Genetic Variation in Young Fraser Fir Progeny Tests

Abstract

Genetic variation among six seed sources of Fraser fir [Abies fraseri (Pursh) Poir.] and genetic parameters for traits important in Christmas tree production were determined by analyzing a series of open-pollinated progeny tests after four years in the field. Highly significant differences were found among seed sources and families within sources (p<0.0001) for height all four years in the field. The individual-tree within population heritability values for the traits measured in year 4 ranged from 0 to 0.44, with height having the highest heritability, overall tree quality having a heritability of 0.14, and bud and branching traits having varying heritabilities. Heritability values for height at age 4 varied greatly among the six sources, from 0.15 for the Black Mountains to 0.67 for the Great Smoky Mountains. Highly significant seed source by site interactions as well as family within source by site interactions exist for height. Stability variance analysis, after removing the environmental heterogeneity, showed significant instability across the test sites for two of the six seed sources for height after four years, and some rank changes occurred. The high heritability values for height show promise for improving Fraser fir for Christmas tree production via breeding because of the importance of height in determining Christmas tree value.

In addition, genetic variation of spring frost damage to the terminal leader and lateral branches in May of 2002, the third year in the field, and how it related to bud flush dates in the nursery as well as parent elevation were studied. Seed sources differed significantly for lateral branch frost damage and families within source differed significantly for both terminal leader and lateral branch frost damage. Greater terminal and lateral frost damage were significantly associated with greater height for all years. As expected, parent elevation was negatively associated with progeny height. Less lateral branch frost damage during the third year in the field was also associated with later terminal and lateral bud flush dates of the same progeny in the nursery. In addition, higher parent elevation was associated with later lateral bud flush dates in the nursery. Terminal and lateral bud flush dates in the nursery showed high individual tree within population heritability values of 0.85 and 0.73, respectively. Similar heritability values for the frost damage measurements were low, 0.045 for terminal leader damage and 0.14 for lateral branch damage. Although taller individual trees appear to be less tolerant of a late spring frost, many of the same families were ranked in the top 25 for height after four years in the field when only those individual trees with no frost damage were compared to those with frost damage. Therefore, it appears that the fast growing individuals can quickly make up for any loss of height from a late spring frost.