These authors contributed equally to this paper.
Effect of rotation of canola (Brassica napus) cultivars with different complements of blackleg resistance genes on disease severity
Article first published online: 9 JAN 2012
© 2012 The Authors. Plant Pathology © 2012 BSPP
Volume 61, Issue 5, pages 934–944, October 2012
How to Cite
Marcroft, S. J., Van de Wouw, A. P., Salisbury, P. A., Potter, T. D. and Howlett, B. J. (2012), Effect of rotation of canola (Brassica napus) cultivars with different complements of blackleg resistance genes on disease severity. Plant Pathology, 61: 934–944. doi: 10.1111/j.1365-3059.2011.02580.x
- Issue published online: 4 SEP 2012
- Article first published online: 9 JAN 2012
- Published online 9 January 2012
- avirulence effector genes;
- durable disease resistance;
- Leptosphaeria maculans;
- resistance genes
Blackleg disease (phoma stem canker) caused by the fungus Leptosphaeria maculans is a major disease of canola (oilseed rape, Brassica napus) worldwide. Canola plants in pots were exposed to blackleg-infested stubble of canola with different complements of resistance genes and then assessed for disease. Plant mortality was reduced when plants were exposed to stubble from a cultivar with a different complement of resistance genes compared to stubble of a cultivar with the same resistance gene. These findings were consistent with 7 years of field surveys, which showed that changes in selection pressure as a result of extensive sowing of cultivars with major-gene resistance, termed ‘sylvestris resistance’, dramatically influenced the frequency of virulent isolates in the population towards particular resistance genes, and therefore disease severity. All these data were supported by PCR-genotyping surveys of fungal populations whereby the frequency of virulence alleles of avirulence genes AvrLm1 and AvrLm4 changed significantly depending on the resistance gene present in the cultivar from which the isolates were cultured. This is the first example of a study showing that sowing of canola cultivars with different complements of resistance genes in subsequent years, i.e. rotation of resistance genes, minimizes disease pressure by manipulating fungal populations. This approach provides a valuable disease management strategy for canola growers and is likely to be applicable to other plant diseases.