Studies on genetic relationship between the SSR molecular markers and the heterosis in maize

The experimental materials were tropical subtropical maize inbred lines from CIMMYT and temperate lines representing main heterotic groups in China .By SSR molecular markers,13 pairs of primers whose bands are clear and discrepant were selected out of 40. The 72 alleles identified were served as raw data for estimating genetic similarities among 14 lines, involving 13 loci. The average number of alleles per SSR locus was 5.53 with a range from 2 to 8. Polymorphic index content (PIC) values varied from 0.11 to 0.84 with an average of 0.65. The maize inbred lines tested were divided into 6 heterotic groups according to the results of SSR molecular markers. Cluster analysis by UPGMA placed the temperate lines in six clusters corresponding to the heterotic groups determined by their pedigree analysis. The coefficients between the genetic distance of SSR molecular markers and the heterosis of F_1 yield were not significant. Therefore, SSR can be used to divide heterotic groups, not to predict heterosis.