Matings of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) were performed to develop inbreeding levels with inbreeding coefficient (F) values from 0.0 to 0.75. A strong inverse linear relationship was found between filled seed per cone and F at values ≤0.5. The following mean filled seed per cone values were obtained: outcross (F = 0.0), 31.6; half-sib cross (F = 0.125), 21.3; full-sib cross (F = 0.25), 16.7; parent–offspring backcross (F = 0.25), 15.5; self (F = 0.5), 1.2; second generation self (F = 0.75), 0.03. Parental effects on filled seed per cone were large, accounting for about 50% of the total variation. The use of related clones in a seed orchard will result in less inbred seed than expected under total panmixia, owing to decreased filled seed production at all inbred levels. Also, breeding programs will require increased effort to obtain seed when mating designs include crosses between related trees.

In advanced generation seed orchards, tradeoffs exist between genetic gain obtained by selecting the best related individuals for seed orchard populations, and potential losses due to subsequent inbreeding between these individuals. Although inbreeding depression for growth rate is strong in most forest tree species at the individual tree level, the effect of a small proportion of inbreds in seed lots on final stand yield may be less important. The effects of inbreeding on wood production of mature stands cannot be assessed empirically in the short term, thus such effects were simulated for coastal Douglas fir [ Pseudotsuga menziesii var. menziesii (Mirb.) Franco] using an individual-tree growth and yield model TASS (Tree and Stand Simulator). The simulations were based on seed set, nursery culling rates, and 10-year-old field test performance for trees resulting from crosses between unrelated individuals and for inbred trees produced through mating between half-sibs, full-sibs, parents and offspring and self-pollination. Results indicate that inclusion of a small proportion of related clones in seed orchards will have relatively low impacts on stand yields due to low probability of related individuals mating, lower probability of producing acceptable seedlings from related matings than from unrelated matings, and a greater probability of competition-induced mortality for slower growing inbred individuals than for outcrossed trees. Thus, competition reduces the losses expected due to inbreeding depression at harvest, particularly on better sites with higher planting densities and longer rotations. Slightly higher breeding values for related clones than unrelated clones would offset or exceed the effects of inbreeding resulting from related matings. Concerns regarding the maintenance of genetic diversity are more likely to limit inclusion of related clones in orchards than inbreeding depression for final stand yield.

International audienceAbstractContextThe effects of inbreeding on growth traits have been studied and are fairly well understood in young conifers. However, in trees approaching mid-rotation, this information is not widely available at present. AimThe aim of this study is to assess inbreeding depression in mid-rotation coastal Douglas-fir in growth traits, survival, and wood density.MethodsSeveral levels of inbreeding were created in coastal Douglas-fir, using a nine-clone founder population to produce 148 families with varying levels of inbreeding ranging from f = 0 (outcrossed) to f = 0.5 (selfed). The trees were planted in 1987 on two farm-field sites in coastal BC. Here, we report effects of inbreeding in height, diameter, tree volume, survival, and wood density in 26-year-old trees.ResultsPrevious results obtained from this test population showed negative near linear effects with levels of inbreeding in seed production, nursery growth performance, and growth traits in the field assessed at age 10. At age 26, inbreeding depression was highest in survival, ranging from 20 to 80 % for f = 0.125 and f = 0.5, respectively. In contrast, the most severe inbreeding depression among the three levels of inbreeding was only 4 % for wood density at f = 0.5 (selfing). Inbreeding depression in height, diameter at breast height (dbh), and volume increased linearly from f = 0 to f = 0.25, then leveled off.ConclusionFounder genotypes had varied responses to inbreeding as parental breeding values across inbreeding levels were inconsistent (in magnitude, sign, and trait). No differences in levels of inbreeding depression were found between full-sib matings and parent-offspring matings. These findings have implications for the testing of parents within sublines, where inbreeding is accumulated in sublines. However, since parents respond differently to levels of inbreeding, their performance may not be well correlated to their quality as outcrossing parents

Effects of stem girdling on cone yield and endogenous phytohormones and 4 metabolites in developing long shoots of Douglas-fir (Pseudotsuga menziesii) 5 6Lisheng Kong (1, 5*), Patrick von Aderkas (1), Stacey J Owen (2), 7Barry Jaquish (3), Jack Woods (4), Suzanne R. Abrams (2) Stem-girdling treatments were applied in early spring to stimulate cone formation in 37 two genotypes of interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) 38 Franco). After girdling treatments, male cone yield increased significantly in the next 39 growing season. The increase was 14-fold in genotype 9137. In genotype 9550, more 40 than 8,700 male cones were induced from each tree whereas no male cones were 41 found in controls. Female cone yield was zero in controls and low for girdled trees in 42 both genotypes. Multiple phytohormone-related compounds, including gibberellins 43 (GAs), cytokinins, indole-3-acetic acid (IAA), abscisic acid (ABA) and their selected 44 metabolites, were analyzed in developing long shoots after girdling treatments by high 45 performance liquid chromatography-electrospray ionization tandem mass 46 spectrometry (HPLC-ESI-MS/MS) in multiple reaction monitoring mode. 47Concentrations of GA 4 were slightly higher at week 2 following girdling treatment, 48 whereas at week 8 lower GA 4 concentrations were found in girdled samples. Stem 49 girdling did not affect concentrations of IAA and major cytokinins, such as zeatin 50 riboside and isopentenyl adenosine. Concentrations of ABA differed two-fold between 51 the genotypes. Although girdling treatment did not cause differences in ABA 52 concentrations, it generally resulted in higher concentrations of ABA glucose ester. 53

In lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm), cone initiation and gender differentiation are site-specific in long-shoot buds with female cones in the distal portion and male cones in the proximal portion. By using high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) in multiple reaction monitoring (MRM) mode, cytokinins, indole-3-acetic acid (IAA), gibberellins (GAs), abscisic acid (ABA) and their selected metabolites, were investigated in developing long-shoot buds from multiple genotypes. Spatially, higher concentrations of trans-zeatin riboside (t-ZR) and dihydrozeatin (dhZR) existed in the distal parts of long-shoot buds, whereas concentrations of isopentenyl adenosine (iPA), IAA, GA 24 , ABA, ABA glucose ester (ABA-GE) and phaseic acid (PA) were higher in the proximal parts in all investigated genotypes. In long-shoot buds of genotypes with a history of high female cone yield, concentrations of t-ZR and the ratio of zeatin-type to isopentenyl-type cytokinins were higher in the entire buds, whereas dhZR or IAA was higher either in the distal or in the proximal part respectively. In low female cone yielding genotypes, concentrations of c-ZR, iPA, ABA-GE and PA were higher in both of the parts, whereas ABA was higher mainly in the distal part with higher GA 24 in the proximal part. Temporally, concentrations of several hormone-related compounds showed obvious changes in late June and late July, prior to male and female cone bud differentiation. This study reveals that the local hormonal status in a long-shoot bud at specific developmental stages may play an important role in gender determination and cone yield. 3Abbreviations: HPLC-ESI-MS/MS, high performance liquid chromatographyelectrospray ionization tandem mass spectrometry; MRM, multiple-reaction monitoring; GA, gibberellin; ABA, abscisic acid; PA, phaseic acid; DPA, dihydrophaseic acid; 7'-OH ABA, 7'-hydroxy ABA; neoPA, neophaseic acid; ABA-GE, abscisic acid glucose ester;IAA, indole-3-acetic acid; IAA-Asp, indole-3-acetic acid aspartate; IAA-Glu, indole-3-acetic acid glutamate;