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Crop Science Abstract -

Performance of Genetically Comparable Diploid and Tetraploid Alfalfa: Agronomic and Physiological Parameters1


This article in CS

  1. Vol. 15 No. 2, p. 211-214
    Received: July 26, 1974

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  1. M. W. Dunbier,
  2. D. L. Eskew,
  3. E. T. Bingham and
  4. L. E. Schrader2



Diploid and tetraploid alfalfa (Medicago sativa L. sensu lato) populations were produced sexually utilizing numerically unreduced gametes and parthenogenetically developed haploids of 4x-2x crosses. The advantage of the procedure over colchicine doubling is that genetically comparable populations, rather than individuals, at different ploidy levels can be studied. Additionally, both ploidy levels were in the same cytoplasm. Populations were grown in field plots to determine dry matter (DM) production and in a space-planted nursery for analysis of the following characters; percentage total nonstructural carbohydrates (TNC), percentage total nitrogen (N), fresh weight/trifoliolate leaf, glucose-6-phosphate dehydrogenase activity (G6PDA), deoxyribonucleic acid (DNA) and water soluble protein concentration (WSP).

As expected, concentrations of DNA, WSP, and N were basically the same in diploids (D) and tetraploids (T). T/D ratio was 2.10 for DM yield, 2.05 for fresh wt/trifoliolate, 2.09 for DNA/trifoliolate, and 1.78 for G6PDA/trifoliolate, indicating these characters were strongly influenced by ploidy. G6PDA/trifoliolate was higher in tetraploids but significantly higher in only one D-T comparison, indicating that activity of this enzyme was influenced by factors in addition to ploidy. Phenotypic differences are thus demonstrated to be the result of a complex interaction between increasing gene dosage (polyploidy) and genetic regulation.

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