Effects of some biological agents on the growth and biochemical parameters of tomato plants infected with Alternaria solani (Ellis & Martin) Sorauer

The effects of three biological control agents (BCAs) including Funneliformis mosseae BEG12 (FM) as arbuscular mycorrhizal fungi (AMF), Bacillus velezensis V40K2 (BV) as plant growth-promoter rhizobacterium (PGPR) and Trichoderma viride NTC2 (TV) as plant growth-promoter fungus (PGPF) against Alternaria solani (Ellis & Martin) Sorauer (AS) were studied. For this purpose, 2.5 g FM (150 spores g(-1)) was inoculated in the seed bed. After seedling emergence, TV (1 x 10(6) spor/ml) as well as BV (1 x 10(8) CFU mL(-1)) were inoculated. Then, onee week after TV and BV treatments, 1 x 10(6) spore mL(-1) of AS was inoculated by spraying on each plant. It was found that the single, double and triple combinations of these selected biocontrol agents against pathogen generally suppressed the disease severity and stimulated the plant growth. Compared to other treatments without any positive effects, the use of the AM fungal treatment had positive effects on the total phenolic content as well as antioxidant activity. Also, the highest total phosphorus content was observed in FM + TV + AS (7.3%) and AS (8.0%) treatments. No statistically significant difference was observed among the combinations in terms of the AMF colonization rate and soil spore density, which showing that mycorrhizal dependency did not occur in the FM + TV + BV + AS treatment (-6.7). However, compared to the control group, this treatment did not affect on disease suppression and plant growth parameters.