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 imp ortant group of plant parasitic nematodes that show high similarity among s ibling 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 Ra dopholus similis from broad host and geographic origins was examined to com pare isozyme patterns of esterase (EST), hexoquinase (HK), isocitrate dehyd rogenase (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 population s. The greatest intraspecific diversity was found within P. coffeae based o n the isozyme patterns for MDH, PGI and PGM. Intraspecific variability was also detected among R. similis populations, which showed two isozyme patter ns in EST and PGI systems. Less intraspecific variation was found within th e P. penetrans group. The P. goodeyi population from Cameroon differed from the other populations in this specific group in its MDH, PGI and PGM pheno types. Highly similar banding patterns of EST, MDH and PGI activity were fo und among the P. scribneri populations and the one population of P. agilis. A cluster analysis of the 40 populations, generated from the four enzyme b anding patterns, produced groupings that broadly matched the previous class ification into specific groups, reflecting intraspecific variability in som e cases. The results confirm the potential use of isozyme patterns as marke rs for these nematode species and their value for diagnostic application.