Biological Control of Alternaria solani by Trichoderma longibrachiatum in Tomato Under Greenhouse Conditions

Abstract

Early blight caused by Alternaria solani is a destructive foliar disease limiting tomato productivity under protected cultivation systems. Greenhouse experiments were conducted to evaluate the biological control potential of Trichoderma longibrachiatum against A. solani and its influence on disease suppression and plant growth performance in tomato. Antagonistic activity of T. longibrachiatum was initially assessed under laboratory conditions using dual culture assays, where significant inhibition of pathogen mycelial growth was observed through competition, hyphal interaction, and production of antifungal metabolites. Greenhouse trials were subsequently performed using tomato plants treated with spore suspensions of the biocontrol agent prior to pathogen inoculation. Plants treated with T. longibrachiatum showed substantial reduction in disease incidence and severity compared with untreated infected controls. Suppression of lesion expansion and delayed symptom development indicated effective antagonistic action of the bioagent against the pathogen. In addition to disease reduction, treated plants exhibited improved growth parameters including plant height, root development, biomass accumulation, and leaf number, suggesting a plant growth–promoting effect of the antagonist. Environmental conditions within the greenhouse, particularly moderate temperature and high relative humidity, favored pathogen development, however, application of T. longibrachiatum significantly restricted fungal colonization and sporulation on infected tissues. The biocontrol agent demonstrated stable rhizosphere establishment and compatibility with greenhouse cultivation practices. Results indicate that T. longibrachiatum possesses strong potential as an eco-friendly alternative to synthetic fungicides for management of tomato early blight under protected cultivation systems.