Determination of biological control possibilities of Alternaria solani (Ell. and G. Martin) sor. isolated from tomato fields in van

In this study, it was aimed to determine the possibilities of biological control against Altenaria solani (Ell. and G. Martin) Sor. (AS) which causes problems in tomato areas in Van. Ten isolates were selected from A. solani isolates identified in the scope of survey in Gevaş, Edremit and Erciş districts of Van. The selected isolates were subjected to pathogenicity test and EAb 1 isolate was determined as the most virulent pathogen. Three different biological control agents were used against this pathogen isolate. These were identified as (I) Glomus mosseae (Gm) selected from arbuscular mycorrhizal fungus (AMF), (II) Bacillus velezensis V40K2 isolate selected from plant growth promoting rhizobacteria (PGPR) antagonists and (III) Trichoderma viride NTC2 isolate selected from Trichoderma spp. It has been found that the single, double and triple combinations of the selected biocontrol agents with the pathogen generally suppress the disease severity and increase the plant growth. While total chlorophyll content did not change in all combinations, it was determined that total amount of phenolic substances increased in single combinations of antagonist microorganisms and antioxidant activity increased significantly in Gm treatment group compared to other applications. Total phosphorus content was generally increased in all combinations with AS and Gm compared to control group. While no statistically significant difference was observed between the treatment groups in terms of AMF colonization rate and soil spore density, it was found that mycorrhizal dependence did not occur in four combinations (Gm + NTC2 + V40K2 + AS). In addition, it was determined that this combination had no effect on disease severity and plant development compared to the control group.