Fig. 2. Principal coordinate analysis of individuals from seven tropical maize populations based on modified Roger's distance. PC1 and PC2 are the first and second principal coordinate, respectively. Heterotic Group A (Pop21, Pop22, and Pool24, open squares), Heterotic Group B (Pop25, filled triangles; Pop32, open triangles), and populations not yet assigned to heterotic groups (Pop29, open diamonds; Pop43, filled diamonds) are shown.