A SERIES OF OAT-MAIZE CHROMOSOME ADDITION LINES FOR PHYSICAL MAPPING OF THE MAIZE GENOME

¹ Department of Agronomy and Plant Genetics and Plant Molecular Genetics Institute, University of Minnesota, 411 Borlaug Hall, 1991 Buford Circle, St. Paul, MN 55108-6026, USA

² US Department of Agriculture - Agricultural Research Service and Department of Agronomy and Plant Genetics, University of Minnesota, 411 Borlaug Hall, 1991 Buford Circle, St. Paul, MN 55108-6026, USA

In vitro rescued immature oat x maize F₁ embryos can in some cases retain individual maize chromosomes in addition to a complete haploid oat genome. About 8.5 % of these embryos germinate with varied frequencies among different oat genotypes and develop F₁ plants with 21 oat and possibly one or more maize chromosome(s). From more than 24,000 crosses of Zea mays cv. Seneca 60 to Avena sativa cvs. Starter, Gaf Park, Sun II, Preakness, Stout, Kanota, and Dumont, a total of 43 newly recovered F₁ plantlets retained maize chromosomes; 28 with one of the ten maize chromosomes, nine with two maize chromosomes, four with three maize chromosomes, and one with four maize chromosomes. The maize-specific dispersed repeat STS marker Grande-1-LTR served to distinguish genotypes with maize chromatin. Added maize chromosomes were identified using chromosome arm-specific SSR markers. FISH of maize genomic DNA to root tips and PCR on leaf DNA using chromosome-specific sequences as probes revealed occasional differences in the maize chromosome constitution between roots and shoots or among tillers of F₁ plants. These differences likely indicate chimerism in the original meristem caused by the maize chromosome elimination process and/or chromosomal instability among the meristem cells. Chromosomal differences were not observed among leaf tissues within individual tillers. Meiotic restitution provides fertility of F₁ plants. Resulting doubled haploid F₂ offspring that possess one homologous maize chromosome pair (2n = 6x+2 = 44) were produced and characterized morphologically and by molecular and cytogenetic means. The usefulness of the series of oat-maize addition lines is demonstrated by allocation to chromosome of a set of previously unmapped DNA sequences and their use as a source for radiation hybrid lines. This material is based upon work supported by the National Science Foundation under Grant No. 9872650.