A complex Solanum americanum resistance gene locus confers resistance to multiple Phytophthora species 

The genus Phytophthora contains many economically important plant pathogens. The most well- known is Phytophthora infestans, the causative agent of potato late blight and the pathogen responsible for the Irish potato famine in the 1840s. Field infection results in substantial annual crop losses and multiple fungicide sprays are required for blight control. The non-tuber bearing potato relative Solanum americanum (S.am) exhibits strong "non-host" resistance (NHR) to P. infestans. S.am is the source of two late blight resistance genes, Rpi-amr1 and Rpi-amr3, that confer strong resistance against multiple P. infestans isolates. To understand NHR and facilitate its transfer into cultivated potato varieties we aim to clone additional Rpi genes from S.am. We have identified several "non-amr1,3" resistance genes including Rpi-amr5, which maps to a cluster of 16 NLRs. We used virus-induced gene silencing, CRISPR and stable transformation of S. americanum to confirm the identity of Rpi-amr5. Interestingly, from another accession, we identified an Rpi-amr5 allele (named Rpc2) which also confers strong resistance to Phytophthora capsici, a pathogen of tomato and pepper. I will report on the characterisation of these genes, their potential for elevating resistance in crop species, and the identification of recognised effectors from P. infestans and P. capsici.