FITNESS COSTS OF CHEMICALLY-INDUCED RESISTANCE: DOUBLE EDGED SWORD OR (UN)STABLE EQUILIBRIUM?

M. Iriti, F. Faoro

Abstract


Plant fitness costs are referred to as the trade off between resources allocated for growth and reproduction and disease resistance. Nevertheless, plants have coevolved with their enemies, thus relying on the sustainability of costs involved in defence response under natural conditions. At the cultivar level, the gap left by insufficient pre-infectional barriers is filled by a set of reactions that follow pathogen recognition and lead to systemic acquired resistance (SAR). In this view, inducible defence mechanisms may have been favoured by natural selection whenever their efficacy could be coupled with minimized costs. By adopting induced resistance as a facultative trait, plants have acquired some benefits over a constitutive defence strategy. They avoided the diversion of essential available resources from growth and breeding and the accumulation of auto-toxic secondary metabolites, when not under pathogen pressure (Heil, 2002). The emergence of agriculture, around 10,000 years ago, inevitably altered this scenario, unbalancing the equilibrium between constitutive and inducible defence systems. Crops selection, mainly addressed to quality and yield traits, has inadvertently led to the loss of defence alleles.

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DOI: http://dx.doi.org/10.4454/jpp.v88i1.827

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