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Somatic embryogenesis (SE) cloning techniques for Nordmann fir Christmas tree production have been pursued and refined in Denmark, and three SE clonal trials with 201 SE clones from seeds of 27 Nordmann fir trees and seedlings from bulk harvest seeds in Georgia, Caucasus, were established from 2014 to 2015. This study was the first to evaluate the genetic performance of these SE clones in different sites. In addition, the performance of SE clones and (zygotic) normal seedlings in the field was compared in this study. This study was based on three key groups of traits for Christmas tree production, measured 5 and 6 years after planting: growth, commercial tree quality, and disorder. Seedlings grew faster and had better Christmas tree quality than SE clones. There were significant family effects for all traits, indicating that a good family also produced good clones on average. Growth and disorder traits were under moderate genetic control, with estimated broad-sense heritability (H2) from 0.19 to 0.31 and from 0.20 to 0.28, respectively. Quality traits had low to moderate H2, ranging from 0.09 to 0.24. Significant genotype-by-environment interactions were shown for Christmas tree quality, post-harvest needle retention, and branch angle, suggesting the importance of choosing the right clone at each site. There was no significant interaction in height among the years. Superior clones, compared to the unbred seed source, were identified by combining several important traits. Overall, the somatic clones were well established but had slower growth compared to standard seedlings. [ABSTRACT FROM AUTHOR]

Despite a much later inception of somatic embryogenesis (SE) propagation protocols for gymnosperms than for angiosperm species, SE is becoming increasingly important due to its applications for commercial forestry. For many conifers, there are however still major bottlenecks in the SE plant production process limiting the use of SE for forestry operations, Christmas tree production and research projects. In the present case study, the effects on plant growth from different cultural factors applied during the SE developmental process were studied in two conifer species of high value for Christmas tree production. Seven clones of Abies nordmanniana and two clones of Abies bornmuelleriana were included in the study. Accumulated effects from cultural treatments were recorded from the start of germination of mature embryos of different quality scores through development into plants in the third growing period. Experimental factors of the cultural treatments included were: germination temperature, germination time, light conditions, survival ex vitro and traits for plant growth and vitality. The results reveal that most of the studied experimental factors influenced plant growth during the first three years however their relative importance was different. Plant survival rate at end of the nursery stage was strongly impacted by germination temperature (p<0.001), initial embryo score (p=0.007), clone (p<0.001) and to a lesser extend week of germination (p=0.017). This case-study highlights and quantifies the strong interrelation between the developmental steps of somatic embryogenesis and show the importance of considering all cultural steps when optimizing SE plant production protocols. [ABSTRACT FROM AUTHOR]

In Europe, the most widely used Christmas tree species, Abies nordmanniana, has a long history of infestation with the adelgid Dreyfusia nordmannianae . Since 2011, the species has furthermore been increasingly damaged by the fungus Neonectria neomacrospora . The objective was to study whether infestations by N. neomacrospora were facilitated by the presence of adelgids in Nordmann fir and to explore the genetic components of this potential interplay. The damage caused by D. nordmannianae and N. neomacrospora in two Nordmann fir clonal seed orchards in Denmark was evaluated in 2014, and an experimental infestation was conducted to test the performance of Nordmann fir somatic embryogenesis-derived trees exposed to N. neomacrospora and D. nordmannianae individually or in combination by setting up an artificial infestation chamber. The genetic correlation between the two diseases was 0.54 at two clonal seed orchards, indicating that the trees susceptible to N. neomacrospora were also susceptible to D. nordmannianae or vice versa. In the experimental test, only trees in the treatment with both D. nordmannianae and N. neomacrospora developed needle loss and dieback symptoms. Thus, both the field evaluations and the experimental test revealed an interplay between D. nordmannianae and N. neomacrospora damage on Nordmann fir trees. Future studies should explore in more detail how D. nordmannianae interacts with N. neomacrospora . Our findings and future studies on this topic could have important implications for suitable breeding programs for Nordmann fir Christmas trees and forest pest management. [ABSTRACT FROM AUTHOR]

A field test with 26 provenances of subalpine fir and corkbark fir was established at three sites in Denmark and one site in Iceland in 1999. Survival, growth and Christmas tree quality were assessed after 10 growing seasons in Denmark and 12 in Iceland. Provenances showed significant differences for all measured traits. The western-most subalpine fir provenances from Washington state and British Columbia showed the overall best results in Denmark with the highest survival (after 15 years), fastest growth in height and highest Christmas tree quality and profitability as well as both good postharvest needle retention and high resistance to pests. The corkbark fir provenances also showed high Christmas tree quality and the lowest frequency of fork formation, but corkbark fir provenances also exhibited the poorest postharvest needle retention. In Iceland, the corkbark fir provenances generally showed the highest survival rate and Christmas tree quality. The White River provenance from British Columbia is recommended for use in Denmark. The Mount Taylor provenance from the Cibola National Forest in New Mexico is recommended for use in Iceland. [ABSTRACT FROM AUTHOR]

Noble fir is the leading Christmas tree produced in the US Pacific Northwest (PNW). This study is based on evaluations of 24,721 trees collected from five native collection regions in Oregon and Washington plus imported seed from Denmark. The major collection areas were further subdivided into provenances utilizing 16 in the PNW and 6 from Denmark. A total of 22 test sites were evaluated from progeny trials planted between 1996 and 2007. Traits important for commercial Christmas tree production were evaluated and include commercial height, tree grade, value and colour. Tree height and quality were positively correlated while colour showed little correlation with either trait. Provenances from the Oregon Coast and Willapa Hills, Washington provided the highest potential gain for Christmas tree market value. Provenances from Denmark exhibited superior colour and slow growth. For breeding purposes, the gain from backwards selection estimated a range of improvement in marketable value from 0.91 to 1.22 Euros per tree. [ABSTRACT FROM AUTHOR]

• Context: Many tree breeding programmes rely entirely on clonal seed orchards as the link between breeding activities and forestry, and are thereby also exposed to yearly fluctuations in the orchard crops. • Aims: The main objective was to study the impact of year and clone fluctuations in strobili production on genetic worth, as well as on genetic diversity, of 18 consecutive commercial seed orchard crops. • Methods: In a mature Abies nordmanniana clonal seed orchard, a yearly visual assessment of female and male strobili was carried out on a total of 18 clones (260 ramets), and coupled with clone breeding values. • Results: Despite large annual and clone variation, and year-by-clone interaction in strobili production, the orchard's genetic worth was somewhat uniform when considering four evaluated traits in the 11 years of superior or medium crop size. These years accounted for 95% of the accumulated cone crop over the whole period (18 years). Noteworthy deviations were only seen in the seven poorest seed years, comprising the remaining 5% of the total cone crop, where genetic diversity measures were also low. • Conclusion: Avoiding small crop years seems to be a reasonable way to avoid fluctuations in the commercial seed orchard product. [ABSTRACT FROM AUTHOR]

Conservation through utilization is a controversial strategy that deserves more attention from researchers and practitioners. This case study focuses on Abies guatemalensis, a Vulnerable Mesoamerican conifer that is illegally used for timber, shingles, charcoal and Christmas tree production. Conservation of the remnant populations would preserve some unique montane forests, with concomitant benefits for local water supplies and prevention of landslides. As a conservation tool we suggest establishment of additional A. guatemalensis Christmas tree plantations. These could generate income for local farmers and help halt poaching from natural stands. So far, 51 such plantations have been established in Guatemala but practical knowledge of cultivation is limited and production dominated by a few large plantations. Seed for Christmas tree plantations needs to be carefully selected because there are marked differences among populations in germination, seedling height increment and greenery quality. Insect pests such as the balsam twig aphid Mindarus sp. couldlimit cultivation. A market study showed that c. 23% of households in the major Guatemalan cities buy A. guatemalensis Christmas trees but currently only 2.3% of these are plantation-grown. The prices of illegal and certified Christmas trees are, however, converging, making plantation trees more competitive. Because of the market characteristics and the potential for establishment of plantations, we are moderately optimistic that the conservation through utilization strategy may be successful for this species in Guatemala. [ABSTRACT FROM AUTHOR]

Nordmann fir [ Abies nordmanniana (Stev.) Spach.] is a widely used Christmas tree species in northern Europe. In recent years there has also been increasing interest in using Nordmann fir as a Christmas tree in North America. Postharvest quality is a central characteristic for high-quality Christmas trees. To examine the genetic variation in needle retention, a series of experiments was conducted using cut branches from a grafted seed orchard with 23 clones and a progeny trial comprising 19 open-pollinated clonal progenies of the orchard. For both clones and open-pollinated families strong genetic differences were seen in needle retention when branch samples were allowed to dry. Based on one progeny trial, single tree heritabilities were estimated in the range of 0.27–0.31 after 10–15 days of drying. A parent–offspring regression indicated a higher heritability. These results indicate that breeding efforts can be used to improve significantly the postharvest needle retention characteristics of Nordmann fir Christmas trees. [ABSTRACT FROM AUTHOR]

Needle retention is an important trait when selecting for high quality Christmas trees. Nordmann fir [Abies nordmanniana (Stev.) Spach.] is generally considered to have good needle retention, but recent research has shown that when cut trees are allowed to dry, significant needle loss problems can develop. This has the potential to limit the use of this species in situations where trees are harvested early, shipped long distances, sold in warm weather markets and displayed for extended periods of time. A set of 39 provenances where tested to identify provenance differences in needle retention. Branches where collected in two consecutive years in October in 1999 and 2000 and November 2000. Small branch samples where cut and displayed indoors under controlled conditions and allowed to dry. Strong provenance differences in needle loss were seen for all three test dates. No significant interactions were seen among the October collections, but significant rank changes occurred from October to November. Predicted (BLUP) provenance mean values ranged between 11% and 27% for needle loss when branches where allowed to dry, averaging all three tests. Despite only one test location, the study clearly indicates that it should be possible to select for provenances with generally better needle retention characteristics. [ABSTRACT FROM AUTHOR]

Postharvest moisture and needle retention of boughs was examined for four Danish and five U.S. provenances of noble fir grown in Denmark. Boughs were displayed indoors under controlled conditions, and data were collected relating to rates of moisture loss and needle retention. Small current-year shoots had moisture and needle loss patterns similar to larger bough material. Postharvest quality of the Danish and U.S. provenance boughs was very similar. There was also a high correlation between the moisture level of the boughs and shoots, indicating that it should be possible to use small shoots to assess differences in moisture retention in future tests. [ABSTRACT FROM AUTHOR]

In three Nordic field trials, 26 provenances of Abies lasiocarpa (Hook.) Nutt. and Abies lasiocarpa var. arizonica (Merriam) Lemmon were evaluated 3 yrs after establishment. The focus was on 16 traits important for adaptation, establishment and production of Christmas trees. For all three sites in Denmark, Norway and Iceland, survival ranged from 89 to 96%. Provenances showed statistically significant differences for all but two traits. For all traits there was significant interaction between provenance and site. Analysis of ecovalens showed that for most traits, only a limited number of provenances contributed substantially to the interaction. Therefore, a large proportion of the provenances showed a fairly consistent ranking across sites. The frequency of potential Christmas trees in the provenances ranged from 10 to 49%. Southern provenances from New Mexico and Arizona seemed to have the best potential for producing high-quality Christmas trees. The southern provenances added substantially to the interaction between provenance and site for budset, lammas growth and colour. When using multivariate statistical methods on all measured traits, the provenance clusters fitted neatly into six distinct geographical regions. [ABSTRACT FROM AUTHOR]

Christmas tree is an important specialty crop. In Europe, the main Christmas tree species is Nordmann fir (Abies nordmanniana (Steven) Spach) and nearly 42 million trees are sold each year. This paper focuses on three key traits for Christmas tree production: growth (including branching), commercial tree quality, and post-harvest needle retention. The objectives of the study are to estimate genetic variation and heritability, genotype-by-site interaction, and genetic correlations among traits, and to illustrate and discuss potential gains from selection. The field trial series comprises 10 sites, 7 provenances, and 128 single-tree open-pollinated offspring from five Danish seed sources (in total 45,531 trees). At year 7 from planting, growth and quality were assessed on all sites. A subset of three sites were sampled twice (in October and November) for evaluation of post-harvest needle retention. Heritabilities across sites were 0.23, 0.21, and 0.13 for tree height, number of branches, and Christmas tree score, respectively. Heritability for post-harvest needle retention increased from 0.28 in October to 0.55 in November. Average additive genetic site-by-site correlation for tree height was 0.72, for number of branches 0.86, and for Christmas tree score 0.72, indicating that the genotype-by-site interaction is small and not important. Post-harvest needle retention did not correlate to any other traits. Potential gains from backward selection and grafting superior plus-trees in clonal seed orchards, e.g. the 15–20 best ones, were estimated to be 20% in Christmas tree score, number of branches, and height, and 65% in November post-harvest needle retention. [ABSTRACT FROM AUTHOR]

Pedigree reconstruction via DNA markers and subsequent quantitative genetic analyses in production stands of trees is an alternative to traditional forest tree breeding. The method requires variable DNA markers; preferably cost-efficient to genotype. We tested the approach in breeding for Christmas tree traits in a Danish landrace of Abies procera. Initial analysis with simple sequence repeats (SSRs) revealed a substantial reduction in genetic diversity of Danish A. procera compared with direct imports from the USA, indicating a genetic bottleneck. Due to the reduced genetic variation, the SSRs were not variable enough for pedigree reconstruction, and 145 single nucleotide polymorphisms (SNPs) were therefore identified and genotyped via high-throughput targeted sequencing. In the field, we phenotypically selected 674 superior trees, based on criteria for good Christmas trees, among 21,000 trees in three Christmas tree plantations originating from an A. procera clonal seed orchard. By SNP-genotyping and parentage analysis, pedigree was reconstructed for the selected individuals, and genetic predictions for the Christmas tree traits were estimated. A final selection of 45 trees out of the 674 genotyped, based on an index of predicted values for different traits, foresees a gain in the Christmas tree score and branch angle score of 16% and 10%, respectively. The study clearly demonstrated the benefits of pedigree reconstruction, even though mass selection seemed to give similar gain. Primarily, the possibilities to control the level of inbreeding, and to check whether the production stands, from where we select trees, actually originate from the declared and desired parent pool. [ABSTRACT FROM AUTHOR]