Inheritance and Linkage Studies with Five Isozyme Loci in Soybean1
- Jeffrey Griffin and
- Reid G. Palmer2
Horizontal starch gel electrophoresis, followed by enzyme-specific staining, allows us to separate and visualize several soybean [Glycine max [L.] Merr.] isozymes. Using extracts prepared from the cotyledons of seeds germinated 3 to 4 days, we detect five bands (zones) of aconitase [aconitate hydratase, enzyme commission (EC) 220.127.116.11] activity and one band of endopeptidase activity. We have observed mobility variants of all of these isozymes. An understanding of the genetic basis of the variants would facilitate their use as markers in soybean genetics or breeding studies. One objective of this research was to investigate the inheritance of mobility variants for four of the five aconitase isozymes, as well as a mobility variant for the endopeptidase band. Segregation data (either individual F2 zymotypes or F2 genotypes determined by progeny testing) were collected on F2 populations derived from F1 individuals whose parents had different zymotypes. Mobility variants of the four aconitase isozymes are conditioned by four independent loci with codominant alleles. The aconitase loci and alleles are: Acol (a, b), Aco2 (a, b), Aco3 (a, and Aco4 (a, b, c). The endopeptidase mobility variants are conditioned by the codominant alleles Enp-a and Enp-b. A second objective was to determine if these five isozyme loci are linked to one another, or to other known loci. Data were collected on F2 populations segregating for several loci conditioning isozyme and morpholigical traits. Deviations from independent assortment were determined by Χ2 analysis. Locus Aco3 is linked to the Spl locus; the frequency of recombination varied from 4.6 ± 0.9% in the cross ‘A1937’ ✕ PI 342662A (G. soja Sieb. et Zucc.) to 30.6 ± 3.0% in the cross PI 437728 (G. max) ✕ ‘Evans’. Locus Aco3 also is linked to the T locus, with a recombination frequency of 28.8 ± 4.3%, as determined in the cross ‘Amsoy 71’ ✕ PI 342622A. Both Spl and T are on linkage group 1. The present data allow us to assign Aco3 to linkage group 1, but do not allow us to unambiguously establish its position relative to other markers. The other four loci also were tested for linkage with several loci; Acol (11 loci), Aco2 (10 loci), Aco4 (13 loci) and Enp (8 loci) segregated independent of all loci tested. These five loci conditioning isozyme mobility variants can be useful tools in soybean genetic research.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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