Evaluating eco-friendly botanicals as alternatives to synthetic fungicides against the causal agent of early blight of Solanum melongena

Alternaria solani , causal agent of eggplant early blight, is an important airborne pathogen responsible annually of regrettable losses and reduction in total yield. Fungicide treatments are widely used being the most effective for controlling this disease. It is well acknowledged that the prolonged use of fungicides often causes health risks to human and increases environmental pollution. Different concentrations (5, 10 and 20%) of two aqueous extracts of Ocimum sanctum and Justicia adhatoda were compared with three fungicides (Score 250, 0.5 L/ha; Dithane M-45, 0.2 kg/hl; Folio Gold, 2 L/ha) for their inhibition of mycelial growth in vitro on PDA medium. Disease index (DI), disease severity index (DSI), percentage of leaf area covered by early blight (PLA), percent of plant mortality (PM), catalase (CAT) and peroxidase (POX) activities, superoxide dismutase (SOD), polyphenol-oxidase (PPO), total phenolic content (TPC) and total sugars (TS) were studied to determine the efficiency treatments from plant extract compared with the fungicide application under greenhouse conditions. The results revealed that Score 250 and aqueous O. sanctum extracts (at 20%) seemed to be the most effective under laboratory conditions with mycelial inhibition rate above 82%. In greenhouse experiments, the treatment of eggplant leaves with Score 250 and O. sanctum and J. adhatoda aqueous plant extracts at 20% generated the highest damage reduction (DI 0.374 units/mg protein/min), TPC (> 2.103 mg/g) and TS (> 2.075 mg/g) at 7 days after inoculation. O. sanctum and J. adhatoda at 20% reported positive effects on the inhibition of A. solani as an alternative and eco-friendly approach to fungicides, while preserving the environment. These extracts have a brilliant future in plant protection management to substitute the synthetic fungicides and radically change how we cooperatively and collectively manage our Planet.