Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: 72pg1
WHEAT-AGROPYRON RECOMBINANT CHROMOSOMES WITH LR24 GENE
ANALYZED BY GENOMIC IN SITU HYBRIDIZATION
Jiming Jiang and Bikram S. Gill, Wheat Genetics
Resource Center and Department of Plant Pathology, Kansas
State University, Manhattan, KS 66506, USA.
Sears (Stadler Symposia, Vol.4, 1972) transferred Lr24, a
leaf rust resistance gene, from Agropyron elongatum (2n = 10x =
70) into common wheat (Triticum aestivum, 2n = 6x = 42, AABBDD)
by induced homoeologous chromosome pairing between A. elongatum
chromosome 3Ag, carrying Lr24, and wheat chromosomes 3D or 3B.
Twenty of Sears' 3Ag/3D and 3Ag/3B recombinant lines were
analyzed by genomic in situ hybridization (GISH) using
biotin-labeled genomic DNA of A. elongatum as a probe. The
breakpoint of most of the wheat-Agropyron recombinant chromosomes
are located in the distal half of the chromosomes. Only two
recombinants have a breakpoint in the proximal half of the
chromosomes. Two 3Ag/3D interstitial translocations carrying
Lr24 (Sears 1983) were also analyzed. The Agropyron chromosome
segments in these lines, supposed to be in the middle of the 3D
long arm, are located at the terminal part of the recombinant
chromosomes. Our results suggest that: i) the leaf rust
resistance gene Lr24 is located in the distal part of 3Ag long
arm; ii) most of the wheat-Agropyron chromosome recombination
occur at the terminal and subterminal parts of the chromosomes;
iii) the apparently interstitial translocations contain the 3Ag
segment in the terminal position.
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