The wild tomato species Solanum chilense is divided in geographically
and genetically distinct populations that show signs of defense gene
selection and differential phenotypes when challenged with several
phytopathogens, including the oomycete causal agent of late blight
Phytophthora infestans. To better understand the phenotypic diversity of
this disease resistance in S. chilense and to assess the effect of plant
genotype vs. pathogen isolate, respectively, we evaluated infection
frequency in a systematic approach and with large sample sizes. We
studied 85 genetically distinct individuals representing nine
geographically separated populations of S. chilense. This showed that
differences in quantitative resistance properties can be observed
between but also within populations at the level of individual plants.
Data also did not reveal clear indications for complete immunity in any
of the genotypes. We further evaluated the resistance of a subset of the
plants against P. infestans isolates with diverse virulence properties.
This confirmed that the relative differences in resistance phenotypes
between individuals were mainly determined by the plant genotype under
consideration with modest effects of pathogen isolate used in the study.
Thus, our report suggest that quantitative resistance against P.
infestans in natural populations of a wild tomato species S. chilense is
likely not the result of specific adaptations of hosts to the pathogen
but of basal defence responses that depend on the host genotype and are
pathogen isolate-unspecific.