Laminarin-triggered defence responses are geographically dependent in natural populations of Solanum chilense

Natural plant populations are polymorphic and show intraspecific variation in resistance properties against pathogens. The activation of the underlying defence responses can depend on variation in perception of pathogen-associated molecular patterns or elicitors. To dissect such variation, we evaluated the responses induced by laminarin (a glucan, representing an elicitor from oomycetes) in the wild tomato species Solanum chilense and correlated this to observed infection frequencies of Phytophthora infestans. We measured reactive oxygen species burst and levels of diverse phytohormones upon elicitation in 83 plants originating from nine populations. We found high diversity in basal and elicitor-induced levels of each component. Further we generated linear models to explain the observed infection frequency of P. infestans. The effect of individual components differed dependent on the geographical origin of the plants. We found that the resistance in the southern coastal region, but not in the other regions, was directly correlated to ethylene responses and confirmed this positive correlation using ethylene inhibition assays. Our findings reveal high diversity in the strength of defence responses within a species and the involvement of different components with a quantitatively different contribution of individual components to resistance in geographically separated populations of a wild plant species. Large-scale screenings reveal geographically distinct intraspecific differences in the dominant physiological pathogen defence responses upon glucan elicitor treatment in a wild tomato species.

Automated summary

Natural plant populations show polymorphism and intraspecific variation in resistance against pathogens. Perception of pathogen-associated molecular patterns or elicitors can activate defence responses, and this variation was evaluated in the wild tomato species Solanum chilense. The diversity in basal and elicitor-induced levels of reactive oxygen species and phytohormones was measured in 83 plants from nine populations. Geographical origin influenced the effect of individual components on infection frequency of Phytophthora infestans, with a direct correlation found between ethylene responses and resistance in the southern coastal region.