Possibilites of using some endophytic Pseudomonas and bacillus species in the management of Erwinia persicina soft rot in lettuce

In this thesis, it was investigated the possibilities of usage of some Pseudomonas spp and Bacillus spp isolates as an alternative management strategy for the causal agent of soft rot in lettuce. In this scope, 23 Pseudomonas spp and 16 Bacillus spp which were obtained from healthy lettuce plants, were selected from the Plant Related Bacterial Culture Collection of Ankara University Faculty of Agriculture Department of Plant Protection.In addition to these 39 isolates, 6 bacterial endophyes were isolated from healty tomato seedlings, variety Şencan. To assess the efficacy of these endophytic bacteria, in vitro testing against the pathogenic E. persicina isolate Ep_Tr2 was conducted using the disk diffusion method. Six bacterial strains were chosen based on the results of the disk diffusion method and were employed in the in vivo experiments. In vivo experiments were conducted in a controlled climate room in sterille pots which consist of sterilized turf. During the in vivo experiments, a suspension of the selected endophytic bacteria at a concentration of 109 CFU/mL was applied to healthy lettuce seedlings using two different methods: either by spreading it onto the leaves or by immersing the roots in it. To assess the application time on symptom development, selected endophytic bacteria were applied in four different times. Healthy lettuce seedlings were applied by the endophytes 72, 48, 24 hours before pathogen inoculation and at the same time with the pathogen. The results were assessed on a scale ranging from 0 to 4, based on the severity of symptom formation observed 14 days later, and were subjected to statistical analysis using one-way ANOVA. The results indicated that when B. mojavensis Bmj1 and P. putida L2B were applied to the leaves of the lettuce seedlings 24 hours before the inoculation of the pathogenic bacterium, there was a significant and statistically noticeable reduction in symptom formation. The results scored the statistical significance of the 24-hour prior application. However, the application of these bacterial strains to the root did not yield positive outcomes in terms of disease prevention or symptom reduction. These findings represent the initial research results in our exploration of an alternative approach to combat the multi-host pathogenic Erwinia persicina in lettuce.