| Abstract | dc.description.abstract | Isoelectrofocusing of superoxide dismutase (SOD) isoforms was carried out on the extracts of 117 nematode populations
belonging to the so-called Xiphinema americanum-group. These populations came from the USA (77), Chile (5), Argentina (1),
Venezuela (5), Portugal (15), Italy (2), Crete (1), Montenegro (1), Slovakia (4), Hungary (3), Egypt (1) and India (2). A total of
17 bands of enzyme activity were observed in the screening, whilst single enzyme phenotypes showed from two to eight bands. The
high degree of SOD polymorphism of this nematode collection was grouped by cluster analysis into seven distinct homogeneous groups
characterised by specific combinations of SOD markers. Sub-groups could be discriminated for larger groups. The small Groups 3 and 5
were constituted mostly by populations from USA east coast states (i.e., NY and PA, respectively). The larger Group 1 resulted from the
association of populations coming from various and distant North American States. In other large groups, North American populations
were associated with South American and European populations. Overall, the data presented here suggest that geographic separation and
different hosts do not seem to be the source of genetic diversity for the X. americanum-group. When an adequate number of populations
were collected from the same country, the variability expressed by such a sub-sample was comparable to that of the whole nematode
collection. For the first time, homogeneous populations of a large collection of X. americanum-group populations were associated by
molecular means in order to explore further approaches that may help resolve the recalcitrant taxonomy and phylogeny of this much
debated group. | en |
