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    Author(s): Ronald C. Schmidtling; E. Carroll; T. LaFarge
    Date: 1999
    Source: Silvae Genetica. 48(1): 35-45.
    Publication Series: Miscellaneous Publication
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    Loblolly pine (Pinus taeda L.) megagametophytes and embryos were examined electrophoretically to compare the extent and distribution of genetic variability in allozymes of selected and wild populations. Range-wide collections of three different types were investigated in this study. These consisted of seed sampled from (1) a provenance test established in 1953; (2) bulk seed sampled from collections obtained from natural stands; and (3) seed harvested from clones used to produce improved seed in a tree improvement program.

    All 18 loci tested were found to be polymorphic. The average number of alleles overall (Na) was 3.8. Expected heterozygosities (He) varied from 0.193 in the 70-year old orchard clones, to 0.174 in the 40-year-old provenance test samples, to 0.163 in the embryos of the bulk collections. The maximum FST was 0.066 for the provenance test populations, which indicates that only a small proportion (6.6 percent) of the total variation in allozymes was attributed to population differences. In spite of this, the populations were well differentiated in multivariate analysis.

    In controlled-pollinated progeny tests of the orchard selections, there was a negative association between growth and the presence of rare alleles in the parent. A rare allele at the IDH locus was associated with slower growth, probably because it indicated hybridization with the slower-growing shortleaf pine (P. echinata Mill.).

    Allozyme variation as well as variation in cortical monoterpenes and fusiform rust resistance suggests that loblolly pine resided in two refugia during the Pleistocene; one in south Texas/northeast Mexico and one in south Florida/Caribbean. The two populations migrated to the northern Gulf Coastal Plain at the beginning of the Holocene and merged just east of the Mississippi River.

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    Schmidtling, Ronald C.; Carroll, E.; LaFarge, T. 1999. Allozyme diversity of selected and natural loblolly pine populations. Silvae Genetica. 48(1): 35-45.

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