RIBOSOMAL DNA VARIATIONS IN ERIANTHUS, A WILD SUGARCANE RELATIVE (ANDROPOGONEAE-SACCHARINAE)

Variation at the 18S + 26S and 5S ribosomal DNA loci was assessed on 6 2 Erianthus Michx. clones, representing 11 species, and 15 clones from two Saccharum L. species used as a reference. Genus-specific markers for Erianthus Michx. sect. Ripidium Henrard (Old World species) were i dentified. Ribosomal DNA units in Erianthus sect. Ripidium exhibited a n additional BamHI site compared to Saccharum, and 5S units showed len gth and restriction-site differences between Erianthus and Saccharum. These markers will be useful to follow introgression in Saccharum x Er ianthus hybrids. Six ribosomal units (for 18 + 26S genes) were reveale d in Erianthus sect. Ripidium, differing by restriction-site positions and/or length. These results provided new information on species rela tionships and evolution within the genus Erianthus. The Indonesian and Indian forms of E. arundinaceus (Retz.) Jeswiet gave different restri ction patterns, which were similar to those of E. bengalense (Retz.) R . C. Bharadwaja and E. procerus (Roxb.) Raizade, respectively. The two 2n = 20 species, E. ele-phantinus Hook.f. and E. ravennae (L.) P. Bea uv., could also be differentiated at this locus. Two of the New World Erianthus species studied, E. rufipilus (Steud.) Griseb. and E. longis etosus Andersson, appeared more like Erianthus sect. Ripidium, whereas E. trinii Hack. and E. brevibardis Michx. showed patterns consistent with Miscanthus sinensis Andersson and S. spontaneum L., respectively. Finally, the comparison of rDNA restriction maps among Erianthus sect . Ripidium, Saccharum, sorghum and maize, led to unexpected conclusion s concerning the relationships between the different genera and the po sition of Erianthus in the ''Saccharum complex''.