Recombination Within The Apospory Specific Genomic Region Leads To The Uncoupling Of Apomixis Components In Buffelgrass

Apomixis allows the clonal propagation of maternal genotypes through seed.  Gametophytic apomixis is usually divided into 2 components; apomeiosis - the creation of an unreduced embryo sac and parthenogenesis - the development of the egg cell into an embryo without fertilization.  In the closely related grass species Pennisetum squamulatum and Cenchrus ciliaris (syn. P. ciliare), apomixis is controlled by a single dominant “locus”, the Apospory Specific Genomic Region (ASGR).  Six SCAR markers have been identified which always co-segregate with apospory in both P. squamulatum and C. ciliaris.  A screen of progeny from a cross of sexual x apomictic C. ciliaris genotypes identified a plant, A8, retaining only two of the six ASGR-linked SCAR markers.  RFLP analysis and additional SCAR and CAPS markers from ASGR-linked BAC clones were generated to help identify the extent of recombination within the ASGR.   While the A8 plant forms aposporous embryo sacs, seedlings produced from aposporous embryo sacs are 6X in ploidy level and hence have lost the capacity for parthenogenesis.  This plant represents the first documented separation of the two components of apomixis among Pennisetum species and their close relatives.