Effector-mediated discovery of a novel resistance gene against Bremia Lactucae in a nonhost lettuce species

A.K.J. Giesbers, Alexandra Pelgrom, R.G.F. Visser, R.E. Niks, Guido Van Den Ackerveken, M.J.W. Jeuken*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

23 Citations (Scopus)


Candidate effectors from lettuce downy mildew (Bremia lactucae) enable high-throughput germplasm screening for the presence of resistance (R) genes. The nonhost species Lactuca saligna comprises a source of B. lactucae R genes that has hardly been exploited in lettuce breeding. Its cross-compatibility with the host species L. sativa enables the study of inheritance of nonhost resistance (NHR). We performed transient expression of candidate RXLR effector genes from B. lactucae in a diverse Lactuca germplasm set. Responses to two candidate effectors (BLR31 and BLN08) were genetically mapped and tested for co-segregation with disease resistance. BLN08 induced a hypersensitive response (HR) in 55% of the L. saligna accessions, but responsiveness did not co-segregate with resistance to Bl:24. BLR31 triggered an HR in 5% of the L. saligna accessions, and revealed a novel R gene providing complete B. lactucae race Bl:24 resistance. Resistant hybrid plants that were BLR31 nonresponsive indicated other unlinked R genes and/or nonhost QTLs. We have identified a candidate avirulence effector of B. lactucae (BLR31) and its cognate R gene in L. saligna. Concurrently, our results suggest that R genes are not required for NHR of L. saligna.
Original languageEnglish
Pages (from-to)915-926
JournalNew Phytologist
Issue number3
Publication statusPublished - Nov 2017


  • Lactuca saligna
  • avirulence
  • effector-triggered immunity (ETI)
  • lettuce downy mildew
  • nonhost resistance
  • oomycete
  • quantitative trait locus (QTL)
  • R gene


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