Comportamento de híbridos de milho inoculados com os fungos causadores do complexo grãos ardidos e associação com parâmetros químicos e bioquímicos

Abstract

The goal of this work was to evaluate corn hybrids developed by seed companies in Brazil, inoculated and not inoculated with fungi Fusarium verticilioides, Stenocarpella maydis and Stenocarpella macrospora, under conventional and direct sowing cropping systems, in two crop seasons and verify the association with chemical and biochemical grain characteristics, which can be directly related to tolerance to the fungi. Grain yield, percentage of rotten grain, fatty acids levels, heat resistant proteins, and lipoxygenase enzyme activity were measured. The significance of the contrast between hybrids considered resistant versus susceptible, for grain yield and rotten grains percentage identified genotypes with higher tolerance the fungi F. verticilioides, S. maydis and S. macrospora. Grain yield and the percentage of rotten grains were influenced by: hybrid type, crop season and by artificial fungi inoculations, being more pronounced in plants coming from direct planting system. There is no association between grain yield and percentage of rotten grains which demonstrated that losses caused by incidence of grain rot disease in corn are not a quantitative character. There are differences in levels of linoleic acid among corn hybrids groups studied, with higher values being obtained in tolerant to grain rot complex. Based on concentration of heat resistant protein fractions it was possible to verify the presence of specific bands in the tolerant hybrids and more specifically in those of 50 kDa molecular weight. The electrophoresis profiles for lipoxygenase reveal higher band intensity for the hybrids tolerant to the corn grain rot causing fungi.