Potato Cyst Nematodes (PCN) are a major and growing problem for potato growers globally, they attack the roots of potatoes, destroying the crop and causing early senescence in plants, and worldwide, they are typically specified as a quarantine pest.  While chemical controls can mitigate the negative impact on yield to a limited extent, they cannot clear a field of nematodes.  Genetic resistance is therefore an effective and important part of PCN management.  This approach is particularly relevant to Scotland because PCN-infested fields cease to be usable to grow seed potatoes, production of which is particularly important to the Scottish industry.  There are two species of PCN, G. rostochiensis, for which there are well established and effective resistance genes in use, and G. pallida to which most commercial potato varieties remain susceptible.  There are potatoes with genes known to confer protection against G. pallida, but these genes are not present in commercial potato varieties.  The use of susceptible varieties in the ground is leading to a rapid spread of G. pallida, making potato production less viable and threatening UK seed potato production.  The identification of robust genetic defence against G. pallida to facilitate the breeding of potatoes with resistance to both species of PCN is therefore an important pillar in maintaining effective commercial potato production in the UK and globally.  The aim of this study was to examine the effectiveness of potato varieties containing differing combinations of these resistance genes in combatting attach by populations of G. pallida with differing virulence.

Scientists at the James Hutton Institute collected data over a number of years on the quantity of cysts infecting potatoes exposed to G. pallida populations of varying virulence together with the genetic data associated with each potato variety.  However, the design of the experiments and the potato varieties varied across years, so a generalised linear mixed model approach was used to combine and analyse data across multiple years and potato varieties, quantifying the extent to which the presence of known resistance genes were predictive of resistance to PCN attack.  The analysis found that the gene conferring protection against G. rostochiensis provided no protection against G. pallida, but that potato varieties with both the G. pallida resistance genes had protection against populations of G. pallida, although the presence of either of these resistance gene alone would have been insufficient to provide protection.  These results can now form the basis of a breeding programme for potato varieties with durable resistance to PCN attack.

This work was done in collaboration with James Price and Vivian Blok at the James Hutton Institute and was funded under the Scottish Government's Strategic Research Programme for environment, agriculture and food.