The study investigates the effects of R. solani inoculation on the germination and early development of Lactuca sativa L. seeds using a low-cost, image-based monitoring system. Multiple cameras were deployed to continuously capture images of the germination process in both infected and control groups. The objective was to assess the impact of the pathogen by analyzing germination dynamics and growth over time. To achieve this, a novel image analysis pipeline was developed. The algorithm integrates both morphological and spatial features to identify and quantify individual seedlings, even under complex conditions where traditional image analyses fails. A key innovation of the method lies in its temporal integration: each analysis step considers not only the current status but also their developmental across prior time points. This approach enables robust discrimination of individual seedlings, especially when overlapping leaves significantly hinder object separation. The method demonstrated high accuracy in seedling counting and vigor assessment, even in challenging scenarios characterized by dense and intertwined growth. Results confirm that R. solani infection significantly reduces germination rates and early seedling vigor. The study also validates the feasibility of combining low-cost imaging hardware with advanced computational tools to obtain phenotyping data in a non-destructive and scalable manner. The temporal integration enabled accurate quantification of germinated seeds and precise determination of seedling emergence timing. This approach proved particularly effective in later stages of the experiment, where conventional segmentation techniques failed due to overlapping or intertwined seedlings, making accurate counting. The method achieved a coefficient of determination of 0.98 and a root mean square error (RMSE) of 1.12, demonstrating its robustness and reliability.