Co-application of Brassinolide and Pyraclostrobin Improved Disease Control Efficacy by Eliciting Plant Innate Defense Responses in Arabidopsis thaliana

Applying
brassinolide (BL, a phytohormone) in combination
with
pyraclostrobin (Pyr, a fungicide) has shown effective disease control
in field trials. However, the mechanism by which BL + Pyr control
disease remains uncertain. This work compared the disease control
and defense responses of three pretreatments (BL, Pyr, and BL + Pyr)
in Arabidopsis thaliana. We found that
BL + Pyr improved control against Pyr-sensitive Hyaloperonospora
arabidopsidis and Botrytis cinerea by 19 and 17% over Pyr, respectively, and achieved 29% control against
Pyr-resistant B. cinerea. Furthermore,
BL + Pyr outperformed BL or Pyr in boosting transient H2O2 accumulation, and the activities of POD, APX, GST,
and GPX. RNA-seq analysis revealed a more potent activation of defense
genes elicited by BL + Pyr than by BL or Pyr. Overall, BL + Pyr controlled
disease by integrating the elicitation of plant innate disease resistance
with the fungicidal activity of Pyr.