Título da Tese:  


Orientador: Prof. Dr. Miguel Machinski Junior

Data da Defesa: 07/11/2013



Introduction: Toxigenic fungi are contaminants of grains and food in the plantations and storages. The main genres of toxin producers are Aspergillus, Penicillium and Fusarium. These fungi cause discoloration, nutritional changes and loss of dry in grains. The production of aflatoxin by Aspergillus and fumonisin by Fusarium verticillioides has affected in a markedly way some important cultivation in Brazil, among them the corn crop. The corn (Zea mays L.) is the second most cultivated cereal in Brazil, behind only soybeans. It is an agricultural crop of great economic and social importance, both on agricultural subsistence and agricultural trade, being produced in all regions of the country. Epidemiological knowledge on the toxigenic profile of fungi is important for the development of actions that can minimize their impact on production and quality of cereals. Fungal synthetic chemical inhibitor agents are frequently used in the conservation of grains; however, there is a series of problems related to the development of fungal resistance to these compounds. With the intense use of synthetic fungicides in Brazil, high levels of toxic sediments have been generated, causing environment, human and animal losses. Due to these disadvantages associated with the use of theses agents, there is a worldwide tendency of reducing their use on grains and grocery. Natural extracts of plants can provide an alternative for the use of these synthetic chemical agents. In fact, problems related to fungal growth and the production of mycotoxins in isolated corn is relevant in Brazil, considering that the country is an important producer and exporter of grains, as well as for the relevance of corn high consumption in natura by the Brazilian population. Objective: Determining Curcuma longa L. anti-fungal activity and the toxigenic profile of filamentous fungi in different agrometeorological subregions in Brazil. Materials and Methods: For the evaluation of Curcuma longa L. and curcumin essential oil, the C. longa oil was extracted by rotaevaporator. C. longa and curcumin essential oil effects on mycelial development, spore viability and sporulation were determined through A. flavus inoculum in solid cultivation – Yeast Extract Sucrose and the essential oil addition in different concentrations. The colonies morphology was performed by Scanning Electron Microscopy (SEM), and the chemical identification of Curcuma longa L. rhizome essential oil compounds, by gas chromatography-mass spectrometry (GC/MS) and by Nuclear Magnetic Resonance (NMR). For the determination of isolate Fusarium verticillioides toxigenic profile in different Brazilian agrometeorological subregions, corn grain samples were collected from corn plantations in the final phase of maturation of 2008/2009 crop, in different Brazilian municipalities. Afterwards, the corn grains were plated in semi-selective cultivation for the growth of Fusarium, for 3 to 5 days in 25 ºC and a 12 hours photoperiod for the identification of species based on polymerase chain reaction (PCR) technique, applying specific primers VER1/VER2. For the determination of the toxigenic profile, a 5mm diameter mycelial disc of isolated F. verticillioides was inoculated in Erlenmeyer containing 50 mL of half liquid, and incubated under stirring at 180 rpm during 14 days at 28 ºC in shaker. For the detection and quantification of fumonisins, chromatography in high efficiency liquid phase was used with fluorescence detection system and the chemical derivation with o-phthaldialdehyde (OPA). Results and Discussion: In the analysis and identification of the essential oil compounds, ar-turmerone (33,2%), a-turmerone (23,5%) and b-turmerone (22,7%) were found as major components.         Curcuma longa L. essential oil antifungal activity on A. flavus was observed from a 0,10% concentration, proving an accentuated effectiveness of this oil. In 2,5 and 5% concentrations, the inhibition was of 74,3 and 77,8%, respectively, what can be explained by the fact that the essential oil lipophilic properties help in the penetration of the cell membrane and in the polysaccharide accumulation, under hydrous stress conditions, leading to a rupture of the plasmalemma in the fungal cells. Yet, the tests performed allowed to observe a greater efficacy of C. longa essential oil in relation to curcumin on mycelial growth, germination and count of A. flavus spores, what can be explained by the fact that the compounds in the essential oil present a synergistic effect among themselves, different from the using of a single compound. The results obtained by SEM showed the inhibition of A. flavus conidiophores production exposed to different concentrations of the essential oil in relation to positive control. The data also demonstrated that the hyphae cytoplasm membranous structures were the essential oil main targets. In relation to the isolated Fusarium verticillioides toxigenic profile of Brazilian corn, it was observed that fumonisins B1 e B2.

 Keywords: Anti-fungal activity, Aspergillus flavus, Fusarium verticillioides, Corn, Mycotoxins, Toxigenic profile.


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