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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
    PDF: View PDF  (843 KB)

    Description

    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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    Citation

    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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