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Poster

Session: Session 1 Presenting Authors at Posters (Evens)

P-022 - Deciphering cacao pod defense responses to Phytophthora palmivora and P. megakarya using comparative RNA-seq analyses

Tuesday, July 15, 2025
09:55 - 11:30  
Location: Confex Hall 3
Extracellular & Intracellular non-self recognition & signaling

Black pod rot, caused by Phytophthora palmivora and P. megakarya, significantly impacts cacao production worldwide, posing a major threat to this economically important crop. Given the limitations of current agronomic control methods, breeding resistant clones is critical for managing this disease. While black pod rot resistance is mainly described as a quantitative trait, bioassays using zoospores on unwounded pods suggested qualitative resistance in some clones. Our study aims to elucidate the molecular basis underlying resistance or susceptibility of cacao clones by characterizing their transcriptional responses to each Phytophthora spp. We selected ten cacao clones with varying degrees of resistance to each pathogen and used RNA-seq to profile gene expression on pods at 12h and 48h post-inoculation. Differential gene expression was similarly high across genotypes at 12 hpi regardless of the Phytophthora spp., but increased at 48 hpi, reflecting the genotype-specific susceptibility to the pathogens. Consistent with the absence of complete resistance to P. megakarya in all genotypes, a common set of 417 genes were upregulated at 48 hpi in response to P. megakarya, including genes involved in defense response and abscisic acid signaling. These and further findings will advance our understanding of host-pathogen interactions in cacao and may identify critical candidate genes for breeding resistant cultivars, ultimately contributing to improved crop protection strategies.