Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: HIGH RESOLUTION MAPPING OF THE HOR1/MLA/HOR2 REGION OF
CHROMOSOME 5S IN BARLEY REVEALS EVIDENCE OF SEQUENCE DUPLICATION
HIGH RESOLUTION MAPPING OF THE HOR1/MLA/HOR2 REGION OF
CHROMOSOME 5S IN BARLEY REVEALS EVIDENCE OF SEQUENCE DUPLICATION
Richard A. DeScenzo 1,2, Roger P. Wise 1,2.3, and Mamatha
Mahadevappa 2,3. 1 Field Crops Research, USDA-ARS, 2 Department
of Plant Pathology, and 3 Interdepartmental Genetics Program Iowa
State University, Ames, IA 50011
A high resolution mapping population consisting of 270
individual, putative homozygous, recombinant lines, each
representing an independent recombination event between the Hor1
and Hor2 loci, was used to construct a high density RFLP map of
the Hor1/Mla/Hor2 region. To identify informative markers for
screening the recombinant line population, the Franger (Mla6) and
Rupee (Mla13) parental lines were screened for RFLPs using 12
restriction endonucleases and 35 cDNA and genomic clones, that
had been shown to map to barley chromosome 5 or wheat group 1.
As a result, 61 probe/enzyme combinations were chosen to screen
the homozygous recombinant line population. Analysis of the RFLP
mapping data indicated 10 of 20 markers were located within the
Hor1/Hor2 interval. Map distance between Hor1 and Hor2 was
calculated to be approximately 9.8 cM. Eight of the remaining
markers were mapped outside of the Hor1/Hor2 interval and
proximal to Hor1. Six of the recombinant lines had regions of
DNA which were heterozygous at one or more RFLP loci within the
Hor1/Hor2 interval. In addition, five of the probes used in this
study hybridized to multiple sites. Probe BCD249, a cDNA-derived
barley clone, hybridized to two loci 0.4 cM apart (bcd249.1 and
bcd249.2), indicating a sequence duplication event within the
interval. Data from the high resolution RFLP map of the
Hor1/Hor2 region was integrated with previous recombination data
which positioned the Mla6, Mlal3, and Mlal4, resistance alleles,
in relation to Hor1 and Hor2.
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