Comparative Transcriptome and Metabolome Analysis of Resistant and Susceptible Species Upon Infection by the Oomycete .

is a destructive oomycete pathogen that causes devastating disease in black pepper, resulting in a significant decline in yield and economic losses. (black pepper) is documented as susceptible to , whereas its close relative is known to be resistant. However, the molecular mechanism underlying the resistance of remains obscure. In this study, we conducted a comparative transcriptome and metabolome analysis between and upon infection and found substantial differences in their gene expression profiles, with altered genes being significantly enriched in terms relating to plant-pathogen interaction, phytohormone signal transduction, and secondary metabolic pathways, including phenylpropanoid biosynthesis. Further metabolome analysis revealed the resistant to have a high background endogenous ABA reservoir and time-course-dependent accumulation of ABA and SA upon inoculation, while the susceptible had a high background endogenous IAA reservoir and time-course-dependent accumulation of JA-Ile, the active form of JA. Investigation of the phenylpropanoid biosynthesis metabolome further indicated the resistant to have more accumulation of lignin precursors than the susceptible , resulting in a higher accumulation after inoculation. This study provides an overall characterization of biologically important pathways underlying the resistance of , which theoretically explains the advantage of using this species as rootstock for the management of oomycete pathogen in black pepper production.