Breeding tools to prevent production losses caused by Erwinia: Reduced susceptibility/enhanced resistance to soft rot

Soft rot diseases are caused by a range of Pectobacteriaceae, mutually referred to as soft rot Pectobacteriaceae (SRP). Also in potato cultivation these bacteria cause serious problems. Currently, cultivation and hygiene measures are the only means to deal with SRPs in potato. Still, in seed potato cultivation in the Netherlands SRP induced losses account for 22 M annually.

Losses are due to downgrading and rejection of seed lots, soft rot during storage and costs to prevent SRP spread during harvest, storage and seed multiplication. The complexity of the SRP problem is due to different Dickeya and Pectobacterium species and subspecies that can cause both latent and symptomatic infections. In addition, the SRP epidemiology is complex as the inoculum sources are diverse (seed tubers, flooding, aerosols, rain and insects) and the different plant organs show different susceptibility levels and symptoms (tuber soft rot, blackleg, slow wilt). Breeding for resistance against SRPs has not yet been successful. For a successful breeding approach, all infection routes and stages should be taken into account.

In this project we will pursue a combined approach to reduce susceptibility and enhance resistance to SRP in potato. To reduce susceptibility we will genetically determine why some varieties in the current germplasm are more susceptible than others and develop tools to select against super-susceptibility. Secondly, we will target susceptibility (S) genes to enhance resistance and deploy them in non-GM way. Thirdly, we will deploy recently discovered SRP resistances from a wild potato plant. The genes underlying the reduced susceptibility and enhanced resistance will be introgressed and combined in cultivated potatoes. To accomplish these three goals, dedicated high throughput bioassay for the different infection routes and stages will be deployed and further developed.

This combined approach will generate plant material and unique insights in SRP pathogenicity that can be applied directly in potato and provides a model for SRP diseases in other crops. The total package of genetic improvement will provide an outlook to potato varieties with SRP resistance. These varieties will be resilient to SRP infection and climate induced changes in pathogen population and will strongly contribute to robust novel agricultural systems like mixed and stripped cropping.