GENETIC EFFECTS OF DOMESTICATION IN WESTERN HEMLOCK, TSUGA HETEROPHYLLA

摘要

Rates of genetic diversity were inferred from allelic variation in western hemlock (Tsuga heterophylla (Raf.) Sarg) using starch gel electrophoresis. Nine enzyme stains were employed to identify fourteen isozyme loci The concluding allelic variation was then used to compare differing orchard conditions with natural stands of western hemlock The main goal was to measure the effectiveness of seed orchard and seed collection protocol in maintaining natural genetic structure A measure of gene diversity,H_t was fairly high for both the natural populations (0.146) and the seed orchard populations, within which it ranged from 0.141 for full-sib orchards (FS) to 0 164 for the offspring from supplemental mass pollination (SMP) Large amounts of genetic variation in western hemlock accords with the life history and patterns of morphological and physiological variability This trend was also seen in observed heteiozygosity H_0 (0.154) for the SMP compared to the unimproved orchards (0.136), These results indicate that the maintenance of genetic diversity may be higher for the SMP treatment. This is expected as SMP have been shown to minimize self-fertilization, increase the genetic base through the introduction of desirable genotypes and improve parental balance. Another possible explanation is the crossing of distinct lines in the orchard therefore leading to more diverse populations. As a conclusion homoginzation of allelic diversity, as a result of genetic drift within the orchards has not been shown to lead to less genetic diversity