Effect of Domestication on Plant Biomass and Induced Systemic Resistance in Tomato (Solanum lycopersicum L.).

Inoculating tomato plants with beneficial microorganisms such as Trichoderma harzianum has been shown to stimulate their immune system, reducing the severity of a range of pathogens. This phenomenon is known as induced systemic resistance (ISR). The exact mechanisms regulating ISR are unclear, though it has been theorized that the beneficial microorganisms produce elicitors that are recognized by host receptors, activating a chain of signals in several pathways that modify biochemistry and physiology and help plants withstand this biotic stress. For example, changes in biomass, nutrient absorption, internal hormone balance, photosynthesis and carbohydrate metabolism have been observed in response to inoculation. However, not all tomato genotypes respond positively to ISR, making this phenomenon unreliable as an effective disease control strategy. It is possible that during domestication, selection for features that enhanced yield could have come at the expense of those that contribute to ISR, because this phenomenon may require resources that would otherwise be allocated to reproduction. If this did occur, it may be possible to identify those features and reintroduce them into modern varieties. To test this hypothesis, we quantified effects of T. harzianum inoculation on plant biomass and spread of two pathogens with different modes of action (Botrytis cinerea and Phytophthora infestans) in tomato genotypes representing a range of domestication. This included a tomato wild ancestor (L. pimpinellifolium), a landrace (designated ‘Colombia’), an heirloom (Corbarino) and a modern hybrid variety (Iron Lady). Increased plant biomass and resistance to both pathogens occurred in a genotype specific manner, with the landrace exhibiting the greatest stimulation of plant biomass and only genotype with reduced severity of both pathogens. Results of this study indicate that landraces may hold valuable genetic resources that could be introduced into modern tomato varieties, making ISR a more consistent and reliable method of broad-spectrum disease control.