Characterisation of Trichoderma sp. BI 7376 and Pseudomonas chlororaphis subsp. aurantiaca BI 7439 as maize seed treatment for commercial traits

In previous experiments, Trichoderma sp. BI 7376 and Pseudomonas chlororaphis subsp. aurantiaca BI 7439, applied as seed treatments, controlled soilborne Fusarium culmorum on maize. The current paper is focused on a deeper characterization of the effects of both strains. The experiments were conducted as pot tests with artificial inoculation of the substrate with F. culmorum, or with maize seed lots infected with Fusarium spp. When seeds were treated with Trichoderma strain BI 7376, Pseudomonas strain BI 7439 or with the chemical active ingredient thiram and stored before they were sown in substrate inoculated with F. culmorum, the protection by all agents declined. During the storage period of 211 days, the activity of thiram and Trichoderma strain BI 7376 dropped by about 38% and 57%, respectively. After 36 days of storage, Pseudomonas strain BI 7439 failed to provide any protection, which was obviously related to the observed total loss of viable cells of this agent. Moreover, we observed that both strains protected against soilborne F. subglutinans and F. verticillioides, showing that their activity was not limited to F. culmorum which was used in the previous experiments. Further, experiments with seed lots suspected or known to be infected with Fusarium species indicated that Trichoderma strain BI 7376 also controlled seedborne inoculum. When electron seed treatment was followed by application of Trichoderma strain BI 7376, both seed- and soilborne infections were controlled, showing that the concept of using a combination of a physical seed treatment and microbial antagonists appears feasible.