Genetic diversity in tropical maize inbred lines: heterotic group assignment and hybrid performance determined by RFLP markers

Tropical maize inbred lines, eight derived from a Thai synthetic population (BR-105) and 10 from a Brazilian composite population (BR-106), were assay ed for restriction fragment length polymorphisms with 185 clone-enzyme comb inations. The aim of this study was to investigate genetic distances among tropical maize material and their relationship to heterotic group allocatio n and hybrid performance. Genetic distances (GDs) were on average greater f or BR-105 x BR-106 lines (0.77) than for BR-106 x BR-106 (0.71) and for BR- 105 x BR-105 (0.69) lines. Cluster analysis resulted in a clear separation of BR-105 and BR-106 populations and was according to pedigree information. Correlations of parental GDs with single crosses and their heterosis for g rain yield were high for line crosses from the same heterotic group and low for line combinations from different heterotic groups. Our results suggest that RFLP-based GDs are efficient and reliable to assess and allocate geno types from tropical maize populations into heterotic groups. However, RFLP- based GDs are not suitable for predicting the performance of line crosses f rom genetically different heterotic groups.