Local Trichoderma strains as a control strategy of complex black root rot disease of strawberry in Egypt

Abstract

Abstract Background Economics and human safety to avoid health risks caused by fungicides are materializing new era of biological pest control. Trichoderma species ranked high among other agents to control complex black root rot disease of strawberry caused by Fusarium solani, Rhizoctonia solani, and Pythium sp. Our study aimed to document the efficacy of local strains representing T. harzianum, T. viride, T. virinis, and T. koningii against such a disease. Materials/methods These strains were cultured separately on potato dextrose broth medium to test their inhibitory effect against strawberry black root rot in vitro and in vivo. Strawberry growth and yield were also assessed relative to the untreated check and the fungicide Actamyl. Activity of peroxidase and chitinase were measured in plant leaves using spectrophotometer. Results Each of the antagonistic fungal strains significantly reduced growth area of all pathogenic fungi collectively causing the disease. Trichoderma harzianum, T. viride, and T. koningii reduced the growth area more than 90.6% for all tested pathogenic fungi. Each species significantly reduced disease incidence and severity under field conditions. The highest reduction in the disease incidence and severity, 83.3 and 88.5% respectively, was attained by mixture of the four species. This mixture increased the strawberry fresh and dry weight by 83.3 and 176.9%, respectively, and the yield by 117.1%. All Trichoderma species tested significantly increased the activity of two plant defense-related enzymes of strawberry plants against the pathogens. Their mixture attained the highest increase of peroxidase and chitinase activity by 150 and 160.9%, respectively. Conclusions While the fungal mixture could considerably increase the strawberry fresh and dry weight as well as the yield, it suppressed the incidence and severity of the disease. So, integrated pest management in ways that make these biocontrol agents complementary or superior to chemical fungicides should further be examined against this disease.