Potencial antagonista e controle in vitro de Alternaria solani por fungos sapróbios

Abstract

Alternaria solani, the etiological agent of early blight, is considered a phytopathogen of great economic impact on tomato crop, causing great losses to farmers. The aim of this study was to assess the antagonistic potential for direct confrontation, the production of volatile compounds and the in vitro antimicrobial activity of saprobic fungal filtrate against A. solani. Thus, the phytopathogen A. solani was confronted with the saprobic fungi Volutella minima, Memnoniella echinata, M. levispora, Curvularia eragrostidis, C. inaequalis, Gonytrichum chlamydosporium, G. macrocladum, Pseudobotrytis terrestris, Pithomyces chartarum, Lappodochium lageniforme, Dictyochaeta simplex, Stachybotrys nephrosfora and S. globosa, to observe inhibition zone formation and aggressiveness of the fungi according to a score scale. The phytopathogen growth was also evaluated at the concentration of 20% to select the saprobe filtrate with antimicrobial activity. Subsequently, the selected saprobe filtrates were studied at the concentrations of 5; 10; 15 and 20%, evaluating the mycelial growth of A. solani. The saprobes L. lageniforme and G. macrocladum showed greater mycelial growth, compared to A. solani, at seven days after transferring the phytopathogen. At 15 days, only L. lageniforme contained the pathogen. In the direct confrontation test, the fungi L. lageniforme and G. macrocladum occupied a larger area on the Petri dish, in contrast to the pathogen. The fungal filtrates G. macrocladum, C. inaequalis, P. terretris, S. globosa and C. eragrostidis, at a concentration of 20%, promoted a reduction in the mycelial growth of A. solani by 34, 21, 19, 10 and 10%, respectively. Analyzing the effect of the filtrate concentrations on the mycelial growth of A. solani, dose-dependence was observed in all treatments, with maximum growth inhibition for filtrates of G. macrocladum, C. inaequalis, P. terretris, S. globosa and C. eragrostidis, respectively, at the concentration of 20%.