Fig. 10

Hypothesized model for cucumber age-related resistance to P. capsici. In young susceptible fruit there is low accumulation of potentially antimicrobial specialized metabolites. Furthermore, a delayed response (> 8 hpi) to pathogen sensing may be too late to limit pathogen establishment. In resistant-aged fruit, the accumulation of metabolites could directly inhibit pathogen growth. Developmentally regulated expression of receptor-like gene(s) allows the sensing of pathogen-associated molecular patterns or effectors, and thus mediates an early response to infection. Transcription factors such as WRKY33 are expressed and their downstream targets including ethylene synthesis genes and other defense genes are activated. In resistant-aged fruit, metabolism of reactive oxygen species (ROS) is also activated in an early response to infection likely further mediating a strong defense response. By 24 hpi pathogen presence is limited on the fruit surface and mostly non-viable spores and hyphae remain