Effects of a fraction from maize root exudates on haploid strains of Sporisorium reilianum f. sp zeae

Sporisorium reilianum f. sp. zeae is the causal agent of head smut of maize . Although the main symptom of this disease is the formation of a black fun gal sorus on the reproductive parts of the maize, the infection always occu rs via the roots. Early infection stages are characterised by a hyphal prol iferation of the fungus around the roots. In this paper, we describe effect s of a fraction extracted from maize root exudates on growth of S. reilianu m f. sp. zeae. The fungus grew as a yeast form on artificial medium, but in presence of these fractions, some yeasts switched to a hyphal form. In add ition, an increased proliferation of the yeast form was also observed with exudates from a variety of maize susceptible to head smut. In the presence of exudates obtained from a tolerant variety of maize, proliferation of the yeast form was inhibited, whereas the induction of yeast-hypha transition was always observed. These results indicated that some molecules in root ex udates could play a role in the pre-infectious stage between maize and S. r eilianum f. sp. zeae.