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  • Eucalyptus  (2)
  • Filled seeds  (1)
  • Genetic mapping  (1)
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  • 1
    ISSN: 1432-2242
    Keywords: Key words Eucalyptus ; Genetic mapping ; QTL ; Stability ; Marker-assisted selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The objective of this study was to use random amplified polymorphic DNA (RAPD) to determine the genetic location and effects of genomic regions controlling wood density, stem growth and stem form in two species of Eucalyptus. Two hundred F1 trees generated from an interspecific cross E. urophylla×E. grandis between two elite trees were used. Genetic maps were constructed for each parent with markers segregating in the 1:1 ratio in FS progeny. A total of 86 and 92 markers distributed among 11 linkage groups covered 1295 cM and 1312 cM for the E. urophylla and E. grandis parent, respectively. Traits were measured three times up to selection age (38 months). The magnitude of the phenotypic variation explained by the joint action of the segregating quantitative trait alleles indicated that genetic factors of large effect were involved in the control of the studied characters. Several regions controlling part of the variation for the studied traits were identified by interval mapping. Some regions of the genome exerted effects on more than one trait, providing a genetic explanation for at least some of the correlation between the traits. On the basis of an age-by-age analysis, a partial stability of QTL expression was observed with 68% of the QTL being expressed at two ages and 32% being age-specific. No QTL were significant for all three ages. Taking advantage of repeated measurements on the same material across different ages, we investigated with a maximum statistical power, the effect of marker genotype on traits, with age and QTL×age interaction effects being removed. A two-way analysis of variance made it possible to detect significant marker-trait associations over the period studied. Most of them had already been detected in the annual analysis. This result is very encouraging for the application of marker information to the early selection of hybrid trees to be vegetatively propagated for the production of clonal varieties.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 92 (1996), S. 347-356 
    ISSN: 1432-2242
    Keywords: Pinus pinaster ; Inbreeding depression ; Filled seeds ; Adult growth ; Genetic load
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between inbreeding depression and inbreeding coefficient (F) for several important traits was investigated in an 11-year trial of maritime pine (Pinus pinaster). Five levels of inbreeding (F=0; 0.125; 0.25; 0.5; 0.75) were obtained in a mating design involving ten plus-trees, or their progenies, as parents (total of 51 families). For F=0.75, the mean inbreeding depressions were 27% for height, 37% for circumference at breast height (63% for bole volume), 23% for basal straightness (better straightness of the inbred trees), and 89% for female fertility (number of cones). Large differences were observed among inbred families for the same level of inbreeding. The evolution of depression with F was more or less linear, depending on the traits. Significant differences among F-levels appeared very early for height (from 5-years of age). Inbreeding depression was much more expressed during unfavorable years than during favorable years for yearly height growth. When compared with other Pinus species, maritime pine appears to be less affected by inbreeding, especially for the percentage of filled seeds and general vigor. A reduced genetic load in maritime pine may result from the evolutionary history of the species and its scattered distribution.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 94 (1997), S. 796-803 
    ISSN: 1432-2242
    Keywords: Key words RAPD ; Genetic distances ; Heterosisbreeding ; Prediction ; Eucalyptus ; Interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Within the context of the reciprocal recurrent selection scheme developed in 1989 by CIRAD-Forêt on Eucalyptus, RAPD essays were performed to assess the genetic diversity in the two species E. urophylla and E. grandis. The molecular markers were split into two parts: the specific markers (present with different frequencies in the two species) and the common markers (present with similar frequencies in the two species). The study analyses the structure of genetic diversity within and between the two species of Eucalyptus. Different genetic distances are worked out for use in prediction equations of the individual tree trunk volume of hybrids at 38 months. Each distance is expressed as the sum of the general genetic distance and the specific genetic distance. The general genetic distance based on the double presence plus the double absence of bands seems to be an interesting co-variate to use in a factor regression model. Through this model the distance calculated between species explains the general combining ability (GCA) and the specific combining ability (SCA) of the phenotypic character with a global coefficient of determination of 81.6%.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2242
    Keywords: Key words Analysis of interaction ; Heterosis breeding ; Clustering procedure ; AMMI model ; Eucalyptus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The Eucalyptus breeding program of URPPI (a partnership between CIRAD-Forêt, Centre National de la Recherche Forestière du Congo, and Unité d’Aforestation Industrielle du Congo) consists of a reciprocal recurrent selection scheme developed in the Congo between the two species Eucalyptus urophylla and Eucalyptus grandis. Two approaches are proposed in order to model and predict the specific combining ability (SCA) between these species. The clustering approach uses a simultaneous clustering procedure of the two species based on SCA and reveals heterotic groups coherent with the geographical origins of E. urophylla genotypes. The second approach uses a multiplicative model to partition the SCA into three multiplicative terms explaining 95% of the interaction.
    Type of Medium: Electronic Resource
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