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Height, basal diameter, diameter at breast height, bud burst, and leaf development were recorded in a 5-year-old hybrid aspen clonal trial. The field trial consisted of four aspen hybrid clones (Populus tremula x Populus tremuloides) and one local P. tremula seedling source. Phenological traits were observed in the 3rd year. Growth patterns were recorded during the 3rd and 4th years. Phenological traits were explored in relation to hybrid vigor expressed as growth traits. Differences were observed for phenological and growth traits among hybrid clones and P. tremula. The growth period varied from 143â158 days for the four hybrid clones, and was 112 days for P. tremula. The correlation between growth period and yield was highly significant. The annual growth rate of height for the hybrids was 4.2 cm per 7 days (2.4 for P. tremula) in the 3rd year and 6.4 cm per 7 days (2.9 for P. tremula) in the 4th year. After 5 years, mean estimated stem volume of the hybrids was 3.9 times that of P. tremula. Significant clone by year interaction was observed for height, diameter, and volume growth. The hybrid vigor seems to be mainly attributable to a longer growth period.

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 ( 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.Pinus sylvestris

Tree height data from 33 progeny trials of Scots pine ( L.) were used to determine the effect of within-plot subsampling on the magnitude of statistically detectable differences between families, family heritability and correlation of family means based on different sample sizes. The results indicated that in trials established with a standard plot configuration of 25 trees per plot, measuring only 10â15 trees gives nearly the same precision as with assessment of all the plot trees. Even as few as 4â6 trees assessed per plot may constitute a sufficient sample if families or parental trees of extreme performance are being selected. Trials established with non-contiguous plots were found to be more efficient than those established using multiple-tree contiguous plots.Pinus sylvestris

A simulation approach was applied to study the pattern of environmental variability and the relative statistical efficiency of 14 different plot types. The study material consisted of two nine-year-old field tests of Scots pine ( L.). The area of the test sites was 1.57 and 0.67 hectares. The efficiency was measured as the error variance attached to the estimate of family mean and the total size of a test needed to detect a given, least significant difference between two family means. The statistical efficiency tended to decline along with increasing plot size. The importance of plot shape was negligible compared to plot size. The highest efficiency was obtained with single-tree plots. Non-contiguous plots appeared to be considerably more efficient than block plots of equal size. The effects of intergenotypic competition on the choice of plot type are discussed.Pinus sylvestris

Heterobasidion parviporum is a fungal pathogen that is drastically damaging Norway spruce (Picea abies) in Europe. The infections will result in root and stem rot, causing significant economic losses for forest owners. Previous studies have shown that the PaLAR3 gene, which encodes the leucoanthocyanidin reductase enzyme, can increase resistance to H. parviporum in Norway spruce. The presence of the B allele at the PaLAR3 locus has been associated with higher (+)‐catechin concentrations and increased enzyme production in inoculation experiments, resulting in inhibited pathogen growth. The control of H. parviporum involves a multifaceted approach, including silvicultural and sustainable forestry practices, genetic resistance and chemical/biological control. In this study, we determined the PaLAR3 genotypes in a representative sample of Norway spruce breeding materials from southern Finland and examined their effect on necrosis caused by H. parviporum in spruce stems. The results showed that the homozygous PaLAR3BB genotype was present in only 9% of the trees. However, the necrotic area interacted with homozygous PaLAR3BB under low‐water treatment. These findings support the idea that the PaLAR3 locus may be a valuable marker for identifying P. abies resistance to different strains of Heterobasidion parviporum. [ABSTRACT FROM AUTHOR]

A solid starting point for assessing tree-improvement programs would be to determine the effect of genetic gain in economic terms at stand level. This paper presents a stand-level optimization analysis of the use of improved seed material in reforestation from the perspective of forest owners. We used a genetic algorithm to study the effects of optimized stand management on the bare land value (BLV) for both genetically improved and unimproved reforestation material, with increase in BLV (ΔBLV > 0) representing the deployment benefit over the standard tree-improvement program. The stand-level optimization analysis was applied to a case representative of economic and climatic circumstances in Finland. The results show that the absolute increase in the BLV is distinctly higher in southern Finland than in central Finland, let alone northern Finland, regardless of the interest rate (3% or 4%) or genetic gain (3% or 15%). Sensitivity analyses revealed that market-related risks need to be taken into account carefully. Our tentative results provide new insight on the financial incentives for using genetically improved seed material in Scots pine (Pinus sylvestris L.) stand establishment under varying climatic conditions, but the subject merits further investigation--with greater detail and a more systematic data structure. Resume: Un bon point de depart pour evaluer les programmes d'amelioration des arbres consisterait a determiner l'effet du gain genetique en termes economiques a l'echelle du peuplement. Cet article presente une analyse d'optimisation, a l'echelle du peuplement, de l'utilisation de semences ameliorees pour le reboisement, du point de vue des proprietaires forestiers. Nous avons utilise un algorithme genetique pour etudier les effets de l'amenagement optimise de la foret sur la valeur du terrain nu (VTN) tant pour le materiel de reboisement genetiquement ameliore que non ameliore. L'accroissement de la VTN (ΔVTN > 0) represente le benefice de deploiement par rapport au programme standard d'amelioration des arbres. L'analyse d'optimisation a l'echelle du peuplement a ete appliquee a un cas representatif des conditions economiques et climatiques rencontrees en Finlande. Les resultats montrent que l'accroissement absolu de la VTN est nettement plus eleve dans le sud de la Finlande que dans le centre, sans mentionner le nord, peu importe le taux d'interet (3 ou 4 %) ou le gain genetique (3 ou 15 %). Des analyses de sensibilite ont revele qu'il faut accorder une attention particuliere aux risques associes au marche. Nos resultats provisoires fournissent de nouvelles donnees sur les incitatifs financiers a utiliser des semences genetiquement ameliorees pour l'etablissement de peuplements de pin sylvestre (Pinus sylvestris L.) sous diverses conditions climatiques, mais le sujet merite d'etre etudie davantage, de facon plus detaillee et avec une structure de donnees plus systematique. [Traduit par la Redaction], Introduction With pines (Pinus L.), genetic improvement through breeding, selection, and testing has had a significant impact on the productivity and quality of plantations established worldwide (Mullin et al. 2012). [...]

The most destructive root rot pathogen of Norway spruce (Picea abies) in Finland is Heterobasidion parviporum. After primary infection, this pathogen spreads from tree to tree through root contacts and eventually causes high levels of root and stem rot. Locus PaLAR3 has been associated with root rot resistance of Norway spruce, and higher resistance in Norway spruce against H. parviporum has been noted when trees have allele PaLAR3B instead of the more common PaLAR3A. In this study we tested if trees with homo‐ or heterozygous PaLAR3B allele can better resist the infection through root contacts. The study was established in 2018 in a site where spruce trees had grown at a dense spacing for 10 years. The 72 trees were cut down and a mixture of four H. parviporum strains was inoculated on the stumps. After 3 years, 459 trees surrounding the inoculated stumps were harvested and analysed. Based on the presence of conidiospores, forty percent (40%) of the trees were infected by H. parviporum. The homozygous PaLAR3B genotype was found only in 1% of the trees. There were no differences in infection rates between the genotypes AA and AB (or BB). Similarly, the distance from inoculated stump or the diameter of the tree did not influence the infection rate. [ABSTRACT FROM AUTHOR]

Root and stem rot caused by Heterobasidion annosum is a severe problem in boreal Scots pine. Dissecting the features of disease resistance is generally an essential step in resistance breeding in plants and forest trees. In this study, we explored inherent resistance factors of Scots pine against H. annosum. A total of 236 families consisting of 85 full-sib (FS), 35 half-sib population mix (HSpm), and 116 half-sib (HS) families of Scots pine seedlings were inoculated with a H. annosum isolate. We sampled needle tissues before inoculation for terpene measurements and RNA sequencing. Based on the lesion area, the extremes of 12 resistant and 12 susceptible families were selected for further analyses. Necrotic lesions resulting from fungal infection were in a weak to moderate relationship with the plant height. Monoterpenes were the principal terpene compounds observed in Scots pine seedlings. Concentrations of 3-carene were significantly higher in pine genotypes inherently resistant compared with susceptible seedlings. By contrast, susceptible genotypes had significantly higher proportions of a-pinene. Gene ontology analysis of differential expressed transcripts (DETs) revealed that response to biotic factors was enriched in resistant seedlings. Functional characterization of individual DETs revealed that higher expression of transcripts involved in response to abiotic stress was common in susceptible genotypes. This observation was supported by the annotation of hub genes in a key module that was significantly correlated with the lesion trait through weighted gene co-expression network analysis (WGCNA) of 16 HS and HSpm samples. These findings contribute to our understanding of constitutive resistance factors of Scots pine against Heterobasidion root and stem rot diseases. [ABSTRACT FROM AUTHOR]

Great interests in silver birch (Betula pendula) forests have increased in an attempt to handle biodiversity and resilient forest management with more broad-leaved forests. However, up-to-date silver birch growth and yield models are still needed to predict the stand development in the future and support operational forest management and planning. The objectives of this study were to develop site index and stand characteristic models for silver birch plantations. Data for modelling were from the thinning and spacing experiments and tree breeding trials on silver birch plantations in southern and central Finland. The dominant height and site index (SI) models were fitted using the nonlinear mixed effect regression approach based on the Chapman-Richards function with the genetic effect from improved seedlings. The modelling result indicated a logical growth performance over age and higher dominant height with genetically improved seedlings. The stand characteristic models for unimproved seedlings were developed using multivariate mixed-effects modelling approach. The targeted, response variables were the basal area-weighted mean height (HW, m), the basal area-weighted mean diameter (DW, cm) and stand basal area (G, m2 ha−1) of silver birch. Stand biological age (AGE, year), SI estimated based on the model of the current study with the base age of 50 years, and the number of silver birch trees (N, trees ha−1) were all commonly applied as highly significant predictor variables for all of HW, DW, and G models. In addition to these predictors, thinning variables, comprised of the time since last thinning in year and the thinning intensity based on G, were highly significant in the DW and G models with logical behavior. Recent thinning affected negatively at first because trees in thinned stands were slimmer than those in unthinned stands that have grown from the early stage at the same level of N with thinned stands. After 13 years since last thinning, the effect turned positive indicating that the increments were expedited with thinning. Lastly, site type classified as either former agricultural land or forest site was included in the DW and G models. Consequently, all the models developed in this study were evaluated as practicable with easy-to-use predictors and desirable accuracy. • The dominant height and site index models were fitted well with genetic effect using the Chapman-Richards function. • Mean height and diameter and stand basal area were modelled using multivariate regression. • Age, site index, and stem number were the commonly-applied, driving predictors in stand characteristic models. • Thinning variables were highly significant in the models of mean diameter and stand basal area. • Simulations demonstrated model application, performance, and validity adequately. [ABSTRACT FROM AUTHOR]

ABSTRACT Norway spruce is an important coniferous species in boreal forests. Root and stem rot diseases caused by the necrotrophic pathogen Heterobasidion parviporum threaten the wood production of Norway spruce which necessitates the search for durable control and management strategies. Breeding for resistant traits is considered a viable long‐term strategy. However, identification of potential resistant traits and markers remains a major challenge. In this study, short‐term disease resistance screening was conducted using 218 Norway spruce clones from 17 families. Disease resistance was evaluated based on the size of necrosis lesion length following infection with the pathogen. A subset of needles/branches from clones with small (partial resistant) or large (susceptible) lesions were used for terpene analysis and transcriptomic profiling. The results revealed that the content of monoterpene linalool and 1,8‐cineole and their respective encoded genes were significantly more abundant and highly expressed in the partial resistant group. Furthermore, linalool and 1,8‐cineole were demonstrated to have inhibitory effect on the growth of the pathogen H. parviporum, with morphological distortion of the hyphae. RNAseq analysis revealed that transcript of pathogen genes involved in the regulation of carbohydrate metabolism and stress responses were significantly decreased in presence of the terpenes. The results suggest the relevance of monoterpenes together with jasmonic acid precursor and some genes involved in phenylpropanoid biosynthesis, as constitutive tolerance factors for Norway spruce tolerance against necrotrophic pathogen. The high level of necrosis related cell death gene expression might be factors critical for host susceptibility and disease development. [ABSTRACT FROM AUTHOR]

Root and stem rot of conifer trees caused by Heterobasidion annosum species complex leads to huge economic losses in Europe, yet not much is known about the molecular and chemical basis for host resistance. To identify inherent chemical or molecular markers in clones found to be either resistant or susceptible, we sampled needle tissues of all the clones before pathogen inoculation. We conducted a short-term resistance screening by using the pathogen H. parviporum to inoculate 70 Norway spruce clones. Based on lesion size, subsets of highly susceptible and resistant clones were further analyzed. Terpene detection and RNA sequencing were performed to explore inherent variations in genotypes differing in resistance to pathogenic challenge at chemical and transcriptional levels. A negative correlation emerged between resistance and growth. Terpene profiles of resistant clones showed higher content of monoterpenes and sesquiterpenes, with concomitant increased transcript abundance of genes involved in the terpenoid pathway. A set of upregulated genes relevant to flavonoid biosynthesis was observed in resistant genotypes, whereas higher transcripts of lignin biosynthetic genes were prevalent in susceptible clones. Genes involved in flavonoid and lignin biosynthesis as well as terpene content may have a role in facilitating resistance of Norway spruce against H. parviporum. Our results provide strong support on the feasibility of sampling needle tissues before pathogen inoculation, and the approach could be of value for large-scale screening of novel biomarkers for durable resistance. The additional insights could form a basis for further research on resistance screening in this pathosystem. [ABSTRACT FROM AUTHOR]