Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2000
Publication Date: 6/1/2001
Citation: MA, X.F., ROSS, K., GUSTAFSON, J.P. PHYSICAL MAPPING OF RFLP MARKERS IN HOMOEOLOGOUS GROUPS 1 AND 3 CHROMOSOMESOF WHEAT BY IN SITU HYBRIDIZATION. GENOME. 2001. V. 44(3). P. 401-412. Interpretive Summary: The ability of scientists to be able to physically map DNA sequences to locations on chromosomes has severely limited our understanding of the location variation of DNA sequences in plants. The present study was initiated in order to ascertain the physical location of DNA sequences on several wheat chromosomes in order to try and understand if the DNA sequences are scattered throughout the chromosomes or if they cluster in specific chromosomal regions. The DNA sequences were physically mapped to chromosomal regions using a cytological technique that allows one to visualize specific DNA sequences on a chromosome. We found out that the DNA sequences we mapped tended to cluster in the middle of a chromosome arm and were not scattered over the entire chromosome. Also, our physical mapping of the DNA sequence order on the chromosomes was in agreement with the sequence order observed in the genetic and deletion maps. This information will be important to small grain researchers in their attempts to understand where the active regions of chromosomes are by comparing mapped chromosomal regions vs. physical locations, and to other plant scientists who will try to design more efficient crop plants through either classical breeding or biotechnology.
Technical Abstract: By means of in situ hybridization with biotin-labelled DNA probes, 18 RFLP markers were physically located to homoeologous groups 1 and 3 chromosomes in wheat. Most of the markers hybridized to the corresponding chromosomal arms in a physical order which was in agreement with the genetic maps. The distributions of markers in the physical maps were clustered in certain non-C-banded, distal euchromatic areas in most of the arms studied, indicating the presence of recombination hot spots and cold spots in those arms. However, the markers on chromosome 1BS showed a well-dispersed pattern of hybridization, which could be due to the distribution of a large amount of heterochromatin throughout the arm. One internal inversion between Xpsr653 and Xpsr953 was observed on chromsome 1AL. One additional Xpsr688 locus, approximately 20-25% from the centromere, was found on chromosome 1AS and chromosome 1BS. The placement of Xpsr170 on group 3 chromosomes might be the result of a different locus being mapped compared to the genetic map. Xpsr313 was mapped to two loci on chromosome 1DL. Five markers, which had been previously used for deletion-based physical maps, were located to the appropriate bins, consistent with the deletion maps. In this experiment, a 3% hydrogen peroxide pretreatment was used to inactivate any endogenous peroxidase.