Rhizobium affinities and phenetic relationships within the genus Stylosanthes

Abstract

Twenty-one accessions of seven Stylosanthes species were subjected to infection with 25 Rhizobium strains. The introductions differed markedly in the number of Rhizobium strains with which they could fix atmospheric nitrogen. Recommendations for the best strains to use for each introduction are made. Rhizobium affinities, obtained by a numerical analysis of the nitrogen yield of plant tops, are compared with relationships between the hosts based on morphology, cytology, and flowering behaviour. Although the two measures of affinity did not yield identical results, this study indicates the usefulness of Rhizobium affinities in taxonomic studies in much the same way as cytological and chemical information is used. The morphological and other differences between introductions of S. guyanensis were further emphasized by their Rhizobium affinities and it is concluded that four different taxa may be involved.