The effects of founding events and agricultural practices on the genetic structure of three metapopulations of Globodera pallida

To assess the genetic constitution of the Globodera pallida populations in the Netherlands and the effects of agricultural practices, three geographic ally separated metapopulations, in total consisting of 226 local population s, were analyzed by two-dimensional gel electrophoresis (2-DGE) of total pr oteins. This technique allows the accurate assessment of allele frequencies in homogenates of mixtures of individuals. Based on the estimated average heterozygosity, the average proportion of polymorphic loci and the average number of alleles per locus, the genetic diversity among 226 local G. palli da populations was small. The small genetic basis of G. pallida in the Neth erlands will facilitate the identification of Solanum genotypes with a broa d and durable resistance to G. pallida. Instead of clusters of local popula tions with unique alleles, a continuous range of allele frequencies was obs erved. Analysis of the three metapopulations by the Shannon-Weaver index an d Nei's GST revealed that the metapopulation from a region with sandy-loam soils was clearly distinguishable from the remaining two; the local populat ions within this metapopulation were more similar and the genetic diversity within the individual local populations was significantly higher than the local populations from the two remaining regions. These regions are charact erized by wider crop rotation schemes and a very limited use of nematicides . The less intensive cultivation of potatoes in these regions with sandy-cl ay soils resulted in relatively little variation within and more variation between local nematode populations. To our knowledge, the effects of agricu ltural practices on the genetic constitution of potato cyst nematode popula tions have not been pinpointed before.