Unraveling the quantitative pepper - Phytophthora capsici interplay: global assessment of isolate aggressiveness

International audience

anglais. Pepper is one of the most economically important crops worldwide, but its production is often challenged by plant pathogens such as Phytophthora capsici. This oomycete can cause devastating losses, and its high level of global genetic diversity poses a significant challenge for breeding programs aimed at developing resistant pepper varieties. It is acknowledged that resistance to P. capsici mostly follows a nested pattern. However, to better understand the interactions between pepper and P. capsici, we conducted a study to investigate how different P. capsici isolates from various regions of the world interact with different pepper accessions. We inoculated 11 P. capsici isolates from France, Mexico, Korea, China, the USA, and the Asian Pacific on 9 pepper accessions (Capsicum annuum) with varying degrees of resistance to the pathogen. We then assessed the symptoms of the disease. Our results revealed two key findings. Firstly, we observed a quantitative aspect to the plant-pathogen interaction, with some pepper accessions being more resistant to certain P. capsici isolate than others.Secondly, we observed a diverse range of symptom intensities, demonstrating that some P. capsici isolates have high aggressiveness and can infect a broad range of pepper accessions, while others have low aggressiveness and infect fewer accessions. These findings provide important insights on the P. capsici infectivity patterns and have significant implications for breeding programs aimed at developing resistant pepper varieties. By characterizing the isolates and accessions involved in these interactions, we can begin to better understand the complex dynamics of plant-pathogen interactions and develop more targeted breeding strategies to combat this evastating pathogen. In summary, our study highlights the challenges posed by P. capsici to pepper production and provides valuable insights into the complex interactions between this pathogen and its host.