COMPARATIVE MAPPING IN GRASSES - OAT RELATIONSHIPS

The development of RFLP linkage maps in hexaploid and diploid oat allo ws us to study genetic relationships of these species at the DNA level . In this report, we present the extension of a previously developed d iploid oat map (Avena atlantica x A. hirtula) and its molecular-geneti c relationships with wheat, rice and maize. Examination of 92-99% of t he length of the oat genome map with probes common to Triticeae specie s, rice or maize showed that 84, 79 and 71%, respectively, was conserv ed between these species and oat. Generally, the orders of loci among chromosomes homoeologous to oat chromosomes A and D were the most cons erved and those of chromosomes homoeologous to oat chromosome G were t he least conserved. Conservation was observed for blocks ranging from whole chromosomes 101 cM long to small segments 2.5 cM long containing two loci. Comparison of the homoeologous segments of Triticeae, rice and maize relative to oat indicated that certain regions have been mai ntained in all four species. The relative positions of major genes gov erning traits such as seed storage proteins and resistance to leaf rus ts have been conserved between cultivated oat and Triticeae species. A lso, the locations of three vernalization/or photoperiod response gene s identified in hexaploid oat correspond to the locations of similar g enes in homoeologous chromosomes of wheat, rice or maize. The location s of the centromeres for six of the seven oat chromosomes were estimat ed based on the homoeologous segments between oat and Triticeae chromo somes.