Genetic analysis and clonal stability of two yellow cypress clonal populations in British Columbia

Abstract

Genetic analysis of height and form at age 12 years of 697 yellow cypress (Callitropsis nootkatensis [D. Don] Oerst.) clones tested across seven sites in coastal British Columbia (BC) were explored in populations: Population 1 - No Pedigree and Population 2 - Reconstructed Pedigree. Genetic variances were statistically significant but generally higher σ̂g2was observed for Population 2. Height and form were under low to moderate genetic control as indicated by clonal repeatability and estimates were relatively similar between populations. For example, average Ĥ2in Population 2 was 0.31 for height (range: 0.18-0.45) and 0.22 for form (range: 0.06-0.32). While average Ĥ2in Population 1 was 0.25 for height (range: 0.19-0.35) and 0.18 for form (range: 0.09-0.27). The reconstructed pedigree in Population 2 allowed partitioning the genetic variance (σ̂g2) into component parts of additive (σ̂a2), specific combining ability (σ̂s2), and clone (σ̂c2); however, general lack of structure within the population resulted in variance components to be estimated with little precision for additive and specific combining ability. The majority of genetic variation was associated with clone for both traits. For example, σ̂c2accounted for 57.6% and 62.5% of the total genetic variance for height and form, respectively. Growth and form responses of clones across test environments were relatively stable and overall type-B genetic correlations were in excess of 0.8 for both traits implying clones selected for production populations should respond favorably across the seed planning zone for yellow cypress in coastal BC.

Multisite genetic parameter estimates from aCallitropsis nootkatensisdiallel study with clonally replicated progeny

“…The maritime SPU for C. nootkatensis has a large elevational range from 1 m to 1100 m above sea level and a latitudinal span from approximately 48°30=N to 52°00=N (Fig. 1), which is supported by previous genetic testing results (Russell and Krakowski 2012;Baltunis et al 2013). One-hundred and ninety-four parents were crossed using 24 eightparent partial circular diallels to produce 4524 genotypes from 343 full-sib families ( Table 2).…”

“…This ecological zone does not have a designated SPU for breeding and deploying improved material because planting demands are minimal. Although studies have shown yellow cypress to be a generalist with respect to population adaptation (Russell 1992;Russell and Krakowski 2012;Baltunis et al 2013), parent trees were kept separate by diallel, so that any differences among parents from the two geographic areas could be accounted for by including a random term for diallel sets as detailed in Data analysis. The number of parents, partial diallels, and full-sib families, as well as mean number of genotypes per family and total number of genotypes for each series, are detailed in Table 2.…”

“…In a C. nootkatensis clonal study without pedigree structure that was established on seven sites, estimated across-site genetic correlations for growth and form varied from 0.7 to 0.91 (Baltunis et al 2013). These sites were located on ecologically divergent ecosystems, some separated by as much as 1000 m in elevation.…”