GENETIC DIVERSITY IN PERENNIAL RYEGRASS (LOLIUM-PERENNE) EVALUATED BYHYBRIDIZATION WITH RIBOSOMAL DNA - IMPLICATIONS FOR CULTIVAR IDENTIFICATION AND BREEDING

To date, little molecular genetic research has been conducted in Loliu m and the current study is the first investigation of diversity in rib osomal DNA (rDNA) among perennial ryegrass cultivars. Ribosomal DNA pr obes derived from the intergenic spacer (IGS-M) and transcribed (COD-M ) regions of mustard (Sinapis alba) were used to examine 35 perennial ryegrass (L. perenne L.) cultivars for genetic diversity using RFLP me thodology. Analysis of digested genomic DNA on Southern blots revealed only 10 cultivars with unique RFLP patterns. Genetic diversity was ex clusively associated with the IGS-M probe, as the cultivars were all i ndistinguishable when examined with the COD-M probe. This low incidenc e of distinctions was not expected, given that the 35 cultivars were k nown genetically distinct entities, representing the very wide range o f the major phenotypic and physiological characteristics present in co mmercial stocks. Furthermore, the forage cultivars were proportionatel y less polymorphic in comparison to the amenity cultivars. This was al so unexpected as amenity cultivars are recognized as a more closely cl ustered group than the forage cultivars, based on morphological charac teristics. The potential use of rDNA for assessing cultivar diversity and breeding histories in perennial ryegrass is considered.