Trisomic analysis of isozymic loci in tomato species: segregation and dosage effects.

Five isozymic loci were localized in the tomato (Lycopersicon esculentum) genome by trisomic analysis. Results revealed the following locations: Aps-1 on chromosome 6, Est-1 and Prx-2 on chromosome 2, Prx-4 on chromosome 10, and Prx-7 on chromosome 3. Three genes--Aps-1, Prx-2, and Prx-4--showed an arithmetic increase in allozyme concentration in direct proportion to the increase of gene dosage in respective primary trisomics. In contrast, no increase in relative Est-1 isozyme concentration was observed for any primary trisomic type. The phenotypes of the Aps-1, Prx-2, and Est-1 genes showed a pattern of banding intensity proportional to the allelic ratio (+/+/a vs. +/a/a) in primary trisomics; zymotypes of these differential trisomic heterozygotes appeared as "converse images" of each other.