Aspectos morfológicos e moleculares, potencial toxigênico e relações biológicas de Aspergillus seção Flavi em amendoim

Abstract

The agriculture is the most important sector in Brazil´s economy and it contributes with 30% of the national GDP (Gross Domestic Product). Brazilian´s Agriculture is in constant development, as consequence, there is a growing concern about the quality of the products that are offered. The mycotoxins presence, produced mainly in the Aspergillus Flavi section, in peanuts deserves special attention, because it can cause risks to the human and animal health. The aim of the work was to identify the Aspergillus Flavi section species present in peanut grains from different Brazilian regions, using molecular and morphological tools, and the production of aflatoxins B1, B2, G1 and G2 these isolates. The biological relations between peanut seeds and Aspergillus flavus were verified checking the effects of seeds inoculated with different potential and stored under natural and controlled environmental and the transmission rate of A. flavus seeds to plants. The morphological identification was performed in 107 isolated fungus and showed that most of the species found in the analyses were: A. flavus,A. parasiticus and A. tamarii. In the molecular analysis was possible to confirm these species and to identify others, such as A. caelatus and A. minisclerotigenes. The aflatoxin analysis showed that 87% of the isolated fungus are producers of aflatoxin B1 and B2, and 5.06% of isolated fungus are producer of aflatoxin G1 and G2. The results of the biological relations studies showed that in general the highest inoculum potential (seeds exposure by 96 hours in the pathogen colony) caused high damage to the seeds, in both environments (stored and non-stored). According to the results, the different inoculums potential affected the germination test and the fungal incidence and showed proportional increase of the inoculum potential. In the natural conditions the seed germination percentage was lower, while the pathogen incidence was higher in the seeds. However, these parameters were reduced in both storage conditions and the seed vigor was significantly affected. The fungal transmission of contaminated seeds was 21%, being isolated from the cotyledonary insertion of plants and the highest inoculum potential used for this study. In the present work, we conclude that there are different Aspergillus species of the section Flavi associated with the peanut culture and the biggest part of the isolated fungus that were studied are aflatoxin producers. The effects caused by the pathogen on the peanut seeds were drastic, mainly in the higher inoculum potential level in the seeds, and the transmission rate was 21% in the seeds exposed to the pathogen for a longer period of time.