Ulrik Bräuner Nielsen

Microsatellites used to establish full pedigree in a half-sib trial and correlation between number of male strobili and paternal success

Abstract• Paternity was established in a field trial of Abies nordmanniana with open-pollinated (OP) offspring from a clonal seed orchard (CSO) comprising 23 clones.• The purposes were to: (1) investigate the violation of the assumption of true half-sibs in OP progeny trials; (2) assess the value of male strobili scorings to predict paternal contributions in CSOs; and (3) study the bias in breeding values and heritabilities obtained in breeding with OP family trials due to unknown paternity.• The paternal contribution to the offspring varied a lot among the clones, but the resulting violation of the assumption of true half-sibs in the progeny trial was only modest.• On average 84% of the relationships among the offspring were true half-sib, resulting in an average genetic correlation of 0.29 (range 0.26 to 0.33).• Male strobili scorings from the seed harvest year did well in forecasting the paternal contribution to the offspring. The linear regression of sired progeny on the estimated clonal proportion of male strobili explained 76% of the variation.• The large variation in siring success and existence of other types of relationships than true half-sibs among the offspring only gave minor bias in estimated genetic parameters.

Genetic variation in postharvest needle retention among Nordmann fir families and grafted clones

Abstract 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.

Conservation through utilization: a case study of the Vulnerable Abies guatemalensis in Guatemala

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 aremarked differences among populations in germination, seedling height increment and greenery quality. Insect pests such as the balsam twig aphid Mindarus sp. could limit 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.

Nordic provenance trials with Abies lasiocarpa and Abies lasiocarpa var. arizonica: three-year results

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.

Genetic variation in resistance to Dreyfusia nordmannianae Eckst. infestations in Abies nordmanniana (Stev.) Spach

Abstract Nordmann fir ( Abies nordmanniana (Stev.) Spach.) is the main tree species for Christmas tree production in Denmark and adelgid attack is a severe problem. Genetic differences between Nordmann fir provenances, families within provenances and their suitability as host plants for the silver fir woolly adelgid ( Dreyfusia nordmannianae Eckst.) were investigated based on artificial infestations of 63 families originating from three provenances and four provenance samples a total of 2100 seedlings planted in a single field trial. Counts of adelgids, curling of needles due to adelgid attack together with flushing and several growth traits were measured in each tree for 2 consecutive years. The artificial infestation was very efficient, with 97% of the trees infested. Family mean infestation levels ranged from 69.5 to 100% for sistentes in the first year. Very pronounced and significant family differences were seen after the year 2 assessments. Estimated heritabilities, and genetic variation among families showed a much lower level for the adelgid counts than for flushing and growth traits. Strong differences in needle curling were seen for the same infestation levels of adelgids, indicating differences in tolerance among families. Traditional backwards selection based on family means and seed orchard establishment with moderate selection intensities can reduce the future damage level but not eliminate the adelgid problem.

Impact of site and provenance on economic return in Nordmann fir Christmas tree production

Abstract The economic potential of 35 seed lots from Danish landraces of Nordmann fir [Abies nordmanniana (Stev.) Spach.] and seven imported provenances were evaluated for high-value Christmas tree production over a full rotation at six locations in Denmark. Naturally grown Christmas trees were evaluated and no leader length control or trimming of the side branches was allowed, but only simple cutting of double terminal leaders. Seed source as well as site strongly affected the economic revenue. Average net sales price per planted tree ranged over sites from €2.43 to €6.64, and among provenances from €1.38 to €7.06 with an average of €4.95. Changes in prices and grading as seen under cycling market conditions seemed not to affect the economic ranking of the better part of the provenances, whereas discounting the net sales income caused moderate rank changes, reflecting differences in rotation time. Limited seed source by site interactions were present and mainly caused by the slowest growing sources. Among the Danish domesticated seed sources of mostly unknown origin several were as suitable as the tested imported sources. In general, the Danish sources were faster growing than imports, although very large variation was present.

Genetic variation in characters important for noble fir greenery production

Abstract In Europe and North America the cut branches of noble fir (Abies procera Rehd.) are widely used for greenery production for various decorational purposes. In this study, provenance and family variation were evaluated for a set of quality traits related to greenery production as well as to the harvest of cut branches in kg ha–1. The study was based on 11 field trials. Testing showed that Danish second or later generation seed sources had in general a higher greenery quality than imports from the Pacific Northwest of America. Narrow-sense heritabilities estimated for quality traits (colour, coverage and shoot type, and for height growth and branch characteristics) ranged from 0.04 to 0.17. The tested Danish progeny material showed a substantial amount of genetic variation. The estimated gains from backwards selection showed an increase in the quality as well as the quantity of harvestable branches for greenery production. Estimated gain in net income per harvest was, dependent on selection strategy, estimated to vary between ∈600 and 900 compared with unselected.

Species variation in susceptibility to the fungus Neonectria neomacrospora in the genus Abies

ABSTRACT The fungus Neonectria neomacrospora has recently caused an epidemic outbreak in conifer species within the genus Abies in Denmark and Norway. Christmas tree producers in Europe and North America rely, to a large extent, on Abies species. The damage caused by N. neomacrospora, including dead shoot tips, red flagging of branches and potentially dead trees, have therefore caused concern about reduced quality and loss of trees, and thereby of revenue. Field observations of natural infection of 39 taxa, from 32 species, within the genus Abies in the Hørsholm Arboretum, Denmark, were evaluated; significant differences were seen between taxa, that is, species, and between some species and their subspecies. The Greek fir, Abies cephalonica, was the only species without damage. An inoculation experiment on detached twigs with mycelium plugs from a N. neomacrospora culture showed that all species could be infected. The damage observed in the inoculation experiment could explain 30% of the variation in the field observations based on species mean values. The epidemic outbreak and the high number of species susceptible to this fungus indicate that N. neomacrospora requires attention in the cultivation and conservation of Abies species.

Response to selfing in seed set, seedling establishment and nursery growth based on controlled crosses of Abies nordmanniana clones.

Abstract Nordmann fir (Abies nordmanniana) is used for production of high value Christmas trees in short rotation. Potentially all trees are intended to be sold - no thinnings are normally applied. A high proportion of saleable trees per ha is the main key to secure economic return to the growers. Consumers demand a symmetric and rather uniform tree and, dependent on local traditions, it should be more or less dense and narrow. In Denmark, breeding of Nordmann fir and establishment of seed orchards focus on seed supply and improved Christmas tree quality - aiming at adaption and a rather uniform ideotype Christmas tree. Benefits from employing rather few clones, to maximise gain and uniformity, may potentially be counteracted by increased selfing. The objective of this study was to quantify the effect of selfing on percentage of filled seed and nursery establishment of seedlings. Inbreeding depression was seen for filled seeds (40%), growth traits (5-17%), plus mortality and axial damage (5-12 percent units). Many selfed seedlings survive and develop into marketable seedlings, although with a depression in numbers of 23-37%, or 9-12 percent units. Nursery sorting procedures can only partially reduce the number of inbred seedlings in Nordmann fir. The large variation among clones in the response to selfing indicates that knowledge of the behaviour of selfed progeny from specific clones in ‘small number seed orchards’ is of practical interest. Trade-offs between increased gain by selection of few clones and a penalty paid for increased inbreeding need further studies during a full Christmas tree rotation.

Ad hoc breeding of Abies bornmülleriana for Christmas tree production using a combination of DNA markers and quantitative genetics—a case study

Quasi-field trials (QFTs) using offspring from first-generation plus trees of Abies bornmülleriana were established on two sites in Denmark via DNA markers and parentage analysis. The aim of this study was to demonstrate an example of ad hoc breeding to make better genetic material available for Christmas tree production. Assessments of several important Christmas tree quality-associated phenotypic traits were made for all offspring individuals in delineated areas of the production stands, and moreover the best individuals in the whole production stands were identified. Postharvest needle retention was evaluated in the parent population in both 2016 and 2017. The results showed that by combining available methodology and pre-selected material, substantial genetic gain in relation to Christmas tree production in A. bornmülleriana could be achieved. Backward selection seems tempting due to its shorter time horizon for delivering improved genetic material. Postharvest needle retention evaluation can be a cheap but important last step in modifying the backward selection. We propose to combine the results based on QFTs with selective seed harvest and paternity tests to give the best possible starting point for production of clonal A. bornmülleriana plants using somatic embryogenesis (SE).