| dc.description.abstract | The genetic structure, linkage relationships and genetic
variation of Pinus strobus, P. monticola, P. griffithii, P.
peuce and~. koraiensis were investigated by isozyme analysis,
using starch gel electrophoresis, based on tissue from mature
needles and megagametophytes. The possibility of using
isozyme analysis for identification of these species and their
interspecific hybrids was also investigated.
Thirteen enzyme systems were analyzed, most of which were
shown to be under multiple gene control. Thirty-six loci
coded for the 13 enzyme systems in each of the species.
Inheritance studies showed that most of the isozyme variants
were under Mendelian single-gene control.
Determination of linkage relationships among the 36 gene
loci revealed up to three linkage blocks in each species. The
gene arrangement had common relationships for all species.
Generally, one block consisted of LAP2 and MDH3, the second of
IDH and AC02, and the third of MDH2 and LAP 3 . Further
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observations indicated that most of these linked genes were on
the same chromosome. These results are discussed in terms of
the conservative nature of the pine genome and its evolution.
Their practical uses are noted.
Substantial genetic variation was evidenced in all the
species. Based on 8 enzyme systems and 14 isozyme loci, the
mean values of average heterozygosity, proportion of
polymorphic loci, and number of alleles per locus were: P.
strobus - 0.226, 50.0, and 2.5; P. monticola - 0.233, 78.6 and
2.3; P. griffithii - 0.190, 57.1 and 2.1, P. peuce - 0.152,
71.4 and 2.6; and P. koraiensis 0.134, 50.0 and 2.1
respectively. These values are comparable to most other
conifer species.
Genetic similarities and distances, divergence times
based on allele frequencies and other results from a cluster
analysis showed that P. strobus, P. monticola and P.
griffithii were genetically the closest species while P. peuce
and P. koraiensis each formed a separate cluster. The results
are discussed in view of the evolution and conservative nature
of these pines and subsections Cembrae and Strobi.
Several alleles were ~dentified as markers for P strobus,
P. monticola, P. griffithii, P. peuce and P. koraiensis and
their interspecific hybrids. The practical and taxonomic
importance of these marker allozymes is discussed. | en |
