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parameter estimates for wood stiffness, strength, internal checking, and resin bleeding for radiata pine. Canadian Journal of Forest Research 34 : 2601–2610.
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The genotypic and phenotypic correlation and path analysis of plant biomass, plant height, stem diameter and other biomass component traits were analyzed in thirty provenances of Bombax ceiba. In general, the magnitude of genotypic correlations was higher than phenotypic correlations. Stem diameter and plant biomass showed highly significant genotypic correlations with all the traits except the number of secondary branches and plant biomass with leaf biomass. Plant height had the highest positive direct effect on plant biomass followed by the number of primary branches/plant and the number of leaves/plant. On the basis of this study, a higher plant biomass would be achieved through direct selection based on plant height, the number of primary branches and the number of leaves/plant. Therefore, the study is important in selection of traits of economic importance based on other characters, whose direct effect is not visible.
The phenotypic response of genotypes across different environments can be quantified by estimating the genotype by environment interaction (GxE). In a practical sense, GxE means that the relative performance of genotypes does not remain constant under all test conditions. Genetic parameters and genotype by environment interactions for wood density, growth, branching characteristics and stem straightness were investigated in eight radiata pine progeny trials derived from a second generation breeding population in Australia. Five trials were on the mainland, while three trials were in Tasmania. Generally, ĥ2 for density > branch angle > stem straightness > tree diameter > branch size; and significant ĥ2 was observed for all traits and at all trials with only two exceptions. Genetic correlations were estimated among the five traits, and a large negative genetic correlation observed between wood density and tree diameter indicated that a selection strategy should be developed in dealing with this adverse genetic correlation in advanced generations of breeding for radiata pine. Interactions for density, branch angle, and stem straightness were small within the two regions. Overall, branch angle had the least GxE, followed by density and stem straightness. Growth traits (tree diameter and branch size) tended to be the most interactive with substantial GxE present. Genotype by regional interactions (Mainland versus Tasmania) revealed that density and branch angle had the least interactions (ȓB = 0.98 and ȓB = 0.95, respectively). Branch size and tree diameter had the highest interactions among the two regions (ȓB = 0.55 and ȓB = 0.63, respectively). Within Tasmania, only branch size and tree diameter had a sizable interaction within the three sites. In contrast, there was little interaction for tree diameter among the Mainland trials. Branch size in the Mainland trials had a similar size of interaction as in Tasmania. Further research is recommended in identifying the cause of GxE for tree diameter and branch size in radiata pine across the entire radiata pine estate in Australia.
Four hundred and sixty individual families of Pinus radiata, representing all provenances and populations in a 1978 seed collection, plus a local seed orchard control, were planted together in 1980 in a large trial in southern New South Wales, Australia. Provenance means and genetic parameters for growth measured at ages 3, 8 and 26 years plus stem straightness, branch angle and nodality at age 26 years are reported. Large provenance differences were apparent for all traits. The two island provenances, Cedros and Guadalupe, were significantly inferior to the mainland provenances and, due to competition effects, very few trees survived to age 26. Within the mainland provenances, the performance of Año Nuevo and Monterey was almost identical, with Cambria being less vigorous. The best performing seedlot for all traits was the local control. Differences between populations within the mainland provenances were apparent for diameter at age 26 within Año Nuevo and Cambria but not Monterey. Año Nuevo also showed population differences for stem straightness. Heritabilities for early growth were similar within Año Nuevo and Monterey but by age 26, the heritability for diameter was higher in Monterey. Within Cambria, heritabilities for growth and tree form at age 26 were close to zero. Genetic correlations between traits showed similar patterns for each of the mainland provenances, with the exception of correlations with stem straightness within Año Nuevo. Results are discussed in light of recent molecular studies of genetic architecture, levels of inbreeding in the native stands and possible effects of this inbreeding.
J. J. Vargas Hernández, J. López Upton, G. Ramirez Valverde and L. Harrand
To determine the genetic parameters of growth traits and wood density (estimated by Pilodyn penetration) in a population of Eucalyptus grandis formed by families from 11 seed origins in NE Queensland, Australia and a local land race, 8.5-year-old progenies established in three sites in NE Argentina were evaluated. Local trees exhibited higher growth rate at two sites and better stem form, but also deeper Pilodyn penetration, at all sites; thus, there is potential to infuse new genetic variation into the current breeding population in the region. A significant amount of genetic variation was found for all traits assessed, with growth traits [diameter (DBH), height (HT) and volume (VOL)] showing different genetic structure and degree of genetic control as compared to stem straightness (FORM), bark thickness (BARK) and Pilodyn penetration (PILO). The effect of origin was negligible for growth traits while it was important for the other traits, so it should be considered in the selection strategy; in addition, individual heritability for growth traits (0.11-0.16 in the combined analyses) was generally lower than for the other traits (0.20-0.35). Genetic correlations between sites for all traits were high enough to indicate that genotype-environment interaction would not affect the selection program by using a single breeding population for this region. Genetic correlations between growth traits were high (rg > 0.80), and negligible between these and FORM; the only unfavorable genetic correlation was between PILO and BARK (rg = -0.44). Age-age correlations for growth traits and FORM were very high (rg > 0.90). Results suggest that all traits evaluated could be handled in a breeding program, either independently or combined, without negative correlated effects. Early selection for growth traits and stem form is also possible, with major savings in time.
H. S. Ginwal, Pradip Kumar, V. K. Sharma, A. K. Mandal and C. E. Harwood
Results of provenance cum progeny trials of Eucalyptus tereticornis Sm. laid out in 2002 at three sites viz. FRI Campus (Uttaranchal), Chiryanpur (Uttaranchal) and Midnapore (West Bengal) located in tropical region of India are reported and discussed. Thirteen provenances representing 91 families from Australia and Papua New Guinea (PNG) viz. Oro bay to Emo, PNG; Sirinumu Sogeri Plat, PNG; Warwick, QLD; Yurammie, SF, NSW; Buckenbowra SF, NSW; Selection flat SF559, NSW; Credition SF, QLD; Cardwell, QLD; Mitchell River MT Molloy, QLD; Mill stream archer creek, QLD; Helenvale, QLD; Walsh River, QLD; Burdekin River, QLD were evaluated from nursery stage to field performance (age 21months). As a local seed source open-pollinated seeds collected from selected interspecific Eucalyptus F1 hybrid trees of FRI-4, FRI-5 and Mysore gum (Eucalyptus teretirornis) were used to serve as check material (control). Significant differences between the provenances and families at age 21 months were observed for height, clean stem length, collar diameter and field survival. Significant provenance x site interaction was observed for height. In general the north Queensland provenances performed better and in particular two provenances viz. Walsh River, QLD and Burdekin River, QLD ranked the best in comparison to others at this age. Results indicate that significant genetic differences exist between the families and provenances of E. tereticornis. The growth traits were inter-correlated with each other. Geographic clinal variation pattern was observed in some of the growth traits viz. height, clean stem height and collar diameter. There were fair differences between phenotypic and genotypic coefficient of variability. Heritability (narrow sense) values were fairly good for height and clear stem length in comparison to collar diameter. The relative performance of the provenances was fairly consistent throughout test sites.
Demand for planting elite shrub willows as a resource for industrial use such as bioenergy and pulp has been increasing in Jilin province in northeast China. Toward this end, 12 elite willow clones, representing various species and origins, were imported from New York, USA, and planted at Lushui River, Jilin province. Two indigenous species were included in the test as the controls for comparison. This study was an evaluation of their performance in adaptation, growth potential, and wood traits after one rotation (three growing seasons). Results indicated that (1) all clones, but one, showed a parallel phenology to the control, had excellent survival (> 86%) and displayed good frost resistance; (2) compared to the control, most imported clones were comparable in main stem growth (height and diameter), but developed more stems and main roots; and (3) most imported clones had similar lignin, but higher cellulose content relative to the control. These results imply that some of the imported clones should be considered for further evaluation as good sources for both bioenergy and pulping. Based on cluster analysis, six clones were recommended for the upcoming scale-up site-clone trials for yield evaluation.
Miguel Luiz Menezes Freitas, A. L. Coleto, W. Santos, M. A. Moraes, J. Cambuim, S. S. Nascimento, J. Ferracini, E. L. Longui and M. L. T. Moraes
The aim of this study was to determine the genetic variation of growth traits, wood basic density, dry mass of crown, leaf, and stem, and carbon stock within and between two Genipa americana L. provenances. The provenance and progeny test was installed in the Teaching, Research and Extension Farm, located in Selvíria, Mato Grosso do Sul, Brazil. The test was established using a randomized block design with two provenances and 36 progenies, a spacing of 3 x 2 m, four replicates, and six plants per plot. At 11 years of age, height and diameter at breast height (DBH) were measured. To estimate wood basic density, biomass, and carbon stock, 45 plants were thinned. Growth traits for crown, leaf, and stem, as well as wood basic specific gravity showed significant differences. Both provenances present high carbon storage, demonstrating the potential of this species to be included in carbon credit programs that help to minimize the effects of global warming. In general, heritability values were low, suggesting limited genetic control of the evaluated traits. However, the traits presented a high coefficient of genetic variation, indicating adequate sampling among populations; these results are promising for ex situ conservation and for future breeding programs.
Enriched diploid pollen was applied for in vitro pollinations and crossbreeding in the greenhouse to produce high performance triploid aspen and aspen hybrids for cultivation in medium rotation plantations. In addition to crossings within the section Populus, intersectional crossbreeding was performed to combine benefits of intersectional hybridization with those derived from triploidisation.
Both the enrichment of diploid pollen by size fractionation of naturally unreduced pollen and heat treatment of microspore mother cells resulted in a distinct increase of diploid pollen. Using this pollen, six triploid plants were obtained from in vitro pollinations and twenty from crossbreeding in the greenhouse. The triploid plants displayed a high variability in growth performance. Two clones from in vitro pollination and five from crossbreeding in the greenhouse were chosen to estimate growth characteristics. A first assessment of clone performance in an outdoor container test con - ducted over one growing season revealed two triploid clones with a same stem height and a significantly increased basal stem diameter in comparison to the fast-growing triploid reference clone “Astria”. Crossbreeding experiments also resulted in two fast-growing mixoploid clones, which have already been stable for several years.
All in all, in this study, crossbreeding using enriched diploid pollen is proved to be a reliable and applicable approach for an effective breeding of triploid poplars.