Fig. 3.

Comparison of the resistance to Phytophthora root and stem rot among 20 soybean cultivars at different plant ages. Soybean plants were grown for 14, 21, or 28 days and then inoculated with one of 17 Phytophthora sojae isolates. The boxplots were drawn based on the rates of dead plants (%) for the inoculation of plants grown for 14 days (A), 21 days (B), or 28 days (C). The open diamond in the plots indicates the average rate of dead plants for each cultivar. The mean values for each growth period were analyzed with Tukey’s honestly significant difference test. The same letters in boxplots indicate the mean values are not significantly different among the three growth periods (p < 0.01).