Potato genotypes differentially alter the expression of Phytophthora infestans effectors during PAMP-mediated resistance induction

Summary Pathogen recognition by plants via pathogen-associated molecular patterns leads to PAMP-triggered immunity. However, pathogens can modulate it via the secretion of effectors. We hypothesize that in potato, induced defense triggered by a Phytophthora infestans concentrated culture filtrate (CCF) could alter both effector expression and disease severity. CCF was sprayed onto three potato genotypes with different resistance levels, before inoculation with P. infestans . Symptoms were scored visually at 1-4 dpi, while the expression of defense and effector genes was assessed by qRT-PCR. CCF induced most defense genes in Désirée ( PRs, EIN3 ) and Bintje ( PRs, PAL and POX ), but repressed most defense genes in Rosafolia. On the contrary, CCF induced most effector genes in Rosafolia ( Pi03192, Avrblb2, Avr3a, EPIC2B and SNE1 ). INF1 was over-expressed in Bintje, despite its earlier expression in both Désirée and Rosafolia compared to unsprayed controls. Pi03192 was repressed in Désirée, and was expressed earlier in Rosafolia than in controls. However, induced defense responses by CCF significantly reduced lesion areas at 3 dpi only in Désirée. The effectiveness of induced defense thus depends on host genotypes. It results from differential interactions and kinetics of defense and effector genes expressions.