DIFFERENCES BETWEEN ITS REGIONS OF ISOLATES OF ROOT-KNOT NEMATODES MELIODOGYNE HAPLA AND M-CHITWOODI

Restriction enzyme analysis of ribosomal DNA (rDNA) sequences was used to distinguish species and isolates of root-knot nematodes. DNA fragm ents containing the internal transcribed spacer (ITS) rDNA were amplif ied from total DNA of 27 geographic isolates each of Meloidogyne hapla and M. chitwoodi and from one isolate each of M. incognito and M. jav anica by polymerase chain reaction (PCR). The amount of DNA present in a single juvenile was sufficient to amplify these PCR products. The a mplified ITS fragments were relatively short compared to those that ha ve been found for the genera Aphelenchoides, Caenorhabditis, Ditylench us, Heterodera, and Xiphinema. Digestion of the ITS regions with AluI, DraI, and HinfI distinguished M, hapla and M. chitwoodi from each oth er as well as from M. incognita and M. javanica. Results indicated tha t different ITS sequences are present within a single individual of M. hapla. Three isolates of M. chitwoodi that produce isozyme patterns d istinct from other M. chitwoodi isolates also could be distinguished b y ITS restriction fragment length polymorphisms. The possibility that they do not belong to M. chitwoodi proper is discussed.