Detection and analysis of inter- and intraspecific diversity of Pratylenchus spp. using isozyme markers

The root-lesion nematodes of the genus Pratylenchus are an economically important group of plant parasitic nematodes that show high similarity among sibling species. Isozyme patterns obtained by isoelectrofocusing (IEF) were used to differentiate and establish genetic relatedness among Pratylenchus species. A total of 40 populations comprising 9 Pratylenchus species and Radopholus similis from broad host and geographic origins was examined to compare isozyme patterns of esterase (EST), hexoquinase (HK), isocitrate dehydrogenase (IDH), malate dehydrogenase (MDH), phosphoglucose isomerase (PGI), phosphoglucomutase (PGM) and superoxide dismutase (SOD). Of these systems, only EST, MDH, PGI and PGM were useful for differentiation of P. vulnus , P. goodeyi , P. penetrans , P. scribneri , P. thornei and R. similis populations. The greatest intraspecific diversity was found within P. coffeae based on the isozyme patterns for MDH, PGI and PGM. Intraspecific variability was also detected among R. similis populations, which showed two isozyme patterns in EST and PGI systems. Less intraspecific variation was found within the P. penetrans group. The P. goodeyi population from Cameroon differed from the other populations in this specific group in its MDH, PGI and PGM phenotypes. Highly similar banding patterns of EST, MDH and PGI activity were found among the P. scribneri populations and the one population of P. agilis . A cluster analysis of the 40 populations, generated from the four enzyme banding patterns, produced groupings that broadly matched the previous classification into specific groups, reflecting intraspecific variability in some cases. The results confirm the potential use of isozyme patterns as markers for these nematode species and their value for diagnostic application.