ABSTRACT
Con el objeto de caracterizar las poblaciones fúngicas, en particular las especies potencialmente micotoxigénicas, que pueden contaminar los granos de maíz almacenados en silos bolsa con un contenido de humedad superior al recomendado como seguro, se evaluaron 270 muestras extraídas al inicio, a los 90 días y al final de un período de almacenamiento de 5 meses. En dichas muestras se cuantificó e identificó la biota fúngica y se determinó la contaminación con fumonisinas y aflatoxinas. Asimismo, se evaluó el efecto de factores extrínsecos (ambiente), intrínsecos (granos) y tecnológicos (ubicación de los granos en el perfil del silo bolsa) sobre las poblaciones totales y micotoxigénicas. El pH de los granos y el nivel de O2 se redujeron significativamente a los 5 meses, mientras que la concentración de CO2 se incrementó en igual período. Los recuentos totales de la micobiota fueron significativamente mayores en los granos ubicados en el estrato superior del silo bolsa. Se identificaron especies micotoxigénicas de Fusarium, Aspergillus, Penicillium y Eurotium. La frecuencia de aislamiento de Fusarium verticillioides se redujo al final del almacenamiento y Aspergillus flavus solo se aisló en el inicio del almacenamiento. Los recuentos de Penicillium spp. y Eurotium spp. se incrementaron al final del almacenamiento. El 100 % de las muestras presentaron contaminación con fumonisinas, con niveles máximos de 5,707 mg/kg, mientras que las aflatoxinas contaminaron el 40 % de las muestras con niveles máximos de 0,0008 mg/kg. Las condiciones ambientales y de sustrato generadas durante el almacenamiento produjeron cambios en la composición de las poblaciones fúngicas y limitaron el desarrollo de hongos micotoxigénicos y la producción de micotoxinas.
In order to determine the behavior of mycotoxin-producing fungal populations linked with silobags stored corn grains with a moisture content greater at the recommended as safe, 270 samples taken in three times (beginning, 90 days, final) over a five month period of storage were evaluated. The fungal biota was quantified and identified and the contamination with fumonisin and aflatoxin was determined. Extrinsic factors (environment), intrinsic factors (grains) and technological factors (location of the grains in the profile of silobag) were taken into account to evaluate the presence and quantity of total and mycotoxigenic fungal populations. The pH of grains and O2 levels were significantly reduced after five months, while CO2 concentration increased in the same period. The total counts of mycobiota were significantly higher in grains located in the top layer of silobag. Mycotoxigenic species of Fusarium, Aspergillus, Penicillium and Eurotium were identified. The frequency of isolation of Fusarium verticillioides decreased at the end of storage and Aspergillus flavus was isolated only at the beginning of storage. The counts of the Penicillium spp. and Eurotium spp. were increased at the end of storage. Fumonisin contamination was found in all the samples (100 %) with maximum levels of 5.707 mg/kg whereas aflatoxin contaminated only 40 % with maximum levels of 0.0008 mg/kg. The environmental and substrate conditions generated during the storage limited the development of mycotoxigenic fungi and mycotoxin production.
Subject(s)
Zea mays , Aflatoxins/isolation & purification , Aflatoxins/adverse effects , Fumonisins/isolation & purification , Fumonisins/adverse effects , Mycotoxins/isolation & purification , Penicillium/isolation & purification , Aspergillus/isolation & purification , Biotic Factors/analysis , Eurotium/isolation & purification , Biota , Fusarium/isolation & purification , Mycotoxins/adverse effectsABSTRACT
Ear rots caused by Fusarium spp. are among the main fungal diseases that contribute to poor quality and the contamination of maize grains with mycotoxins. This study aimed to determine the visual incidence of fungal-damaged kernels (FDKs), the incidence of two main Gibberella (a teleomorph of Fusarium) complexes (G. fujikuroi and G. zeae) associated with maize using a seed health blotter test, and the fumonisin levels, using high performance liquid chromatography, in samples of maize grains grown across 23 municipalities during the 2008/09 and 2009/10 growing seasons. Additionally, 104 strains that were representative of all of the analysed samples were identified to species using PCR assays. The mean FDK was seven per cent, and only six of the samples had levels greater than six per cent. Fusarium spp. of the G. fujikuroi complex were present in 96% of the samples, and G. zeae was present in 18% of the samples (5/27). The mean incidence of G. fujikuroi was 58%, and the incidence of G. zeae varied from 2 to 6%. FB1 was found in 58.6%, FB2 in 37.9%, and both toxins in 37.9% of the samples. The FB1 and FB2 levels were below the quantification limits for 41.3% of the samples, and the mean FB1 levels (0.66 µg/g) were higher than the mean FB2 levels (0.42 µg/g). The PCR identification separated the 104 isolates into three of the G. fujikuroi complex: F. verticillioides (76%), F. subglutinans (4%) and F. proliferatum (2%); and G. zeae (anamorph = F. graminearum) (18%). Our results confirmed the dominance of F. verticillioides, similar to other regions of Brazil, but they differed due to the relatively higher incidence of F. graminearum. Total fumonisin levels were below the maximum limit determined by current Brazilian regulations.