Potato-related plant species exhaust potato cyst nematode

Dutch plant ecologists have investigated how the potato cyst nematode can be controlled using Solanum sisymbriifolium, a member of the potato family. The plant produces a hatching agent which causes the nematode’’s eggs to hatch. However, the nematodes which eat the plant can no longer reproduce.

Potato cyst nematodes attack the roots of potato plants. After harvest the nematodes remain in the soil in the form of cysts. These are the dead bodies of female nematodes that are filled with eggs. The eggs remain dormant until they come into contact with a substance exuded from the roots of potato plants. Solanum sisymbrifolium, a member of the potato family, has been found to exude the same hatching agent as the potato. The substance elicits the development of the eggs into nematodes. Although the nematodes feed on Solanum sisymbriifolium, the plant does not provide the nematodes the opportunity of completing their life cycle and thus reproducing. The reason for this is not yet clear.

The researchers from Wageningen University have extensively investigated Solanum sisymbriifolium so as to optimise the effectiveness of its use. For example, they are determining the minimum size of plant needed to thoroughly clean the soil of cysts. The intention is to cultivate Solanum sisymbriifolium somewhere in the period between potato harvest and the planting of the next potato crop. If the crop is ploughed in it also acts as a green manure crop.

Various companies in the potato sector are involved in the research. One of these, a potato seed company from Groningen, has meanwhile acquired the breeding rights to a number of Solanum sisymbriifolium varieties. At present the plant is only being cultivated on a few hundred hectares on a trial basis. Potato growers will only be able to use the crop on a large scale once the growing conditions under which this Latin-American plant is most effective have been determined. Research must also demonstrate that the plant will not affect potato production.

Potato cyst nematode is difficult to control. Farmers are only allowed to use nematicides (pesticides against nematodes) if there are no other options for control. In the past good results were obtained using potato plants that were resistant to the nematodes. However, the nematode always managed to overcome each line of resistance.

The research is being carried out by plant ecologist Jan Vos and PhD student Bart Timmermans. The idea of using Solanum sisymbriifolium came from Klaas Scholte, a now pensioned former researcher at Wageningen University, who in the 1990s tested about one hundred species from the potato family in pots, in order to find a plant which produced the hatching agent but was also resistant to the nematodes.