Genetic diversity of North American and Old World Saccharum assessed by RAPD analysis

Saccharum (= Erianthus) native to North America is an untapped germplasm for genetic improvement of sugarcane (Saccharum spp. hybrids). There are five species and two varieties native to North America: S. alopecuroideum, S. baldwinii, S. brevibarbe vars. brevibarbe and contortum, S. coarctatum, and S. giganteum. There are three cytotypes of S. giganteum (2n = 30, 60, 90), and they overlap in gross morphology. Our objectives were to compare genetic diversity of North American and Old World members of Saccharum. Bulked DNA for five North American species, three Old World Erianthus spp. sect. Ripidium clones, and five sugarcane cultivars was tested by PCR with 13 RAPD primers. A total of 283 repeatable RAPD bands was scored for the nine taxa. Genetic distance coefficients ranged from 0.365 to 0.767 indicating substantial diversity among taxa. Taxa were assigned to one of three cluster groups: 1) S. baldwinii, S. brevibarbe var. contortum, S. coarctatum, and S. giganteum 2n = 90; 2) S. gig anteum 2n = 30 and 2n = 60, S. alopecuroideum, and sugarcane cultivars; and 3) Old World Erianthus spp. The RAPD analysis indicated that sugarcane was genetically more similar to North American Saccharum than it was to Old World Erianthus. This was unexpected given that North American Saccharum is geographically, cytologically, morphologically, and possibly reproductively isolated from Old World Erianthus and sugarcane. The data support the taxonomic separation of cytotypes of S. giganteum.