Identification of subterranean clover cultivars and their genetic relationships by isozyme analysis

Abstract

Isozyme patterns for the 22 registered cultivars of Trifolium subterraneurn L. are described for 15 enzymes. The patterns discriminated among all cultivars except that Uniwager was isozymically identical with Geraldton, from which it was derived by deliberate mutation. The 17 cultivars which originally came from naturally occurring isolates, as well as Uniwager, appeared to be isozymically homogeneous, whereas three of the five bred cultivars (Nungarin, Esperance and Howard) were polymorphic for at least one locus. The cultivars indicated that T. subterraneum is highly polymorphic at isozyme loci. Excluding the complex esterase patterns, the species was polymorphic at 21 of 26 putative loci, with an average of 2.3 alleles detected per locus. Estimates of genetic distance between the cultivars stemming from natural isolates strongly supported the classification into three subspecies. In addition, the cultivar Woogenellup (syn Marrar) was well separated from all other cultivars of the subspecies subterraneum. Isozyme surveys should therefore provide critical evidence on the role such factors as introduction, natural selection, mutation and outcrossing have had in the origin of variation within subterranean clover in Australia.