Summary
This study demonstrates that high nitrogen fertilisation increases susceptibility of apple trees to scab disease through a trade-off between vigorous shoot growth and phenolic defence compound biosynthesis. Low-nitrogen trees accumulated higher levels of phenolic compounds in young leaves and mounted more effective disease resistance, characterised by smaller lesions and suppressed pathogen sporulation. In vitro studies identified sugar availability as a critical regulatory factor for phenylpropanoid pathway flux, with nitrogen–sucrose balance governing secondary metabolite accumulation.
Regional applicability
The study does not specify geographical location, limiting direct application to United Kingdom apple production conditions. However, the fundamental mechanisms linking nitrogen nutrition, secondary metabolism, and fungal disease resistance are broadly applicable to UK apple orchards, particularly regarding integrated nutrient and disease management strategies. The findings suggest potential for optimising nitrogen input levels to balance productivity with disease resilience in temperate apple production.
Key measures
Lesion size, sporulation extent, phenolic compound concentration, shoot growth rate, sucrose and nitrogen ratios, glucosyl transferase activity
Outcomes reported
The study examined how nitrogen-induced shoot growth affects apple tree susceptibility to Venturia inaequalis (scab) infection and the role of phenolic compound biosynthesis in disease resistance. It measured lesion size, sporulation, phenolic compound concentrations in young leaves, and metabolic pathway activity in both field-grown and in vitro cultured plants.
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