Abstract
Plant exposure to pathogens often triggers oxidative stress, marked by the accumulation of reactive oxygen species (ROS), particularly hydrogen peroxide (H_2 O_2). In this study, we investigated the oxidative stress response of six yam (Dioscorea spp.) landraces of Cross River origin when challenged with yam anthracnose disease (YAD), caused by Colletotrichum alatae. Six yam landraces were arranged in a Randomized Complete Block Design (RCBD) with three replications in a field trial using minisetts planted under natural anthracnose pressure to evaluate disease susceptibility. Disease severity was scored using a standardized scale, and resistance levels were inferred from symptom expression. To assess oxidative stress, 3,3'-Diaminobenzidine (DAB) staining assays were performed on leaf samples to visualize H_2 O_2 accumulation. The differential oxidative stress responses among landraces suggest that H_2 O_2 accumulation correlates with susceptibility to YAD. Yeibo exhibited minimal oxidative stress, with low H_2 O_2 accumulation and showed strong resistance to YAD. Okpolukata and Esange displayed intermediate H_2 O_2 levels, suggesting a balanced oxidative response. Results from the field showed that Esange was resistant, while Okpolukata was susceptible to YAD. Obuna Otayi Kabor and Efala showed high H_2 O_2accumulation and were highly susceptible to YAD. Ija demonstrated fluctuating H_2 O_2 levels but was classified as resistant under field conditions. Landraces like Yeibo, with lower oxidative stress, may possess more efficient antioxidant defense systems, contributing to better growth and yield. In contrast, excessive ROS in susceptible landraces may impair physiological functions, reducing productivity. Here, we show that hydrogen peroxide (H_2 O_2) was produced in susceptible yam landraces subjected to YAD under natural field conditions.