Genetic variation in early fitness traits across European populations of silver birch (Betula pendula)

Given that the ecological niche of tree species is typically narrower for earlier life stages, intraspecific genetic variation at early fitness traits may greatly influence the adaptive response of tree populations to changing environmental conditions. In this study, we evaluated genetic variation in early fitness traits among 12 populations of Betula pendula from a wide latitudinal range in Europe (41-55 degrees N). We first conducted a chamber experiment to test for population differences in germination and the effect of pre-chilling treatment on seed dormancy release. We then established three common gardens spread across the species latitudinal range in order to evaluate levels of quantitative genetic variation and genotype-by-environment interaction at different early life traits. Our results showed significant variation in chamber germination rates among populations (0-60 %), with southern populations exhibiting lower germination. Pre-chilling treatments did not generally improve germination success. Population seedling emergence rates in the field were correlated with chamber germination rates, though being an order of magnitude lower, with an average ranging from 0 to 1.3 % across gardens. Highly significant variation was found in field emergence rates among populations, and between seed-crop years within populations, but not among families within populations. Populations differed in seedling height, diameter, slenderness and budburst date, with significant among-family variation. Population latitude was positively associated with chamber germination rate and with seedling emergence rate in one of the central field sites. Overall, genetic, environmental and demographic factors seem to influence the observed high levels of variation in early fitness traits among B. pendula populations. Our results suggest limited regeneration capacity for the study species under drier conditions, but further field trials with sufficient replication over environments and seed crops will improve our understanding of its vulnerability to climate change

Strategy for long-term breeding of Picea abies in Lithuania: short overview

This paper presents the newly suggested long-term breeding strategy for Norway spruce in Lithuania to share with the optimisation approach, which may be useful in synchronising the long-term breeding and gene conservation plans in neighbouring regions. The breeding programme in Lithuania is at a stage where the long-term plans need to be developed. Our strategy is to proceed with a closed-nucleus breeding population which is structured into subpopulations according to adaptation zones (4-5 subpopulations). The size of each subpopulation is 50 unrelated and progeny-tested individuals. The breeding cycle consists of double- pair mating and a balanced within-family selection forward. The candidates will be clone-tested. Advanced genotypes will be selected into an advanced nucleus; an isolated foreign breeding population is planned. Positive assortative mating is used for deployment. An experimental "shuttle-breeding" strategy may be tested: selection with avery high intensity, controlled crosses, nursery tests for vigour and growth rhythm, cloning by hedges into short-rotation clonal plantations

Gene conservation and breeding programmes for Picea abies in Lithuania: present-day achievements

At present, Norway spruce stands occupy 22% of the total forest area in Lithuania. Most of them are located in the northeastern highland (Žemaitija) and the central part of the country. 25% of the spruce-dominated stands are pure, the rest are mixed. Natural calamities like storms, droughts, and pests cause substantial damage and occur quite frequently. About 40 thousand ha of stands are cut after each storm. The mean wood yield of the spruce stands is 304 m3 ha-1, and the current annual increment is 6.2 m3 ha-1. The climatic conditions of Lithuania are variable enough to cause differentiation of habitats. For Norway spruce, 6 provenance regions have been established. The national gene conservation programme is based on (a) in situ genetic reserves, seed collection stands, and selected genotypes, and (b) ex situ clonal archives, seed orchards, experimental plantations, and gene bank collections. The present-day breeding of Norway spruce comprises family tests of populations for individual and population selection, and plans for inter-population hybrids. A strategy for Norway spruce breeding has been approved for the years 2004-2013. There is a genetically diverse material for future breeding: long-distance provenance tests, and population and family tests. Assessments of two provenance tests (aged 9 and 17 years) in central Lithuania revealed superior performance of central and northeastern Polish provenances: superior height, good stem quality, and late bud-burst in spring. This may be attributed to the favourable effect of transfer: avoidance of spring frosts (late bud-burst and good stem quality), and utilisation of the later part of the growing period for growth (late bud-set and superior height). Norway spruce is a climax species with different domestic and Darwinian fitness. Therefore, we suggest that the domestic fitness of local genotypes may be improved by introducing a few Polish clones in Lithuanian breeding populations

Genetic control of intra-annual height growth in 6-year-old Norway spruce progenies in Latvia

Coupling growth with periods of favourable weather conditions minimizes risks of frost damage and maximizes annual height increment. The phenology of the formation of height increment is therefore a trait related to the adaptability of trees to annual weather fluctuations. Strong genetic control of the timing of the onset and cessation of shoot elongation has been reported for Norway spruce, but little is known about its fluctuations that occur during the growth period. The strength of the genetic control of the height growth rate was assessed for young (6 years old) Norway spruce progenies originating from six open-pollinated stands from two local provenance regions. In 2010, the length of the growing period for the studied trees was ca. 60 days. Trees from the more continental provenance region, which had later onset and cessation of height growth (by ca. 2.5 days), exhibited slightly lower increments (by ca. 1%). Accordingly, the provenance region had a significant effect on height growth at the beginning and end of the growing period. Nevertheless, considerable genetic control of the growth rate was found throughout the entire growing period (particularly at the beginning and cessation, ha2 ≥ 0.20), except for a week-long interval around mid-summer (ha2 = 0.07). Similarly, the coefficient of additive genetic variation suggested that breeding could be applied for the improvement of height growth intensity throughout the season. The phenotypic correlations between weekly growth rates and tree height (before growth) were mostly non-significant, suggesting varying mechanisms of control, hence possibility for simultaneous improvement of the traits by breeding

Adaptive responses to temperature and precipitation variation at the early-life stages of Pinus sylvestris

Summary Early-stage fitness variation has been seldom evaluated at broad scales in forest tree species, despite the long tradition of studying climate-driven intraspecific genetic variation. In this study, we evaluated the role of climate in driving patterns of population differentiation at early-life stages in Pinus sylvestris and explored the fitness and growth consequences of seed transfer within the species range. We monitored seedling emergence, survival and growth over a 2-yr period in a multi-site common garden experiment which included 18 European populations and spanned 25° in latitude and 1700 m in elevation. Climate–fitness functions showed that populations exhibited higher seedling survival and growth at temperatures similar to their home environment, which is consistent with local adaptation. Northern populations experienced lower survival and growth at warmer sites, contrary to previous studies on later life stages. Seed mass was higher in populations from warmer areas and was positively associated with survival and growth at more southern sites. Finally, we did not detect a survival–growth trade-off; on the contrary, bigger seedlings exhibited higher survival probabilities under most climatic conditions. In conclusion, our results reveal that contrasting temperature regimes have played an important role in driving the divergent evolution of P. sylvestris populations at early-life stages