Physical mapping of restriction fragment length polymorphisms (RFLPs) in homoeologous group 7 chromosomes of wheat by in situ hybridizations

Abstract

In situ hybridization with biotin-labelled DNA probes was used to determine the physical location of markers from an RFLP-based genetic map of homoeologous group 7 in wheat (Triticum aestivum L.). The observed results indicated all probes hybridized to the corresponding group 7 chromosomes of all three wheat genomes and that the gene orders on the physical map were basically the same as that of the RFLP-based genetic map. The distance for each marker from the centromere on the physical map was different from those shown on the genetic map. Comparison of the genetic distance and the physical distance between two pairs of markers (Xpsrl29 to Xpsrl21, and Xpsrl29 to XpsrllT) showed that the region between Xpsrl29 and Xpsrl21 contains a potential ‘hot’ spot of recombination on the chromosome arm. There appears to be considerable differences in crossing-over along the chromosomes. Most of the polymorphic markers are physically located in the middle portion of the chromosome arm to which they were genetically located, indicating reduced recombination in the centromeric and telomeric regions. Markers on the physical map were located outside the C-banded regions. The translocation break point involving 7BS and a colinear relationship among the homoeologous group 7 chromosomes are discussed. © 1995 The Genetical Society of Great Britain.