INHERITANCE OF PARTHENOGENESIS IN POA-PRATENSIS L - AUXIN TEST AND AFLP LINKAGE ANALYSES SUPPORT MONOGENIC CONTROL

Gametophytic apomixis in Kentucky bluegrass (Poa platensis L.) involve s the parthenogenetic development of unreduced eggs from aposporic emb ryo sacs. Attempts to transfer the apomictic trait beyond natural sexu al barriers require further elucidation of its inheritance. Controlled crosses were made between sexual clones and apomictic genotypes, and the parthenogenetic capacity of (poly)diploid hybrids was ascertained by the auxin test, A bulked segregant analysis with RAPD and AFLP mark ers was then used to identify a genetic linkage group related to the a pomictic mode of reproduction. This approach enabled us to detect both an AFLP marker located 6.6 cM from the gene that putatively controls parthenogenesis and a 15.4-cM genomic window surrounding the target lo cus. A map of the P. pratensis chromosome region carrying the gene of interest was constructed using additional RAPD and AFLP markers that c o-segregated with the parthenogenesis locus. Highly significant linkag e between parthenogenesis and a number of AFLP markers that also appea red to belong to a tight linkage block strengthens the hypothesis of m onogenic inheritance of this trait. If a single gene is assumed, apomi ctic polyploid types of P. pratensis would be simplex for a dominant a llele that confers parthenogenesis, and this genetic model would be fu rther supported by the bimodal distribution of the degree of parthenog enesis exhibited in the (poly)diploid progenies from sexual x apomicti c matings. The molecular tagging of apomixis in P, pratensis is an ess ential step towards marker-assisted breeding and map-based cloning str ategies aimed at investigating and manipulating its mode of reproducti on.