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|Title:||Genetics of peroxidase isoenzyme polymorphisms in maize (Zea mays L.)|
|Authors:||Hamill, Doris Elizabeth|
|Abstract:||Peroxidase isoenzyme polymorphism in maize was investigated using horizontal starch gel electrophoresis at pH 8.1. Crude preparations of tissues were subjected to electrophoresis and the resulting gels were stained with a suitable hydrogen peroxide - hydrogen donor solution to indicate the zones of peroxidase activity. Three hydrogen donors - guaiacol, benzidine, and o-dianisidine were examined. Certain peroxidase isoenzymes did not stain with guaiacol, while all isoenzymes reacted similarly with benzidine or o-dianisidine. O-dianisidine provided stable reaction products and was selected in preference to benzidine for further studies. Thirteen tissues from over 300 different inbred lines, tropical races, and genetic stocks were surveyed to assess the total peroxidase isoenzyme variation within the species. At least 21 different peroxidase isoenzymes, 12 anodal and 9 cathodal, were observed in anyone maize plant. Tissues varied greatly in isoenzyme complement, and certain isoenzymes were tissue specific. The peroxidase isoenzyme patterns of root, leaf blade, leaf sheath, internode, and anther were analyzed at several different stages of growth, and were found to change with growth and development of the tissue. Roots showed a decrease in peroxidase isoenzymes during maturation while leaf blade, leaf sheath, and internode increased in isoenzyme complexity. This increase in number of isoenzymes in leaf and internode material appeared to be correlated with the cessation of elongation of these tissues. The role of peroxidase with regard to auxin metabolism was discussed. Immature anthers showed more isoenzymes than did mature pollen which possessed a highly unique peroxidase isoenzyme pattern. Five of the peroxidase isoenzyme systems were subjected to genetic analysis and were found to be under control of S different loci designated Px1, Px2, Px3, Px4, and Px5. The Pxl peroxidase migrated cathodally and was found in roots and some leafy tissues. Four electrophoretic variants including a null were observed for this system, and genetic analyses carried out on seedling root extracts indicated that each variant was conditioned by one allele of a single locus. The four alleles were designated Px^(1)l, Px^(2)l, Px^(3)l, Px^(null)l. The Pxl locus was determined not to be located on the long arm of Chromosomes III, IV, or X or on the short arm of Chromosomes VII or IX. The Px2 peroxidase system moved anodally and was found exclusively in pollen following anthesis. It was found to be a product of one locus with 2 alleles, Px^(1)2 and Px^(2)2, each conditioning an electrophoretic variant. No null was observed. The Px3 peroxidase was an anodal multiple band complex found in mature leaf, internode, husk, and root tissue, but stained most intensely in fully elongated tissues. Two isoenzyme patterns were observed, and genetic data from both leaf blade and root tissues indicated that each pattern was under the control of an allele at a single locus. Px4 and Px5 peroxidases both migrated cathodally and were found in leaf material. Each comprised a monogenic system with presence - absence alleles. The absence allele was dominant for locus Px4 while the presence allele was dominant for locus Px5. There was no evidence of linkage for Px3, Px4, and Px5.|
Thesis (Ph. D.)--University of Hawaii, 1970.
Bibliography: leaves -80.
vii, 80 l graphs, tables
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|Appears in Collections:||Ph.D. - Horticulture|
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