The B rassica napus blackleg resistance gene LepR3 encodes a receptor‐like protein triggered by the L eptosphaeria maculans effector AVRLM 1

SummaryLepR3 , found in the B rassica napus cv ‘ S urpass 400’, provides race‐specific resistance to the fungal pathogen L eptosphaeria maculans , which was overcome after great devastation in A ustralia in 2004. We investigated the LepR3 locus to identify the genetic basis of this resistance interaction. We employed a map‐based cloning strategy, exploiting collinearity with the A rabidopsis thaliana and B rassica rapa genomes to enrich the map and locate a candidate gene. We also investigated the interaction of LepR3 with the L . maculans avirulence gene AvrLm1 using transgenics. LepR3 was found to encode a receptor‐like protein ( RLP ). We also demonstrated that avirulence towards LepR3 is conferred by AvrLm1 , which is responsible for both the Rlm1 and LepR3 ‐dependent resistance responses in B . napus . LepR3 is the first functional B . napus disease resistance gene to be cloned. AvrLm1 's interaction with two independent resistance loci, Rlm1 and LepR3 , highlights the need to consider redundant phenotypes in ‘gene‐for‐gene’ interactions and offers an explanation as to why LepR3 was overcome so rapidly in parts of A ustralia.