Multiplication of some South American and European Populations of Potato Cyst Nematodes on Potatoes Possessing the Resistance Genes H1, H2 and H3.

Ability to overcome the resistance of genes H1, H2 and H3 incorporated in potato cultivars was compared in 44 South American and nine European populations of potato cyst nematodes (Globodera spp.) by recording the development of females on rooted stem cuttings grown in pots in a glasshouse. Most of the South American populations were able to multiply on all the potato plants containing resistance genes, whereas the European populations were unable to overcome the resistance of at least one of the genes. Of particular note, however, was a population of Globodera rostochiensis from Italy which overcame resistance conferred by gene H1. Our results suggest that European populations of potato cyst nematodes contain only a fraction of the genetic variability found in South American populations. [ABSTRACT FROM AUTHOR]