Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: HIGHER LEVEL OF RECOMBINATION IN WHEAT IS DUE TO MORE
CROSS-OVERS/ARM AND LOCALIZED RECOMBINATION HOT-SPOTS
HIGHER LEVEL OF RECOMBINATION IN WHEAT IS DUE TO MORE
CROSS-OVERS/ARM AND LOCALIZED RECOMBINATION HOT-SPOTS.
Kulvinder Gill and Bikram Gill, Wheat Genetic Resource Center,
Department of Plant Pathology, Kansas State University,
Manhattan, KS-66506.
Contrary to the popular belief, recombination in wheat and
its related species is more than 1-2 cross-overs/arm. The total
genetic length of our RFLP genetic linkage map of Triticum
tauschii, the D-genome progenitor of wheat, is 3479 cM with an
average of about 500 cM/chromosome. The genetic length increases
uniformly with increased number of markers, with an average of 20
cM/marker. The genetic distance/chromosome varies from 265 cM
(4D) to 671 cM (5D). These two chromosomes have 26 and 60
markers, respectively. We investigated the reasons for higher
levels of recombination in wheat (Triticum aestivum) using
chromosome deletion lines to precisely determine physical
distance among the markers, and chromosome 5B recombinant
population using 5B substitution line from Triticum dicoccoides).
The 5B substitution line was crossed to 'CS', the F1 was crossed
to mono 5B, and 41 chromosome plants were selected and selfed in
order to recover recombinant 5B chromosome in homozygous state.
Since there was only one cycle of meiosis followed by fixing the
recombinant chromosome in homozygous state, crossing-over in each
plant can be seen by arranging the RFLP scoring data in the same
order, from centromere toward telomere, as they appear on the
physical map. We mapped 12 DNA probes for the long arm of group
5 of wheat. Out of 55 plants, 3 plants have four crossovers, two
have three, seven have two, and 17 have single cross-over. We
detected two obvious recombination hot-spots. One was around Ph1
gene region where we detected 4 crossovers in a chromosome region
that is physically submicroscopic. The second hot-spot is
between the probes wg1026 and bcd 450. The two probes are
physically present in the chromosome region spanning less than 5%
of the arm but has 12 crossovers between the two markers. In
addition, 4 gene conversion like events were also observed.
Double crossovers were observed in the chromosome region that is
genetically only 7-15 cM.
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