Diversity among Cynodon accessions and taxa based on DNA amplification fingerprinting

The genus Cynodon (Gramineae), comprised of 9 species, is geographically wi dely distributed and genetically diverse. Information on the amounts of mol ecular genetic variation among and within Cynodon taxa is needed to enhance understanding of phylogenetic relations and facilitate germplasm managemen t and breeding improvement efforts. Genetic relatedness among 62 Cynodon ac cessions, representing eight species, was assessed using DNA amplification fingerprinting (DAF). Ten 8-mer oligonucleotides were used to amplify speci fic Cynodon genomic sequences. The DNA amplification products of individual accessions were scored for presence (1) or absence (0) of bands. Similarit y matrices were developed and the accessions were grouped by cluster (UPGMA ) and principal coordinate analysis. Analyses were conducted within ploidy level (2x = 18 and 4x = 36) and over ploidy levels. Each primer revealed po lymorphic loci among accessions within species. Of 539 loci (bands) scored, 496 (92%) were polymorphic. Cynodon arcuatus was clearly separated from ot her species by numerous monomorphic bands. The strongest species similariti es were between C. aethiopicus and C. arcuatus, C. transvaalensis and C. pl ectostachyus, and C. incompletus and C. nlemfuensis. Intraspecific variatio n was least for C. aethiopicus, C. arcuatus, and C. transvaalensis, and gre atest for C. dactylon. Accessions of like taxonomic classification were gen erally clustered, except the cosmopolitan C. dactylon var. dactylon and C. dactylon var. afganicus. Within taxa, accessions differing in chromosome nu mber clustered in all instances indicating the 2x and 4x forms to be closel y related. Little, if any, relationship was found between relatedness as in dicated by the DAF profiles and previous estimates of hybridization potenti al between the different taxa.