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Predicting individual breeding values and making forward selections from open-pollinated progeny test trials for seed orchard establishment of interior Lodgepole Pine (Pinus contorta ssp. latifolia) in British Columbia
Abstract
Ten-year height data from three open-pollinated lodgepole pine progeny test trials were analysed in order to select individuals
for seed orchard establishment in the low and high elevation seed-planning units (TOLO and TOHI) of the new Thompson Okanagan
seed planning-zone in interior British Columbia, Canada. The total test population had about 35,000 individuals from 362 families
of 9 provenances and was divided into two portions, each serving as the base population for its appropriate seed-planning
unit. For each population, various genetic parameters were estimated and individual breeding values were predicted. Combined-site
estimates of individual, family, and within-family heritability ranged from 0.23 to 0.38, 0.77 to 0.84, and 0.17 to 0.29,
respectively. Estimated coefficients of type-b genetic correlation were greater than 0.81, indicating little G×E interaction
in this region. Provenance effects were large. Larch Hills and Inonoaklin River were the two superior provenances with an
expected gain of 13% and 10% in stem volume at rotation age of 60years in TOLO. Individual breeding values was not uniformly
distributed among provenances and the top 100 individuals originated from 20 families in TOLO and 32 families in TOHI. Co-ancestry
among these individuals should not be a serious concern in seed orchard establishment as the predicted genetic loss due to
excessive inbreeding is only 1.06% in TOLO and 0.6% in TOHI. The status numbers of the two prospective seed orchards are 32
and 44, respectively, and both are well above the required minimum of 10 in British Columbia. Using unrelated clones for seed
orchard establishment may result in reduced optimum genetic gain and thus is not a favourable option.
... Clones for seed orchards are commonly selected directly from progeny test material ( Zobel and Talbert 1984). The selection of genetically superior individuals on individual breeding values predicted from progeny tests is a good alternative for increasing the production of genetically improved seeds by the establishment of a seed orchard (Xie et al. 2007) or for deciding what trees should be rogued in a progeny test to obtain a breeding seed orchard (Zas 2008b). The main problem is choosing how many trees to select, to avoid a drastic reduction in the genetic diversity and to assure thereby long-term response to selection. ...
Sweet chestnut (Castanea sativa Mill.) is a broadleaved species widely distributed in the Mediterranean regions of Europe and Asia, highly valued and traditionally cultivated for its wood and nuts. In the Iberian Peninsula, it covers an area of approximately 256,000 ha, with more than 70% of its area located in the north. Based on the scattered distribution of C. sativa and its restricted gene flow, an important genetic differentiation is expected to exist among populations because of local environment adaptations, although the large area occupied by domesticated populations could affect this differentiation. Studies of neutral genetic diversity in C. sativa reveal a geographic structure of populations across Europe largely related to refugia identified by fossil pollen studies. However, studies of adaptive variation are scarcer and the number of populations considered is less representative.
For this reason, the first objective in this thesis was to carry out a complete study of the quantitative genetic variation existing between and within European and Spanish populations of C. sativa for several adaptive traits; this is discussed in chapter I and completed with the results presented in chapter II. The study of chapter I focused on two provenance-progeny trials established in the Atlantic region of Galicia: one with six European populations and the other with six Spanish populations, all from differentiated and representative regions of the geographic range of C. sativa in the Iberian Peninsula and Europe. An added value of this study is that the last evaluation was carried out in 12-year-old plants; to date, previous related studies have only been conducted on juvenile plants. The results of the statistical analysis based on mixed models indicated that high differentiation exists among populations regarding phenology, growth, conformation, and survival. This differentiation increases with the age of the plants in flushing and height. Additionally, the genetic variation between populations showed a latitudinal clinal variation reflecting the later flushing and bud set and increased growth of the populations in northern latitudes. Intra-population genetic variability, although smaller, was also considerable, and the estimation of genetic parameters enabled us to determine that flushing is under strong genetic control whereas growth traits showed high coefficients of additive genetic variation.
In chapter II, two experiments were developed from a provenance-progeny trial including nine Spanish populations that were previously analyzed with microsatellites, classifying them into the two genetic pools present in the peninsula: Northern and Mediterranean. In the first experiment, annual growth rhythm was evaluated in the nursery during the first 3 years after the establishment of the test, registering the same variables as in the tests of chapter I. In the second experiment, the plants were subjected to controlled conditions of hydric stress and temperature to evaluate other related traits such as defoliation, number of dry apices, and dry weight of roots, stems, and leaves. Statistical analyses of both experiments confirmed the inter- and intra-population genetic variation previously indicated, and the tendency of northern populations to show higher breeding values in growth and late phenology.
The results obtained in the second experiment of chapter II led us to develop the second objective, and allowed us to show that the Mediterranean populations in the center and south of the Iberian Peninsula have better values of survival and a greater development of the radical system in drought conditions. Significant genetic variability was also identified within populations, with high coefficients of adaptive variation for dry weight traits. This result, together with the observed different behaviors of families in drought conditions, suggests that C. sativa has an important capacity to adapt to possible climatic changes.
The third objective of this work focused on the role of natural selection in the population differentiation observed in adaptive characteristics. The statistical design developed in the experiments of chapter II allowed us to estimate the index of population differentiation for quantitative traits (𝑄𝑆𝑇). The comparison of this index with its homolog for molecular data (𝐹𝑆𝑇) confirmed population local adaptation through differential natural selection in flushing, bud set, and height; this would explain the clinal variation observed previously in these characteristics. However, the breeding values of the populations indicated that the population differentiation, particularly for growth traits, does not follow a continuous variation. In the drought experiment, inter-population differences obtained for the evaluated traits did not correlate with the latitude of the provenances. However, high 𝑄𝑆𝑇−𝐹𝑆𝑇 differences were obtained for dry weight, bud set, growth, and survival. For a better understanding of our results, we also estimated correlations between breeding values of the progenies included in each population and ancestry values in the Mediterranean gene pool of the corresponding parents, confirming the adaptive differences between the North and the Mediterranean gene pool populations, and also defining an ecotypic variation.
The last two aims of the thesis focused on the current Forest Breeding Program of Chestnut in Galicia (2010), developed by the Forest Research Center of Lourizán (FRCL). To date, the breeding programs carried out in Europe have focused on the search for resistance to Phytophthora spp. This is because of the elevated incidence of ink disease and its associated high levels of mortality in different regions from the end of the 19th century. In Spain, since the introduction of seeds from the Asian species (Castanea crenata Sieb and Zucc and Castanea mollissima Bl.) in 1920, hybridization techniques have been developed to obtain C. crenata x C. sativa resistant hybrids. Subsequent studies of vegetative propagation, ink resistance, genealogical identification, and the selection of trees for wood production, which were carried out in FRCL, resulted in the approval of 32 clones in 2007 as base material for the production of wood; some of these clones are currently used as rootstocks (clones 7521, 111, and 2671) or as dual-purpose (wood and fruit) trees (clone 90044). However, limitations common to all these studies must be addressed. The C. sativa trees used as parents for controlled crosses were selected in the Atlantic area of Galicia and, consequently, the hybrids are poorly adapted to the more continental conditions of the interior of Galicia. It is also necessary to incorporate breeding strategies in wood quality and to obtain resistance to Cryphonectria parasitica and Dryocosmus kuriphilus. Moreover, while vegetative propagation has been used as the main tool to obtain clones for chestnut wood production, knowledge about the genetic control of inheritance of the traits of interest is limited, so the use of clonal propagation is not sufficiently justified.
The FRCL Forest Breeding Program of Chestnut was developed with the aim of achieving long-term genetic gains in characteristics related to the production of wood, dual-purpose trees, new disease-resistant hybrids, and rootstocks better adapted to cold and drought. The Main Breeding Population (MBP) consists of several subpopulations to maintain as high a genetic diversity as possible, among which 200 superior trees selected in different areas of Galicia have a relevant role. The Elite Population (EP) is composed of several groups that show high growth, wood quality, resistance to diseases, and resistance to cold and drought. Controlled crosses of these groups in a semi-dialell enable these characteristics to be combined and to precisely determine how these traits are inherited in terms of additive and non-additive components of genetic variance.
The fourth objective of our study is related to the selection of individuals for the MBP and EP from a trial of progenies obtained from 36 plus trees in the Atlantic area of Galicia (chapter III). Three selection strategies were developed based on estimated genetic parameters and correlations, which enabled 32 trees to be selected for the MBP, 31 for the establishment of a clonal seed orchard, and three for the growth breeding group of the EP. For the MBP and clonal seed orchard, high expected genetic gain was estimated regarding volume and straightness, as well as high genetic diversity. For the growth breeding group, a combined selection index was developed for joint characteristics that achieved a considerable increase in the estimated genetic gain in volume and straightness, and a high genetic gain for apical dominance. This index, applied in the field provenance-progeny trials of European and Spanish populations, allowed trees selected from different origins to form part of the EP, specifically in the drought and cold-resistant breeding groups, which also provided high genetic gains in volume and conformation.
Finally, as the ultimate objective of our study, a trial consisted of 16 full-sib families from controlled crosses was evaluated to estimate the additive and non-additive components of genetic variance in adaptive traits; growth and quality traits (chapter IV). The parents of the controlled crosses were trees of the wood quality and resistance to Phytophthora spp. groups of the EP. The additive component of the variance was found to be considerably higher than the dominance component for all traits, although dominance variance was important in flushing, and epistatic deviations were shown to be very high in growth traits. The estimation of different types of heritability, such as individual half-sib and full-sib heritabilities, and clonal heritability, enabled us to propose different selection strategies to continue the breeding plan. The most important of these is the selection of parents which must continue to be part of the EP and can also be the parents of other controlled crosses to increase genetic gains in growth or, for example, to delay the flushing period of the offspring. It also allowed the discarding of clonal propagation as an effective method to obtain genetic gains in some traits such as stem straightness.
... There are strong differences in the magnitude of heritability estimates for height growth between CP and OP sites (Fig. 2), which are likely due to inflated additive variance estimates for test populations with half-sib families collected from wild stands. Xie et al. (2007) suggest that the coefficient of relatedness among trees within half-sib families from natural stands is higher than expected due to breeding among close relatives within a local Fig. 6. The projected distribution of breeding zones based on climate normals . ...
The optimum deployment of select material from tree breeding programs is affected by the presence of genotype–environment interactions (G × E) and further complicated by future climate change. Here, we analyzed tree height data from 28 progeny test sites in a multi-environment trial (MET) dataset for two testing cycles of the lodgepole pine (Pinus contorta Douglas ex Loudon) breeding program in British Columbia to characterize one approach to investigating the climatic variables influencing G × E and the potential impacts of climate change. Linear mixed model analysis was conducted using an approximate reduced animal model with a factor analytic (FA) variance model to estimate the complex additive (co)variance structure. Test sites were grouped according to patterns of G × E, and climate modelling was employed to project historical and future deployment zones for each group. Based on these findings, it appears that breeding groups with historically wide deployment zones from northern environments will become less important as the climate warms, and therefore investment should be directed toward southern breeding groups, which will be useful across a very wide geographic range in the near to mid-term future.
... Clones for seed orchards are commonly selected directly from progeny test material (Zobel and Talbert 1984). The selection of genetically superior individuals on individual breeding values predicted from progeny tests is a good alternative for increasing the production of genetically improved seeds by the establishment of a seed orchard (Xie et al. 2007) or for deciding what trees should be rogued in a progeny test to obtain a breeding seed orchard (Zas 2008b). The main problem is choosing how many trees to select, to avoid a drastic reduction in the genetic diversity, and to assure thereby long-term response to selection. ...
Second-year traits of growth, stem form, terminal
flushing, and survival were assessed in 1770 ramets from 295
clones of 16 full-sib families of Castanea spp. Additive, dominance,
and epistatic genetic variances were estimated in a
clonally replicated incomplete 5 × 4 factorial test. Parents of
the mating design were selected mainly on their phenotypes
for wood quality (Castanea sativa traditional varieties) and
their proven resistance to Phytophthora spp. (Asiatic species
and Castanea crenata ×C. sativa hybrids). Additive genetic
variances were estimated to be 1.7–9 times greater than the
dominance components. Inferred epistatic variance components
showed a significant role in controlling growth traits
and branch length. Narrow- and broad-sense heritability estimates
showed that terminal flushing date was the most heritable
trait, followed by height. The high estimates of half-sib,
full-sib, and clonal mean heritabilities for almost all traits suggest
that different strategies of backwards and forwards selection
could be proposed. The ranking of the breeding values of
parents allow us to select the best parents for new crosses and
extend the mating design. Favorable genetic correlations were
found between growth traits and straightness, so multi-trait
selection looks promising. Our results provide the first information
on the partitioning of genetic variance in Castanea
spp. and a starting point for devising new selection strategies.
... In C. hystrix, no reports are available on the use of OP progenies for describing the structure of the genetic variance. In addition, no estimates have been published of the breeding values of C. hystrix, although predictions of breeding values for other forest tree species are a standard prectices (XIE et al., 2007;ISIK et al., 2008;IWATA et al., 2011;HARDNER et al., 2012;DENIS and BOUVET, 2013). At this time, studies on the genetics of C. hystrix have focused on height (H), diameter at breast height (DBH), ground diameter (GD), and crown width (CW); these related traits are the most important for wood production at initial breeding effort (GREAVES et al., 1997). ...
Castanopsis hystrix A.DC. is one of the most important and multipurpose tree species native to China. 157 open-pollinated families collected from 11 provenances in Guangdong, Guangxi, and Fujian province were used to estimate genetic parameters for height (H), diameter at breast height (DBH), ground diameter (GD), and crown width (CW) for each province and combined three provinces at ages from 3 to 9 years. The variance component was small and non-significant among provenances but was highly significant among families within provenances for H, DBH, GD, and CW. Heritability estimates were significant except for a few traits from Fujian's provenances. Heritability ranged from 0.20 to 0.57 for H, 0.19 to 0.38 for DBH, 0.21 to 0.55 for GD, and 0.09 to 0.39 for CW. Heritability estimates for H and DBH decreased with increased age for each province and combined three provinces. Significantly high genetic correlations were observed for ageage and trait-trait correlations, indicating that genetic performance at one trait was well correlated with another trait. In total, 22 families and 60 individuals were selected for backward and forward selection based on breeding values.
... In some of these, it is reported that the estimated heritability degrees for height ranged between 0.09 and 0.74 (I ık, 1986;I ik and Kaya, 1995;Kaya and I ık, 1997;I ık, 1998;I ık et al., 1999;I ık and I ık, 1999). In previous studies, high heritabilities were calculated for both Turkish red pine and other tree species (Yıldırım, 1992;I ık et al., 2001;Vargas-Hernandez et al., 2003;Fedorkov et al., 2005;Xie et al., 2007;Codesido and Fernandez-Lopez, 2008;Gülcü and Üçler, 2008). ...
In this study, some adaptive traits (growth, stem, branching and crown characteristics) in a seven-year old plantation of Turkish red pine (Pinus brutia Ten.) were studied in 2008. The experiment was established by using 1+0 bare-root seedlings from 5 seed stands and 5 seed orchards from the same origins in 2001. Randomized block design with three replications was used in the field. There were a total of 100 families, 10 from each of these 10 populations were used in the experiment. Each family was represented with 10 seedlings in each replication. Populations and families within each population were significantly different for all traits both in the seed stands and in the seed orchards. The percent of genetic variation caused by population was considerable except for branch length ranging from 0.19 to 18.28% especially in the seed stands. Variance components due to families in the seed orchards were in general higher than those in the seed stands. Individual heritabilities varied in 0.45 - 0.90 range. Family heritabilities ranged from 0.76 to 0.88. These results indicated that combined population, family and within family selection for studied traits would result in considerable gain in this species.
... Clones for seed orchards are commonly selected directly from progeny test material (Zobel and Talbert 1984). The selection of genetically superior individuals on individual breeding values predicted from progeny tests is a good alternative for increasing the production of genetically improved seeds by the establishment of a seed orchard (Xie et al. 2007) or for deciding what trees should be rogued in a progeny test to obtain a breeding seed orchard (Zas 2008b). The main problem is choosing how many trees to select, to avoid a drastic reduction in the genetic diversity, and to assure thereby long-term response to selection. ...
Total height, diameter, index volume, stem straightness, apical dominance, and survival were assessed at 8 years from seed in an open-pollinated progeny test of 36 families of European chestnut (Castanea sativa Miller) established at two sites in the Atlantic area of Galicia, Spain. Iterative spatial analysis was applied to eliminate the effect of the spatial dependence in the original data and to estimate accurately genetic parameters for evaluating the potential for selection of the measured trees. Spatial analysis was very beneficial for growth traits and survival, but less so if at all for form traits. Estimated individual heritabilities ranged from moderate to high for growth traits (
) and stem straightness (
). High coefficients of additive genetic variance were obtained for volume (
) and straightness (
). Phenotypic and estimated genetic correlations between growth traits were very high, and correlations between sites indicated that there was no important family × site interaction. No adverse correlations between traits were evident. The results indicate the ample potential for selection in the current progeny trial, where responses to within-family and combined selection for growth traits may be high. Accordingly, three selection scenarios were addressed with the aim to initiate the selection of individuals for implementing the Forest Breeding Plan of Galicia for European chestnut.
... Another large body of work on lodgepole pine was published by Koch (1987), which examined phenotypic variation for dozens of characteristics across the natural range of the species. Many other studies followed, ranging from mating systems in natural populations (e.g., Epperson and Allard 1984), biogeography of the species with molecular and quantitative studies Guries 1982a, 1982b;Wheeler and Critchfi eld 1985;Yang et al. 1996;Godbout et al. 2008), leaf chemistry (von Rudloff andLapp 1987), variation in quantitative traits of interest in genetic improvement programs (Xie et al. 2007), disease and pest resistance (Yanchuk et al. 1988;, and more recently examination of the impacts of climate change on the potential adaptation and optimization of populations (Rehfeldt et al. 1999;Wang et al. 2006). ...
This chapter reviews the historical context, economic importance, objectives and achievements to-date for many of the more important conifers undergoing domestication through genetic improvement programs around the world. These provide examples of the context in which genomic technologies will have an impact in forestry. Unlike many other crop plants and livestock animals, forest trees have only been exposed to a few cycles of breeding and selection, and most retain very large amounts of genetic variation in natural populations. These factors present both opportunities and hurdles in the effective application of genomic technologies to existing operational breeding programs.
This study addresses the increasing demand for large-diameter production timber, and considers the time and space variability of half-sib families of Pinus massoniana. Height, diameter at breast height (DBH) and timber volume of 440 open-pollinated half-sib progeny families were investigated in 14 progeny trials in different years and production regions. An evaluation of the genetic variation of all half-sib families was carried out during the sustainable rapid growth period and individual volumes were characterized as a major index. ANOVA analysis showed that there was considerable variance in the growth traits of most families in different years and on different sites. The variations caused by temporal and spatial changes of the mating system required three selection methods for analysis. The results show that there were differences among the heritabilities of different growth traits by different half-sib progenies. Average heritability values of height, DBH and volume were 0.33, 0.34 and 0.36, respectively. Forty-five superior families were selected in every progeny test, 12 were selected in progeny trials by different years and five in different habitat progeny trials. Three superior families (Gui GC553A, Gui GC414A and Gui GC431A) were selected, although in different years and production regions. The genetic gains of timber volume of these selected r families ranged from 1.20 to 47.00%, which could provide a foundation for superior wood property selection and serve as material for seed improvement and extension in surrounding areas.
Prediction of breeding values(BV) is the major component of the evaluation of forest genetics. In this paper, we introduced the main methods and principles predicting the breeding values in forest trees and with special reference to Larix kaempferi, and discussed their applications in the prediction of breeding values and the selection of optimal genotypes. The results indicate that breeding values could be precisely predicted by best linear unbiased prediction(BLUP) or best linear prediction(BLP) based on balanced or quasi-balanced data as well as unrelated and unbalanced data. BLP was a simpler method, while BLUP was most suitable when predicting breeding values for the materials that are related or have different genetic effects. Selection index would be an optimal approach for multi-trait selection. Finally, we discussed the applications and issues of these two methods in the forest genetic evaluation.
A breeding population of Quercus glauca has been established via simple direct selection. Seedlings from naturally crossed seeds of 35 selected families growing in Jeju Island were placed using stroll repeated planting into two experimental forest located at Hannam and Sanghyo in Jeju. After 3 years of planting, characteristics of growth were examined. Growth pattern of trees in Sanghyo was better than those in Hannam. The average heights of filial were 66.8 cm in Hannam and 92.5 cm in Sanghyo. Root collar diameters of filial in Hannam and Sanghyo were 9.3 mm and 12.2 mm, respectively. A great weather differences especially in precipitation and temperature were shown between two test sites. The result of difference of growth pattern between two sites could be useful in provenance adaptability test. Data within families and individuals obtained from this study was also useful for establishment of seed orchard of Q. glauca.
Risks associated with clonal forestry are mainly biological. Among such risks, propagation failure, cultivar decline, and imperfect clonal evaluation all call for specific, targeted countermeasures; delayed failure of clones, however, calls mainly for risk spread. Propagation failures often reduce genetic gain and/or narrow the genetic base. Cultivar decline typically stems from maturation, especially in conifers, and can preclude successful clonal forestry. Maturation can be much delayed by hedging, serial propagation, coppicing (if possible), and cold-storage of tissue, but effectively halting maturation probably requires embryogenesis together with cryogenic storage. Totally restoring juvenility in vegetative material is an ideal, but it is still seldom achievable. Other possible forms of cultivar decline include plagiotropism, and virus infection in hardwoods. Inadequate clonal evaluation can lead to delayed underperformance, especially where genotype-site interaction is important. Clonal failure can result from biotic and climatic events, which may be unpredictable. Climatic damage may affect only occasional clones, but biotic damage is often more comprehensive. Risk spread, however, will not counter agents that cause unacceptable failure rates among deployed clones. Theoretically, as the effective number of unrelated clones exceeds about 20, the additional protection conferred by risk spread becomes marginal, and genetic gain can become significantly eroded. How to deploy a portfolio of clones, in options ranging from intimate mixture to monoclonal mosaics, is debatable. The appropriate choice can depend on various factors, including the nature of likely damage, the epidemiology of the pathogen or insect pest, the silvicultural regime, and the logistics of possible salvage harvesting.
Six hundred 7-year-old Eucalyptusnitens (Dean & Maid.) trees from 50 open-pollinated families were measured for wood density and Pilodyn penetration across two contrasting sites in eastern Victoria, Australia. Eight Pilodyn observations, two from each of four aspects, were made at a height of 1.3 m. Density was measured on whole disks cut from 1.3 m. Heritability of Pilodyn penetration and disk density at 1.3 m were 0.60 and 0.73, respectively. Phenotypic and genetic correlations between Pilodyn penetration and density at 1.3 m were −0.59 and −0.92, respectively. The high repeatability of Pilodyn penetration (0.90) suggests that only two observations per tree would be required for indirect selection of density. Direct index selection for density gave an expected 13% gain (assuming a selection intensity of 1%), compared with a 11% gain by using indirect Pilodyn selection, a selection efficiency of 84%. However, Pilodyn sampling is faster, cheaper, and not destructive, thus resulting in overall higher expected gains for selection of trees or culling of seedling seed orchards in comparison with the more destructive direct assessment of density.
Adequate production of soybean [Glycine max (L.) Merr.] in Nigeria depends on selection of varieties combining high grain yield with stability. Soybean farmers are recurrently faced with the limitation of selecting the best genotype for available environments at their disposal for the production of this crop. Soybean genotypes (23) and two landraces were therefore evaluated in three environments: Abeokuta, Ibadan upland and Ibadan in-land valley in 2017 to select genotype that combines high yield and stability. The experiment in each environment was arranged in a randomized complete block design with three replicates. Data were collected on grain yield and yield component characters. The grain yield data were analyzed using genotype + genotype x environment interaction (GGE) biplot to select desirable genotypes for grain yield and stability; the yield component data were also analyzed using analysis of variance (ANOVA). The variation attributable to G by E interaction was significant except number of branches per plant. Abeokuta was identified as the most representative environment for soybean production. The genotypes TGX 2007-4F, TGX 2016-2E and TGX 2007-1F were the best yielding genotypes in the most discriminating environment – Ibadan upland, thus highly recommended for that specific location. Genotype TGX 2027-7E (G25) was the most stable genotype but was low yielding. Genotypes TGX 2027-3E, TGX 2016-2E, TGX 2007-4F, TGX 2009-1F and TGX 2027-4E, which combined high yield and stability, can be recommended to growers in these three (or similar) environments.
Variation in flowering was analysed in a combined provenance-progeny trial with lodgepole pine (Pinus contorta Dougl. ex Loud, var. latifolia Engelm.) in central British Columbia (BC). The study included 14 provenances from BC, western Alberta, and the Yukon, with 15 families per provenance and 12 trees per family. Female strobili production was assessed at 10, 11 and 29 years age, male strobili production at 11 and 29 years and height at 24 years age. Strobili production varied significantly among provenances. Provenances from the Yukon, northern BC and high elevation in southern BC had the slowest height growth and also the lowest production of male and female flowering at 29 years. Genetic correlations between height and flowering were generally weak. Narrow-sense heritability's for strobili production varied from 0.13 to 0.64. Genetic correlations for strobili production in different years were positive both for female (0,53-0.78) and male flowering (0,32). Genetic correlations between male and female flowering were mostly negative but weak. The results demonstrate that selection of families for height in lodgepole pine should not notably affect the reproductive capacity. The results also suggest that male and female flowering capacity are two moderately to highly heritable but genetically rather independent characters.
The paper is open access on http://www.tuzvo.sk/files/fg/volumes/2001/FG08-4_323-329.pdf
This report describes the procedures that are currently used in British Columbia for predicting the breeding values of parents, estimating the genetic worth of orchard seedlots, and projecting the yields of genetically improved stocks. Breeding value is a measure of the genetic quality of an individual as a parent. There are several procedures available for its estimation/prediction. Among those, the best linear prediction (BLP) relaxes most of the assumptions required by the others and minimizes the error variance of prediction. In most situations in British Columbia, it should provide predictions with satisfactory accuracy and precision with greatly reduced computational complexity. In this province, breeding value for growth potential is expressed as percent gain of stem volume over the unimproved population at a designated rotation age.Genetic worth is an important attribute of the genetic quality of a seedlot. It represents the average level of genetic gain expected for the trait of concern at a designated rotation age when a seedlot is used for reforestation. Currently, the genetic worth of a seedlot is estimated by the mean breeding value of all the parents, including those that contribute to pollen contamination and supplemental mass pollination, weighted by their proportional gamete contributionsThe yield of a genetically improved plantation is projected by incorporating the genetic worth of the seedlot into the existing growth model developed based on extensive data from managed unimproved stands. The current approach not only takes account of the stand dynamics determined by site conditions and silvicultural regimes but also the declining nature of expected gain over time because of imperfect age-age genetic correlation.Because of errors from genetic and environmental sampling, measurement, and analysis, as well as possible violation of model assumptions, estimates/predictions may still be subject to errors and/or biases. Various conservative measures have been taken to minimize any possible upwards biases. As more matured data and advanced analytical technologies become available, both the accuracy and precision will be improved. The advancement made in the procedures described in this document should contribute to superior decisions in many aspects of forest management. West. J. Appl. For. 18(2):88100.
The traditional way to avoid related mating and subsequent inbreeding depression in seed orchards is to use only unrelated clones for orchard establishment. As tree-breeding programs move to advanced generations, relatedness (coancestry) among candidates for seed orchard selections becomes more common, especially for high breeding value candidates. The traditional way of selecting the ones with the highest breeding value, provided they are unrelated, is referred to Restricted Selection (RS). In order to consider breeding value as well as relatedness, an alternative selection method, based on a value criterion for the whole group of selected clones, is presented in this paper. The method, here called Group Merit Selection (GMS), is based on a suggestion by Lindgren and Mullin (1997), but modified for seed orchard selection by neglecting selfing and self-coancestry. The method can be regarded as the selection of a group of clones that maximizes expected genetic value (predicted genetic gain minus inbreeding depression). A case study was conducted in which twenty clones for a seed orchard were selected among second-generation loblolly pine (Pinus teada L.) selections from the NCSU-Industry cooperative breeding program. Assuming an observed inbreeding depression of 40% for one unit coefficient of inbreeding, penalty constants based on estimated breeding values at age 8 was corresponding with inbreeding depression. That gave 12% more genetic value for GMS than Restricted Selection. Predictions of the penalty constant considering additional relevant factors (such as pollen contamination, breeding values based on immature trials, and unrepresentative experimental sites) resulted in selection of the same clones. Changes among the selected clones did not occur until relatedness reached twice the penalty constant, suggesting that GMS solutions are rather robust.
In advanced generation seed orchards, tradeoffs exist between genetic gain obtained by selecting the best related individuals for seed orchard populations, and potential losses due to subsequent inbreeding between these individuals. Although inbreeding depression for growth rate is strong in most forest tree species at the individual tree level, the effect of a small proportion of inbreds in seed lots on final stand yield may be less important. The effects of inbreeding on wood production of mature stands cannot be assessed empirically in the short term, thus such effects were simulated for coastal Douglas fir [ Pseudotsuga menziesii var. menziesii (Mirb.) Franco] using an individual-tree growth and yield model TASS (Tree and Stand Simulator). The simulations were based on seed set, nursery culling rates, and 10-year-old field test performance for trees resulting from crosses between unrelated individuals and for inbred trees produced through mating between half-sibs, full-sibs, parents and offspring and self-pollination. Results indicate that inclusion of a small proportion of related clones in seed orchards will have relatively low impacts on stand yields due to low probability of related individuals mating, lower probability of producing acceptable seedlings from related matings than from unrelated matings, and a greater probability of competition-induced mortality for slower growing inbred individuals than for outcrossed trees. Thus, competition reduces the losses expected due to inbreeding depression at harvest, particularly on better sites with higher planting densities and longer rotations. Slightly higher breeding values for related clones than unrelated clones would offset or exceed the effects of inbreeding resulting from related matings. Concerns regarding the maintenance of genetic diversity are more likely to limit inclusion of related clones in orchards than inbreeding depression for final stand yield.
In most breeding programs of plant and animal species, genetic data (such as data from field progeny tests) are used to rank parents and help choose candidates for selection. In general, all selection processes first rank the candidates using some function of the observed data and then choose as the selected portion those candidates with the largest (or smallest) values of that function. To make maximum progress from selection, it is necessary to use a function of the data that results in the candidates being ranked as closely as possible to the true (but always unknown) ranking. Very often the observed data on various candidates are messy and unbalanced and this complicates the process of developing precise and accurate rankings. For example, for any given candidate, there may be data on that candidate and its siblings growing in several field tests of different ages. Also, there may be performance data on siblings, ancestors or other relatives from greenhouse, laboratory or other field tests. In addition, data on different candidates may differ drastically in terms of quality and quantity available and may come from varied relatives. Genetic improvement programs which make most effective use of these varied, messy, unbalanced and ancestral data will maximize progress from all stages of selection. In this regard, there are two analytical techniques, best linear prediction (BLP) and best linear unbiased prediction (BLUP), which are quite well-suited to predicting genetic values from a wide variety of sources, ages, qualities and quantities of data.
Height, diameter at breast height and stem volume of 610 open-pollinated lodgepole pine families from 42 provenances covering the entire interior range of the species in Canada were measured periodically up to 20 years (age 24 from seed) at a provenance-family plantation in central British Columbia. Genetic variation in growth was large at both provenance and family levels. Provenance effect was always greater than family effect and the difference tended to increase as the test aged. Estimates of heritabilities for provenance means, family means, individual values, and within family deviations were high, ranging from 0.77 to 0.97, 0.41 to 0.50, 0.28 to 0.42, and 0.22 to 0.35, respectively. Age-age correlations were strong and always positive, varying from 0.85 to 1.00 for provenance means and from 0.51 to 0.98 for additive genetic effects. Genetic age-age correlations demonstrated a strong linear relationship with the natural logarithm of the juvenile- mature age ratio. The expected annual genetic gain was maximised by selection at the earliest assessment ages (i.e., 7 years for height and 14 years for diameter and stem volume) for stem volume at age 24 years, regardless of the selection schemes. Selection based on stem volume was always more efficient than based on height or diameter alone. High heritabilities, strong positive age-age genetic correlations, and early sexual maturity of lodgepole pine suggest a great potential of early selection in this species.
The present paper is an attempt to compare the methods of estimating genetic correlations, one from the original variance and covariance analyses and the other from the two-way analysis of variance.
By contrasting the expected mean squares in the latter in terms of variance and covariance in the former, the standard estimation formula of genetic correlation was expressed by means of variance components in the two-way analysis.
Genetic and phenotypic parameters of growth and wood density were calculated for two open-pollinated progeny trials of Tasmanian Blue Gum (Eucalyptus globulus ssp. globulus) in Portugal. These parameters are used to develop selection indices and predict genetic responses for different strategies. Mean individual heritabilities (averaged across the two trials) of height and wood density were high (h2 = 0.34 ± 0.10 and 0.65 ± 0.12, respectively) and those of sectional area and dry weight were intermediate (h2 = 0.18 ± 0.06 and 0.21 ± 0.11). Mean genetic correlations (across trials) were strongly positive (0.94 ± 0.05 to 0.99 ± 0.03) between dry weight and height or sectional area, and moderate (0.17 ± 0.20) between dry weight and wood density. Sectional area and height were slightly negatively correlated (-0.08 ± 0.25 to -0.09 ± 0.17) with density.
Selection indices constructed to maximize genetic gain in dry weight gave results which clearly favored indirect selection on height. A genetic gain of around 47% in dry weight may be expected from second-generation selection of 1 tree in 200 for E. globulus in Portugal. Marginal deterioration can occur in wood density unless family means for either dry weight or density are included in the index with height. A strong response in wood density from index selection requires a substantial sacrifice of gains in dry weight. For. Sci. 38(1):80-94.
Juvenile-mature correlations in the literature were analyzed and found to be more predictable than may have been expected by those who have dealt with them. Age-age correlations except those involving very young ages, usually 1-3 years, can be estimated with reasonable accuracy by a single regression equation which applied to several species and studies. Applicability of the equation to genetic test situations may be possible. After predicting age-age correlations, optimum selection age was estimated for several economic rotations. These ages for 30- and 40-year economic rotations were 6 and 8 years respectively for the conditions specified. Forest Sci. 26:571-580.
A base breeding population of 13,000 trees from about 300 Eucalyptus nitens families of open-pollinated origin in 6 provenances of native forest stands, was established in 8 tests, analyzed for genetic parameters and used for breeding value and gain prediction. Traits considered were basal area (BA), basic density (BD), and kraft pulp yield (PY) in 4- to 8-yr-old trees. Measurement of PY, whether taken as individual trees (PYI) or composites (PYC), were considered as the same trait, since the average Type B genetic correlation (rBg) between PYI and PYC was 0.94. Trees with the "early-adult form" typically from the Errinundra provenance appeared to have the poorest PY, averaging 1 to 3% points lower than all the other provenances. This provenance was excluded from detailed genetic analyses. Significant differences among the other five provenances were found for all traits. Four provenances were reasonably similar, but northern New South Wales was estimated to be lowest for BA and PY, and highest for BD. Single-site biased heritabilities (h²b) varied substantially from site to site, and averaged 0.32 ± 0.05 for BA, 0.43 ± 0.09 for BD, 0.37 ± 0.08 for PY. Heritability estimates from combined-site analyses were 0.19 for BA, 0.42 for BD, and 0.37 for PY. Genotype x environment (g x e) interaction was estimated using rBg. For BD and PY, rBg was 0.94, indicating no major g x e. Moderate g x e interactions were detected for SA, with rBg at 0.60. Genetic correlation between BA and PY, and between BD and PY were favorable, but between BA and BD was unfavorable (genetic correlation = 0.24, 0.41 and -0.24 respectively). For. Sci. 44(4):587-598.
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