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    Description

    Polymix outcross (X), full-sib (FS), and wind-pollination (WP) families were produced on 25 seed trees and 10 half-sib families on 10 of the same trees in a Pseudotsuga menziesii (Mirb.) Franco var. menziesii seedling seed orchard. Seedlings were raised at two sowing densities for 2 years in the nursery, and inbreeding depression in seedling size related to inbreeding effect on growing season length and growth rate. Seedling mortality was light and not affected by inbreeding. Mean inbreeding depression (ID) for 2-year size traits was 6% (height) and about 8% (diameter) per 10% increase of F, the inbreeding coefficient, and was linear with the increase in F over the range of F used. Both amount of ID and its fit to linearity differed greatly among seed trees. Elongation season was significantly and slightly shorter for FS than for X families; second-year relative elongation rate was nonsignificantly larger for FS than for X families. Inbred families had nonsignificantly larger within-plot variance and significantly larger coefficients of within- plot variance than X families. Sowing density was not a significant factor except in diameter and height/diameter ratio. Results are discussed in terms of plant growth habit and possible gene action. Wind-pollination, compared with X, families were significantly shorter by 3.8% and significantly smaller in diameter by 4.6% with much variation among family groups. About half of the height difference could be explained by seed weight; the remainder could have been due to pollen contamination or natural inbreeding. Progenies of the two pollen types did not differ for phenological traits, even though the seed orchard was in a drier, more inland location than the parent-tree locations. Progenies of WP had nonsignificantly larger within-plot variance thatn X progenies.

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    Citation

    Sorensen, Frank C. 1997. Effects of sib-mating and wind pollination on nursery seedling size, growth components, and phenology of Douglas-fir seed-orchard progenies. Canadian Journal of Forest Research. 27: 557-566

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