Characterization of Stylosanthes introductions by using seed protein patterns

Abstract

Seed protein patterns of 182 Stylosanthes accessions, representing 16 species and two hybrids, were obtained by polyacrylamide gel electrophoresis of crude extracts. All species could be recognized by examination of photographs and densitometer traces of the gels. Within the species capitata, guyanensis, hamata and viscosa considerable variation occurred, whilst the variation in humilis, scabra and fruticosa was not as great. Data from the densitometer traces were analysed by various methods of pattern analysis and the resulting classifications compared. A variance-standardized Euclidean distance coefficient was found to be the similarity measure of choice, whilst selection of fusion strategy was not as critical.Species relationships obtained by using the chemical data were not in agreement with the accepted taxonomic division of the genus into the sections Styposanthes and Stylosanthes. A classification based on the complete data set was compared with a working classification based on morphological and agronomic data, which is used in the agronomic assessment of the genus. Only within S. scabra did the two classifications conform. Morphological–agronomic (M–A) types within the species hamata and subsericea could be distinguished by the examination of the fine structure of the densitometer traces, whilst groups based on protein data in the species ahumilis, guyanensis, fruticosa and viscosa did not correspond with M–A groups. The application of seed protein patterns as a rapid and inexpensive means of identifying introductions of the genus at the species level, as well as characterizing types within certain species, is proposed.