Molecular genetics of growth and development in Populus. 1. Triploidy in hybrid poplars.
1993
Bradshaw H.D. Jr. | Stettler R.F.
While constructing a genetic linkage map of a hybrid poplar genome (Populus trichocarpa x Populus deltoides), several restriction fragment length polymorphisms (RFLPs) were identified for which the parental trees are heterozygous. Although 8 of the 11 F(1) hybrid offspring inherited, as expected, single RFLP alleles from each parent, 3 F(1) trees in the mapping pedigree inherited both maternal alleles along with a single paternal allele at some loci. Aneuploidy or polyploidy in these 3 F(1) trees due to partial or complete nondisjunction during female gametogenesis is the simplest explanation for this finding. Of the 3 F(1) offspring with supernumerary RFLP alleles 2 have triploid nuclear DNA contents as measured by flourescence flow cytometry; the 3rd F(1) with supernumerary alleles has a sub-triploid nuclear DNA content and is probably aneuploid. Among the tri/anueploid 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 inflorescence completed their development in the absence of embryo formation. The (probably) aneuploid F(1) 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.
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