Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: 52pg1
MOLECULAR MARKER AND QUANTITATIVE TRAIT MAPPING IN DOUGLAS-FIR
K.D. Jermstad 1, A.M. Reem 1, N.C. Wheeler 2 and D.B. Neale 1
1 Institute of Forest Genetics, Pacific Southwest Research
Station, US Forest Service. 2 Wayerhaeuser Company
We are constructing a genetic linkage -map for Douglas-fir
(Pseudotsuga menziesii [Mirb.] Franco) based on restriction
fragment length polymorphism (RFLP) and random amplified
polymorphic DNA (RAPD) markers. The mapping population is a
3-generation outbred pedigree constructed by Weyerhaeuser
Company. This cross was selected because we expect it is
segregating for loci which determine the time of bud flush and
bud set. We will attempt to map QTLs for these important traits
once the genetic map is completed. Segregating RFLP loci are
identified by hybridizing southern blots containing
HindIII-restricted DNAs from the 4 grandparents and 2 Fl parents
with three types of DNA probes: 1) Douglas-fir cDNA probes, 2)
Douglas-fir genomic-DNA probes and 3) mapped RFLP probes from
loblolly pine (Pinus taeda L.) (Devey et al, 1991. TAG vol.
83:238-242). Five of six Douglas-fir cDNAs hybridized and showed
polymorphism in the parents. Probe pCabDF1 revealed a single
locus with two alleles. The four remaining probes showed
polymorphisms at each of two loci. A small proportion (32%) of
Douglas-fir genomic-DNA probes were polymorphic. All of these
are segregating in the cross and thus can be mapped. A large
proportion (75%) of loblolly pine cDNA probes hybridized to
Douglas-fir genomic DNA; 50.5% of the probes detected
polymorphism and segregate in the F2. In summary, an estimate
of 121 segregating loci have been identified thus far in parental
screening. We are also mapping RAPD markers in the
three-generation pedigree. Segregating RAPDs are identified
based on six megagametophytes (lN) from each of the two F1s.
Preliminary screening of six megagametophytes from each mother
tree with 119 primers showed 66 segregating loci with an average
of 0.55 loci per primer. Primers that show segregation are used
on a sample of 23 megagametophytes from each parent. Segregating
RAPDs will then be mapped in the F2 population. The F2s will be
clonally propagated for future use in quantitative trait mapping
studies and also to provide a lasting source of material for
RFLP-RAPD mapping.
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