Natural Mutations in Inbred Lines of Maize and Their Heterotic Effect. II. Comparison of Mother Line Vs. Mutant When Outcrossed to Unrelated Inbreds

Schuler, J.F.; Sprague, G.F.

Genetics 41(2): 281-291

1956


ISSN/ISBN: 0016-6731
PMID: 17247627
Accession: 014114030

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Abstract
The homozygous dominant genotype, with the general symbol DD, was compared with the heterozygous genotype in a genetically heterozygous but homogeneous background by means of the following crosses (cf. PBA, XXV, Abst. 3022). Eight pairs of inbred lines were each crossed with three DD testers unrelated to them and derived by diploidization of monoploids. Each pair of inbred lines consisted of the original mother line and its identical substrain except for one of the homozygous recessive mutations corresponding to dd, for the following characters: crinkled leaf, narrow leaf, brachytic stalk, green stripe, two nonallelic types of dwarfness and two nonallelic small-seeded conditions. No evidence was obtained of overdominance for yield. Data on other attributes occasionally indicated a superiority of the heterozygotes over the homozygous dominants. Variance ratios provided evidence of differences in genetic composition between mother lines and mutants. The possible causes of heterozygosity in inbreds are briefly discussed.