The quick and the deadly: growth vs virulence in a seed bank pathogen
Article first published online: 12 APR 2010
No claim to original US government works. Journal compilation © New Phytologist Trust (2010)
Volume 187, Issue 1, pages 209–216, July 2010
How to Cite
Meyer, S. E., Stewart, T. E. and Clement, S. (2010), The quick and the deadly: growth vs virulence in a seed bank pathogen. New Phytologist, 187: 209–216. doi: 10.1111/j.1469-8137.2010.03255.x
- Issue published online: 4 JUN 2010
- Article first published online: 12 APR 2010
- Received: 13 January 2010, Accepted: 23 February 2010
- Bromus tectorum (cheatgrass);
- Drechslera campanulata;
- necrotrophic pathogenesis;
- Pyrenophora semeniperda (black fingers of death);
- seed bank pathogen;
- virulence evolution
- •We studied the relationship between virulence (ability to kill nondormant Bromus tectorum seeds) and mycelial growth index in the necrotrophic seed pathogen Pyrenophora semeniperda. Seed pathosystems involving necrotrophs differ from those commonly treated in traditional evolution-of-virulence models in that host death increases pathogen fitness by preventing germination, thereby increasing available resources. Because fast-germinating, nondormant B. tectorum seeds commonly escape mortality, we expected virulence to be positively correlated with mycelial growth index.
- •We performed seed inoculations using conidia from 78 pathogen isolates and scored subsequent mortality. For a subset of 40 of these isolates, representing a range of virulence phenotypes, we measured mycelial growth index.
- •Virulence varied over a wide range (3–43% seed mortality) and was significantly negatively correlated with mycelial growth index (R2 = 0.632). More virulent isolates grew more slowly than less virulent isolates.
- •We concluded that there is an apparent tradeoff between virulence and growth in this pathogen, probably because the production of toxins necessary for necrotrophic pathogenesis competes with metabolic processes associated with growth. Variation in both virulence and growth rate in this pathosystem may be maintained in part by seasonal variation in the relative abundance of rapidly germinating vs dormant host seeds available to the pathogen.