Effector-Mediated Suppression of Programmed Cell Death by <i>Phytophthora palmivora</i> in Oil Palm

<i>Phytophthora palmivora</i> is the pathogen causing bud rot in oil palm <i>(Elaeis guineensis</i>). This pathogen secretes effector proteins that manipulate host defenses, contributing to disease progression. In this study, we systematically investigated the role of specific effector proteins in suppressing programmed cell death (PCD) in oil palm leaflets. Our approach included using genomic and transcriptomic data from a Colombian <i>P. palmivora</i> isolate alongside the coexpression network of a substantial effector dataset. From this analysis, ten candidate effectors were selected, characterized, and evaluated for their ability to suppress PCD in oil palm leaflets through transient expression via biolistics. Several effectors exhibited significant anti-PCD activity in susceptible and less susceptible oil palm genotypes. Notably, the effectors Avr3F (689), RxLR (1540), and RxLR (1546) demonstrated suppression of PCD in both genotypes, while the other effectors played variable roles in PCD regulation. Phylogenetic analysis further identified distinct clades among the effectors, possibly associated with their functional activities. Additionally, specific motifs, such as RXLR-dEER, K, and Y, appeared to correlate with PCD suppression. This research enhances our understanding of the molecular mechanisms underlying the interaction between <i>P. palmivora</i> effectors and oil palm host responses, highlighting these proteins’ genotype-specific regulation of PCD. The findings contribute valuable insights into plant–pathogen interactions and offer potential avenues for targeted disease control strategies in the oil palm industry.