Abstract
Phytophthora infestans is the causative agent of late blight and one of the most economically significant diseases of Solanaceous crops. Detached leaf assays are useful tools to efficiently assess how differing environmental conditions and management controls may affect the infection process and overall disease severity. However, these protocols need refinement to more fully reflect natural infection processes in the field. In a detached leaf assay experiment to study the infection rate and the development of late blight as affected by initial sporangia concentration, greenhouse-grown tomato (Solanum lycopersicum), potato (Solanum tuberosum), and eggplant (Solanum melongena) were used. The study showed a clear dose-dependent response: high concentrations of sporangia (50,000/ml and 10,000/ml) caused rapid and extensive spot formation, while at low concentrations (2,000/ml), symptoms were mild and control leaves remained healthy. The spread of the spots and the percentage of the affected area were assessed using the ImageJ program for 7 days. The results confirm the effectiveness of the detached leaf method for quantifying pathogen aggressiveness and provide insight into the early stages of host-pathogen interaction.