Inheritance of the Isozyme Isocitrate Dehydrogenase (IDH) in a Natural Population of Polyploid White Clover (Trifolium Repens L.)

Abstract

An electrophoretic study of segregation of isocitrate dehydrogenase (IDH) was undertaken in polyploid white clover (Trifolium repens L.). The study aimed to test the conflicting theories on enzyme inheritance patterns in this species. A number of controlled sellings and reciprocal crosses were performed as well as a study of distribution of alleles in a natural Danish population of white clover. The result of the selfmg experiment was that the chosen material is strongly self-incompatible. The offspring from the crosses showed that two isoloci were present and that the alleles in these segregate in a Mendelian fashion. Five different IDH-phenotypes, composed of two alleles, where found in the natural population. This contrasts with previous findings, for this and other allotetraploid species, of one variant and one invariant isolocus. Maximum likelihood analysis of the distribution of these phenotypes showed that the two alleles were equally common on an overall population basis. Each of these alleles were, however, most frequent in one of the isoloci. The findings reported here strongly support the theory that white clover is an allotetraploid, showing disomic inheritance.