Genetic Diversity among Pentaploid Buffelgrass Accessions
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Crop Science Society of America. Buffelgrass [Pennisetum ciliare (L.) Link (syn. Cenchrus ciliaris L.)], an important pasture and range grass in the arid semi-tropics and tropics, has excellent drought-tolerance but lacks winter hardiness. It is a polymorphic, apomictic species and its most common chromosome number is 2n = 4x = 36. Eighty-six pentaploid (2n = 5x = 45) accessions from South Africa were deposited into the USDA National Germplasm System (NPGS) in 1976 and these were more winter-hardy than all tetraploid accessions. Prior to 1976, only 31 pentaploids were in the NPGS but they lacked cold tolerance. Since 1976, ten pentaploid accessions with unknown cold tolerance have been added to the NPGS and they were included. The genetic diversity among all these pentaploid accessions was investigated to determine if the winter-hardy and non-winter-hardy genotypes were distinct. Amplified fragment length polymorphisms were used to determine the genetic diversity and phylogenetic relationships among the accessions. Ten primer combinations generated 862 polymorphic bands; the number of bands identified by each primer ranged from 74 to 117 (mean 93.4). Unweighted pair group method with arithmetic mean (UPGMA) cluster analysis and principal coordinate analysis revealed two groups with one separating into two sub-groups and one sub-group separating into two subdivisions. Genetic similarity coefficients ranged from 0.39 to 0.98 (mean 0.74). These findings show considerable genetic diversity among the pentaploid accessions. Most cold-tolerant and non-cold-tolerant genotypes separated by subgroups but not by group. Nine tetraploid accessions, included for reference, clustered into several subgroups. The pentaploid genotypes appear to have polyphyletic origins.
