Comparative DNA Profiling of U‐3 Turf Bermudagrass Strains

Long‐term maintenance of genetic fidelity of clonally propagated bermudagrass (Cynodon spp.) cultivars is difficult. Contamination may arise through mechanical mixtures, the presence of viable seed, and somatic mutations. DNA amplification fingerprinting (DAF) was used to compare genetically putative ‘U‐3’ bermudagrass [Cynodon dactylon (L). Pers.] selected in the early 1930s with bermudagrass currently produced in Oklahoma and sold as U‐3. Four samples of putative U‐3 and seven samples of Oklahoma U‐3 were tested. Foundation class ‘Tifway’ (C. dactylon × C. transvaalensis Burtt‐Davy), along with two other commercially labeled Tifway strains, were included as reference standards to gauge genetic diversity. Six DAF primers were used to differentiate the 14 bermudagrass strains used in this study. The DAF analysis of all bermudagrass strains produced an average of 56.0 ± 5.9 SE polymorphic bands/primer. Comparisons among the putative and Oklahoma grown U‐3 strains resulted in 37.1 ± 5.1 SE polymorphic bands/primer. Phenetic analyses using both the UPGMA algorithm and principal coordinate analysis revealed a wide separation between the putative U‐3 and the Oklahoma strains identified as U‐3. Putative U‐3 samples collected from three mid‐Atlantic golf courses clustered tightly as did all U‐3 strains from Oklahoma. A putative U‐3 strain from Illinois clustered with putative U‐3 from the mid‐Atlantic golf courses, but was distinct. The Oklahoma U‐3 strains were equally distant from Foundation class Tifway as they were from putative U‐3. The Oklahoma U‐3 collections appear genetically identical and likely resulted from mechanical contamination of a true U‐3 nursery plot that served as a source of planting stock for sod growers.