PLOIDY LEVEL DETERMINATIONS IN BUFFALOGRASS CLONES AND POPULATIONS

Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] is the subject of b reeding programs for turfgrass use because of its drought and heat tol erance, low growing habit, and low management input. Three ploidy leve ls are known to exist (x = n = 10), but plants at each level are nearl y morphologically indistinguishable. In this paper, now cytometry was evaluated as a means of determining ploidy levels of 31 buffalograss c lones and 34 seeded populations. Six clones were analyzed for nuclear DNA base-pair composition by now cytometry. Based on DNA contents, buf falograss clones can be grouped into four sets corresponding to chromo some 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 hexap loids, respectively. Chromosome numbers explained most of the DNA cont ent variation as shown by the strong linear relationship between DNA c ontent and chromosome number. Cultivar 315 is a pentaploid and is the first report of a pentaploid among buffalograss. Seeded populations an alyzed include those exclusively tetraploid, mixture of tetraploid thr ough hexaploid, and those exclusively hexaploid. Aneuploids between pe ntaploid and hexaploid levels were noted. No differences were observed between ploidy levels or genders with regard to base-pair composition .