Abstract

CANCELLED due to illness - Different Approaches to Breed for Resistance to Late Blight in Potato

Richard Visser, Professor/Head, Wageningen University & Research Centre

Potato severely suffers from the devastating late blight disease, which is caused by Phytophthora infestans. This oomycete pathogen secretes host-translocated RXLR effectors that include avirulence (AVR) proteins, which are targeted by resistance (R) proteins from wild Solanum species. The availability of both the genome sequences from the pathogen and the host plant enables us to embark on different strategies to try and understand the interaction between the two but also to design methods for durable resistance against the pathogen. We are on the one hand able to localise and map Rpi- genes (resistance genes against P. infestans) on the genome and at the same time to clone homologous of the genes already isolated from wild species. We have generated a genome-wide infection-ready library of P. infestans RXLR effectors that we have been using to accelerate cloning and specificity profiling of R genes. This effectoromics strategy has proven effective and complementary to classical breeding approaches. We have identified and characterized ~a dozen R-AVR pairs that can be immediately exploited to accelerate and improve late blight resistance breeding. We performed a case-study to dissect the resistance of the potato cultivar Sarpo Mira, which has retained resistance in the field over several years. Using effectors, we distinguished activity of four pyramided qualitative R genes and a quantitative R gene that was only detected under field conditions in Sarpo Mira. Furthermore we generated cis-genic potatoes containing different R genes which were tested in the lab and the field for several years as a way to achieve durable resistance against the disease. The status of the R-AVR cloning, analysis and deployment will be discussed.