Inheritance of Aconitase, Shikimate Dehydrogenase, and Phosphoglucose Isomerase in Guayule

Abstract

Starch gel electrophoresis was carried out to investigate inheritance of aconitase (ACO), shikimate dehydrogenase (SKDH), and phosphoglucose isomerase (PGI) in guayule (Parthenium argentatum Gray). Self-incompatibility of diploid guayule (2n = 36), prevented production of F2 generations. A series of crosses was made for segregation analysis. The enzyme ACO showed two zones of activity—one monomorphic and the other polymorphic, representing one locus with two alleles. SKDH was found to be coded by two loci with three alleles at each locus. Four zones of activity were found for PGI. PGI-1, the fastest zone, was poorly resolved and appeared variable. Segregation data indicated that PGI-2 is monogenic and controlled by five codominant alleles. Poor resolution of PGI-4 made it impossible to determine whether PGI-3 was the product of a separate locus or resulted from intergenic cross dimerization between PGI-2 and PGI-4. The dimeric characteristic of PGI-2 and the monomeric structure of SKDH and ACO-1 in guayule agreed with the protein structures previously reported for these enzymes in other plant species. The isozyme variation of this investigation maybe used in a breeding program to identify sexual and maternal type progenies of facultative apomictic guayule plants at the early seedling stage.