Quantitative resistance increases the durability of qualitative resistance to Leptosphaeria maculans in Brassica napus

Hortense Brun, Anne-Marie Chevre, Bruce D.L. Fitt, Stephen Powers, Anne-Laure Besnard, Magali Ermel, Virginie Huteau, Bruno Marquer, Frederique Eber, Michel Renard, Didier Andrivon

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191 Citations (Scopus)


It has frequently been hypothesized that quantitative resistance increases the durability of qualitative (R-gene mediated) resistance but supporting experimental evidence is rare. To test this hypothesis, near-isogenic lines with/without the R-gene Rlm6 introduced into two Brassica napus cultivars differing in quantitative resistance to Leptosphaeria maculans were used in a 5-yr field experiment.
Recurrent selection of natural fungal populations was done annually on each of the four plant genotypes, using crop residues from each genotype to inoculate separately the four series of field trials for five consecutive cropping seasons. Severity of phoma stem canker was measured on each genotype and frequencies of avirulence alleles in L. maculans populations were estimated.
Recurrent selection of virulent isolates by Rlm6 in a susceptible background rendered the resistance ineffective by the third cropping season. By contrast, the resistance was still effective after 5 yr of selection by the genotype combining this gene with quantitative resistance. No significant variation in the performance of quantitative resistance alone was noted over the course of the experiment.
We conclude that quantitative resistance can increase the durability of Rlm6. We recommend combining quantitative resistance with R-gene mediated resistance to enhance disease control and crop production.

Original languageEnglish
Pages (from-to)285-299
Number of pages15
JournalNew Phytologist
Issue number1
Publication statusPublished - 2010


  • Brassica napus (oilseed rape)
  • durable disease resistance
  • Leptosphaeria maculans (blackleg or phoma stem canker)
  • plant-pathogen coevolution
  • R-gene mediated resistance
  • sustainable disease control


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