ABSTRACT. The objective of this study was to evaluate the transmissibility of F. verticillioides, in corn seeds, when inoculated in different phenological stages. The plants were inoculated with the pathogen at the following stages: V7, V9, R1, R2, R4, and R6. The experiments were conducted in pots, in a completely randomized design, with six replications. The fungus infection rate in the seeds was verified through the health test (Blotter Test). The significance of the contrast between the phenological stages and in the two experiments (rainy season and dry season), and productivity showed plant-seed transmission of F. verticillioides in all phenological stages. The PCR technique was able to reveal up to the lowest level, 1% incidence of F. verticillioides in corn seeds. There was a significant difference between the times of plant inoculation and the incidence of the fungus in the seeds. Plants inoculated in the reproductive phase transmitted F. verticillioides for seeds with the highest rate of infection, in the two experiments, in the rainy season (V7 - 48; V9 - 46; R1 - 77.33; R2 - 84; R4 - 96; R6 - 96.67; and Test - 14.67%), and dry season (V7 - 46.67; V9 - 66; R1 - 75.33; R2 - 95.33; R4 - 98; and R6 - 97.33%). In this way, the present work demonstrated that in the reproductive phenological stages R2, R4, and R6, the corn plant was more susceptible to infection with F. verticillioides, and that it also resulted in a decrease in grain productivity.

Resumo Existem poucos estudos relacionados ao impacto de queimadas sobre os fungos habitantes do solo presente no cerrado. Objetivou-se com este trabalho identificar a micoflora presente em amostras de solos, antes e após o processo de queimada em duas profundidades, observando a interferência deste processo na população de fungos habitantes do solo. As amostras foram coletadas em uma área, no município de Jaú do Tocantins, Estado do Tocantins. Foram instalados bioensaios em delineamento experimental inteiramente casualizado, com quatro repetições e cinco tratamentos, representados por diferentes concentrações de solução do solo. A identificação dos fungos foi feita, em nível de gênero, de acordo com suas estruturas morfológicas formadas em meio de cultura, através de observações em microscópio ótico. Na área antes da queimada, observou-se a presença de maior diversidade de gêneros e quantidade de colônias fúngicas. O contrário foi constatado na área posteriormente submetida à queimada, que apresentou menor número de colônias fúngicas. Dos gêneros identificados, destacaram-se Aspergillus, Penicillium, Cladosporium, Fusarium, Mucor, Pythium e Trichoderma, que apresentaram maior número de colônias em quantidades representativas. Observou-se ainda uma redução em torno de 45% na população de fungos antagonistas. Foi possível constatar que o uso do fogo na vegetação influenciou negativamente as populações microbianas presentes nas camadas mais superficiais do solo de cerrado.

Abstract There are few studies related to the impact of burnings on soil fungi present in the cerrado. The aim of this work was identifying the mycoflora in cerrado soil samples before and after burning process at two depths; observing the interference of this process in the fungi soil inhabitants population. The samples were collected in area, in the municipality of Jaú do Tocantins, State of Tocantins. Bioassays were installed in a completely randomized experimental design, with four replicates and five treatments, represented by different concentrations of soil solution. The identification of the fungi was made at the genus level according to their morphological structures formed in culture medium through optical microscope observations. In the before burning area we observed greatest diversity of genera and fungi colonies. The opposite was found in the area subsequently submitted to the burning process, showing minor fungal colonies. Among the genera identified, Aspergillus, Penicillium, Cladosporium, Fusarium, Mucor, Pythium and Trichoderma were the most representative colonies. We observed a reduction of 45% approximately in the population of antagonistic fungi. It was found that the use of fire in vegetation negatively influenced microbial populations present in the surface layers of cerrado soil.