Ploidy level determinations in buffalograss clones and populations

Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] is the subject of breeding programs for turfgrass use because of its drought and heat tolerance, low growing habit, and low management input. Three ploidy levels are known to exist (x = n = 10), but plants at each level are nearly morphologically indistinguishable. In this paper, flow cytometry was evaluated as a means of determining ploidy levels of 31 buffalograss clones and 34 seeded populations. Six clones were analyzed for nuclear DNA base-pair composition by flow cytometry. Based on DNA contents, buffalograss clones can be grouped into four sets corresponding to chromosome number or ploidy level. Mean DNA contents were 0.93, 1.80, 2.15, and 2.63 pg DNA/nucleus for diploid, tetraploid, pentaploid, and hexaploids, respectively. Chromosome numbers explained most of the DNA content variation as shown by the strong linear relationship between DNA content and chromosome number. Cultivar 315 is a pentaploid and is the first report of a pentaploid among buffalograss. Seeded populations analyzed include those exclusively tetraploid, mixture of tetraploid through hexaploid, and those exclusively hexaploid. Aneuploids between pentaploid and hexaploid levels were noted. No differences were observed between ploidy levels or genders with regard to base-pair composition