Fig. 4

TcCSE is involved in resistance of T. cacao to P. palmivora. A Expression of TcCSE (SCA6_Chr6v1_17513) across each population for control (blue) and treatment (yellow). In each population, expression is consistently higher after treatment. However, the difference in gene expression between control samples and treatment samples was only significant in the Nanay population (FDR-adjusted p-value < 0.05). Open diamonds indicate mean expression for susceptible genotypes and open circles indicate mean expression for resistant genotypes. The top and bottom of the box and whisker plots represent the 75th and 25th percentiles, respectively. Whiskers represent 1.5 times the interquartile range. B Relative abundance (intensity) of caffeic acid in N. benthamiana plants transformed with p35s:TcCSE or a control backbone (“empty”) vector control, at both 48 and 96 h post transformation. Means are shown as open triangles. Over-expression of TcCSE results in significantly higher caffeic acid accumulation relative to controls (t-test 48 hpi: p-value = 0.0164; t-test 96 hpi: p-value = 0.0174). C Mycelial area of P. palmivora cultures grown on plates of V8 media versus plates of V8 media amended with 2 mM caffeic acid. Means are shown as open triangles. Plates amended with 2 mM caffeic acid significantly inhibited mycelial growth (t-test: p-value < 0.001). D Relative abundance of theobromine from water (“mock”) or P. palmivora zoospore droplets placed on cacao leaves, or zoospores only (not in contact with leaf). Means are shown as open diamonds. Cacao leaves challenged with zoospores accumulated significantly more theobromine than either mock inoculated or zoospore-only controls (t-tests: p < 0.001). Mock inoculated leaves had significantly more theobromine than zoospore-only controls (t-test: p-value = 0.022). E Relative abundance of caffeic acid in samples challenged with plugs of V8 media (blue) versus plugs of P. palmivora mycelia (yellow). There were no significant differences between treatment, phenotype, or the treatment:phenotype interaction (one-way ANOVA, Intensity ~ Treatment + Phenotype + Treatment:Phenotype: p > 0.05)