A molecular map of the apomixis-control locus in Paspalum procurrens and its comparative analysis with other species of Paspalum

Since apomixis was first mapped in Paspalum, the absence of recombination that characterizes the related locus appeared to be the most difficult bottleneck to overcome for the dissection of the genetic determinants that control this trait. An approach to break the block of recombination was developed in this genus through an among-species comparative mapping strategy. A new apomictic species, P. procurrens (Q4094) was crossed with a sexual plant of P. simplex and their progeny was classified for reproductive mode with the aid of morphological, embryological and genetic analyses. On this progeny, a set of heterologous rice RFLP markers strictly co-segregating in coupling phase with apomixis was identified. These markers were all located on the telomeric region of the long arm of the chromosome 12 of rice. In spite of the lack of recombination exhibited by the apomixis-linked markers in P. procurrens, a comparative mapping analysis among P. simplex, P. malacophyllum, P. notatum and P. procurrens, allowed us to identify a small group of markers co-segregating with apomixis in all these species. These markers bracketed a chromosome region that likely contains all the genetic determinants of apomictic reproduction in Paspalum. The implications of this new inter-specific approach for overcoming the block of recombination to isolate the genetic determinants of apomixis and gain a better comprehension of genome structure of apomictic chromosome region are discussed.