Studies on relations of SSR markers and heterosis in maize

Seventeen elite maize (Zea mays) inbred lines were assayed for polymorphism at 71 SSR marker loci by using polyacrylamide gels. The 384 alleles identified were served as raw data for estimating genetic similarities among these lines. The average number of alleles per SSR locus was 5.4 with a range 2 to 12. Polymorphic index content (PIC, a measure of discrimination ability) values varied from 0.278 to 0.896 with an average of 0.672. Cluster analysis by UPGMA placed the inbred lines in six clusters corresponding to the heterotic groups determined by their pedigree analysis. Significant coefficients were existed between the genetic distance of SSR molecular markers and the heterosis of kernel yield among the inbred lines, but the value coefficents were small (0.443 and 0.310 respectively). After the SSR cluster analysis, the correlation analysis showed that the coefficient indices of above were increased to 0.682 and 0.609, respectively. They were both in significant levels. Therefor, clustering the inbred lines reasonably and choosing two reasonable inbred lines to mate may avoid the mating among the intraspecific lines and decrease the blindness and amount of work in maize breeding program.