Fungivory: a new and complex ecological function of Doru luteipes (Scudder) (Dermaptera: Forficulidae) / Fungivoria: uma nova e complexa função ecológica de Doru luteipes (Scudder) (Dermaptera: Forficulidae)

We report the discovery that the earwig predator Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidae) feed on Puccinia polysora Underw uredospore, the causal agent of Southern Rust of Corn (SRC), which is a primary disease affecting the maize crop in Brazil. We performed experiments in laboratory and greenhouse to test the effect of D. luteipes (1st/2nd and 3rd/4th instars, and adults) fungivory on the P. polysora uredospore concentration. All trials showed a significant reduction of the initial concentration of uredospore. There was a reduction in uredospore concentration with increase in number of D. luteipes feeding on them. We also tested the uredospore consumption by quantifying its percentage in the feces of D. luteipes. Nymphs of the 2nd, 4th instar and adults fed 88%, 85%, and 83.8% of the uredospore, respectively. For nymphs of the 3rd instar, the percentage of uredospore consumption (75.6%) was statistically significant compared with the other groups. In greenhouse experiment, at twenty-eight days after plant inoculation with 9.9 x 104 uredospores, the percentage of uredospore consumption was 81.7%. Our results confirmed the fungivory of D. luteipes on P. polysora uredospore. This is the first report of D. luteipes fungivory, which may play an important role in the biological control of P. polysora in corn.

Relatamos a descoberta de que o predador Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidae) se alimenta de uredosporos de Puccinia polysora Underw, o agente causal da ferrugem polisora que é uma doença primária que afeta a cultura do milho no Brasil. Realizamos experimentos em laboratório e em casa de vegetação para testar o efeito da fungivoria de D. luteipes (1º/2º e 3º/4º iìstares e adultos) sobre a concentração de uredosporos de P. polysora. Todos os ensaios mostraram uma redução significativa da concentração inicial de uredosporos. Houve uma redução na concentração de uredosporos com o aumento do número de D. luteipes alimentando-se deles. Também testamos o consumo de uredosporos quantificando sua porcentagem nas fezes de D. luteipes. Ninfas do 2º e 4º ínstar, assim como adultos, alimentaram-se de 88%, 85% e 83,8% dos uredosporos, respectivamente. Para ninfas do 3º ínstar, a porcentagem de consumo de uredosporos (75,6%) foi estatisticamente significativo em comparação com os outros grupos. No experimento em casa de vegetação, aos 28 dias após a inoculação das plantas com 9,9 x 104 uredosporos, a porcentagem de consumo de uredosporos foi de 81,7%. Nossos resultados confirmaram a fungivoria de D. luteipes em uredosporos de P. polysora. Este é o primeiro relato de fungivoria de D. luteipes, que pode ter papel importante no controle biológico de P. polysora em milho.

Atividade de nucleação de gelo e densidade populacional do patógeno podem ser fatores que contribuem para o progresso da doença mancha branca do milho / Ice nucleation activity and density of the pathogen population may be factors that contribute to the progression of maize white spot disease / La actividad de nucleación de hielo y la densidad de población del patógeno pueden ser factores que contribuyen al progreso de la enfermedad mancha blanca del maíz

A Mancha Branca do Milho (MBM) é uma doença foliar que tem causado perdas apreciáveis, tanto qualitativas como quantitativas para a produção de milho. Seu agente etiológico, a Pantoea ananatis, é uma bactéria epifítica, Gram-negativa formadora de colônia amarela, capaz de formar gelo, mesmo em ambiente tropical (ice nucleation activity - INA). Este estudo teve por objetivo caracterizar isolados de P. ananatis quanto à atividade INA e avaliar o efeito da densidade bacteriana na expressão do fenótipo INA e no processo de desenvolvimento da doença. O agente patogênico foi isolado de lesões iniciais da doença, as anasarcas, e avaliado quanto à expressão do fenótipo INA em diferentes concentrações bacterianas. O mesmo foi feito com isolados epifíticos obtidos da superfície foliar de plantas de milho sadias. Dos 24 isolados bacterianos estudados, apenas 13 apresentaram o fenótipo INA+. A expressão deste fenótipo foi dependente da densidade celular. Isolados INA+ e INA­ foram inoculados em folhas destacadas e em plantas da cultivar HS200 a campo, em diferentes concentrações do inóculo. Nenhum isolado INA­ reproduziu sintomas em laboratório. Dos cinco isolados INA+ somente um deles reproduziu sintomas em laboratório. Em campo o isolado INA+ foi capaz de promover lesões em todas as concentrações avaliadas. Conclui-se que a atividade de nucleação de gelo pela bactéria P. ananatis é dependente da linhagem e da densidade bacteriana e este fenômeno pode estar envolvido no desenvolvimento dos sintomas da MBM.(AU)

Maize White Spot Disease is a leaf disease that has caused considerable losses, both qualitative and quantitative for corn production. Its etiologic agent, Pantoea ananatis, is an epiphytic, Gram-negative, yellow colony-forming bacterium, capable of forming ice, even in tropical environments at temperatures where this normally does not occur (Ice Nucleation Activity - INA). This study aimed at characterizing P. ananatis isolates in terms of INA activity and evaluating the effect of bacterial density on the expression of the INA phenotype and on the disease development process. The pathogen was isolated from the initial lesions of the disease, the anasarcas, and were evaluated for the expression of the INA phenotype in different bacterial concentrations. The same procedure was performed on epiphytic isolates obtained from the leaf surface of healthy maize plants. From the 24 bacterial isolates studied, only 13 presented the INA+ phenotype. The expression of this phenotype is dependent on cell density. INA+ and INA­ isolates were inoculated on detached leaves and on plants of cultivar HS200 in the field, in different concentrations of the inoculum. No INA­ isolates reproduced symptoms in the laboratory. From the five INA+ isolates, only one of them reproduced symptoms in the laboratory. In the field, the INA+ isolate was able to promote lesions in all concentrations evaluated. It can be concluded that the ice nucleation activity by P. ananatis is dependent on the strain and bacterial density and this phenomenon may be involved in the development of Maize White Spot Disease symptoms.(AU)

La mancha blanca del maíz es una enfermedad de la hoja que ha causado pérdidas considerables, tanto cualitativas como cuantitativas para la producción de maíz. Su agente etiológico, Pantoea ananatis, es una bacteria epífita, Gram-negativa, formadora de colonias amarillas, capaz de causar hielo, incluso en ambientes tropicales a temperaturas donde esto normalmente no ocurre (actividad de nucleación de hielo - INA). Este estudio tuvo como objetivo caracterizar los aislados de P. ananatis en términos de actividad de INA y evaluar el efecto de la densidad bacteriana en la expresión del fenotipo de INA y en el proceso de desarrollo de la enfermedad. El patógeno se aisló de las lesiones iniciales de la enfermedad, las anasarcas, y se evaluó la expresión del fenotipo INA en diferentes concentraciones bacterianas. Lo mismo se hizo con aislamientos epifitos obtenidos de la superficie de la hoja de plantas de maíz sanas. De los 24 aislados bacterianos estudiados, solo 13 presentaron el fenotipo INA+. La expresión de este fenotipo depende de la densidad celular. Se inocularon aislamientos INA+ e INA- en hojas desprendidas y en plantas del cultivar HS200 en el campo, en diferentes concentraciones del inóculo. Ninguno aislado INA- reprodujo síntomas en el laboratorio. De los cinco aislamientos de INA+, solo uno de ellos reprodujo síntomas en el laboratorio. En el campo, el aislado INA+ pudo promover lesiones en todas las concentraciones evaluadas. Se concluye que la nucleación de hielo por P. ananatis depende de la cepa y la densidad bacteriana, y este fenómeno puede estar involucrado en el desarrollo de los síntomas de la enfermedad de la mancha blanca del maíz.(AU)

Saccharomyces cerevisiae populations and other yeasts associated with indigenous beers (chicha) of Ecuador

ABSTRACT Chicha, a type of beer made mainly with maize or cassava, is a traditional fermented beverage of the Andean region. There have only been a few studies on yeasts associated with chicha fermentation, and the species diversity occurring during the production of this beverage is not known. The objective of this study was to determine the biodiversity of yeasts in chicha, and to characterize the Saccharomyces cerevisiae populations associated with the production of chicha de jora, seven-grain chicha, chicha de yuca, and chicha de morocho in Ecuador. The molecular diversity of S. cerevisiae populations was determined by restriction polymorphism mitochondrial profiles. The beverages were characterized based on their physicochemical parameters. Twenty-six species were identified, and the most prevalent species were S. cerevisiae and Torulaspora delbrueckii. Other yeast species were isolated at low frequencies. Among 121 isolates of S. cerevisiae, 68 different mtDNA molecular profiles were identified. These results showed that chichas are fermented by a high number of different strains of S. cerevisiae. Some other species provided a minor contribution to the fermentation process. The chicha presented generally similar physicochemical parameters to those observed for other traditional fermented beverages, and can be considered as an acid fermented beverage.

Endophytic fungi from selected varieties of soybean (Glycine max L. Merr.) and corn (Zea mays L.) grown in an agricultural area of Argentina / Hongos endófitos aislados de cultivares de soja (Glycine max L. Merr) y maíz (Zea mays L.) presentes en áreas agrícolas argentinas

Endophytic fungi are ubiquitous and live within host plants without causing any noticeable symptoms of disease. Little is known about the diversity and function of fungal endophytes in plants, particularly in economically important species. The aim of this study was to determine the identity and diversity of endophytic fungi in leaves, stems and roots of soybean and corn plants and to determine their infection frequencies. Plants were collected in six areas of the provinces of Buenos Aires and Entre Ríos (Argentina) two areas were selected for sampling corn and four for soybean. Leaf, stem and root samples were surface-sterilized, cut into 1 cm² pieces using a sterile scalpel and aseptically transferred to plates containing potato dextrose agar plus antibiotics. The species were identified using both morphological and molecular data. Fungal endophyte colonization in soybean plants was influenced by tissue type and varieties whereas in corn plants only by tissue type. A greater number of endophytes were isolated from stem tissues than from leaves and root tissues in both species of plants. The most frequently isolated species in all soybean cultivars was Fusarium graminearum and the least isolated one was Scopulariopsis brevicaulis. Furthermore, the most frequently isolated species in corn plants was Aspergillus terreus whereas the least isolated one was Aspergillus flavus. These results could be relevant in the search for endophytic fungi isolates that could be of interest in the control of agricultural pests.

Los hongos endófitos son ubicuos y se encuentran en el interior de los tejidos de las plantas de manera asintomática. Se sabe muy poco acerca de la diversidad y la función de estos hongos, particularmente en especies de importancia económica. El objetivo de este trabajo fue determinar la diversidad y la frecuencia de colonización de hongos endófitos en raíces, tallos y hojas de 2 variedades de maíz y de 4 variedades de soja; las muestras se tomaron de 6 áreas diferentes ubicadas en las provincias de Buenos Aires y Entre Ríos (Argentina). Con un bisturí estéril se obtuvieron porciones de 1 cm² de raíz, tallo y hoja, que fueron colocados en placas con agar papa dextrosa más antibiótico. Las especies de hongos fueron identificadas a partir de características morfológicas y moleculares. La colonización de hongos endófitos en soja estuvo influenciada por la variedad y por el tipo de tejido, en tanto que en el maíz solo hubo influencia del tipo de tejido. El mayor número de endófitos se encontró en los tallos de ambas especies. El aislamiento más frecuente en todas las variedades de soja fue Fusarium graminearum y el menos frecuente Scopulariopsis brevicaulis. En ambas variedades de maíz la especie con mayor frecuencia de aislamiento fue Aspergillus terreus y la de menor fue Aspergillus flavus. Estos resultados son relevantes para la búsqueda de especies de hongos endófitos que podrían ser de interés en el control de plagas agrícolas.

Antibiosis of Trichoderma spp strains native to northeastern Mexico against the pathogenic fungus Macrophomina phaseolina

Abstract Sampling of agricultural soils from the Mexican northeastern region was performed to detect Trichoderma spp., genetically characterize it, and assess its potential use as a biologic control agent against Macrophomina phaseolina. M. phaseolina is a phytopathogen that attacks over 500 species of cultivated plants and causes heavy losses in the regional sorghum crop. Sampling was performed immediately after sorghum or corn harvest in an area that was approximately 170 km from the Mexico-USA border. Sixteen isolates were obtained in total. Using colony morphology and sequencing the internal transcribed spacers (ITS) 1 and 4 of 18S rDNA, 14 strains were identified as Trichoderma harzianum, T. koningiopsis and T. virens. Subsequently, their antagonistic activity against M. phaseolina was evaluated in vitro, and 11 isolates showed antagonism by competition and stopped M. phaseolina growth. In 4 of these isolates, the antibiosis phenomenon was observed through the formation of an intermediate band without growth between colonies. One strain, HTE808, was identified as Trichoderma koningiopsis and grew rapidly; when it came into contact with the M. phaseolina colony, it continued to grow and sporulated until it covered the entire petri dish. Microscopic examination confirmed that it has a high level of hyperparasitism and is thus considered to have high potential for use in the control of this phytopathogen.

Fermentação em estado sólido de Aspergillus parasiticus e produção de aflatoxinas / Solid state fermentation of Aspergillus parasiticus and aflatoxin production

Aflatoxinas são metabólitos secundários de fungos com grande potencial carcinogênico, produzidos principalmente por Apergillus flavus e Aspergillus parasiticus. Em vista da ampla variedade de alimentos em que se encontram essas micotoxinas, o presente estudo teve como objetivo determinar condições de cultivo para o Aspergillus parasiticus e produção das quatro principais aflatoxinas (AFB1, AFB2, AFG1 e AFG2) considerando diferentes substratos conhecidos pela contaminação por estas micotoxinas, entre eles arroz branco, arroz cateto, amendoim, milho e farinha de trigo integral, e diferentes valores de umidade e pH. Ao analisar por cromatrografia em camada delgada os extratos dos diferentes substratos, verificou-se a produção de aflatoxinas em todos os alimentos, porém na cromatografia líquida de alta eficiência foi possível perceber a maior produção de aflatoxinas no arroz cateto e na farinha de trigo integral. Para a continuidade do trabalho, utilizou-se o arroz cateto e então preparou- se diferentes meios sólidos com valores de pH entre 3,5 e 7,5 e umidade entre 42 % e 62 %. Ao analisar por CLAE, todas as amostras apresentaram produção de AF, porém as amostras com o maior valor de água agregada (62%) apresentaram maior produção enquanto a variação de pH não apresentou influência nesta produção.

Aflatoxins are secondary metabolites of fungi with great carcinogenic potencial, mainly produced by Aspergillus flavus and Aspergillus parasiticus. In order of the wide variety of foods where mycotoxins are found in, this study aimed to determine growth conditions for Aspergillus parasiticus and production of four major aflatoxins (AFB1, AFB2, AFG1 and AFG2) considering different substrates known for contamination by these aflatoxins, including white rice, cathetus rice, peanuts, maize and whole wheat flour, and different pH and humidity values. When extracts of different substrates were analyzed by thin layer chromatography, it has been verified the production of aflatoxins in all foods; however, when high performance liquid chromatography (HPLC) analysis was performed, the greater production of aflatoxins was observed in cathetus rice and whole-wheat flour. Cathetus rice was then selected to continue the study and different solid medium with pH values between 3.5 and 7.5 and humidity percentages between 42 % and 62 % were prepared. When analyzed by HPLC, all samples showed production of aflatoxins, but the samples with higher humidity value (62%) showed greatest production while the pH changes had no effect on this production.

Selection of potential biological control of Exserohilum turcicum with epiphytic microorganisms from maize / Selección de microorganismos epifíticos de maíz como potenciales agentes de biocontrol de Exserohilum turcicum

The aims of this study were to select microbial isolates from phyllosphere of maize and to examine their antagonistic activity against Exserohilum turcicum. Selection was performed through the ability of isolates to compete with the pathogen using an index of dominance and to affect growth parameters of E. turcicum. Most of the epiphytic populations obtained for the screening were bacteria. These isolates were found in the order of 6 log CFU/g of leaf fresh weight. According to similar morphological characteristics and staining, 44 out of 111 isolates obtained were selected for testing antagonistic effects. At water potential, ψ, −1.38 MPa and −4.19 MPa, three Bacillus isolates showed dominance at a distance (5/0) and a significant reduction of growth rate of the pathogen. Three Bacillus isolates only decreased the growth rate of E. turcicum at −1.38 MPa. At −4.19 MPa the growth rate decreased with three isolates of Pantoea and three Bacillus. In this study a negative and significant correlation was observed between the growth rate of E. turcicum and the dominance index in the interaction of the pathogen with some bacteria. These results show that with decreasing growth rate of the pathogen the dominance index of the interaction increases. Eleven potential biocontrol agents against E. turcicum were selected.

El objetivo de este estudio fue seleccionar aislamientos microbianos de la filósfera de maíz y examinar su actividad antagonista contra Exserohilum turcicum. La selección se realizó a través de la capacidad de los aislamientos de competir con el patógeno usando un índice de dominancia y también la capacidad de afectar los parámetros de crecimiento de E. turcicum. La mayoría de las poblaciones epifíticas aisladas para la selección fueron bacterias. Estos aislamientos se encontraron en el orden de 6 log de UFC por gramo de peso fresco de hoja de maíz. En base a características morfológicas y tintóreas similares, se seleccionaron 44 de 111 aislamientos obtenidos para evaluar su capacidad antagónica. A los potenciales agua, ψ, −1,38 MPa y −4,19 MPa, tres aislados del género Bacillus mostraron dominancia a distancia (5/0) y una reducción significativa de la velocidad de crecimiento del patógeno. Tres aislamientos de Bacillus disminuyeron la velocidad de crecimiento de E. turcicum a −1,38 MPa. A −4,19 MPa la velocidad de crecimiento disminuyó con tres aislamientos de Pantoea y tres de Bacillus. En este estudio se observó una correlación negativa y significante entre la velocidad de crecimiento de E. turcicum y el índice de dominancia cuando el patógeno interactuó con algunas bacterias. Esto estaría indicando que cuando disminuye la velocidad de crecimiento del patógeno se incrementa el índice de dominancia de la interacción. Se seleccionaron once posibles agentes de biocontrol contra E. turcicum.

Optimization of the production of mycorrhizal inoculum on substrate with organic fertilizer

The system for production of inoculum of arbuscular mycorrhizal fungi (AMF) using sand and vermiculite irrigated with nutrient solution is promising. However, organic amendments added to the substrate can stimulate sporulation of AMF and replace the nutrient solution. The aim of this study was to maximize the production of AMF (Acaulospora longula, Claroideoglomus etunicatum, Dentiscutata heterogama and Gigaspora albida) using selected organic substrates (vermicompost, coir dust and Tropstrato) together with sand and vermiculite. The production of spores varied among the tested AMF and according to the organic source added to the substrate. The vermicompost promoted higher sporulation of A. longula in relation to the other AMF and substrates. The Tropstrato® inhibited the sporulation of D. heterogama while the reproduction of C. etunicatum was not affected by the organic compounds. The inoculum of A. longula also showed a high number of infective propagules and promoted biomass accumulation in maize plants. The system of inoculum production using sand and vermiculite + 10% vermicompost favors the production of infective inoculum of A. longula with the fungus benefiting growth of corn plants.

Potential of Microbispora sp. V2 as biocontrol agent against Sclerotium rolfsii, the causative agent of southern blight of Zea mays L (Baby corn)–in vitro studies.

The study was undertaken with the aim of exploring novel and beneficial agro activities of rare actinomycetes like Microbispora sp. V2. The antagonistic activity of Microbispora sp. V2 was evaluated as a biocontrol agents against Sclerotium rolfsii, a soil-borne fungal plant pathogen. The methodology performed for evaluation of biocontrol agent was in vitro evaluation assay which comprised of three tests viz., cellophane overlay technique, seed germination test and Thiram (fungicide) tolerance of Microbispora sp. V2. The isolate was found to inhibit the fungal pathogen Sclerotium rolfsii to 91.43% in cellophane assay. In seed germination assay, Microbispora sp. V2 treated seeds resulted in 25.75% increased germination efficiency, as compared to seeds infected by Sclerotium rolfsii. The isolate Microbispora sp. V2 could tolerate 1000 µg mL-1 of Thiram (fungicide). The in vitro assay studies proved that Microbispora sp. V2 can be used as antifungal antagonist and thus posses’ great potential as biocontrol agent against southern blight caused by Sclerotium rolfsii in Zea mays L (Baby corn) which causes large economical losses.

Incidence and multiplex PCR based detection of trichothecene chemotypes of Fusarium culmorum isolates collected from freshly harvested Maize kernels in Southern India

Hundred Fusarium culmorum strains, isolated from freshly harvested maize grain samples from Southern parts of India, were incubated in czapek-dox medium and analyzed for trichothecene (DON/NIV) production. The mPCR assay was standardized targeting trichothecene metabolic pathway genes viz., Tri6, Tri7, Tri13 for detection of trichothecene (DON/NIV) chemotypes and rDNA gene for specific detection of F. culmorum species. Primers for targeted genes were designed and used to predict whether these isolates could produce deoxynivalenol/nivalenol, 94 isolates were able to produce DON/NIV by mPCR assay. Chemical analysis of DON/NIV was carried out for mPCR positive isolates by high performance-thin layer chromatography (HPTLC). To check the practical usefulness of developed mPCR assay, 150 field samples of maize were evaluated and results were compared with conventional HPTLC method. Out of 150 samples, 34% samples stayed as a positive for NIV contamination whereas 44% were found to have deoxynivalenol contamination. Moreover, mPCR results are equivocally matched with the HPTLC chemical analysis for field samples. Chemotyping of F. culmorum isolates were reported for the first time from India, and highlights the important potential of F. culmorum to contaminate maize with DON/NIV.

Toxigenic potential of Fusarium graminearum isolated from maize of northwest Argentina

Twenty six isolates of Fusarium graminearum from grains of maize hybrids harvested in ±west Argentina were grown on autoclaved rice grain to assess their ability to produce type B trichothecenes. Chemical analysis indicated that 38% of isolates were nivalenol (NIV) producers only, 31% were major NIV producers with high DON(deoxynivalenol)/NIV ratios, 8% were major DON producers with minor NIV production, and 23% were DON producers only. Isolates showed a high variability in their toxigenic potential which was not related to fungal biomass. The distribution of the different chemotypes as well as the high and the low trichothecene-producing Fusarium isolates could not be associated to a geographical origin. Our results confirmed for the first time that isolates of Fusarium graminearum from maize of northwest Argentina are able to produce DON and NIV. A substancial contamination with both NIV and DON is likely in maize from northwest Argentina. Their contents should be quantified in regional surveillances for mycotoxin contamination.

Growth response of maize plantlets inoculated with Enterobacter spp., as a model for alternative agriculture / Respuesta de plántulas de maíz inoculadas con Enterobacter spp. como un modelo de agricultura alternativa

A maize rhizosphere isolate was phenotypically and genotypically characterized and identifed as Enterobacter spp. bacterium. Germinated seeds were inoculated, the plantlets were sown in vermiculite and in soil and grown under laboratory and feld conditions, respectively. The adherence, colonization and plant growth promotion capability of Enterobacter sp. UAPS03001 was evaluated in "Rojo-Criollo" maize under laboratory conditions. Twenty days after inoculation, the treated plantlets showed larger biomass than non-inoculated ones. In feld grown plants, the kernel biomass was also greater in inoculated than in non-inoculated plants. The inoculation of maize sprouts with plant growth- promoting bacteria before their sowing in the feld would be an alternative practice for achieving successful yield in temporal agriculture.

En este trabajo se aisló una bacteria de la rizósfera de maíz, que fue caracterizada mediante métodos fenotípicos y genotípicos e identifcada como Enterobacter sp. UAPS03001. La bacteria fue inoculada en semillas de maíz "Rojo-Criollo" germinadas en forma axénica. Las semillas germinadas e inoculadas se plantaron en vermiculita y posteriormente las plántulas fueron cultivadas en vermiculita o en suelo, para evaluar el efecto promotor del crecimiento vegetal de dicha bacteria, bajo condiciones de laboratorio y de campo. Bajo condiciones de laboratorio, también se evaluó la capacidad de esta cepa para adherirse a las plantas de maíz y colonizarlas. Veinte días después de la inoculación, las plántulas inoculadas mostraron una biomasa mayor con referencia a las no inoculadas. En campo, la biomasa de la mazorca fue también mayor en las plantas inoculadas respecto de las plantas no inoculadas. La inoculación de germinados de maíz con una bacteria promotora del crecimiento vegetal y su posterior transferencia a campo podría ser una práctica alternativa para llevar a cabo una producción exitosa en agricultura de temporal.

Coliformes termotolerantes e fungos em flocos de milho fornecidos na merenda escolar / Thermotolerant coliforms and fungi in corn flakes provided in school meals

O milho e seus derivados podem ser alterados pela ação de bactérias e de fungos, levando a uma redução do valor nutricional e da digestibilidade, causando perdas para a qualidade. Foram avaliadas as condições higiênico-sanitárias do produto flocos de milho fornecido para a merenda escolar no Piauí, através dos resultados do número mais provável (NMP) de coliformes termotolerantes e das contagens de bolores e leveduras (UFC/g), analisadas por seis anos no Laboratório de Microbiologia de Alimentos do Núcleo de Estudos, Pesquisa e Processamento de Alimentos, Centro de Ciências Agrárias da Universidade Federal do Piauí. Para interpretação dos resultados, foram comparadas as legislações anteriores que constituem parâmetros para coliformes termotolerantes e para bolores e leveduras com a legislação vigente. (...) Coliformes termotolerantes foram identificados na minoria das amostras de flocos de milho pesquisadas. Como a legislação atual não abrange contagem de bolores e leveduras, e em apenas uma amostra identificaram-se coliformes termotolerantes dentro do padrão, pode-se afirmar que as amostras analisadas estavam em condições higiênico-sanitárias satisfatórias. Mas como a quantidade de fungos foi superior a especificada na legislação anterior, deve-se atentar para que estudantes possam estar consumindo alimentos contento micotoxinas.

Consumo de fumonisinas y daños a la salud humana / Fumonisin intake and human health

Las fumonisinas son una familia de micotoxinas que contaminan al maíz, alteran el metabolismo de los esfingolípidos y del folato, se asocian con defectos del tubo neural y están catalogadas por la Agencia Internacional de Investigación en Cáncer (IARC por sus siglas en inglés) como posibles carcinógenos humanos. Debido a que en México los derivados de maíz constituyen una parte importante de la dieta y existe alta prevalencia de población genéticamente susceptible a la deficiencia de folato, en este ensayo se presentan las evidencias mundiales y nacionales de la exposición a fumonisinas y la relevancia que para México representa la evaluación de esta exposición.

Fumonisins are mycotoxins that contaminate maize, disrupt the folate and sphingolipid metabolism, are associated with neural tube defects, and are considered by the International Agency for Research on Cancer (IARC) as possible human carcinogens. Since maize-based foods are significant components of the Mexican diet and there is a high prevalence of genetic susceptibility for folate deficiency among Mexicans, this essay presents international and national evidence of fumonisin exposure and the relevance that such exposure represents for Mexico.

Estudio microbiológico y calidad nutricional del ensilaje demaíz en dos ecorregiones de Colombia / Estudo microbiológico e qualidade nutricional da silagem de milho nas duas eco-regiõesda Colômbia / Study of microbiological and nutritional quality of corn silage in two Colombian ecosystems

El presente estudio buscó establecer los cambios en la concentración inicial de los géneros de bacteriasacido lácticas (BAL) en dos variedades de maíz utilizado para ensilar en clima cálido y frío respectivamente.Se realizaron microsilos de 1.5 kg para comparar la curva de crecimiento de cada uno de estos géneros alo largo del proceso, con mediciones en los días 0,1,2,3,4,7,14,28 y 56 de cerrado el silo. Se compararon lasvariaciones en el pH, la concentración de ácido acético, ácido láctico y azúcares reductores en los ensilajesde maíz y se evaluó la variación en la calidad nutricional del forraje fresco con respecto al ensilaje alfinal del proceso. Se observaron diferencias significativas (p<0.05) en las concentraciones iniciales deBAL entre los tratamientos, siendo mayor para el maíz proveniente de clima cálido. El pH para el maízde clima cálido disminuyó significativamente (p<0.05) más rápido que el de clima frio, sin embargo nose encontraron diferencias significativas en su concentración final. Se presentó un incremento en laspoblaciones de BAL, desde el inicio el proceso fermentativo y hasta que el pH alcanzó niveles por debajo decuatro, excepto para el género de pediococos los cuales alcanzaron su mayor crecimiento a pH cercano a3.9, siendo significativamente mayor para las BAL de clima cálido. Inicialmente los géneros de lactobacilosy leuconostoc fueron los más abundantes en ambos climas, seguidos por los streptococos y pediococos. Nose observaron diferencias significativas en las concentraciones de ácidos orgánicos, ni azúcares reductoresentre tratamientos. La calidad nutricional de los ensilajes no varió con respecto al forraje fresco, indicandoun óptimo proceso de ensilaje en donde las perdidas de nutrientes fueron mínimas para ambos climas.

Initial concentration of the most important genus of lactic acid bacteria (LAB) in two maize varieties(warm and cold climate respectively) was evaluated. Growth rate for each genus throughout the process wascompared at 0.1.2.3.4.7.14.28 and 56 days from silage sealed. Variation in pH, acetic acid, lactic acid andreducer sugars concentration were compared within silos. Nutritional quality between fresh forage and finalsilage was also evaluated. Significant differences (p<0.05) were found in the initial concentrations of LABbetween treatments, being greater for warm climate. pH value in this treatment diminished significantly(p<0.05) faster than the one of cold climate, although there were not significant differences in their finalconcentration. An increase in the LAB populations was observed from the fermentation beginning untilpH reached levels below four, except for pediococci genus who reached their greater growth at pH near3,9 being significantly greater for warm climate LAB. Initially the Lactobacilli and Leuconostoc genushad more concentration in both climates, followed by the Streptococci and pediococci. There were notdifferences in the organic acid concentrations, nor reducer sugars between treatments. Silage Nutritionalquality was similar to fresh forage, indicating an optimal conservation process.

O presente estudo procurou estabelecer as mudanças na concentração inicial dos gêneros de bactériasacido lácticas (BAL) em duas variedades de milho usado para silagem de clima quente e frio. Realizaramsemicrosilos de 2 kg para comparar a curva de crescimento da cada um destes gêneros ao longo doprocesso, com medições nos dias 0,1,2,3,4,7,14,28 e 56 de fechado o silo. Compararam-se as variações nopH, a concentração de acido acético, acido láctico e açúcares redutores na silagem de milho. Observaramsediferenças significativas (P<0.05) nas concentrações iniciais de BAL entre os tratamentos, sendomaior para o milho de clima quente. O pH para o milho de clima quente diminuiu significativamente(p<0.05) mais rápido do que o clima frio, no entanto não se encontraram diferenças significativas emsua concentração final. Apresentou-se um incremento nas populações de BAL, desde o início o processode fermentação e até que o pH alcançou níveis por embaixo de 4, exceto para o gênero pediococos osquais atingiram seu maior crescimento a pH próximo a 3.9, sendo significativamente maior para as BALde clima quente. Inicialmente os gêneros de lactobacilos e leuconostoc foram os mais abundantes emambos climas, seguidos pelos streptococos e pediococos. Não se observaram diferenças significativas nasconcentrações de ácidos orgânicos, nem açúcares redutores entre tratamentos.

Differences in intracellular localization of corn stunt spiroplasmas in magnesium treated maize

Maize plants infected with Spiroplasma kunkelii show symptoms similar to that of plants in a magnesium-deficient soil, and it has been shown that the spiroplasma alters the plants' magnesium absorption. In the current study we compared changes associated to either spiroplasma infection, two soil magnesium levels and their combinations. Plant symptoms were recorded and correlated with transmission electron microscopy observations. Plants grown on a high magnesium treatment showed no macroscopical alterations nor organelle ultrastructural alterations, while plants on a low magnesium treatment showed macroscopical vein yellowing and, ultrastructurally, they had most chloroplasts and mitochondrial membranes altered. Infected plants on a low magnesium treatment had an ageing aspect, ultrastructurally showed chloroplast s and mitochondrial alterations similar to those non-infected and grown on a low magnesium treatment, and spiroplasma cells were found in phloem cells, but outside their cytoplasm. Infected plants on a high magnesium treatment showed similar symptoms and ultrastructural alterations as either non-infected plants on the low magnesium treatment or in infected plants on the low magnesium treatment, but differ from them in that the spiroplasma cells were located inside the cytoplasm. Results suggest that magnesium is involved in the plant-pathogen interaction.

Comparative study of the major Iranian cereal cultivars and some selected spices in relation to support Aspergillus parasiticus growth and aflatoxin production

Aflatoxins are toxic fungal metabolites enable to contaminate a wide range of natural substrates. This contamination can be host-specific for different plant species. In this study, the ability of a toxigenic Aspergillus parasiticus to produce various aflatoxins on major Iranian cereals was evaluated with special focus on plant susceptibility to toxin production at cultivar level. Aspergillus parasiticus cultured on major Iranian cereal cultivars and some selected spices was incubated in shaking condition at 28?C for 6 days. The concentration of aflatoxins B1 and total [B1, B2, G1 and G2] was measured by thin layer chromatography. The amounts of aflatoxin B1 produced on maize, wheat and rice cultivars were in the ranges of 1.0-33.9, 41.9-193.7, and 39.1-82.3 micro g/g fungal weight, respectively. Interestingly, genetically modified Bacillus thuringiensis rice [GM rice] of Tarom Molaii cultivar examined for the first time in this study showed less susceptibility to aflatoxin production in comparison with its normal counterpart [P < 0.05]. The mean of aflatoxin production on maize cultivars was less than both wheat and rice cultivars that indicates considerable resistance of maize to aflatoxin compared with two other cereals. Unlike to Cuminum cyminum, both Helianthus annuus and Carum carvi seeds were highly resistant to aflatoxin production. These results indicate that inter- and intra-species differences exist in susceptibility of the major Iranian cereals as well as spices tested to A. parasiticus growth and aflatoxin production. Further studies are recommended to determine resistance markers of selected cultivars of Iranian cereals

Poblaciones de Aspergillus en semillas de maíz y soja de importación Argentina: énfasis en la sección Flavi / Aspergillus population in maize and soja seed imported from Argentina: ephasis on section Flavi

Durante un período de 5 meses se realizaron muestreos seriados en granos de maíz y soja de procedencia Argentina para estudiar la presencia de especies del género Aspergillus (en especial los de la sección Flavi). Para ambos tipos de granos se tomaron 10 muestras mensuales obtenidas de un puerto terrestre (Los Andes, Chile), desde submuestras transportadas en bolsas plásticas y proporcionadas por personal de control sanitario. Los granos se sembraron por duplicado en placas de Petri, utilizando 2 medios: agar malta sal (AMS) y agar agua sal (AAS). Todos los Aspergillus, fueron transferidos posteriormente en agar malta (AM) y agar czapek con extracto de levadura (CYA), para su determinación morfológica final, análisis poblacional, frecuencia de presencia en el tiempo y la posible producción de aflatoxinas (sección Flavi) en medio de cultivo específico. En maíz y soja y en ambos medios, se detectó un total de 1669 colonias del género Aspergillus (1193 en AMS y 476 en AAS), representando 18 taxa, (17 en maíz y 15 en soja), éstos fueron en órden decreciente: Aspergillus flavus, Eurotium amstelodami, E. rubrum, A.ellipticus, A.niger, A.candidus, A.ochraceus, A.terreus, A.versicolor, A.glaucus, A. tamarii, A.clavatus, A.ostianus, A. sydowii, A. fumigatus, A.parasiticus, A.wentii y A. sclerotiorum. Los 5 primeros taxa representaron el 85,7 por ciento de la presencia total. En general en maíz y soja la especie dominante fue A. flavus, mientras E. amstelodami y E. rubrum fueron más frecuentes en soja. Los valores más altos de presencia en maíz fueron en julio y en soja en noviembre. A.flavus presentó alta dominancia en ambos granos, seguida con baja frecuencia de A.tamarii y A. parasiticus. Para un análisis morfológico poblacional se seleccionaron al azar 50 cepas de A. flavus de todos los subtratos y muestras. En AM y CYA, se observaron cabezas radiadas a columnareslaxas mayoritariamente, aproximadamente la mitad de las cepas presentaron cabezas biseriadas y los...

Serial sampling of maize and soja grainsimported from Argentina were carried out for five months in order to study the occurrence of Aspergillus species (mainly those of Flavi section). For both kind of grains, ten monthly samples collected from a terrestrial port (Los Andes, Chile) were taken from subsamples transferred in plastic bags and supplied by sanitary control personnel. Grains were cultured induplicate on Petri dishes by using two media: malt salt agar (AMS)and salt water agar (AAS). All Aspergillusdetected were lately transferred in malt agar (AM) and czapek agar added with yeast extract (CYA) to determine its ultimate morphological character,population analysis, frequency of occurrence in time and possible production of aflotoxins in Flavi sectionin a particular medium of culture.In maize and soja and in both media,1669 colonies of the genus Aspergillus(1193 in AMS and 476 in AAS) was detected, representing 18 taxa, (17 in maize and 15 in soja), which in decreasing order were:Aspergillus flavus, Eurotium amstelodami, E.rubrum, A.ellipticus, A.niger, A.candidus, A.ochraceus, A.terreus, A.versicolor,A.glaucus, A.tamarii, A.clavatus, A.ostianus, A.sydowii, Afumigatus, A.parasiticus, A.wentii and A.sclerotium. The first five taxa represented 85.7 percent of the overall total. In general, the dominant species was A.flavus in maize and soja, whereas E.amstelodamiand E.rubrum were most frequent in soja. Highest values of occurrence in maize were in july and in november, in soja. A.flavus exhibited high dominancein both grains followed by a low frequency of A.tamarii and A.parasiticus. Fifty strains of A.flavus were randomly selected from every substrate and sample in order to carry out a population analysis. In AM and CYA, radiated heads to columnar laxa were mostly observed, about half strains exhibited biserial heads whereas 7-14day conidia (measured with an image processer) did not reveal any further change in...

Avaliação da qualidade microbiológica de minimilho (Zea mays) minimamente processado / Evaluation of microbiological quality of baby corn (Zea mays) minimally processed

Visto que a popularidade de frutas e hortaliças minimamente processadas tem aumentado nos últimos anos devido aos aspectos de conveniência e qualidade, estudou-se o aspecto microbiológico de minimilho minimammente processado e tratado com lactato de cálcio e ácido ascórbico, acondicionado em embalagens plásticas para alimentos, durante 12 dias, sendo a análise realizada de 3 em 3 dias. A análise microbiológica detectou presença do grupo fungos filamentosos e leveduras e contagem de microrganismos psicrotróficos. Quanto aos grupos coliformes totais e fecais, nada foi encontrado, indicando que o processamento foi realizado em boas condições higiênicas.