Yu et al.Combining Ability and Heterosis in Maize efficiency by using both temperate and tropical maize to broaden genetic basis. Large sets of parental lines with available genotypic information can be shared and used in worldwide hybrid breeding programs through an open-source breeding strategy. Potential applications of the reported results in developing hybrid maize breeding strategies were also discussed.

An F1 population was used to analyze the inheritance of random amplified polymorphic DNA (RAPD) markers in tetraploid alfalfa. Of the 32 RAPD markers that were used for a segregation analysis in this study, 27 gave ratios that are consistent with random chromosome and random chromatid segregation at meiosis. However, among all of the RAPD markers (121) that were screened in this study, only one example of a double reduction, that is typical of chromatid segregation, was observed. These results indicate that random chromosome segregation is likely the predominant but not the exclusive mode of inheritance for tetraploid alfalfa. χ2 analyses of cosegregation for RAPD marker pairs derived from the female parent revealed nine linkages that fell into four linkage groups. The recombination fractions among linked marker pairs ranged from 1 to 37%. These are the first molecular linkage groups reported in tetraploid alfalfa. In addition, various strategies for molecular mapping in the tetraploid alfalfa genome are proposed that should be of interest to plant breeders who are planning to use molecular markers for alfalfa or other tetraploid species.