A beneficial root endophyte buffers natural variation in pathogen susceptibility across Arabidopsis accessions
Natalie Peltz, Laura Armbruster, Christopher Stephens, Vivien Joisten‐Rosenthal, Tim Thomsen, Alex W. Yan, Nick Dunken, Renan Granado, Stanislav Kopriva, Juliette de Meaux, Gregor Langen, Anna Koprivova, Björn Usadel, Alga ZuccaroSummary
Host genetic diversity shapes pathogen susceptibility within plant populations, raising the question of whether beneficial root microbes can buffer these differences. The fungal root endophyte
Serendipita indica
(
Si
) promotes plant growth and can mitigate disease caused by the pathogen
Bipolaris sorokiniana
(
Bs
). Here, we assessed how natural host genetic variation influences
Si
‐mediated protection against
Bs
in
Arabidopsis thaliana
.
We screened 47
A. thaliana
accessions for susceptibility to
Bs
with and without
Si
colonization and performed phenotypic, transcriptomic, and comparative genomic analyses of two genetically and geographically proximate Swedish accessions, T510 and T530, that differed strongly in
Bs
colonization.
Si
conferred consistent protection against
Bs
across all accessions, despite variation in baseline susceptibility and immune‐gene content. T510 and T530 differed in
Bs
colonization, disease symptoms, transcriptional responses, and immune‐gene repertoires, including presence–absence variation of the TIR‐NLR gene
ISI
. T530 lacks
ISI
, and mutation of
ISI
in Col‐0 increased
Bs
susceptibility, demonstrating that
ISI
contributes to root immunity. However,
Si
‐mediated protection was retained in the absence of
ISI
, demonstrating that
ISI
is not required for this protective effect.
Beneficial fungal endophytes can thus buffer phenotypic consequences of natural variation in pathogen susceptibility, stabilizing disease outcomes across genetically diverse plant populations.