DETECTION OF THE APOMICTIC MODE OF REPRODUCTION IN MAIZE-TRIPSACUM HYBRIDS USING MAIZE RFLP MARKERS

Polyploid plants in the genus Tripsacum, a wild relative of maize, rep roduce through gametophytic apomixis of the diplosporous type, an asex ual mode of reproduction through seed. Moving gene(s) responsible for the apomictic trait into crop plants would open new areas in plant bre eding and agriculture. Efforts to transfer apomixis from Tripsacum int o maize at CIMMYT resulted in numerous intergeneric F-1 hybrids obtain ed from various Tripsacum species. A bulk-segregant analysis was carri ed out to identify molecular markers linked to diplospory in T. dactyl oides. This was possible because of numerous genome similarities among related species in the Andropogoneae. On the basis of maize RFLP prob es, three restriction fragments co-segregating with diplospory were id entified in one maize-Tripsacum dactyloides F-1 population that segreg ated 1:1 for the mode of reproduction. The markers were also found to be linked in the maize RFLP map, on the distal end of the long arm of chromosome 6. These results support a simple inheritance of diplospory in Tripsacum. Manipulation of the mode of reproduction in maize-Trips acum backcross generations, and implications for the transfer of apomi xis into maize, are discussed.