Apospory-linked molecular markers in buffelgrass

Isolation of a gene controlling apomixis would be useful to plant breeders for fixing hybrid vigor. A single gene encodes for aposporous apomixis in buffelgrass (Pennisetum ciliare L. Link), which is inherited in a autotetraploid fashion. Only two molecular markers linked to the gene are known: C04-600, a RAPD (random amplified polymorphic DNA) and UGT197-144, an STS (sequence-tagged site). The objective of this study was to identify new RAPD markers linked to the apospory locus in buffelgrass and to prepare a linkage map. Sexual clone B-2s was crossed to aposporous buffelgrass cultivar Higgins and to aposporous clone B-12-9. Progeny of each cross were screened for RAPD markers by bulked segregant analysis. Seven preparations of bulked genomic DNA (equal amounts DNA from each of 10 individuals) from sexual or aposporous progeny were examined for RAPD markers. Using 500 decanucleotide primers, we found five new markers potentially linked to the apospory gene. Analysis by MAPMAKER/EXP 3.0¹ indicated markers J16-800 and M02-680 were linked to the apospory gene, as was previously established marker UGT197-144, and the three were placed on the map. Marker A20-730 was loosely linked in both crosses, marker B14-550 was unlinked in the Higgins cross, and marker N15-370 was unlinked in both crosses, and they were not placed on the map. These data provide the first map for the buffelgrass chromosome bearing the apospory gene.