Interactions between Exserohilum turcicum and maize seeds: detection, effects and transmission of the pathogen

Abstract

Due to the great economic and social importance of corn, it is important to study the performance of its seeds in the presence of the pathogen Exserohilum turcicum, prevalent in most regions producing this crop. The lack of more specific information on the relationship between this pathogen and corn seeds in Brazil is still a problem. In view of the growing importance of this pathosystem, the purpose of this research was to evaluate the presence of the pathogen, its effects on the performance and transmission from contaminated seeds and development of a protocol for molecular detection of the fungus in corn seeds. Seeds of a susceptible hybrid of corn were inoculated to obtain four levels of inoculum (N24, N48, N72 and N96) with two isolates of E. turcicum. It was possible to detect the presence of the fungus, in almost all inoculum potentials using the conventional PCR technique, in the inoculated corn seeds, using a primer developed to quantify the same pathogen in corn leaves. The primer pair used is specific for E. turcicum and is capable of detecting the pathogen in concentrations up to 0.0000147ng / μL. In analyzes using the real-time PCR technique, it is possible to quantify the genomic DNA present in the inoculated corn seeds with minimum incidence levels of 0.5%. The effects of the pathogen on seed performance were evaluated by germination, health and vigor tests. The presence of E. turcicum isolates in corn seeds was detrimental to the development of seeds inoculated with this pathogen, with variations between the factors used for this type of evaluation. The height of plants from seeds inoculated with both isolates of E. turcicum was not affected, contrary to vigor and germination, mainly in the treatment of greater inoculum level. Evaluating plants from the inoculated seeds, it was observed that the percentage of death in pre-emergence increased with the increase of the level of inoculum in the seeds, regardless of the isolate and the temperature of cultivation. The rate of total transmission of the pathogen in study was 55.27%, which occurred at the highest level of inoculum present in the seed.