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Intraspecific variation in non-selected natural populations of Douglas-fir (Pseudotsuga menziesii (MIRB.) Franco) Fashler, Anita Marie Kvestich

Abstract

Seedlings from the International Union of Forestry Research Organizations (I.U.F.R.O) collections in 1966 and 1968 sampling the range of Douglas-fir from northern California to British Columbia were used to establish a provenance-progeny test at the University of British Columbia Research Forest in Haney. The study analyzed height growth in a total of 384 half-sib families representing 48 provenances. The objectives were 1) to estimate the degree of genetic variation between and within, provenances for height growth, 2) to estimate the additive genetic variance, 3) to estimate narrow sense heritability, 4) to estimate juvenile x mature correlation, and 5) to select the best provenances and progenies for the Haney planting site. Results from seed zone analysis showed that the most significant differences in the genetic variation in height growth of juvenile Douglas-fir trees was found in the relative sizes of the variance between provenances (Vp) and the variance between families within provenances (Vf/p). Provenances most adapted to Haney conditions exhibited Vf/p and Vep as the dominant contributors to the phenotypic variation. For less adapted provenances, Vp was of greater importance. In all zones the greatest component of variance was due to the variance of individual trees within families (Vep). Variance due to block x provenance interaction (VpxB) was the next largest variance between blocks (VB). Estimates for additive genetic variance and heritability for seed zones were quite high. Low values for their respective standard errors indicated high reliability in the results. High values of heritability indicated that there are opportunities for significant improvement by selection in Douglas-fir. Results from the juvenile x mature correlation analysis indicated that reliable selection of the best and deletion of the poorest provenances and families may begin at age five years. It is recommended that selection in seed zones 2 and 3 and the best provenances from seed zone 1 would yield the best results for the Haney site. As an example of genetic gain, a selection intensity of only one in four (25%) of the top individuals was chosen. Using this low selection intensity, figures obtained for genetic gain at Haney varied from 17.90% for two year to 10.96% for eight year height growth. Selection in the best provenance, of the best seed zone could increase total height growth by almost 33%. An additional increase of 70% is suggested if the best individual within the best provenance is chosen. Further gains in height growth are possible if higher selection intensities are used.

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