Scanning electron microscopy applied to seed-borne fungi examination

Abstract

he aim of this study was to test the standard scanning electron microscopy(SEM) as a potential alternative to study seed-borne fungi in seeds, by two different conditions ofblotter test and water restriction treatment. In the blotter test, seeds were subjected to conditionsthat enabled pathogen growth and expression, whereas the water restriction method consisted inpreventing seed germination during the incubation period, resulting in the artificial inoculation offungi. In the first condition, seeds of common bean (Phaseolus vulgaris L.), maize (Zea mays L.),and cotton (Gossypium hirsutum L.) were submitted to the standard blotter test and then preparedand observed with SEM. In the second condition, seeds of cotton (G. hirsutum), soybean (Glycinemax L.), and common bean (P. vulgaris L.) were, respectively, inoculated with Colletotrichum gossy-pii var. cephalosporioides, Colletotrichum truncatum, and Colletotrichum lindemuthianum by thewater restriction technique, followed by preparation and observation with SEM. The standardSEM methodology was adopted to prepare the specimens. Considering the seeds submitted to theblotter test, it was possible to identify Fusarium sp. on maize, C. gossypii var. cephalosporioides,and Fusarium oxysporum on cotton, Aspergillus flavus, Penicillium sp., Rhizopus sp., and Mucorsp. on common bean. Structures of C. gossypii var. cephalosporioides, C. truncatum, and C. linde-muthianum were observed in the surface of inoculated seeds