Effects of length of seed chilling period and sowing date on family performance and genetic variances of Douglas-fir seedlings in the nursery
1996
Sorensen, F.C.
Seeds of four full-sibling Douglas-fir families (F) were moist chilled (C) for 14, 33, and 77 days and sown (S) March 29, April 26, and May 24 at two densities (D = 111 and 200 seeds/m2), grown for 2 years in nursery beds and phenology and size traits recorded. The study was analyzed in two parts: part I evaluated seed treatment effects and their interactions with families; and part II investigated the effect of treatments on genetic variances, particularly among-family (sigma 2F) and within-plot (sigma 2w) components and the intraclass correlation for families (tf). In part I there were large and highly significant differences associated with C and S and among F for all traits. Early S combined with long C resulted in early emergence and gave large seedlings with little loss and damage. Many interactions between C and F, and S and F, were significant. Interactions involved rank changes for size but not for phenology traits, and were larger for C X F than for S X F. Seedling density affected seedling size but not phenology, did not interact with seed treatments, and interacted significantly but weakly with families. In part II, C and S, but not D, had significant effects on sigma2 F, sigma2 w, and tf, but not in a predictable manner. Because of significant interactions, it is recommended that standardized seed treatments be used in family nursery tests. This should aid in keeping the results from these tests as repeatable as possible. Long chilling and sowing as early as practicable are recommended to minimize disease losses and winter damages and to provide good nursery stock.
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