Addition of Individual Chromosomes of Maize Inbreds B73 and Mo17 to Oat Cultivars Starter and SunII: Maize Chromosome Retention, Transmission, and Plant Phenotype

Authors: Rines, Howard; PHILLIPS, RONALD - UNIVERSITY OF MINNESOTA; KYNAST, RALF - UNIVERSITY OF MINNESOTA; OKAGAKI, RON - UNIVERSITY OF MINNESOTA; GALATOWITSCH, MARK - UNIVERSITY OF MINNESOTA; HUETTL, PAUL - UNIVERSITY OF MINNESOTA; STEC, ADRIAN - UNIVERSITY OF MINNESOTA; JACOBS, MORRISON - UNIVERSITY OF MINNESOTA; SURESH, JAYANTI - UNIVERSITY OF MINNESOTA; PORTER, H - University Of Minnesota; WALCH, MATTHEW - UNIVERSITY OF MINNESOTA; CABRAL, CANDIDA - UNIVERSITY OF MINNESOTA

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2009
Publication Date: 11/1/2009
Citation: Rines, H.W., Phillips, R.L., Kynast, R.G., Okagaki, R.J., Galatowitsch, M.W., Huettl, P.A., Stec, A.O., Jacobs, M.S., Suresh, J., Porter, H.L., Walch, M.D., Cabral, C.B. 2009. Addition of Individual Chromosomes of Maize Inbreds B73 and Mo17 to Oat Cultivars Starter and Sun II: Maize Chromosome Retention, Transmission, and Plant Phenotype. Theoretical and Applied Genetics. 119(7):1255-1264.

Interpretive Summary: Novel partial hybrid plants have been produced from sexual crosses between two cereals, oat and corn. In these partial hybrids defined physical portions of the DNA of corn, termed chromosomes, have been added to the total DNA of oat. A complete set of these modified oat plants, each carrying a different one of the ten chromosomes that together make up the total genetic information of a corn cell, have been reported previously. These unique materials serve as a valuable tool for simplifying analysis of the structure of the corn's total DNA or genome, which is composed of a linear sequence of about 2.5 billion DNA nucleotide molecules, by allowing analysis of the DNA in any individual corn chromosome isolated from that of the other nine corn chromosomes. The original set of corn chromosome additions to oat were made using a sweet corn hybrid Seneca 60 as the corn parent whereas most corn genetic studies, including the current efforts to sequence the DNA of the corn genome, involve the field corn inbreds B73 and Mo17. Because corn lines vary in their DNA sequences, particularly in the regions between genes, we have produced new sets of corn chromosome additions to oat using B73 and Mo17 as the corn parents. Using these inbred corn lines also allowed us to analyze among corn and oat parent lines relative success frequencies in the various complex steps involved in producing the addition lines and the parent role influencing which of the ten different corn chromosomes were recovered as additions to oat. We recovered self-fertile corn chromosome addition oat plants for eight different chromosomes of B73 and five of Mo17. The addition lines for corn chromosomes 1, 8, and 10 had improved fertility and chromosome transmission compared to the earlier versions from Seneca 60. These new B73 and Mo17 chromosome addition lines provide improved tools for corn researchers and also provide new possibilities for oat researchers to transfer corn genes into oat for oat improvement.

Technical Abstract: Oat-maize addition (OMA) lines with one, or occasionally more, chromosomes of maize (Zea mays L., 2n = 2x = 20) added to an oat (Avena sativa L., 2n = 6x = 42) genomic background can be produced from sexual crosses of oat x maize. Self-fertile disomic addition lines for maize chromosomes 1, 2, 3, 4, 5, 6, 7, 9, and the short arm of 10 and a monosomic addition line for chromosome 8 have been reported previously in which the sweet corn hybrid Seneca 60 served as maize chromosome donor with different oat genotypes, mainly cv. Starter, as recipient. Here we describe the generation of OMA lines with the more defined and widely used inbreds B73 and Mo17 as maize parents in combinations with oat cvs. Starter and Sun II. Fertile disomic OMAs were recovered for B73 chromosomes 1, 2, 4, 5, 6, 8, 9, and a partial 10 and Mo17 chromosomes 2, 4, 5, 6, and 10. These lines together with non-fertile interspecific F1 plants with chromosome 3 and chromosome 7 of Mo 17 provide DNA of additions to oat of all ten individual maize chromosomes between the two inbreds. The Mo17 chromosome 10 OMA was the first fertile disomic OMA obtained carrying a complete chromosome 10, and the B73 OMAs for chromosomes 1 and 8 represent disomic OMAs with improved fertility and transmission of the addition chromosome compared to earlier Seneca 60 versions. Comparisons among the four oat-maize parental genotype combinations revealed varying parental effects and interactions relative to frequencies of embryo recovery, embryo germination, F1 plantlets with maize chromosomes, and the specific maize chromosomes retained and transmitted to F2 progeny. Efforts also are described to improve recovery of fertile OMAs using in vitro meristem propagation and colchicine treatments of non-fertile F1 plants. As opposed to the previous use of hybrid maize, the recovered B73 and Mo17 OMAs provide consistent genotypes for use as tools in physical mapping of maize sequences, particularly inter-genic sequences, by simple presence/absence assays. The use of the more defined maize and oat genotypes allowed analysis of parent genotype effects on the frequencies of recovery of specific OMAs and the steps leading to their recovery. The recovered OMAs represent novel materials for maize genomic analysis and other studies and a possible means to transfer maize traits to oat.