Comparative mapping reveals partial conservation of synteny at the apomixis locus in Paspalum spp.

In plants, gametophytic apomixes is a form of asexual reproduction that leads to the formation of seed-dervied offspring that are genetically identical to the mother plant. A common set of RFLP markers, including five rice anchor markers previously shown to be linked to apomixes in Paspalum simplex, were used to detect linkage with apomixes in P. notatum and P. malacophyllum. A comparative map of the regioin around the apomixes locus was constructed for the three Paspalum species, and compared to the rice map. The locus that controls apomixes in P. simplex was almost completely conserved in the closely related species P. malacophyllum, whereas it was only partially represented in the distantly related species P. notatum. Although strong synteny of markers was noted between this locus and a portion of rice chromosome 12 in both P. simplex and P. malacophyllum, the same locus in P. notatum was localized to a hybrid chromosome which carries markers that map to rice chromosomes 2 and 12. All three Paspalum species showed recombinant suppression at the apomixes locus; in the case of P. notatum, this might be due to a heterozygosity for a translocation that most probably negatively interferes with chromosomal pairing near the locus. A common set of markers that show linkage with apomixes in all three Paspalum species define a portion of the apomixis-controlling locus that is likely to contain genes critical for apomictic reproduction.