A Radiation Hybrid System for the Genetic and Physical Mapping of the Corn Genome.

Characterization of the maize genome can be difficult due to its large size and complexity. Processes, such as, mapping of genes and gene families, centromeric analysis, meiotic pairing, and expression analysis are better served with a reduction in genome complexity. This research addressed this need by developing multifunctional genetic materials that include the ability to rapidly map DNA sequences to chromosomes and chromosome segments.

Oat-maize addition (OMA) lines were produced from a cross of maize (Zea mays L., 2n=2x=20) to an oat (Avena sativa L., 2n=6x=42).  One or more individual chromosomes from a maize chromosome donor sweet corn hybrid Seneca 60 were added to an oat genome using mainly cv. Starter as the recipient.  A collection of self-fertile disomic addition lines have been recovered for maize chromosomes 1, 2, 3, 4, 5, 6, 7, 9, short arm of 10 and a monosomic addition line of chromosome 8. OMA lines were also developed using maize inbreds B73 and Mo17 as parents in combinations with oat cvs. Starter and Sun II.  A collection of fertile disomic B73 OMA lines were recovered for chromosomes 1, 2, 4, 5, 6, 8, 9,  a partial 10; and Mo17 OMA lines for chromosomes 2, 4, 5, 6, and 10. Finally, a complete set of OMA lines with all ten individual maize chromosomes between the two inbreds were made complete by the addition of non-fertile interspecific F₁ plants with chromosome 3 and chromosome 7 from Mo17.

Radiation hybrid (RH) lines produced by gamma irradiation of the OMA lines resulted in fertile monosomic lines with sub-chromosomal segments from the maize chromosome donor Seneca 60.  These break lines contain a fragment of an individual maize chromosome through complex rearrangements, including interstitial deletions and translocations to oat.  This further dissection of maize chromosomes represents approximately 685 lines which are characterized by 408 maize single sequence repeat (SSR) markers and categorized into low or medium resolution mapping panels for maize chromosomes 1,2,3,4,5,6,7,9,10.