Jon Kehlet Hansen

Towards domestication of Jatropha curcas

Jatropha curcas L. attracts a lot of interest as a biofuel crop, triggering large investments and rapid expansion of cultivation areas, and yet, it should still be considered as a (semi-)wild, undomesticated plant. To use the full potential of Jatropha and to support further expansion and systematic selection, breeding and domestication are a prerequisite. This review reveals and identifies gaps in knowledge that still impede domestication of Jatropha. Prebreeding knowledge is limited. In particular, the regeneration ecology and the degree of genetic diversity among and within natural populations in and outside the center of origin are poorly studied. There is only a limited understanding of the Jatropha breeding system and the effect of inbreeding and outbreeding. This review presents all currently available and relevant information on the species distribution, site requirements, regeneration ecology, genetic diversity, advances in selection, development of varieties and hybridization. It also describes possible routes to a better Jatropha germplasm, gives recommendations for tackling current problems and provides guidance for future research. We also discuss the participatory domestication strategy of Jatropha integration in agroforestry.

Adaptive potential of ash (Fraxinus excelsior) populations against the novel emerging pathogen Hymenoscyphus pseudoalbidus.

An emerging infectious pathogen Hymenoscyphus pseudoalbidus has spread across much of Europe within recent years causing devastating damage on European common ash trees (Fraxinus excelsior) and associated plant communities. The present study demonstrates the presence of additive genetic variation in susceptibility of natural F. excelsior populations to the new invasive disease. We observe high levels of additive variation in the degree of susceptibility with relatively low influence of environmental factors (narrow‐sense heritability = 0.37–0.52). Most native trees are found to be highly susceptible, and we estimate that only around 1% has the potential of producing offspring with expected crown damage of <10% under the present disease pressure. The results suggest that the presence of additive genetic diversity in natural F. excelsior populations can confer the species with important ability to recover, but that low resistance within natural European populations is to be expected because of a low frequency of the hypo‐sensitive trees. Large effective population sizes will be required to avoid genetic bottlenecks. The role of artificial selection and breeding for protection of the species is discussed based on the findings.

Geographical variation in phenology of Quercus petraea (Matt.) Liebl and Quercus robur L. oak grown in a greenhouse

Abstract Twenty-three provenances of Quercus robur and four of Quercus petraea were tested in a nursery indoor provenance trial. The provenances were sampled in the northern region of Europe. The study revealed large provenance variation in growth, flushing and leaf yellowing. Provenances from Finland and Norway were slow growing compared with those from Denmark, which showed slower growth than Polish, German, Dutch and British provenances. Northern provenances had a slightly significant earlier flushing than southern provenances. Provenances from the Netherlands and the British Isles ceased growth significantly later than provenances from Finland, Norway and Sweden. No significant correlations were revealed between leaf yellowing and growth, flushing and growth or length of growing season and growth, but provenances with late leaf yellowing tended to have higher growth. Provenance and family variation were compared among five Danish provenances. High population differentiation of quantitative traits Q ST values were found for phenology and low values for growth. The study confirms that the adaptive potential for Q. robur is very high. The implications for the movement of forest reproductive material and gene conservation are discussed.

Sitka Spruce (Picea sitchensis (Bong.) Carr.)

Sitka spruce (Picea sitchensis (Bong.) Carr) is native to the Pacific North West of America and was introduced to Western Europe in the early 19th nineteenth century. It is now an important commercial species along the extreme western seaboard of Europe – namely Ireland and Great Britain – and this is where most progress has been made in the area of selection and breeding. Sitka spruce has been the subject of more limited selection and breeding work in some other European countries where it is of secondary or minor significance – Denmark, France, Germany, and Norway. These programmes have now effectively come to a close due to perceived lack of importance. In Sweden Sitka spruce is being planted at an increasing rate and is seen as a species of great potential in the light of climate change.

European silver fir (Abies alba Mill.) provenances from Calabria, southern Italy: 15-year results from Danish provenance field trials

Height after 15 years, bud burst and mortality varied significantly among 13 southern Italian (Calabrian), a central Italian, a German (Schwarzwald), a Romanian (Carpathian), and a Danish provenance of silver fir (Abies alba Mill.) tested in two field trials in Denmark. The variation in height was especially observed in the field trial that was well protected against late frost in the spring and early frost in the fall by a shelter wood of larch. Provenances from the region of Serra San Bruno (Calabria) and two provenances from the region of Gariglione (Calabria) showed superior height growth at this site compared with the remaining provenances. Height was below average for two provenances from the region of Aspromonte (Calabria). The variation in height correlated significantly with biomasses of the same provenances obtained in early tests. Bud burst was earlier among provenances from the regions of Serra San Bruno and Aspromonte. These were also characterised by poor winter-frost resistance in early tests. The Romanian provenance was not represented in the shelter wood trial. The variation in height between provenances in the other field trial was mainly due to the Romanian and the Danish provenance with superior and poorer growth respectively. Otherwise, differences between the remaining provenances were not significant at this site probably due to the influence of frost. Provenances with poor winter-frost resistance had higher mortality at this site.

Growth, stem quality and age-age correlations in a teak provenance trial in Tanzania

Abstract This study examines the growth and stem straightness variation between teak (Tectona grandis L. f.) provenances in a 30-year-old field trial in the coastal lowland of Tanzania. The results are compared with earlier results. The findings demonstrate that it is possible to find large height and yield differences between teak provenances. The best performing provenance grows some 10% (height) to 40% (volume) better than the average. The provenance Topslip, India, consistently proved to be outstanding in terms of growth and stem quality confirming earlier evaluations at age 5 and 17 years. Tanzanian land races also proved to be superior, especially as regards stem straightness.

Root CSA-root biomass prediction models in six tree species and improvement of models by inclusion of root architectural parameters

Models were developed for Norway spruce, Sitka spruce, Scots pine, Pedunculate Oak and European Beech to predict the biomass of individual structural roots based on either basal root cross sectional area (rCSA) assessments (basic models) or on rCSA and additional root architectural measurements (multiple models). The material embraces 1257 roots from 337 trees derived from 33 stands. The soil types of the investigation cover sandy podzols, sandy moraine, brown earth, deep peat, and pseudogley, but all species were not represented on all soil types. The models were developed for stands in three dimension classes depending on the average diameter of the stands and for horizontal roots (angle to the surface less than 45°) and vertical roots (angle to the surface greater than or equal to 45°), respectively. Simple models using rCSA near the stump to predict coarse root biomass (logarithmic models) did not account for stand differences in Norway spruce and Sitka spruce. To eliminate these differences, it was necessary to include root taper and vertical root parameters in the models. Variation between stands concerning the regression between rCSA and root biomass was not found for Pedunculate Oak, Scots Pine or European Beech, but the number of stands of these species was also limited compared with Norway spruce and Sitka spruce.

The genetic and economic gains from forest tree breeding programmes in Scandinavia and Finland

ABSTRACT Plantations of genetically improved forest trees are critical for economic sustainability in forestry. This review summarizes gains in objective traits and the resulting economic impact of tree breeding programmes in Scandinavia and Finland. Genetic improvement of forest trees in these countries began in the late 1940s, when the first phenotypically superior plus-trees were selected from natural environments. The main findings from this review are that (i) tree breeding can increase volume growth in the range 10–25%, and (ii) the bare land value associated with genetically improved trees gives a better return on investment and a shorter rotation period compared to the unimproved forests. As some Nordic countries are quite dependent on the forest industry, breeding programmes that have resulted in economic gains have been beneficial for society. Growth and wood quality traits are often adversely correlated, and the weighting of traits from an economic perspective could provide an index for determining maximum profit from breeding. Tree breeding faces an array of challenges in the future, such as changes in silviculture, climate, new pests and diseases, and demand for wood-based products.

Genetic variation in responses to different soil water treatments in Quercus robur L.

Abstract The effect of soil water content on growth and growth cessation was studied in 18 provenances from northern Europe and 20 Danish open-pollinated families of Quercus robur in a greenhouse experiment. The objective was to study the genotypic responses, phenotypic plasticity and genotype by environment interactions, with regards to growth and to different levels of soil water content. The aim was to increase the knowledge on the genetic and adaptive potential of Q. robur to grow under different water stress conditions. Knowledge on genetic and adaptive potential can be used for practical seed zone management. Differences in growth between provenances were strongly related to latitude. Provenances of southernmost origin reacted vigorously to irrigation compared with Scandinavian provenances. For growth, the rank of provenances was the same at high and medium soil water treatments. Increased growth correlated with a higher number of secondary shoots and a prolonged growing season. Low soil water content initiated early growth cessation in all provenances. Root biomass was affected by soil water treatment and the highest root biomass was observed with medium and high soil water treatments. The results demonstrated a large evolutionary potential in relation to water treatment. The southernmost genotypes responded more strongly in growth to increased soil water level, but the local material showed a large variation and was less prone to early frost damage. The growth of Danish provenances of Q. robur was not reduced with high soil water treatment, in contrast to a study using Danish Fagus sylvatica provenances, indicating that Q. robur is well adapted to high soil water conditions.

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.