Mechanisms of induced resistance in lettuce against Bremia lactucae by DL-β-amino-butyric acid (BABA)

Yigal Cohen, Avia E. Rubin, Gilar Kilfin

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BABA induced local and systemic resistance in lettuce (Lactuca sativa) against the Oomycete Bremia lactucae. Structure-activity analysis showed no induced resistance by related amino-butanoic acids or β-alanine. The R-enantiomer of BABA induced resistance whereas the S-enantiomer did not, suggesting binding to a specific receptor. Other compounds known to be involved in SAR signaling, including abscisic acid, methyl-jasmonate, ethylene, sodium-salicylate and Bion® (BTH) did not induce resistance. Systemic translocation of 14C-BABA and systemic protection against downy mildew were tightly correlated. BABA did not affect spore germination, appressorium formation, or penetration of B. lactucae into the host. Epifluorescence and confocal microscopy revealed that BABA induced rapid encasement with callose of the primary infection structures of the pathogen, thus preventing it from further developing intercellular hyphae and haustoria. Invaded host cells treated with BABA did not accumulate phenolics, callose or lignin, or express HR. In contrast, cells of genetically-resistant cultivars accumulated phenolics, callose and lignin and exhibited HR within one day after inoculation. The callose synthesis inhibitor DDG did not inhibit callose encasement nor compromised the resistance induced by BABA. PR-proteins accumulated too late to be responsible for the induced resistance. DAB staining indicated that BABA induced a rapid accumulation of H2O2 in the penetrated epidermal host cells. Whether H2O2 stops the pathogen directly or via another metabolic route is not known.

Original languageEnglish
Pages (from-to)553-573
Number of pages21
JournalEuropean Journal of Plant Pathology
Issue number4
StatePublished - Apr 2010

Bibliographical note

Funding Information:
Acknowledgement The guidance of Dr. A. Perelaman in processing the laser confocal micrographs is gratefully acknowledged. The authors gratefully acknowledge funding from the European Community under the Sixth Framework Program for Research, Technological Development and Demonstration Activities, for the Integrated Project QUALITYLOWINPUTFOOD, FP6-FOOD-CT-2003-506358.


  • Butanoic acids
  • Downy mildew
  • Induced resistance


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