IDENTIFICATION OF CYST NEMATODES OF AGRONOMIC AND REGULATORY CONCERN WITH PCR-RFLP OF ITS1

The first internally transcribed spacer region (ITS1) from cyst nemato de species (Heteroderidae) was compared by nucleotide sequencing and P CR-RFLP. European, Asian, and North American isolates of five heterode rid species were examined to assess intraspecific variation. PCR-RFLP patterns of amplified ITS1 DNA from pea cyst nematode, Heterodera goet tingiana, from Northern Ireland were identical with patterns from Wash ington State. Sequencing demonstrated that ITS1 heterogeneity existed within individuals and between isolates, but did not result in differe nt restriction patterns. Three Indian and two U.S. isolates of the cor n cyst nematode, Heterodera zeae, were compared. Sequencing detected v ariation among ITS1 clones from the same individual, between individua ls, and between isolates. PCR-RFLP detected several restriction site d ifferences between Indian and U.S. isolates. The basis for the restric tion site differences between isolates from India and the U.S. appeare d to be the result of additional? variant ITS1 regions amplified from the U.S. isolates, which were not found in the three India isolates. P CR-RFLP from individuals of the U.S. isolates created a composite patt ern derived from several ITS1 types. A second primer set was specifica lly designed to permit discrimination between soybean (H. glycines) an d sugar beet (H. schachtii) cyst nematodes. Fok I digestion of amplifi ed product from soybean cyst nematode isolates displayed a uniform pat tern, readily discernible from the pattern of sugar beet and clover cy st nematode (H. trifolii).