Construction of a sorghum RFLP linkage map using sorghum and maize DNA probes

Previous reports on sorghum restriction fragment length polymorphism (RFLP) mapping have been limited to the use of heterologous maize clones. In this study, both sorghum and maize probes were used to construct an RFLP map based on an F2 population from a cross between sorghum lines BSC 35 and BTX 631. A set of single-or low-copy number clones from a sorghum genomic library was preselected to use as hybridization probes. Forty-nine of the 101 clones (49%) tested were polymorphic between the two parental lines. In comparison, 53 of the 135 maize probes (39%) detected polymorphism with the same restriction enzymes. In total, 71 RFLP markers (38 sorghum and 33 maize) were placed into 15 linkage groups spanning 633 cM with an average marker distance of 8.9 cM. Comparison of our linkage map with other published sorghum maps, based on maize probes, showed resemblance for several linkage groups, indicating that these maps can be integrated. Homologous sorghum probes are useful in improving the coverage and resolution of RFLP linkage map in sorghum.