A new single-locus cytogenetic mapping system for maize (Zea mays L.): overcoming FISH detection limits with marker-selected sorghum (S. propinquum L.) BAC clones.
The development of a cytogenetic map for maize (Zea mays L.) is shown to be feasible by means of a combination of resources from sorghum and oat that overcome limitations of single-copy gene detection. A maize chromosome-addition line of oat, OMAd9.2, provided clear images of optically isolated pachytene chromosomes through a chromosome spread and painting technique. A direct labeled oligonucleotide fluorescence in situ hybridization (FISH) probe MCCY specifically stained the centromere. The arm ratio (long/short) for maize chromosome 9 in the addition line was 1.7, comparable to the range of 1.6-2.1 previously reported for maize chromosome 9. A sorghum (Sorghum propinquum L.) BAC library was screened by hybridization with each of three maize core-bin-marker (CBM) probes: umc109 (CBM9.01), umc192/bz1 (CBM9.02), and csu54b (CBM9.08). A single BAC clone for each marker was chosen; designated sCBM9.1, sCBM9.2, or sCBM9.8; and used as a FISH probe on pachytene spreads from OMAd9.2. In each case, discrete FISH signals were observed, and their cytogenetic positions were determined to be 9S.79 (at position 79% of the length of chromosome 9 short arm) for sCBM9.1, 9S.65 for sCBM9.2, and approximately 9L.95 for sCBM9.8. These map positions were co-linear with linkage-map positions for these and other loci common to the linkage and cytogenetic maps. This work represents a major breakthrough for cytogenetic mapping of the maize genome, and also provides a general strategy that can be applied to cytogenetic mapping of other plant species with relatively large and complex genomes.
Koumbaris
George L
GL
Department of Biological Science, The Florida State University, Tallahassee, FL 32306-4370, USA.
Bass
Hank W
HW
D018554:Avena / Q000235:genetics; D002874:Chromosome Mapping / Q000379:methods*; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics; D032461:Chromosomes, Plant / Q000235:genetics; D005819:Genetic Markers / Q000235:genetics; D018745:Genome, Plant; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D006109:Poaceae / Q000235:genetics*; D045868:Sorghum / Q000235:genetics; D003313:Zea mays / Q000235:genetics
D005819:Genetic Markers