Isozyme variation in wild and cultivated species of the genus Trifolium L.(Leguminosae)

Isozyme patterns for PGI (phosphoglucoisomerase), MDH (malate dehydrogenase ), EST (esterase) and SOD (superoxide dismutase) were evaluated in 36 acces sions of eight Trifolium species, namely T. incarnatum, T. polymorphum, T. pratense, T. repens, T. resupinatum, T. riograndense, T. subterraneum and T . vesiculosum. Similarity between species and accessions was estimated by J accard's similarity index based on presence or absence of bands. The UPGMA method was utilized for the groupings and dendrogram construction with the aid of the NTSYS-PC program. Interspecific similarity was low (J less than or equal to 0.351). The dendrogram presented eight groups, each one corresp onding to a taxonomic species. Most of the accessions of the same species g rouped together at J > 0.50, except T, riograndense, T. repens and T. prate nse. These three species showed the lowest similarity between their accessi ons, reflecting higher intraspecific variation. Some accession-specific ban ds were identified. The species groupings are consistent with traditional t axonomic species delimitation. Therefore isozyme patterns, especially when several systems are employed, are useful and reliable biochemical markers f or the taxonomic delimitation and characterization of Trifolium germplasm. (C) 2000 Annals of Botany Company.