Classical and molecular approaches for managing nematodes affecting potato

Potato cyst (Globodera spp.), root-knot (Meloidogyne spp.), and root lesion (Pratylenchus spp.) nematodes are the most economically important nematode s of potatoes in temperate climates. Potato cyst nematodes occur worldwide and include two species, Globodera pallida (the white cyst nematode) and Gl obodera rostochiensis (the golden nematode), each composed of several patho types. The gene HI, which confers a high level of resistance to the golden nematode pathotype Ro1, has been bred into several potato cultivars that ar e grown worldwide. Mapping of the H-1 gene has led to the development of a molecular marker to screen segregating populations for resistance to the go lden nematode and to monitor the use of resistant cultivars in statutory co ntrol programs. Pathotype Ro2 of the golden nematode that overcomes H-1-med iated resistance was recently discovered in New York State in the United St ates, and a high level of resistance to this pathotype has been identified. Several sources of resistance to G. pallida are known and have been used i n traditional potato breeding programs to develop cultivars resistant to th is species. Molecular markers that are closely linked to genes for resistan ce to two G. pallida pathotypes have been identified in different regions o f the potato genome. Although resistance to root-knot and root lesion nemat odes has been identified, limited success has been realized in the use of t his resistance either through classical or molecular techniques to manage t hese nematodes on potatoes. Engineered resistance genes are currently being developed that may prove effective against both species of potato cyst nem atodes as well as other nematode parasites of potato.