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  • Interspecific hybrid  (2)
  • Inbreeding depression  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Molecular genetics of growth and development in Populus. I. Triploidy in hybrid poplars (1993)
    Springer
    Theoretical and applied genetics 86 (1993), S. 301-307 
    Details
    ISSN: 1432-2242
    Keywords: RFLP ; Polyploid ; Nondisjunction ; Interspecific hybrid ; Cottonwood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary While constructing a genetic linkage map of a hybrid poplar genome (Populus trichocarpa x P. deltoides), we identified several restriction fragment length polymorphismus (RFLPs) for which the parental trees are heterozygous. Although 8 of the 11 F1 hybrid offspring inherited, as expected, single RFLP alleles from each parent, 3 F1 trees in the mapping pedigree inherited both maternal alleles along with a single paternal allele at some loci. Aneuploidy or polyploidy in these 3 F1 trees due to partial or complete nondisj unction during female gametogenesis is the simplest explanation for this finding. Of the 3 f1 offspring with supernumerary RFLP alleles 2 have triploid nuclear DNA contents as measured by fluorescence flow cytometry; the 3rd F1 with supernumerary alleles has a sub-triploid nuclear DNA content and is probably aneuploid. Among the tri/aneuploid hybrids, leaf quantitative traits either are skewed toward those values characteristic of the P. trichocarpa female parent (adaxial stomate density, petiole length: blade length ratio; abaxial color) or show transgressive variation (epidermal cell size). Abaxial leaf color was used to screen a large population of P. trichocarpa x P. deltoides hybrids for further evidence of tri/aneuploidy. In each case where a “white” abaxial leaf surface was observed and the nuclear DNA content measured, the hybrid proved to be tri/aneuploid. All sexually mature female triploids examined were sterile, although the inflorescences completed their development in the absence of embryo formation. The (probably) aneuploid F1 hybrid is a fertile female. Of 15 female P. trichocarpa parents used in crosses to P. deltoides, 10 produced one or more tri/aneuploid hybrid offspring. In an intraspecific cross using a P. trichocarpa female that had produced triploid hybrids with five different P. deltoides males, no tri/aneuploid offpsring were found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222092
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative genetics of growth and development in Populus. I. A three-generation comparison of tree architecture during the first 2 years of growth (1994)
    Springer
    Theoretical and applied genetics 89 (1994), S. 1046-1054 
    Details
    ISSN: 1432-2242
    Keywords: Interspecific hybrid ; Tree architecture ; Quantitative genetics ; Quantitative trait loci ; Populus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract One approach to gain an insight into the genetics of tree architecture is to make use of morphologically divergent parents and study their segregating progeny in the F2 and backcross (B1) generations. This approach was chosen in the present study in which material of a three-generation pedigree growing side by side in a replicated plantation, was analyzed. The pedigree included Populus trichocarpa (T) and P. deltoides (D) parents, their F1 and F2 hybrids and their B1 hybrids to the D parent. The trees were grown in the environment of the T parent and measured for the first 2 years of growth. Nine quantitative traits were studied at the stem, branch and leaf levels of tree architecture, in which the original parents differed. Strong F1 hybrid vigor relative to the better parent (T) was expressed in growth and its components. Most quantitative traits in the F2 and B1 hybrids were intermediate between the T and D parents but displayed a wide range of variation due to segregation. The results from the analysis of variance indicated that all morphometric traits were significantly different among F2 and B1 clones, but the B1 hybrids were more sensitive to replicates than the F2. Broad-sense heritabilities (H 2) based on clonal means ranged from moderately high to high (0.50–0.90) for the traits studied, with H 2 values varying over age. The H 2 estimates reflected greater environmental “noise” in the B1 than in the F2, presumably due to the greater proportion of maladaptive D alleles in those hybrids. In both families, sylleptic branch number and length, and leaf size on the terminal, showed strong genetic correlations with stem growth. The large divergence between the two original parents in the traits studied, combined with the high chromosome number in Populus (2n=38), makes this pedigree well suited for the estimation of the number of quantitative trait loci (QTLs) underlying quantitative variation by Wright's biometric method (1968). Variation in several traits was found to be under the control of surprisingly few major QTLs: 3–4 in 2nd-year height and diameter growth, a single QTL in stem diameter/height ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224537
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular genetics of growth and development in Populus. II. Segregation distortion due to genetic load (1994)
    Springer
    Theoretical and applied genetics 89 (1994), S. 551-558 
    Details
    ISSN: 1432-2242
    Keywords: Cottonwood ; Inbreeding depression ; Lethal equivalent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Distortion of expected Mendelian segregation ratios, commonly observed in many plant taxa, has been detected in an experimental three-generation inbred pedigree of Populus founded by interspecific hybridization between P. trichocarpa and P. deltoides. An RFLP linkage map was constructed around a single locus showing severe skewing of segregation ratio against F2 trees carrying the P. trichocarpa allele in homozygous form. Several hypotheses for the mechanism of segregation distortion at this locus were tested, including directional chromosome loss, segregation of a pollen lethal allele, conflicts between genetic factors that isolate the parental species, and inbreeding depression as a result of genetic load. Breeding experiments to produce inbred and outcrossed progenies were combined with PCR-based detection of RFLPs to follow the fate of the deficient allele throughout embryo and seedling development. A recessive lethal allele, lth, inherited from the P. trichocarpa parent, was found to be tightly linked to the RFLP marker locus POP1054 and to cause embryo and seedling mortality. Heterozygotes (lth/+) appear to be phenotypically normal as embryos, seedlings, and young trees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222447
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