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    Author(s): Bohun B. Kinloch Jr.
    Date: 1992
    Source: Can. J. Bot. 70: p. 1319-1323
    Publication Series: Miscellaneous Publication
    PDF: Download Publication  (1.0 MB)


    The gametic frequency of a dominant allcle (R) for resistance to white pine blister rust, a disease caused by an introduced pathogen (Cronartium ribicola), in natural populations of sugar pine was estimated by the kind of leaf symptom expressed after artificial inoculation of wind-pollinated seedlings from susceptible seed-parent genotypes (rr). Gene frequency increased clinally from near 0 in the southern Cascade Range to 0.08 in the southern Sierra Nevada, but it was not correlated with any major climatic gradient. Because R expresses a typical hypersensitivity response to pathogenesis, it has probably always functioned in disease resistance. A candidate pathogen for this function is C. occidentals, cause of pinyon blister rust, and a close relative of C. ribicola. Increase in allele frequency was positively associated with the proximity of sugar pine to single-leaf pinyon pine populations. Although sugar pine is not presently a natural host of pinyon rust, R may be a relict gene that protected sugar pine from this endemic pathogen in recent geologic epochs, when both pines are known to have been more intimately associated.

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    Kinloch Jr., Bohun B. 1992. Distribution and frequency of a gene for resistance to white pine blister rust in natural populations of sugar pine. Can. J. Bot. 70: p. 1319-1323


    Cronartium ribicola, genetic resistance, Pinus lambertiana, population genetics

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