Accumulation of reactive oxygen species (ROS) after soybean cyst nematode (SCN) infection in the roots of Peking and PI88788 (resistant) and Williams 82 (susceptible) soybeans assayed at 5, 10, and 15 days post infection. H2O2 accumulation was determined at 5 (A), 10 (B), and 15 (C) days after SCN infection. C and N represent uninfected and infected roots, respectively. FW: fresh weight. Values are mean ± standard error of combined data from two separate three-fold replicated experiments. * indicates statistically significant differences between uninfected and infected roots (p < 0.05).