Current issue: 57(2)
Under compilation: 57(3)
Estimates of individual heritability and genetic correlation are presented for a set of 10 growth and quality traits based on data from 16 Scots pine (Pinus sylvestris L.) progeny trials in Finland. Seven of the traits (tree height, stem diameter, crown width, Pilodyn value, branch diameter, branch angle and branch number) were objectively measured, whereas three traits (stem straightness, branching score and overall score) were assessed visually. The genetic correlations were mostly moderate or low, and favourable from the tree breeder's point of view. All variables related to tree size correlated relatively strongly and positively. Tree height exhibited a more favourable genetic relationship with the crown form traits than diameter, the latter showing positive correlation with branch diameter. Except for the slight negative correlation between branch angle and branch diameter, the branching traits were not notably correlated. The pilodyn value was positively correlated with stem diameter, reflecting negative correlation between diameter growth and wood density. The highest genetic correlations occurred among the two visually evaluated quality scores and branch diameter. All of the heritabilities were less than 0.4. Overall score, Pilodyn, branch angle, branching score and tree height showed the highest heritability.
Harvest index and number of associated traits were measured in a 16-year-old Scots pine (Pinus sylvestris L.) progeny test based on full-sib families. It was found that harvest index is a highly heritable trait and that a number of yield components are positively correlated with it. It is suggested that harvest index and tree ideotypes should be the basis of selection in cultivated trees. It is emphasized that an integrated approach to tree improvement including silviculture, soil science, industrial and economic constraints and tree breeding is a prerequisite for maximal response.
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The paper discusses the theoretical basis of quantitative analysis of the effect of genotype and environment in forest trees. Perhaps the main problem in the understanding of the laws of intrapopulation variability of the species of woody forest plants is the study of the structure of their populations. It may be characterized by a number of parameters. The intrapopulation variability of quantitative characteristics appears as a result of environmental and genetic factors, but to determine the relative weight of these factors in a concrete case is not easy. The study of the structure of a population by its quantitative characteristics has a wider task: to establish the relevance of the hereditary differences of the individuals of a population. Also, the differences caused by diverse growth conditions and how they are reflected in the level of general phenotypic variability of the quantitative characteristics in a given population has to be identified. The author gives examples of assessment of heritability in forest trees.
The PDF includes a summary in Finnish.
The study material included 600 Scots pine (Pinus sylvestris L.) grafts from the Tohmajärvi seed orchard in Eastern Finland. Their broad sense heritability for the height growth was 0.92, for the number of branches 0.87 and for the angle of branching 0.84. Grafts from Central Finland had cones more often than the southern ones, the frequencies being 26.3% and 11.2%. It seems that dominance plays a significant role in the genetical variation of this seed orchard and that height growth is probably more rewarding breeding characteristic than quality, the difference being small, however.
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Field experiments of Scots pine (Pinus sylvestris L.) was established by planting seedlings grown from seeds collected from open-pollinated plus trees throughout the country. The 36 progenies represented were planted in 4 blocks as 2+2 transplants in 1960. The main characteristics of the seedlings were measured in 1966 and 1968. Considerable damage had been caused to the stands by moose (Alces alces) and Melampsora pinitorqua Rostr., consequently, therefore, only normally developed seedlings were measured.
Highly significant differences between progenies were found in the number of branches in 1968 and in the ratio of height of tree to the length of the longest branch. In 1968, the differences in height between progenies were not significant, but there were significant differences between blocks both in tree height and length of terminal shoot. Obviously, the edaphic heterogeneity of the site has influenced mainly the juvenile growth of the plants, because in the length of the terminal shoot there could be seen also significant differences between the progenies. There were no significant differences between the progenies in the length of the longest branch, in the angles of the thickest branches, in stem taper and in the diameter of the thickest branch.
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Genetic variation in the physiological characteristics and biomass accumulation of Acacia mangium Willd. was studied in both field and laboratory conditions. Variation in the growth characteristics, foliar nutrient concentration, phyllode anatomy and stomatal frequency was analysed in 16 different origins under field conditions in Central Thailand. Family variation and heritability of growth and flowering frequency were calculated using 20 open-pollinated families at the age of 28 months. The effect of environmental factors on diameter growth in different provenances is also discussed.
Under laboratory conditions, such physiological characteristics as transpiration rate, leaf conductance and leaf water potential were measured at varying soil moisture conditions. The responses of photosynthesis, photorespiration and dark respiration as well as the CO2 compensation point to temperature and irradiance were also investigated. All physiological characteristics indicated differences among provenances. An attempt was made to relate the results obtained in the laboratory to the growth performance in the field. Recommendations on provenance selection for the planting of A. mangium in Thailand are also given.
The PDF includes a summary in Finnish.
Heritability of first and second-year height growth of Pinus sylvestris (L.) plants was studied using three different mating designs. Plants grew in a plastic greenhouse during the first growth period. During the second growth period they were exposed to open air conditions.
Heritability values varied from zero to 42%. An average heritability based on six separate calculations (two from each mating design) was computed and its reliability was discussed. This heritability value was 18%.
Different ways of improving heritability estimates was discussed and the need of more investigations on trait quality in relation to fitness and on the effect of natural selection and population strategy was emphasized.
We studied variations on different traits of Parkia timoriana (D.C.) Merr. in twelve provenances systematically from their source of origin to a controlled environment where representative seedlings were grown. Among the provenances, P1 gave the best result for seed traits including germination traits, P7 for pod traits and P10 for seedling vigour. Effects of seasonal distribution of rainfall and temperature on seed and pod traits were also determined by computing multiple regression analysis. The results displayed winter rainfall and summer temperature as the most important factor determining pod and seed traits. Latitude also significantly (P < 0.001) affected PWT (r = 0.52), SWP (r = 0.46) and SW (r = 0.50). A common garden study for germination and seedling growth indicated P1 and P10 provenance as the best among all. Seeds drawn from P10 gave the highest seedling vigour with an average growth rate of 0.61 cm/day from 90th to 180th day. Highest broad-sense heritability values (h2) were observed in germination traits, followed by seedling collar diameter. The lowest h2 was observed for seedling height.
Phenology can have a profound effect on growth and climatic adaptability of long-lived, northern tree species such as Scots pine (Pinus sylvestris L.), where the onset of growth in the spring is triggered mainly by accumulated heat, while cessation of growth is related to the joint effect of photoperiod and temperature. In this study, the objectives were: (1) to compare shoot phenology of genetic material from Scandinavia (maritime climate origin) and northern Russia (continental climate origin) sources, under field conditions in both Scandinavia and Russia (maritime and continental growth conditions); and (2) to estimate the heritabilities of phenological parameters. The material used was part of a larger provenance test series involving Scots pine populations and open-pollinated plus-tree families from Russia, Sweden and Finland. Terminal shoot elongation was measured on multiple occasions during the seventh growing season from seed at a trial near Bäcksjön (Sweden) and Syktyvkar (northern Russia). We calculated the regression of relative shoot elongation over accumulated heat sum above +5 °C using an exponential expression. Seedlings of Swedish and Russian provenance had similar heat-sum requirements for growth onset and cessation in both trials. More northern provenances started onset and cessation at a lower temperature sum, but heat accumulation requirements for onset were not fixed. Scots pine may suffer from spring frost due to earlier growth onset in a warming climate. Variation and heritability of phenological traits show potential to adapt Scots pine to new climate conditions by breeding.
Genetically improved Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) are extensively used in operational Swedish forestry plantations. However, relatively little is known about the stem slenderness (height-diameter ratio) of genetically improved material. Thus, in this study we investigated effects of plus-tree selection on stem slenderness of Norway spruce and Scots pine in Sweden by evaluating both the plus-tree selection and a large number of progeny trials. Species-specific models for predicting the height-diameter ratio were estimated using regression and mixed model approach. Our results show that phenotypic plus-tree selection promoted less slender Norway spruce trees and more slender Scots pine trees compared to neighboring trees. Similar results were also found for the progeny trials which indicated that genetics played a prominent role in the phenotypic appearance. Compared to the progeny of neighboring trees, Norway spruce plus-tree progenies had a 5.3% lower height-diameter ratio, while Scots pine plus-tree progenies had a 1.5% greater height-diameter ratio. The narrow sense heritability for height-diameter ratio was 0.19 for Norway spruce and 0.11 for Scots pine, indicating that it is possible to modify the height-diameter ratio by breeding. Correlation coefficients between breeding values for height-diameter ratio and diameter were negative for Scots pine (–0.71) and Norway spruce (–0.85), indicating that selection for diameter only would result in less slender stems of both species. Similar correlations were also found between breeding values for height-diameter ratio and height of Scots pine (–0.34) and Norway spruce (–0.74).