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Pollination dynamic in an advanced generation Douglas-fir seed orchard Lai, Ben Shu Kwan

Abstract

The objective of seed orchard management is to maximize the genetic gain while maintaining sufficient level of genetic diversity in the orchard’s crops; however, balancing these two parameters is a challenging task. Eight polymorphic nuclear microsatellite DNA markers were used to construct the full pedigree of 801 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) bulk seeds from 49 orchard parents and 4 external supplemental mass pollination (SMP) donors. Parental balance curves indicated that 80% of the gametes were produced by 23, 45 and 37% of females, males and clones, respectively. Contamination was found to be 10.36% with overhead cooling applied. Selfing rate was found as 15.23% due to the over representation of few orchard clones. The aggregate SMP (internal & external) success rate was estimated to be 15.02%. The female, male and clonal effective population size (Ne) was estimated to be 6.49, 26.00 and 13.70, respectively. The reduction of Ne is mainly the result of unequal parental contribution and to a minor extent by the co-ancestory of the orchard’s parents. The seed crop’s genetic worth was estimated to be 10.23 and -1.07 for volume and wood density, respectively. High correlations between visual reproductive assessment methods F2 (r = 0.90 P < 0.01) and M3 (r 0.77, P < 0.05) with DNA analysis give credence to the visualize assessment methods. The result of this study indicated that the seed orchard deviated from the ideal conditions affecting the expected genetic diversity and gain estimates.

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