La produzione di seme apomittico in Poa pratensis L.: controllo genetico della partenogenesi.

Gametophytic apomixis in Poa pratensis L. involves the parthenogenetic development of unreduced eggs from aposporic embryo sacs. Attempts to transfer the apomictic trait beyond natural sexual 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 AFLP markers was then used to identify a genetic linkage group related to the apomictic mode of reproduction. This approach enabled to detect an AFLP marker located 6.6 cM from the gene that putatively controls parthenogenesis and a 15.4 cM genomic window surrounding the target locus. A map of the P. pratensis chromosome region carrying the gene of interest was constructed using additional AFLP markers that co-segregated with the parthenogenesis locus. The highly significant linkage between parthenogenesis and a number of AFLP markers that also appeared to belong to a tight linkage block strengthens the hypothesis of monogenic inheritance of this trait. Assuming a single gene, apomictic polyploid types of P. pratensis would be simplex for a dominant allele that confers parthenogenesis and this genetic model would be further supported by the bimodal distribution of the degree of parthenogenesis exhibited in the (poly)diploid progenies from sexual x apomictic matings. The molecular tagging of apomixis in P. pratensis is an essential step towards marker-assisted breeding and map-based cloning strategies aimed at investigating and manipulating its mode of reproduction.