Genetic relationships among Stylosanthes species revealed by RFLP and STS analyses

Abstract 

Genetic relationships between 6 unclassified taxa and 24 known species of the genus Stylosanthes were investigated by RFLP and STS analyses. This allowed the diploid taxa used in this study to be classified into nine basal (genome) groups. Representative species in these groups included ’S. seabrana’/S. hamata (Group A), S. viscosa (Group B), S. humilis (Group C), S. macrocephala/S. bracteata (Group D), S. pilosa (Group E), S. leiocarpa (Group F), S. guianensis (Group G), S. tomentosa (Group H) and S. calcicola (Group I). Polyploid taxa used were grouped into five classes based on their putative genomic structures. These are AABB for S. scabra, S. aff. scabra, S. sericeiceps, S. aff. hamata and S. tuberculata; AACC for S. mexicana, S. subsericea, S. sundaica and S. sp.A; DDEE for S. capitata; AAFF for S. sympodialis; and AABBXX for S. erecta, with XX representing an unknown genome. Of the 6 unclassified taxa, three were diploids and 3 tetraploids. Of the 3 diploids, the genome of S. sp. was markedly distinct from those of all other diploids analysed in this study, with that of S. leiocarpa being the closest. The genome of S. sp.B was similar to that of S. humilis, with an average dissimilarity value of 15% between them. The genome of S. aff. viscosa was very similar to that of S. viscosa. Genetic variation between these 2 taxa was not larger than that within each of the 2 taxa. Of the 3 tetraploids, the genomic structure of S. sp.A was similar to those of S. mexicana, S. sundaica and S. subsericea, and the genomic structures of S. aff. scabra and S. aff. hamata were similar to those of S. scabra and S. sericeiceps.