Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: 87pg1
GENOMIC MAPPING IN FLAX (LINUM USITATISSIMUM).
M. Gorman and M. Parojcic Biology Dept. Baldwin-
Wallace College, Berea, OH 44017 and C. Cullis Biology
Dept. Case Western Reserve. U. Cleveland, OH 44107.
We have been developing a linkage map for flax. The map was
started using RFLPs and a few traditional markers, but recently
RAPD markers have been added. The mapping populations have been
the F2 from two crosses between diverse cultivars. These have
been productive populations, as 40% of the random PstI probes
tried revealed a RFLP in F2 DNA digested with one of 3 enzymes.
Four out of 5 cloned gene probes also had a RFLP, and greater
than 50% of the primers tested yielded a RAPD (the primers were
pre-selected for amplifying multiple bands). Preliminary
segregation data for 22 RFLPs, 16 RAPDs, 4 isozyme and 4
morphological polymorphisms has been collected. The map
distribution of the RFLPs has not been random with 20 out of 22
falling into 5 linkage groups (out of 15 potential). Flax
chromosomes contain large blocks of heterochromatin covering more
than 30% of the genome, so there may be no PstI markers in these
regions. While the data is still limited, the RAPD markers have
been more dispersed. Six mapped to these same 5 groups, but the
other 10 segregated independently or formed new groups. We have
also obtained the first estimate for the relationship between map
units and physical distance in flax. A probe for a sub-set of
the 5S RNA gene family was found to reveal 3 RFLPs in one of the
F2 populations. These RFLP's were linked with only 2.7 cM
separating them. Pulse-field gels have shown that this 5S
sub-set is a single locus of < 500 kb in one of the parents.
This translates into an estimate of 185 kb per cM, but this
tandomly repeated locus may not be typical of the genome.
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