GENETIC DIVERSITY AMONG A COMPLEX OF CEREAL CYST NEMATODES INFERRED FROM RFLP ANALYSIS OF THE RIBOSOMAL INTERNAL TRANSCRIBED SPACER REGION

This study examined the restriction polymorphism (RFLP) of the nuclear ribosomal DNA in Heterodera avenae, H. filipjevi, H. mani, H. latipon s, and the taxonomically unclear Gotland strain in order to establish a molecular characterization and phylogenetic relationships in the com plex of cereal cyst nematodes (CCN). The internal transcribed spacer ( ITS) and 5.8S rDNA were amplified by PCR from a single female or a cys t of 27 different geographic isolates of the CCN complex and one popul ation of H. schachtii, used as outgroup. The amplified product was 1.2 kb long and 14 of 15 enzymes produced restriction fragments for each isolate. Relationships between populations were determined from UPGMA analysis based on distance values calculated from RFLP data. Digestion s with TaqI clearly differentiated H. avenae, H. latipons, and a group composed of H.filipjevi and the Gotland strain. Six endonucleases (Ha eIII, HinfI, ItaI, PstI, TaqI, and Tru9I) produced the same restrictio n pattern with H. filipjevi and the Gotland strain, and both were clea rly separated from H. avenae with PstI. Restriction sites have reveale d a mixture of the species H. latipons and H. avenae, and possible inf raspecific variation in H. avenae. The inferred phylogenetic relations hips of species in the CCN complex are in agreement with their morphol ogical characterization.