributing to NTD etiology.</p> / Dissertation

Plant-wide communication between tissues and cells is organized, in part, by a suite of compounds called hormones. I have chosen to focus on the effects of one plant hormone, ethylene; how its synthesis is controlled and how its perception is mediated to differentially control cell development and response to pathogens. In the production of ethylene, one level of control is by modulating the levels of the immediate precursor to ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC). I characterize here a plant encoded gene homologous to bacterial ACC Deaminases, AtACD1, and show through up- and down-regulation of the gene that it can modulate the plants sensitivity to exogenous ACC. Once ethylene is produced, it is sensed in Arabidopsis thaliana by a family of 5 receptors. I show that ETR2 in Arabidopsis is responsible for modulation of the microtubule cytoskeleton assembly as loss-of –function mutations to this gene cause randomized microtubule assembly in trichomes and increase sensitivity to microtubule depolymerising drugs in root hairs. In studies of plant:pathogen interactions, ethylene is a central signaling agent required for plant resistance. While it has been shown that etr1 mutants show increased susceptibility to fungal pathogens, exogenous ethylene has also been shown to speed the progress of pathogenesis. Using Fumonisin B1 (FB1) to induce cell death I show that etr1-1 has accelerated cell death while ein4-1 has a reduced rate of necrosis. Further to this, mutations to the other three ethylene receptors do not have any effect on the rate of cell death. My interest in cell development led to the characterization of an activation tagged Populus tremula x P. alba line with increased trichome initiation. The gene responsible for these phenotypes was identified as PtMYB186, which also affected growth rate, transpiration rate, photosynthetic capacity, and resistance to the Tussock moth larvae. Together these studies provide a new framework for our understanding of how the ethylene signal is modulated in plants and the controls behind cellular development. This knowledge will help reconcile studies which show that ethylene has different effects on plant development and provide new avenues of research into trichome development. / Thesis (Ph.D, Biology) -- Queen's University, 2009-01-13 10:08:03.605

In this work we investigated the in vivo and in vitro ecological conditions that can favour the fumonisin production, both free and hidden forms, in the maize-Fusarium verticillioides pathosystem. Samples of different maize hybrids have been collected from dough to the harvest maturity to follow the trend of fungal incidence and both fumonisin forms contamination, but also the changes in chemical composition. Differences in the level of contamination have been found among hybrids during the growing season. Furthermore, the production of fumonisins has been found correlated to the total lipids content, another parameter that changed during the growing season. This finding underlined the existence of a relationship between toxin contamination and fatty acids composition of the hybrids. Recently the existence of a cross talk between plant and pathogen has been demonstrated, based on some oxidized signal molecules (oxylipins) produced from fatty acid precursors. This result was also confirmed by the molecular analysis on the in vitro pathosystem that showed differences in the activation of the genes involved in plant and fungal oxylipins production during the incubation time. Also post-harvest contamination of maize was investigated in this study, with particular attention to the effects of the drying treatment, a common post-harvest practice aimed at decreasing the water availability, and to the storage capacity of a new low cost storage system, silo bag. The drying treatment was showed to affect fumonisins content, in particular an increased fumonisins contamination was detected after heat treatments. This increment seemed to be produced by chemical changes of matrix components, caused by high temperature, that produced the release of hidden fumonisin in free form. Silo bags were shown to be an effective system to store cereals because no significant change occurred in fungi or toxins contamination during a 9-month storage. Therefore, being more flexible and less expensive than traditional store houses, they should be very useful for farmers.

Ubiquitous in agro-environments, Fusarium species infect and damage economically important crops and contaminate food commodities with harmful secondary metabolites called mycotoxins. In addition, human infection by pathogenic Fusarium strains has now emerged as a major problem particularly among individuals with suppressed immunity. Trichothecenes, deoxynivalenol, nivalenol, rnoniliforme and fumonisins are potent toxins produced by Fusorium species including F. poae, F. nygami, F. oxysporum, F. proilferatum and F. verticillioides. The last three, together with F. solani and F. chlamydosporum are presently recognised as major role players in the occurrence of fusarioses in individuals with compromised immunity. In subsistence situations in rural areas of South Africa, a variety of traditional leafy vegetables, collectively known as morogo, supplement maize-based staple diets with minerals and vitamins. The utilisations of these traditional vegetables are generally based on indigenous knowledge pertaining to production and processing. Morogo plants are not natural hosts to mycotoxigenic and mycotic Fusarium species that are mainly associated with pathogeneses of grain crops such as maize. However, morogo growing in close proximity of maize in typical subsistence agricultural situations might be at risk of Fusarium contamination from maize. The study was conducted in the Dikgale Demographic Surveillance Site (DDSS), a rural area in the Limpopo Province characterised by the production of maize and different types of traditional morogo for household subsistence. HIVIAIDS is prevalent in the Limpopo Province. Chronic dietary exposure to Fusarium toxins and disseminated fusarioses might enhance disease outcomes associated with AIDS in affected individuals, thus adding to the burden of disease in DDSS communities. The aim of the study was to investigate the occurrence of mycotic and mycotoxigenic Fusarium species in traditional morogo and ago-environments in DDSS. Questionnaires were employed to obtain relevant information and indigenous knowledge from communities of Sefateng. Madiga, Mantheding and Moduane related to the utilisation of raditional morogo. At each village thepe (amaranth) and lerotho (African cabbage) were sampled on two occasions, namely before maize planting (M-) and when maize was fully grown (M+). Maize, soil and air were sampled at the same time. Botanical species identification was carried out on specimens of lerotho and thepe from each village. Lerotho. thepe, maize, soil and air samples were subjected to mycological analysis to determine the average fungal levels and Fusarium species that occurred. Samples of fresh and traditionally sun-dried samples of thepe and lerotho were analysed by HPLC for fumonisins. Average fungal plate counts of morogo from all four villages were notably higher in lerotho compared to thepe. Lerotho sampled from M- fields of Madiga, Mantheding and Moduane exhibited higher average fungal levels than those from the M+ fields. However, in lerotho sampled from the M+ field of Sefateng average fungal levels were significantly higher than that of the M- field. Fungal levels in maize growing close to morogo were lowest in Sefateng and highest in Moduane. The highest fungal counts in soil were reported for Sefateng's M- field and the lowest for Sefateng M+ field. Fungal levels were high in air samples of M+ fields of all four villages and the lowest in M- field of Sefateng. The majority Fusarium isolates retrieved from morogo and environmental samples belonged to known mycotoxigenic and/or mycotic species, though predominant species and levels thereof varied in samples from M- and M+ fields of the four villages. Fusarium levels in thepe from both M- and M+ fields were shown to be lower as in lerotho. In samples of the Sefateng M- field, F. poae occurred predominantly in lerotho, thepe, soil as well as air, while F. subglutinans was the predominant species in lerotho and air samples of Mantheding. In Sefateng samples from M+ field, F. chlamydosporum predominated among isolates retrieved from lerotho, F. prolifiratum and F. gramenearum among those from maize and F. solani among those from soil and air. F. proliferatum dominated among isolates from lerotho, maize, soil and air of M+ sites of Madiga and F. chlamydosporum in soil and air samples of Mantheding. HPLC analysis detected fumonisin B1 in traditionally sun-dried as well as fresh samples of lerorho as well as thepe. The occurrence of mycotoxigenic and rnycotic Fusarium species in traditional morogo and agro-environments might be an aggravating health risk factor for DDSS communities. / Thesis (M. Environmental Science (Water Science))--North-West University, Potchefstroom Campus, 2007.

Ubiquitous in agro-environments, Fusarium species infect and damage economically important crops and contaminate food commodities with harmful secondary metabolites called mycotoxins. In addition, human infection by pathogenic Fusarium strains has now emerged as a major problem particularly among individuals with suppressed immunity. Trichothecenes, deoxynivalenol, nivalenol, rnoniliforme and fumonisins are potent toxins produced by Fusorium species including F. poae, F. nygami, F. oxysporum, F. proilferatum and F. verticillioides. The last three, together with F. solani and F. chlamydosporum are presently recognised as major role players in the occurrence of fusarioses in individuals with compromised immunity. In subsistence situations in rural areas of South Africa, a variety of traditional leafy vegetables, collectively known as morogo, supplement maize-based staple diets with minerals and vitamins. The utilisations of these traditional vegetables are generally based on indigenous knowledge pertaining to production and processing. Morogo plants are not natural hosts to mycotoxigenic and mycotic Fusarium species that are mainly associated with pathogeneses of grain crops such as maize. However, morogo growing in close proximity of maize in typical subsistence agricultural situations might be at risk of Fusarium contamination from maize. The study was conducted in the Dikgale Demographic Surveillance Site (DDSS), a rural area in the Limpopo Province characterised by the production of maize and different types of traditional morogo for household subsistence. HIVIAIDS is prevalent in the Limpopo Province. Chronic dietary exposure to Fusarium toxins and disseminated fusarioses might enhance disease outcomes associated with AIDS in affected individuals, thus adding to the burden of disease in DDSS communities. The aim of the study was to investigate the occurrence of mycotic and mycotoxigenic Fusarium species in traditional morogo and ago-environments in DDSS. Questionnaires were employed to obtain relevant information and indigenous knowledge from communities of Sefateng. Madiga, Mantheding and Moduane related to the utilisation of raditional morogo. At each village thepe (amaranth) and lerotho (African cabbage) were sampled on two occasions, namely before maize planting (M-) and when maize was fully grown (M+). Maize, soil and air were sampled at the same time. Botanical species identification was carried out on specimens of lerotho and thepe from each village. Lerotho. thepe, maize, soil and air samples were subjected to mycological analysis to determine the average fungal levels and Fusarium species that occurred. Samples of fresh and traditionally sun-dried samples of thepe and lerotho were analysed by HPLC for fumonisins. Average fungal plate counts of morogo from all four villages were notably higher in lerotho compared to thepe. Lerotho sampled from M- fields of Madiga, Mantheding and Moduane exhibited higher average fungal levels than those from the M+ fields. However, in lerotho sampled from the M+ field of Sefateng average fungal levels were significantly higher than that of the M- field. Fungal levels in maize growing close to morogo were lowest in Sefateng and highest in Moduane. The highest fungal counts in soil were reported for Sefateng's M- field and the lowest for Sefateng M+ field. Fungal levels were high in air samples of M+ fields of all four villages and the lowest in M- field of Sefateng. The majority Fusarium isolates retrieved from morogo and environmental samples belonged to known mycotoxigenic and/or mycotic species, though predominant species and levels thereof varied in samples from M- and M+ fields of the four villages. Fusarium levels in thepe from both M- and M+ fields were shown to be lower as in lerotho. In samples of the Sefateng M- field, F. poae occurred predominantly in lerotho, thepe, soil as well as air, while F. subglutinans was the predominant species in lerotho and air samples of Mantheding. In Sefateng samples from M+ field, F. chlamydosporum predominated among isolates retrieved from lerotho, F. prolifiratum and F. gramenearum among those from maize and F. solani among those from soil and air. F. proliferatum dominated among isolates from lerotho, maize, soil and air of M+ sites of Madiga and F. chlamydosporum in soil and air samples of Mantheding. HPLC analysis detected fumonisin B1 in traditionally sun-dried as well as fresh samples of lerorho as well as thepe. The occurrence of mycotoxigenic and rnycotic Fusarium species in traditional morogo and agro-environments might be an aggravating health risk factor for DDSS communities. / Thesis (M. Environmental Science (Water Science))--North-West University, Potchefstroom Campus, 2007.

Made available in DSpace on 2014-06-11T19:28:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-06-14Bitstream added on 2014-06-13T20:37:15Z : No. of bitstreams: 1 siloto_ev_me_botfmvz.pdf: 809179 bytes, checksum: 7511ba3985111f498b7461c523562d75 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / Os efeitos da aflatoxina e fumonisina e sua associação, sobre a produção e a qualidade dos ovos em poedeiras comerciais, foram avaliados bem como a eficácia de um adsorvente glucano em promover a redução e/ou eliminação total destes efeitos. Foram utilizadas 168 poedeiras com 37 semanas de idade, por um período experimental de 56 dias. O delineamento experimental foi inteiramente casualizado em esquema fatorial 3x2 + 1 (3 tratamentos com micotoxinas: aflatoxina (AF), fumonisina (FU) e aflatoxina + fumonisina (AF + FU); 2 tratamentos com e sem adsorvente; e grupo controle sem micotoxinas e adsorvente), totalizando 7 tratamentos e 6 repetições com 4 aves/gaiola. As rações foram contaminadas, isoladamente ou em combinação, com 1ppm de AF e 25ppm de FU e o adsorvente foi incluído na concentração de 2kg/ton ração. Os tratamentos com presença de AF apresentaram as menores porcentagens (p = 0,0594) de postura (76,72% para AF e 77,38% para AF+FU). A massa de ovos obteve a menor média (p<0,05) no tratamento com AF+FU (49,49 g) que foi diferente do grupo controle (64,06 g). O tratamento com AF apresentou maior espessura e resistência de casca comparado ao grupo controle e ao tratamento com FU. O uso do adsorvente no tratamento com AF reduziu a resistência da casca voltando aos valores próximos aos do controle. As alterações observadas neste estudo são indicativas da toxicidade da aflatoxina na concentração de 1 ppm. Os efeitos da fumonisina foram menos evidentes em função da baixa dose utilizada neste estudo (25mg/kg). O uso de glucano na concentração de 2 kg/ton foi efetivo em reverter alguns dos efeitos tóxicos da aflatoxina e, em menor extensão da fumonisina, quando estas micotoxinas estavam separadamente na ração de poedeiras comerciais / The present study was conducted to evaluate the effects of aflatoxin and fumonisin and their association on production and egg quality in laying hens and was also evaluated the effectiveness of an adsorbent glucan to promote the reduction and/or total elimination of these effects. One hundred and sixty-eight 37-wk-old laying hens were used for a trial period of 56 days. The experimental design was a completely randomized with 3x2+ 1 factorial arrangement (three treatments with mycotoxins: aflatoxin (AF), fumonisin (FU) + fumonisin and aflatoxin (AF + FU), two treatments with and without adsorbent, and the control group without mycotoxin and adsorbent), totaling seven treatments, six replicates and four birds per cage. The mycotoxins were added to rations, singly and in combination, at levels of 1 ppm AF and 25 ppm FU and the adsorbent was included in the dosage of 2kg/ton .The treatments with the presence of AF had the lowest percentages (p = 0,0594) of stance (76,72% to AF and 77,38% to AF + FU). The egg mass received the lowest average (p<0,05) in the treatment with AF + FU (49,49 g) which was different from the control group (64,06 g). Treatment with AF showed higher values of thickness and peel strength compared to the control group and treatment with FU. The use of the adsorbent in the treatment with AF reduced the strength of the shell back to values near baseline. The changes observed in this study are indicative of the toxicity of aflatoxin at a concentration of 1mg/kg. The effects of fumonisin were less evident because of the low levels used in this study (25mg/kg). The level of glucan added to the diets was effective to prevent some of the toxic effects of aflatoxins and to a lesser extent of fumonisin, when the mycotoxins were separately in the diet of laying hens

O projeto avaliou os efeitos da aflatoxina B1 (AFB1) e fumonisina B1 (FB1), isoladas e associadas, sobre a produtividade e a qualidade dos ovos de codornas poedeiras (Coturnix coturnix japonica). Duzentas e oitenta e oito aves, adquiridas com idade de 8 semanas, foram subdivididas em 6 grupos experimentais (48 aves por grupo) e submetidas a 6 tipos de tratamentos, constituídos por rações contendo AFB1 e FB1 nas concentrações: (0 AFB1+0 FB1), (0 AFB1+10 mg/kg FB1), (50 &microg/kg AFB1+0 FB1), (50 µg/kg AFB1+10 mg/kg FB1), (200 µg/kg AFB1+0 FB1), e (200 µg/kg AFB1+10 mg/kg FB1). As aves foram alimentadas durante 140 dias (5 ciclos de 28 dias). Os parâmetros de produtividade foram avaliados semanalmente, através do consumo de ração, peso dos ovos, índice de conversão alimentar e curva de produção. A qualidade dos ovos foi avaliada a cada ciclo de 28 dias, cada ovo produzido nesse dia foi analisado individualmente para a determinação do valor de unidade Haugh, gravidade específica e percentual do peso da casca. Ao final do 5º período experimental, o peso médio dos ovos foi significativamente menor (p < 0,05) nas aves alimentadas com 10 mg FB1/kg, 50 &microg/kg AFB1, 200 µg/kg AFB1 e com o tratamento de associação de 10 mg FB1/kg + 50 µg/kg AFB1. Em relação à produção de ovos, as codornas alimentadas com 10 mg FB1/kg apresentaram uma diminuição significativa (p < 0,05), ao final do 3º, 4º e 5º ciclos. O consumo médio diário de ração foi significativamente menor (p< 0,05) nas aves alimentadas com 10 mg FB1/kg, ao final do 4º e 5º ciclos, enquanto que os níveis de 50 ou 200 µg/kg AFB1 provocaram uma diminuição significativa (p < 0,05), ao final do 5º período experimental. Ao final do 1º, 2º e 5º ciclos, o consumo médio de ração foi significativamente menor (p< 0,05) nas aves tratadas com 10 mg FB1/kg + 50 µg/kg AFB1. Os índices de conversão alimentar e os valores de Unidades Haugh não foram afetados (p > 0,05) pelos tratamentos. A gravidade específica dos ovos foi significativamente menor (p < 0,05) ao final do 5º ciclo, nas aves tratadas com 10 mg FB1/kg + 200 µg/kg AFB1. Observou-se uma diminuição significativa (p < 0,05) na porcentagem do peso de casca, nas aves tratadas com 10 mg FB1/kg ao final do 1º ciclo, entretanto, houve um aumento significativo (p < 0,05) nos tratamentos com 200 µg/kg AFB1 e também com 10 mg/kg FB1 + 50 µg/kg AFB1 ao final do 1º ciclo. Já ao final do 5º ciclo, o aumento na porcentagem de peso de casca (p < 0,05) ocorreu somente nas aves tratadas com 10 mg/kg FB1 + 200 µg/kg AFB1. Os resultados demonstraram que a administração prolongada de FB1 e AFB1, isoladas ou associadas nos níveis utilizados no presente experimento, pode causar prejuízos econômicos aos produtores de ovos de codornas. / This study evaluated the individual and combined effects of aflatoxin B1 (AFB1) and fumonisin B1 (FB1) on egg quality and performance of laying Japanese quail (Coturnix coturnix japonica). Two hundred twenty-eight birds were purchased at 8 week of age and randomly distributed into 6 experimental groups and given rations containing AFB1 and FB1 at the following levels: (0 AFB1+0 FB1), (0 AFB1+10 mg/kg FB1), (50 &microg/kg AFB1+0 FB1), (50 &microg/kg AFB1+10 mg/kg FB1), (200 &microg/kg AFB1+0 FB1), e (200 &microg/kg AFB1+10 mg/kg FB1). The birds were fed for 140 days (5 28-day laying periods). Each treatment consisted of four replicates of twelve quail. Egg production and individual egg weight were checked daily. Feed consumption and feed utilization were determined weekly. Eggs laid in the last day of each 28-day laying period were collected and submitted to individual analysis for specific gravity, Haugh units and percent egg shell. Results showed that average egg weight at the end of the fifth cycle was significantly lower (p < 0,05) for groups fed 10 mg FB1/kg, 50 &microg/kg AFB1, 200 &microg/kg AFB1 and also for the group fed 10 mg FB1/kg + 50 &microg/kg AFB1. Average egg production significantly decreased (p < 0,05) for groups fed 10 mg FB1/kg by the end of the third, fourth and fifth cycles. Feed consumption was significantly lower (p < 0,05) for group exposed to 10 mg FB1/kg, by the end of fourth and fifth cycles, whereas birds fed 50 or 200 &microg/kg AFB1 showed a significant decrease (p < 0,05) on feed consumption, by the end of fifth cycle. Birds exposed to 10 mg FB1/kg + 50 &microg/kg AFB1 also showed lower values (p < 0,05) of feed consumption, by the end of first, second and fifth cycles. Feed utilization and Haugh units were not affected (p > 0,05) by AFB1 and FB1. Average egg specific gravity was significantly lower (p < 0,05) for group fed 10 mg FB1/kg + 200 &microg/kg AFB1, by the end of fifth cycle. Percent egg shell was significantly lower (p < 0,05) for group exposed to 10 mg FB1/kg, by the end of the first cycle, however, birds exposed to 200 &microg/kg AFB1 and also to 10 mg/kg FB1 + 50 &microg/kg AFB1, showed a significantly increase (p < 0,05) of percent egg shell, by the of the first cycle. Percent egg shell was significantly higher (p < 0,05) for group fed 10 mg/kg FB1 + 200 &microg/kg AFB1 , by the end of fifth cycle. The results obtained in the present study showed that the prolonged administration of FB1 and AFB1, singly or combined at the levels checked, may cause economic losses to the quail egg producers.

O presente trabalho teve o objetivo de avaliar os efeitos da fumonisina B1 (FB1) sobre a produtividade e a qualidade dos ovos de codornas em início de postura. Para esse fim, 128 aves de 7 semanas de idade foram aleatoriamente distribuídas em quatro grupos experimentais (32 aves por grupo), tendo sido administrada ração contendo 0 (controle), 10, 50 e 250 mg de FB1/kg, durante 28 dias. Cada tratamento esteve constituído por quatro replicatas de oito codornas. A produção e o peso dos ovos foram avaliados diariamente. O consumo de ração e a conversão alimentar foram mensurados semanalmente. Os ovos produzidos no último dia de cada período de 7 dias foram coletados e submetidos à analise individual de densidade, unidade Haugh e percentual de peso da casca em relação ao peso total do ovo. No vigésimo oitavo dia experimental, foram coletadas amostras de sangue para análise de perfil de função hepática (proteína total, albumina, AST, GGT e ácido úrico) e hemograma. Dezesseis aves de cada tratamento foram sacrificadas por deslocamento cervical, e os fígados, rins e coração foram removidos, pesados e submetidos à análise histopatotológica. Comparado com os grupos controles, as codornas alimentadas com ração contendo concentração >= 50 mg de FB1/kg reduziram (p < 0,05) o consumo de alimentos e apresentaram menor (p < 0,05) ganho de peso. Entretanto, a conversão alimentar foi aumentada (p < 0,05) apenas para as aves que receberam 250 mg de FB1/kg na dieta. A produção média de ovos apresentou-se significativamente menor (p < 0,05) para o grupo exposto a 250 mg de FB1/kg. O peso dos ovos diminui significativamente (p < 0,05) para as aves alimentadas com ração contendo concentração de 250 mg de FB1/kg. As médias de densidade e unidade Haugh não foram afetadas (p > 0,05) pela FB1. O peso das cascas dos ovos diminuiu (p < 0,05) nos grupos que receberam concentração >= 50 mg de FB1/kg na dieta. Entretanto, o percentual de casca não foi afetado pela FB1. Comparados com os grupos controle, os tratamentos que receberam concentração >= 50 mg de FB1/kg na dieta apresentaram maior (p < 0,05) peso relativo de fígado. Os pesos relativos do rim e do coração não foram afetados (p > 0,05) pela FB1. Comparando-se com o controle, as aves que receberam concentração de 250 mg de FB1/kg na dieta apresentaram redução (p < 0,05) da porcentagem do hematócrito. Os demais parâmetros do hemograma avaliados não foram afetados (p > 0,05) pela FB1. Com exceção do número de leucócitos aumentado no tratamento 10 mg de FB1/kg de ração (p < 0,05), os parâmetros do leucograma avaliados não foram afetados pela FB1 (p > 0,05). O valor de AST para o tratamento 250 mg de FB1/kg de ração encontrou-se aumentado (p < 0,05) quando comparado ao controle. Os outros parâmetros de bioquímica sérica avaliados no presente estudo não foram afetados pela FB1 (p > 0,05). Com relação aos achados histopatológicos, não houve diferença entre os tratamentos, em tecido hepático, renal e miocárdio, comparando-se com o grupo controle. Esses resultados sugerem que codornas são sensíveis aos efeitos tóxicos da FB1, em níveis que foram descritos como sendo de ocorrência natural, em condições de campo. Os dados indicaram que a exposição a FB1 em níveis >=50 mg de FB1/kg podem afetar adversamente o desempenho de codornas, o que enfatiza a importância do controle da contaminação por FB1 nas rações de codornas. / A 28-d experiment was conducted to evaluate the effect of fumonisin B1 (FB1) on egg production and egg quality of young laying Japanese quail fed contaminated rations. To this end, 128 7-wk-old birds were randomly distributed into four experimental groups (32 birds per group) and given rations containing 0 (controls), 10, 50 and 250 mg FB1/ kg feed. Each treatment consisted of four replicates of eight quail. Egg production and egg weights were checked daily. Feed consumption and feed use were determinated weekly. Eggs laid in the last day of each 7-d period were collected and subjected to individual analysis for specific gravity, Haugh units and percentage eggshells. On day 28, 12 quail from each treatment (4 replicates of 3 birds each) were bled by cardiac puncture and samples used for serum chemistry analyses (total protein, albumin, AST, GGT, and uric acid). Sixteen quail from each treatment were sacrificed by cervical dislocation, and liver, kidney, and heart were removed, weighed and collected for histopathological examination. Compared with controls, quail fed >= 50 mg FB1/ kg had reduced (p < 0.05) feed intake and lower (p < 0.05) body weight gain. However, feed use was only reduced (p < 0.05) for birds fed 250 mg FB1/ kg. Average egg production was significantly lower (p < 0.05) for group exposed to 250 mg FB1/ kg. Egg weight was significantly decreased (p < 0.05) for birds fed 250 mg FB1/ kg. Average specific gravity and Haugh units were not affected (p > 0.05) by FB1. Eggshell weight was reduced (p < 0.05) for birds fed >= 50 mg FB1/ kg. However, percentage eggshell was not affected by FB1. Compared with controls, quail fed >= 50 mg FB1/ kg had increased (p < 0.05) relative liver weight. Relative kidney weight and relative heart weight were not affected (p > 0.05) by FB1. Compared with controls, birds fed 250 mg FB1/ kg diet had reduced (p < 0.05) hematocrits. FB1 had no effet on hematological values evaluated (p > 0.05) but on hematocrits. Despite the icreased (p < 0.05) on total white blood cell count for quail fed 10 mg FB1/ kg diet, FB1 had no effect on heterophil, lymphocyte and monocyte counts (p > 0.05). Compared with controls, AST concentrations were higher (p < 0.05) in quail fed 250 mg FB1/ kg diet. It was not observed any histopathological change in liver, kidney and heart samples from any treatment group, compared with controls. These results suggest that quail are sensitive to the toxic effects of FB1 at levels that have been reported to occur in feedstuff under field conditions. Data indicated that exposure to FB1 at levels >= 50 mg/ kg could adversely affect quail performance, emphasizing the importance of controlling fumonisin contamination in quail rations.

Cowpea, Vigna unguiculata (L.) Walp. is an important edible legume crop gaining recognition in the world generally and in Africa particular. The seed is a very good source of vegetable protein for millions of people living in sub-Saharan Africa. Cowpea seed are susceptible to global post-harvest losses caused by insect damage, microbial deterioration and other factors especially when stored at high ambient temperatures and relative humidities. The detection of Fusarium species and fumonisins associated with cowpea seed was primarily investigated in this study. Secondly, the antifungal activity of extracts from three Rubiaceae plant species was evaluated against five Fusarium species. Column chromatography was used in an attempt to isolate potential compounds from the plant extracts. Cowpea seed samples were obtained from a local market of a rural community in Mpumalanga Province, South Africa and were analysed for seed mycoflora and various fungal genera including, Aspergillus spp., Fusarium spp. (Fusarium oxysporum. F. solani, F. subglutinans, F. verticillioides and F. proliferatum), Penicillium spp., Chaetomium spp., Chrysonilia spp., Cladosporium spp., Monascus spp., Phoma spp., Mucor spp., Alternaria alternata, Epicoccum spp. and Lasiodiplodia theobromae were isolated from the seed samples. Some Fusarium species including F. oxysporum, F. verticillioides, F. subglutinans, F. solani and F. proliferatum were cultured on maize patty media and analysed for fumonisin production. Fumonisin detection was conducted using the VICAM Affinity method. Only Fusarium subglutinans and F. oxysporum produced fumonisin B analogues ranging between 1.1 - 4.3 ìg/g and 3.47 - 31.66 μg/g, respectively. Neither Fusarium verticillioides, F. solani nor F. proliferatum revealed any production of fumonisin B. Fumonisin B analogues were found to be present in all the cowpea seed samples with levels ranging between 6.2 - 59 μg/g. Purified fumonisin B1 was used to investigate the phytotoxic effects of the toxin in vitro and in vivo on cowpea seedling growth and emergence and also on the ultrastructure of the seed tissue. Surface-disinfected seeds were imbibed in sterile distilled water amended with FB1 at various concentrations (10, 25, 50 and 100 μg/ml) and dry seeds and seeds imbibed in sterile distilled water served as the controls. Percentage germination was determined in vitro and in vivo according to the International Seed Testing Association (ISTA) rules. Root and shoot length was measured after 8 days. Compared to the controls all the concentrations significantly decreased seed germination and the highest concentrations of FB1 (50 and 100 μg/ml) inhibited root and shoot elongation. Transmission electron microscopy (TEM) was used to study sections of the cotyledon and embryonic tissue of cowpea seed. Samples were treated with different concentrations of FB1. Compared to the controls, the degree of damage to the vacuoles, cell walls and lipid bodies of cowpea seed tissue was directly proportional to the concentrations. The efficacy of crude extracts from Morinda citrifolia, Gardenia brighamii, and Psychotria capensis was investigated against various Fusarium species by two methods. The microtitre plate doubling dilution method and bioautography method were used to test methanol, acetone, and dichloromethane extracts of the leaves for their antifungal activity. Psychotria capensis acetone extracts showed the best inhibition against F. proliferatum and F. verticillioides with an MIC of 1.5 mg/ml and an MFC of 1.5 mg/ml. The dichloromethane extracts exhibited no activity against the Fusarium species tested. Column chromatographic purification of methanolic extracts of the leaves of P. capensis led to the isolation and identification of two compounds namely β-sitosterol and a carotenoid derivative. / Dissertation (MSc)--University of Pretoria, 2010. / Plant Science / unrestricted

Stink bugs, including native brown stink bug (Euschistus servus) and invasive brown marmorated stink bug (Halyomorpha halys), cause damage to a variety of crops including field corn (Zea mays). Frequency and size of stink bug infestations have increased in corn fields in the Mid-Atlantic U.S., and there are growing concerns that these infestations may contribute to reductions in grain quality including increased mycotoxin concentrations. Prior research on native and invasive stink bugs has focused on understanding their biology, the damage they cause, and elucidating effective and economic management strategies. However, few studies examined the potential for stink bugs to facilitate fungal infection and mycotoxin contamination of corn grain. Thus, the objectives of this research were to: 1) assess the relationship between invasive brown marmorated stink bug (H. halys) feeding injuries and fumonisin contamination of field corn in the Mid-Atlantic U.S., 2) determine if stink bugs are a vector for mycotoxigenic Fusarium spp. in corn, and 3) evaluate the efficacy of pesticides for mitigating stink bug feeding injury and associated mycotoxin contamination in field corn. A correlation between H. halys feeding injury and fumonisin concentrations was identified, and the ability of H. halys to increase F. verticillioides infection and fumonisin concentrations in corn was demonstrated in field experiments. Fusarium species including fumonisin-producing F. verticillioides and F. proliferatum were isolated from field-collected stink bugs, and in laboratory experiments, E. servus was able to transmit F. verticillioides to non-infected corn ears after feeding on F. verticillioides-infected corn. In field studies, both fungicide and insecticide reduced stink bug-associated mycotoxin concentrations in corn, but levels of control were inconsistent. Thus, additional tactics that target both the stink bug and Fusarium should be implemented to mitigate risks of mycotoxin contamination in corn. / Doctor of Philosophy / Native and invasive stink bugs can severely damage crops including field corn. Frequency and size of stink bug infestations in Mid-Atlantic U.S. corn fields have increased, and there is growing concern that this may contribute to reductions in grain quality. Insect feeding injury is a risk factor for fungal infection and mycotoxin contamination in corn. Mycotoxins are toxic chemicals produced by certain fungi that have detrimental health effects on animals including livestock and humans. The relationship between stink bug feeding injuries and mycotoxin contamination in corn grain is not well understood, and management strategies to minimize the risk of mycotoxin contamination in corn need to be identified. The main goal of this research was to characterize interactions between stink bugs and mycotoxin-producing fungi and identify tactics for controlling both the insect pest and pathogen. Specific objectives were to: 1) assess the relationship between invasive brown marmorated stink bug (H. halys) feeding injuries and fumonisin contamination of field corn in the Mid-Atlantic U.S., 2) determine if stink bugs are a vector for mycotoxin-producing Fusarium spp. in corn, and 3) evaluate the efficacy of pesticides for mitigating stink bug feeding injury and associated mycotoxin contamination in field corn. Results from this work indicated that stink bugs have the ability to cause feeding injuries which facilitate invasion of mycotoxin-producing Fusarium species, leading to increases in mycotoxin concentrations in corn grain. Studies also demonstrated that stink bugs can vector Fusarium species during feeding and increase Fusarium infection of corn resulting in subsequent mycotoxin contamination. Field studies indicated that pesticide applications targeting both the stink bugs and mycotoxigenic fungi may be needed to minimize risk of mycotoxin contamination in corn. However, under low pest pressure, application of pesticides is unlikely to be profitable.