Michael Stoehr

Gain and diversity in advanced generation coastal Douglas-fir selections for seed production populations

Sublines are used in the third-generation breeding and testing of coastal Douglas-fir in British Columbia, with the original intent of selecting only one genotype per subline for production populations (e.g., seed orchards) to eliminate relatedness among parents (therein called “1/SL”). We evaluated three additional selection scenarios that did not consider the subline structure. One of the scenarios strictly selected on the basis of the highest breeding values of the trees (“TOP”); another scenario used the TOP selections, but assigned the number of ramets per selection proportionally to the selection breeding value (“LIND”); lastly, a simulated annealing technique was applied to maximize gain under explicit constraints on coancestry (“OPTS”). All three alternative selection scenarios resulted in some relatedness and coancestry among selections, but the last two provided increases in average breeding values compared to those obtained by the 1/SL scenario. Effective population sizes (and consequently inbreeding coefficients) varied among the three selection scenarios. Effects of the various selections on merchantable volume at rotation age were determined using a linear regression model based on an individual tree model (TASS), which was first run to determine the relationship between merchantable volume and inbreeding (f). LIND and TOP selections yielded the highest breeding values but, due to the increased coancestry among selections, paid a penalty in the merchantable volume determination. OPTS maximized merchantable volume at rotation age 60 after including more than 13 selections with an increase of around 3% over that obtained by the 1/SL selection scenario, with an associated increase in Ne of 50%. Other implications of the three alternative selection scenarios are discussed.

Identification and joint modeling of competition effects and environmental heterogeneity in three Douglas-fir (Pseudotsuga menziesii var. menziesii) trials

Abstract(Co)variance matrices for the assumed model, and thus the specification of the dispersion parameters, should take into account both the negative competition and the positive spatial correlations. In this context, we applied several approaches to identify and quantify the genetic and environmental competition effects and/or environmental heterogeneity in three Douglas-fir genetic trials from the British Columbia tree improvement program in total height and diameter at breast height at ages 12 and 35. Then, we applied an individual-tree mixed model to account jointly for competition effects and environmental heterogeneity (competition + spatial mixed model, CSM). We also compared the resulting estimates of all dispersion parameters and breeding values (BVs) with corresponding estimates from three simpler mixed models. Our analysis revealed that strong spatial environmental variation (predominantly at large-scale) covered the effects of competition in the three Douglas-fir progeny trials. While diameter at breast height at age 35 revealed strong competition effects at both genetic and environmental levels, these effects were not as strong for total height. In general, with strong competition genetic effects, the CSM gave a better fit than the simpler models. Ignoring competition effects and environmental heterogeneity resulted in lower additive genetic variances and higher residual variances than those estimated from the CSM. Ignoring competition effects leads to overestimating environmental heterogeneity, while ignoring the environmental heterogeneity leads to underestimating competition effects. Spearman correlations between BVs predicted from the simplest model and total BVs from the CSM were moderate to high. The implications of all these findings for the genetic improvement of coastal Douglas-fir in British Columbia are discussed.

Evaluating Supplemental Mass Pollination Efficacy in a Lodgepole Pine Orchard in British Columbia using Chloroplast DNA Markers

Supplemental mass pollination (SMP) success in a grafted lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) seed orchard in southern British Columbia was studied by employing four chloroplast DNA (cpDNA) markers to determine fertilization success of 10 pollen parents. SMP was conducted operationally with a bulked pollen mix twice during peak receptivity in the seed orchard. Fertilization success of the 10 SMP parents averaged 16% greater than for wind-pollinated controls in a different section of the orchard. SMP also increased the uniformity of the male contribution in treated seeds.

Within and among family variation of orchard and wild-stand progeny of interior spruce in British Columbia

A common garden study was conducted with seedlings of the interior spruce complex [Picea glauca (Monch) Voss and Picea. engelmannii Parry and their hybrids], comparing seedling height growth using open-pollinated orchard families and wild-stand (WS) families from the same breeding zone. Phenotypic variances of three bulked orchard seedlots and three WS seedlots did not differ. Orchard seedlots had generally higher within-family variance components than WS families. To examine year-to-year variation in orchard seedlots, three seedlots, composed of the same 18 orchard families collected in three different years, were evaluated in the same common garden study. Family mean heights within the three crop years were statistically not different; however, large rank changes in family mean heights and family variances were observed. This study shows that orchard seed derived from breeding programs does not reduce phenotypic variability in commercial plantations. In spite of the moderate to high selection intensities applied to the selection of orchard parents, large amounts of phenotypic variation are maintained because of the lack of coancestry in the orchard pollen cloud and large temporal variation in mating success and fecundity of the various parents contributing to the crop.

Seed cone production enhanced by injecting 38-year-old Larix occidentalis Nutt. with GA4/7

The influence of injecting 38-year-old Larix occidentalis with gibberellin A4/7 (GA4/7) on seed and pollen cone production was studied in western Montana, U.S.A. Two natural stands thinned to several spacings in 1961 were chosen. The two widest spacings were used. In 1991, 60 trees selected for study at each site were randomly divided into two groups of similar DBH, half as controls and half injected in June 1991 with a solution of GA4/7 in ethyl alcohol. The volume injected was adjusted to the DBH of each tree (60 mg per 5 cm diameter). In June 1994, half the trees treated with GA4/7 in 1991 and half the untreated trees were injected with GA4/7 in the same manner as before. In 1992 and 1995, seed cone production increased on GA4/7-treated trees compared to the controls. Pollen cone production was significantly increased by GA4/7 treatment but only at one site. Delayed effects of GA4/7 on seed cone production was not evident in subsequent years after treatment. Foliar and shoot damage on treated trees was attributed to GA4/7 treatment but most trees recovered completely the following year. Finally, GA4/7 treatment did not affect cone length, potential seed per cone or filled seed per cone.

Orchard pollen contamination: joint estimation of realized levels on current growth and future effects on volume and value at rotation in coastal Douglas-fir in British Columbia

ABSTRACT Pollen contamination was evaluated using control-pollinated seedlings pollinated with polymixes of orchard pollen and pure wildstand and wind-pollinated orchard seedlings. At age 7, seedlings pollinated with contaminate pollen were the shortest across all four sites, but had survival levels (83%) similar to open-pollinated (84%) and pure orchard seedlings (86%). Open-pollinated seedlings had intermediate heights while pure orchard seedlings were tallest. The level of pollen contamination in open-pollinated seedlots was estimated to be 26%. Survival for all pollen sources combined was similar at the two high-elevation sites (84%) and low-elevation sites (86%). Using a yield model to compare volume/ha at rotation age for open-pollinated orchard seedlings and pure orchard seedlings, differences were small and increased due to site index (SI; from 3 to 6 m3/ha) but not due to planting density. Equivalent discounted benefits at rotation were 27 vs. 54 C

Effects of crown-pruning on seed and pollen cone production in two lodgepole pine seed orchards in British Columbia

/ha at the two extreme site indices (18 vs. 25), respectively. These projected reductions due to pollen contamination are magnified by the large area that is regenerated annually with orchard seed of coastal Douglas-fir and contamination can cause a reduction in benefits of up to C

Evaluation of mating dynamics in a lodgepole pine seed orchard using chloroplast DNA markers

748,500 per year at the highest SI at a planting density of 1111 trees/ha.

Parental environment aftereffects on germination, growth, and adaptive traits in selected white spruce families

The effects of top pruning on subsequent seed and pollen cone production in lodgepole pine (Pinus contorta Dougl.) grafted clones in two seed orchards were evaluated. In the older orchard (14 years old), three pruning regimes were applied: an untreated control, a moderate pruning where 25% of the crown was removed and a severe pruning where 40% of the crown was removed. In the younger orchard (ten years old), only a control pruning and a severe pruning (50% of crown removed) were applied. Five-year seed cone production was lower in treated ramets compared to controls in both orchards. However, when cumulative seed cone yields were adjusted for reduced tree heights after pruning, differences were no longer significant in the older orchard. Strong clonal variation was observed in seed cone yields in both orchards. Pollen cone development was less variable among treatments in the older orchard. In the younger orchard, controls consistently produced heavier pollen crops. Pruning recommendations for similar orchards are made and results discussed for reducing the impacts of losses in seed cone yields.