No description available.

No description available.

Conidial length, width, septation, curvature and pigmentation of 39 isolates of Bipolaris zeicola (Stout) Shoemaker from different geographical areas and representing distinct physiological races were examined. Wide variability in conidial morphology was found among isolates of each race. No association was found between races or groups of isolates producing the same shape of lesions and conidial morphology. Morphology and expansion of lesions induced by three races of B. zeicola producing different shapes of lesion on susceptible maize (Zea mays L.) inbred lines were studied. Resistant type lesions induced by three races of B. zeicola were indistinguishable based on their shape or size. However, lesion size correlated with the lesion type induced by each race, indicating that it may be useful to evaluate resistance to different races of B. zeicola. Inheritance of reaction to one isolate of the proposed pathotype of B. zeicola was studied. Resistance was controlled by a single dominant gene in the cross Pr x B37. Forty-nine isolates of B. zeicola from different geographical areas including all the previously described races and pathotype were characterized by their disease reaction, severity and symptoms incited on 14 maize inbred lines. Eleven physiological races were distinguished based on their differential reaction on the 14 inbred lines; however, 6 inbred lines were adequate to differentiate the races. A system based on binary notation is proposed to designate races of B. zeicola on maize. Two races induced typical symptoms of Helminthosporium carbonum-toxin (HC-toxin) production on Pr. Seven races produced oval to irregular lesions on susceptible hosts and did not produce typical lesions of HC-toxin production on Pr. One race induced predominantly long, linear lesions, and another was avirulent on all 14 maize inbred lines. / Ph. D.

No description available.

Thesis (DSc (Biochemistry))--Stellenbosch University, 2009. / The fumonisin mycotoxins are known to be the causative principle for several animal diseases and are associated with the development of liver and oesophagus cancer and neural tube defects in humans. The thesis focuses mainly on the characterisation of the compounds from maize cultures of the fungus Fusarium verticillioides, isolated from maize, the toxicological effects in animals, mechanism involved in hepato- and nephrocarcinogenicity and discussing the major differences and contradictions in the literature together with their impact on setting relevant risk assessment parameters to safeguard human health. Controversies include the importance of non-genotoxicity vs genotoxicity in the development of cancer, the role of threshold effects in carcinogenesis and the establishment of realistic risk assessment parameters that will also be applicable in developing countries. Recent approaches suggest that thresholds should also apply for genotoxic carcinogens as interaction with the DNA is only one event in the multi-step process of cancer development and therefore could not be taken as the basis for applying a no-effect threshold for genotoxins. It would appear that a carcinogen such as fumonisin, whether it is labeled genotoxic or non-genotoxic per se, exhibits some degree of risk at any level due to additive or synergistic interactions with other xenobiotics and/or dietary constituents. The underlying mechanisms of fumonisin-induced carcinogenicity includes the disruption of sphingolipid, phospholipids and fatty acid metabolism, which plays a major role in the modulation of apoptotic and cell proliferative pathways related to cancer development. Interactive responses between arachidonic acid and ceramide affect downstream cell signal transduction pathways and depending on the cell type the disruption of these pathways could either stimulate or inhibit cell proliferation which eventually will determine the induction of apoptosis and hence affect cell survival. The modulating roles of dietary constituents such as vitamins, protein and the South African herbal teas are also highlighted as they affected the outcome of toxicological assays, thus determining thresholds of the adverse effects in specific target organs that will impact risk assessment parameters. Regulation of the fumonisins in food and the associated risk are debated from many perspectives. In developing countries there is a lack of quality control implying that maize highly contaminated with mycotoxins may directly enter the food chain of adults and children as control of mycotoxins is difficult or in some cases totally absent. The interaction of politics, economy and technology will eventually determine the impact on health as the regulation of fumonisin in food differs between countries. Knowledge about the biological effects of the fumonisins is currently playing an important role in the development of simple and inexpensive methods to reduce the levels of the fumonisin in maize by targeting specific populations at risk.

Digitized by Kansas Correctional Industries

A study was undertaken from 1993 to 1994 to determine the effects of intercropping (with Glycine max L Merr., Lupinus sp., Trifolium pratense L.-Lolium multiflorum Lam., or Secale cereale L.) and mechanical weeding (with a rigid tines cultivator, Danish tines cultivator or ridge cultivator) on the population dynamics of insect pests (Diabrotica longicornis Say, Lygus lineolaris Palisot de Beauvois, Ostrinia nubilalis Hubner, and Pseudaletia unipuncta Haworth) on corn (Zea mays L.) in L'Assomption and Sainte-Anne-de-Bellevue, Quebec, Canada. / D. longicornis or P. unipuncta populations did not increase. / In 1994, intercropping with T. pratense-L. multiflorum (Sainte-Anne-de-Bellevue) or weeding with the Danish tines cultivator (L'Assomption) increased L. lineolaris populations. / In 1994, intercropping with S. cereale (L'Assomption) ot T. pratense-L. multiflorum (Sainte-Anne-de-Bellevue) increased O. nubilalis populations.

Three cultivators, Rabewerk, Kongskilde and Hiniker, and three intercrops, soybean, lupin and red clover + rye grass were investigated for their impact on the incidence of ear rot of corn, a common disease of maize in eastern Canada. Wheat was seeded in the corn rows to serve as an additional indicator of cultivation and intercropping effects on the pathogen. An artificial inoculum of F. graminearum that produced perithecia and ascospores was used to mimic natural inoculum. / In 1993 and 1994, the infection in the corn was not very severe and there were no differences between the treatments and the controls. / In 1993 and 1994, at both sites, wheat seeds from cultivation trials showed a tendency for greater disease incidence in the non-cultivated herbicide treatment when compared to any of the other cultivator treatments. Cultivators till the soil and bury corn residues, this action led to the destruction of some of the inoculum and a subsequent reduction of the disease incidence in the cultivated plots. / In the intercrop trial of 1993 and 1994, wheat infection was moderate to severe, except at L'Assomption in 1993, but no significant differences were observed among the treatments. It is believed that interplot interference, due to ascospores moving from one plot to the next, masked differences. / The results indicated that weed cultivation would have a negligible or no effect on the development of fusarium ear rot of corn in Quebec. (Abstract shortened by UMI.)

This project investigated the impact of bird predation on insect pest populations within two cornfields of Southwestern Quebec. Birds were excluded from portions of these fields through the use of bird-proof netting. Rhopalosiphum maidis, Ostrinia nubilalis, Agrotis spp. and Sphenophorus spp. were all found at greater densities in plots where birds were excluded as compared with the non covered plots. Only the adult Diabrotica longicornis population was not reduced by birds. Results significantly suggest that birds can reduce insect pest populations. Bird visits in cornfields with respect to distance from field edge, type of edge habitat and corn phenology were also studied. Red-winged Blackbird, Song and Chipping Sparrows and American Robin were the most frequently observed bird species inside cornfields. Early in the summer, birds tended to stay closer to the field edge, especially when composed of mature coniferous trees. Different bird species visited the cornfields at specific periods during corn development.

M.Tech. / Fungi and their mycotoxins are major contaminants of cereals and maize which is the major staple food for Angolan population. The consumption of fungal and mycotoxins contaminated maize can induce health problems as these mycotoxins are known to induce immune suppression and other chronic diseases known as mycotoxicoses. In addition, to these mycotoxins also induce chronic diseases such as cancers of various types (liver, oesophageal, brain). Mycotoxins also immensely affect organs such as fragility and haemorrhage in tissues, liver-necrosis, bile-duct proliferation, caustic effects, intestinal haemorrhage and diarrhoea, adenomatosis, tremors, inco-ordination, mania, coma, photosensitization, sloughing of the extremities, nephrosis, uremia, infertility, prolonged oestrus, huge implications and infections in people with Human immunodeficiency virus (HIV)- AIDS. There is a very little known about the incidence of mycotoxins in Angola, which are associated with Food, Environment and Health. Therefore, the aim of this scientific novel study in history of Angola was to analyse maize samples obtained from major markets in Angola and to establish their quality with regard to mycotoxins and fungi and well as to establish possible links to the prevalent diseases as well as chronic diseases recorded among Angolan populations. To attain these aims, 60 samples of maize were randomly selected and purchased from open rural and nonregulated informal (dusty and food exposed to open air) markets around Luanda, Angola. Luanda, being the capital city of Angola was found to be the best place to sample, because of the presence of huge markets in which food products as well as maize produced in different provinces are delivered and sold to its high population. Thus, sampling in these markets was representative of the whole country and the results obtained give an approximate the status of the quality of maize consumed in different parts of Angola. The result from this study approximates the status of possible health risks that consumers can be exposed due to consumption of these mycotoxins. The samples were analysed in the Food Environmental and Health Research Laboratories at the University of Johannesburg for fungi and mycotoxins contamination using fungal screening methodologies. In terms of mycotoxins extraction, a multi-mycotoxin (solvent-solvent) extraction, solid phase extraction using SAX column for fumonisins (FBs) and immuno-affinity column (VICAM) were used for confirmation of results. Normal thin layer chromatography (TLC), reversed phase thin layer chromatography (RPTLC) (both for FBs confirmation), fluorometer “VICAM” and high performance liquid chromatography (HPLC) were techniques used for mycotoxins detection, identification and quantification. From the results obtained in this study, fungal isolation revealed contamination of the three most important toxigenic species: Aspergillus, Penicillium, Fusarium spp.