Physiological and biochemical responses of Alternaria alternata infected tomato to Trichoderma harzianum and Chaetomium globosum application

Early blight disease caused by Alternaria alternata severely affects tomato growth and productivity. Therefore, to substantiate the increasing demand for tomato fruits, it is essential to explore new strategies to combat the negative effects of the disease. The objectives of this study were to (1) evaluate the effectiveness of Trichoderma harzianum and Chaetomium globosum on disease suppression, (2) determine the influence of the biostimulants on tomato physiological and biochemical traits, and (3) assess the plant innate defense response. In pot experiment, fungal agents were applied to tomato-challenged plants as soil drenches in 8 different treatments. Results revealed that all inoculated plants (T3, T4, T5) exhibited a substantial reduction of disease incidence and severity reached 34 %, 35 %, 26 % and 31 %, 31 %, 16 % respectively compared to infected plants (T2). Such disease stress tolerance was correlated with a significant escalation of tomato growth attributes i.e. plant length, plant FW and DW. The obtained results were consolidated with a noticeable enhancement of the photosynthetic pigments (chlorophyll a, b, and carotenoids) as well as the nitrogen, phosphorus, and potassium (NPK) uptake. Furthermore, a significant reduction in cell stress markers like hydrogen peroxide (H2O2) production, membrane ion leakage and lipid peroxidation (MDA) was detected. Moreover, all enhancements of tomato physiological traits were significantly concurred with up-regulation of plant defense enzymes like peroxidase (POX), polyphenol oxidase (PPO), superoxide dismutase (SOD) and catalase (CAT) 24 h post inoculation reached 3.4, 1.3 1.2, 1.2 folds respectively. Furthermore, both biostimulants were examined for extracellular indole-3-acetic acid (IAA) production. T. harzianum expressed a significant ability for IAA production over C. globosum. Remarkably, the biostimulants consortium showed a significant ability to protect tomato plants. Hence, application of the biostimulants could be a feasible approach for achieving early blight disease resistance. (c) 2024 SAAB. Published by Elsevier B.V. All rights reserved.