Theor Appl Genet (1996) 93:123-135 9 Springer-Verlag 1996 Oscar Riera-Lizarazu 9 Howard W. Rines Ronald L. Phillips Cytological and molecular characterization of oat x maize partial hybrids Received: 5 March 1996 / Accepted: 8 March 1996 Abstract In cereals, interspecific and intergeneric hy- bridizations (wide crosses) which yield karyotypically stable hybrid plants have been used as starting points to widen the genetic base of a crop and to construct stocks for genetic analysis. Also, uniparental genome elimination in karyotypically unstable hybrids has been utilized for ce- real haploid production. We have crossed hexaploid oat (2n=6x=42, Arena sativa L.) and maize (2n=2x=20, Zea mays L.) and recovered 90 progenies through embryo res- cue. Fifty-tw0 plants (58%) produced from oatxmaize hy- bridization were oat haploids (2n=3x=21) following maize chromosome elimination. Twenty-eight plants (31%) were found to be stable partial hybrids with 1-4 maize chromo- somes in addition to a haploid set of 21 oat chromosomes (2n=21+1 to 2n=21+4). Ten of the ninety plants produced were found to be apparent chromosomal chimeras, where some tissues in a given plant contained maize chromo- somes while other tissues did not, or else different tissues contained a different number of maize chromosomes. DNA restriction fragment length polymorphisms (RFLPs) were used to identify the maize chromosome(s) present in the various oat-maize progenies. Maize chromosomes 2, 3, 4, 5, 6, 7, 8, and 9 were detected in partial hybrids and Joint contribution of the Minnesota Agricultural Experiment Station and USDA-ARS. Scientific journal series paper No. 21 859 of the Minnesota Agricultural Experiment Station. Mention of a trademark or proprietary product does not constitute a guarantee or warranty by the USDA-ARS or the University of Minnesota and does not im- ply approval over other products that also may be suitable Communicated by F. Salamini O. Riera-Lizarazu (~,). R. L. Phillips Department of Agronomy and Plant Genetics, and Plant Molecular Genetics Institute, University of Minnesota, 411 Borlaug Hall, 1991 Buford Circle, St. Paul, MN 55108, USA H. W. Rines Plant Science Research Unit, US Dept. of Agriculture, Agricultural Research Service, and Department of Agronomy and Plant Genetics, University of Minnesota, 411 Borlaug Hall, 199l Buford Circle, St. Paul, MN 55108, USA chromosomal chimeras. Maize chromosomes 1 and 10 were not detected in the plants analyzed to-date. Further- more, partial self-fertility, which is common in oat hap- loids, was also observed in some oat-maize hybrids. Upon selfing, partial hybrids with one or two maize chromo- somes showed nearly complete transmission of the maize chromosome to give self-fertile maize-chromosome-addi- tion oat plants. Fertile lines were recovered that contained an added maize chromosome or chromosome pair repre- senting six of the ten maize chromosomes. Four indepen- dently derived disomic maize chromosome addition tines contained chromosome 4, one line carried chromosome 7, two lines had chromosome 9, one had chromosome 2, and one had chromosome 3. One maize chromosome-8 mono- somic addition line was also identified. We also identified a double disomic addition line containing both maize chro- mosomes 4 and 7. This constitutes the first report of the production of karyotypically stable partial hybrids involv- ing highly unrelated species from two subfamilies of the Gramineae (Pooideae - oat, and Panicoideae - maize) and the subsequent recovery of fertile oat-maize chromosome addition lines. These represent novel material for gene/ marker mapping, maize chromosome manipulation, the study of maize gene expression in oat, and the transfer of maize DNA, genes, or active transposons to oat. Key words Arena sativa . Zea mays . Wide hybridization 9 Genomic in situ hybridization 9 Cytogenetics Introduction Interspecific and intergeneric hybridization between crop plants and between crops and their wild relatives has been termed "wide crosses". In cereals, where wide crosses have been particularly useful, karyotypically stable crosses which produce hybrid plants have been used as starting points to widen the genetic base of a crop by the introduc- tion of germplasm from related wild or cultivated species