Towards Sustainable Potato Late Blight Resistance by Cisgenic R Gene Pyramiding

This chapter provides an overview of the possibilities of genetic modification (GM) potato breeding in general and specifically to combat the most important disease, late blight. Potato plants are vulnerable to a number of pests and diseases. An enigmatic question concerns whether individual Rpi genes can confer sufficient broad-spectrum resistance to impart durability. The presence of Rpi genes or transcripts as determined using molecular markers does not warrant their functional expression. Late blight resistance resources from crossable species can be deployed for intragenic or cisgenic breeding strategies. The chapter presents and discusses a pipeline for cisgenic late blight resistance breeding that was developed at Wageningen UR Plant Breeding. If only two Rpi genes are present, often isolates can be identified that overcome recognition mediated by one Rpi gene but not by the other. The late blight-resistant GM potato which was probably closest to commercialization was “Fortuna”.