Intraspecific variation in ribosomal DNA in populations of the potato cystnematode Globodera pallida

The relationships among a number of populations of Globodera pallida from B ritian, the Netherlands, Germany, Switzerland, and South America were exami ned using PCR amplification of the ribosomal cistron between the 18S and 28 S genes that include the two intergenic spacer regions (ITS1 and ITS2) and the 5.8S gene. Amplifications produced a similar-sized product of 1150 bp f rom all populations. Digestion of the amplified fragment with a number of r estriction enzymes showed differences among the populations. The restrictio n enzyme RsaI distinguished the most populations. The RFLP patterns reveale d by this enzyme were complex and could have arisen from heterogeneity betw een individuals within populations and from differences between the repents of an individual. Sequence analysis from six of the populations, together with RFLP analysis of PCR products, shows that there is intraspecific varia tion in the rDNA of G. pallida.