Abstract
Evaluating trade-offs in life-history traits of plant pathogens is essential to understand the evolution and epidemiology of diseases. In particular, virulence costs when the corresponding host resistance gene is lacking play a major role in the adaptive biology of pathogens and contribute to the maintenance of their genetic diversity. Here, we investigated whether life-history traits directly linked to the establishment of plant–nematode interactions, that is, ability to locate and move toward the roots of the host plant, and to invade roots and develop into mature females, are affected in Meloidogyne incognita lines virulent against the tomato Mi-1.2 resistance gene. Virulent and avirulent near-isogenic lines only differing in their capacity to reproduce or not on resistant tomatoes were compared in single inoculation or pairwise competition experiments. Data highlighted (1) a global lack of trade-off in traits associated with unnecessary virulence with respect to the nematode ability to successfully infest plant roots and (2) variability in these traits when the genetic background of the nematode is considered irrespective of its (a)virulence status. These data suggest that the variation detected here is independent from the adaptation of M. incognita to host resistance, but rather reflects some genetic polymorphism in this asexual organism.
Highlights
Trade-offs in life-history traits play a major role in the evolution of host–parasite interactions (Alizon et al 2009)
Ecology and Evolution published by John Wiley & Sons Ltd
We demonstrated that a measurable reproductive fitness cost is associated with unnecessary virulence to both resistance genes in M. incognita: when inoculated on susceptible hosts, the reproductive potential of virulent nematodes is significantly decreased compared to avirulent nematodes (Castagnone-Sereno et al 2007; Djian-Caporalino et al 2011)
Summary
Trade-offs in life-history traits play a major role in the evolution of host–parasite interactions (Alizon et al 2009). Host resistance to one parasite may confer a selective disadvantage when the resistant host is not challenged by such a parasite. These evolutionary constraints are considered key components of the maintenance of genetic diversity in both the parasites and their hosts (Laine and Tellier 2008). Evidence for costs of virulence resulting from trade-offs between life-history traits has been documented in many pathosystems involving bacteria (Leach et al 2001), fungi, and viruses (Laine and Barres 2013). In gene-for-gene interactions, a mutation from avirulence to virulence in the pathogen is associated with increased fitness on the resistant host, but may in turn becomes disadvantageous on a 2015 The Authors.
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