Priming of Defence in Forest Health: Oak Cases of Study

Rosa Sánchez-Lucas, Ph.D. – School of Biosciences, University of Birmingham

Oak trees, like many plants, are constantly challenged by multiple stresses, from pathogens to drought—pressures that are becoming more frequent and severe with climate change. Despite this, plants have evolved sophisticated defence strategies. One of these is priming: a way of “training” their immune system so that they can react faster and stronger when a threat appears. While priming has been studied in several plant species, little is known about how it works in oaks. In our study, we tested whether young oak seedlings could be primed with natural defence-related chemicals—salicylic acid (SA), jasmonic acid (JA), and β-aminobutyric acid (BABA)—before being exposed to oak powdery mildew (Erysiphe alphitoides), a disease to which oaks are highly vulnerable. We found that priming did occur: SA and BABA treatments improved resistance, while JA unexpectedly increased susceptibility. These effects were linked to different defence mechanisms: SA activated gene expression linked to immune pathways, while BABA boosted callose deposition (a plant cell wall barrier). Interestingly, BABA-treated seedlings showed stronger resistance but also slower growth after infection, highlighting potential trade-offs between defence and development.