Selection of potential biological control of exserohilum turcicumwith epiphytic microorganisms from maize

Abstract

The aims of this study were to select microbial isolates from phyllosphere of maiz eand to examine their antagonistic activity against Exserohilum turcicum. Selection was per-formed through the ability of isolates to compete with the pathogen using an index of dominance and to affect growth parameters of E. turcicum. Most of the epiphytic populations obtained forthe screening were bacteria. These isolates were found in the order of 6 log CFU/g of leaf fresh weight. According to similar morphological characteristics and staining, 44 out of 111 isolates obtained were selected for testing antagonistic effects. At water potential, ψ, −1.38 MPa and−4.19 MPa, three Bacillus isolates showed dominance at a distance (5/0) and a significant reduc-tion of growth rate of the pathogen. Three Bacillus isolates only decreased the growth rate of E. turcicum at −1.38 MPa. At −4.19 MPa the growth rate decreased with three isolates of Pantoea and three Bacillus. In this study a negative and significant correlation was observedbetween the growth rate of E. turcicum and the dominance index in the interaction of thepathogen with some bacteria. These results show that with decreasing growth rate of the pathogen the dominance index of the interaction increases. Eleven potential bio control agents against E. turcicum were selected.