The effect of fludioxonil + metalaxyl-M on the mycelial morphology, sporulation and fumonisin B1 production by Fusarium verticillioides 103 F was evaluated. Scanning electron microscopy analysis showed that the fungicide caused inhibition of hyphal growth and defects on hyphae morphology such as cell wall disruption, withered hyphae, and excessive septation. In addition, extracellular material around the hyphae was rarely observed in the presence of fludioxonil + metalaxyl-M. While promoting the reduction of mycelial growth, the fungicide increased sporulation of F. verticillioides compared to the control, and the highest production occurred on the 14th day in the treatments and on the 10th day in the control cultures. Fumonisin B1production in the culture media containing the fungicide (treatment) was detected from the 7th day incubation, whereas in cultures without fungicide (control) it was detected on the 10th day. The highest fumonisin B1 production occurred on the 14th day, both for the control and for the treatment. Fludioxonil + metalaxyl - M can interfere in F. verticillioides mycelial morphology and sporulation and increase fumonisin B1 levels. These data indicate the importance of understanding the effects of fungicide to minimize the occurrence of toxigenic fungi and fumonisins.

Propôs,neste trabalho, avaliar o efeito da inoculação de sementes com Pseudomonas fluorescens e adubação NPK (nitrogênio, fósforo e potássio) na composição química e contaminação por fungo-fumonisina de grãos de milho. O delineamento experimental foi bloco casualizado em fatorial 2 x 3, correspondente à inoculação com P. fluorecens (não inoculada ou inoculada) e níveis de adubação NPK (0, 125 e 250 kg ha-1, formulados 08-28-16) com 4 repetições. Os parâmetros avaliados foram composição química (proteína e cinzas), contaminação fúngica (bolores e leveduras) e fumonisinas B1 (FB1) e B2 (FB2). Os dados foram submetidos à análise de variância, comparação de médias pelo teste de Tukey e correlação de Pearson, pelo teste-t (p < 0,05). Inoculação com P. fluorescens e adubação mineral não apresentaram efeito individual sobre os parâmetros avaliados (p > 0,05). A interação entre fatores, com incremento no nível de adubação NPK e uso de P. Fluorescens, resultou em aumento no teor de cinzas e proteína (p < 0,05) e reduziu a contaminação por leveduras no grão, favorecendo o crescimento de Fusarium spp. (r = -0,40; p < 0,05). Os níveis de fumonisinas totais (FB1 + FB2) observados estão enquadrados nos limites máximos tolerados, estabelecidos por órgãos de vigilância sanitária.

The study aimed to evaluate the effect of inoculation of seeds with Pseudomonas fluorescens and NPK fertilization (nitrogen, phosphorus and potassium) on chemical composition and contamination by fungal-fumonisin of maize grains. The experiment was conducted in randomized block design in factorial 2 x 3, corresponding to inoculation with P. fluorescens (non-inoculated or inoculated) and levels of NPK fertilization (0, 125 and 250 kg ha-1, formulation 8-28-16), with 4 replications. The parameters evaluated were chemical composition (protein and ash), contamination by fungal (mold and yeast) and fumonisins B1 (FB1) and B2 (FB2). The data were subjected to analysis of variance, comparisons of means by Tukey test and Pearson correlation by test-t (p < 0.05). Inoculation with P. fluorescens and mineral fertilizer as an isolated factor did not affect the parameters evaluated (p > 0.05). The interaction between factors, increase in NPK level and use of P. fluorescens, resulted in increase in protein content and ash (p < 0.05), and reduction in contamination by yeast of the grain, favoring the growth of Fusarium sp. (r = -0.40, p < 0.05). The levels of total fumonisins (FB1+FB2) observed are above the maximum tolerated limit established by health surveillance agencies.

Sitophilus zeamais Motschulsky é uma das principais pragas do milho armazenado, sendo controlado, principalmente, com inseticidas. Porém, devido às conseqüências indesejáveis desses químicos sobre o meio ambiente e a saúde humana, outras táticas de controle têm sido investigadas, especialmente o desenvolvimento de plantas resistentes. A presença de inibidores de amilase nos grãos de milho pode interferir na digestão do inseto. Esta pesquisa foi desenvolvida com o objetivo de avaliar a resistência de híbridos de milho ao ataque de S. zeamais, correlacionada com a presença de inibidores de amilase e com a composição nutricional dos grãos. Adultos do gorgulho-do-milho foram expostos a amostras de grãos de diferentes híbridos a 27 ± 1ºC e 75 ± 5% de UR. Avaliou-se o ciclo biológico, peso dos adultos, índice de suscetibilidade e consumo dos grãos. Os resultados foram correlacionados com a composição dos grãos (teores de umidade, cinzas, lipídios, proteínas e carboidratos) e com a atividade de inibidores de amilase. A atividade inibidora de amilase foi determinada incubando-se o inibidor com 0,2 unidades de amilase durante 30 min. a 25°C, medindo-se posteriormente a atividade amilásica residual pelo método iodométrico. Dos parâmetros nutricionais avaliados, somente o conteúdo de lipídios correlacionou-se significativamente com o índice de suscetibilidade (r = 0,46). Os inibidores de amilase obtidos pela extração com etanol ou tampão correlacionaram-se negativa e significativamente com o índice de suscetibilidade (r = -0,58), sugerindo que esses inibidores contribuem para a resistência de híbridos de milho ao ataque de S. zeamais.

Sitophilus zeamais Motschulsky is one of the major pests of stored corn and it is mainly controlled by insecticides. However, due to the undesirable consequences of chemicals on the environment and human health other control measures have been investigated, especially the development of resistant plants. The presence of amylase inhibitors in corn kernels may interfere with the insect digestive process. This research was developed in order to evaluate resistance of corn hybrids to the attack of S. zeamais correlated with amylase inhibitors and nutritional composition of corn kernels. Adults of the maize weevil were exposed to grain samples of different corn hybrids at 27 ± 1°C and 75 ± 5% R.H. Biology, susceptibility index and grain consumption were evaluated. The results were correlated to the grain components (moisture content, ashes, lipids, proteins and carbohydrates) and with the amylase inhibitor activity. The amylase inhibitor activity was determined by incubating the amylase inhibitor with 0.2 units of amylase for 30 min at 25°C, and measuring the residual amylase activity determined by the iodine method. From the nutritional parameters evaluated, only the lipid content correlated significantly with the susceptibility index (r = 0.46). The amylase inhibitors obtained by the extraction with either ethanol or buffer were significantly and negatively correlated with the susceptibility index (r = -0.58), indicating that the inhibitors contribute to the resistance of corn hybrids to the attack of S. zeamais.

Studies were carried out to isolate microorganisms from corn and silage screened for their ability to inhibit F. moniliforme growth (strain 113F) in association with fumonisin detoxification. Among 150 isolates four Gram-positive bacilli and one yeast with inhibitory activity were selected. The inhibition zone ranged from 50 to 72.5 mm using cultures, and from 25 to 52.5mm for crude alcoholic extract. The isolates S9, S10, S69 (sporulated bacilli) and SE3071 (yeast) degraded 43, 48, 83 and 57% of the initial FB1 concentration, respectively. The pH increased gradually in the medium during incubation for biodegradation process.