Abstract
Analysis of megagametophytic and embryonic allozyme variants in nine enzymatic systems encoded by 14 loci was conducted on 30 western white pine (Pinus monticola Dougl.) trees from a natural stand on Vancouver Island, B.C. The segregation of allozymes in megagametophytes of heterozygous trees indicated distinct, simple, Mendelian inheritance. The stand heterozygosity parameters (proportion of polymorphic loci (0·64), average number of alleles per locus (1·79), and average expected heterozygosity (0·18)) were identical to those reported from a broadly-based survey of the species (Steinhoff et al., 1983). Comparison of progeny (viable embryo) and parental genotypic distributions indicated a major genetic shift between the two life-cycles phases. Among the progeny, heterozygotes occurred less frequently than expected under panmixia, while the reverse was observed for the parental population. Single-locus estimates of outcrossing rate varied between 0·751 and 1·043 and were significantly heterogeneous. Comparison between the single-locus estimates and the multilocus estimate (0·977) of outcrossing rates indicated that most of the inbreeding detected was due to consanguineous matings, rather than selfing. This form of inbreeding was consistent with the clustering of genotypes in the stand. Single-tree estimates of outcrossing rate varied considerably among trees and ranged between 0·682 and 1·207, indicating that some trees might possess high self compatibility and tolerate high selfing, or that violation of mixed-mating assumptions occurred. The implications of the apparent inbreeding on the derivation of genetic estimates from open-pollinated seeds and on seed crops for production plantations are discussed.
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El-Kassaby, Y., Meagher, M., Parkinson, J. et al. Allozyme inheritance, heterozygosity and outcrossing rate among Pinus monticola near Ladysmith, British Columbia. Heredity 58, 173–181 (1987). https://doi.org/10.1038/hdy.1987.31
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DOI: https://doi.org/10.1038/hdy.1987.31
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