Salicylic acid induces cultivar specific compromises in yield, fruit quality and defense metabolism of heat stressed strawberry.

Heat shock poses a major threat to strawberry production, impairing both yield and fruit quality. This study investigated the potential of salicylic acid (SA) spraying (1 mM) to mitigate heat-induced damage (42 °C) in 'Camarosa' and 'Paros' cultivars. Results showed heat shock was the primary factor driving a severe decline in fruit yield by 61%. Although SA failed to mitigate yield loss, it induced divergent, cultivar-specific strategies in biomass partitioning and defense metabolism. 'Camarosa' deployed an inducible, high-cost acclimation strategy, upregulating PAL activity by 56.3% and reconfiguring biomass towards roots, whereas 'Paros' exhibited constitutive tolerance but greater fruit weight sensitivity (34.3% vs. 15.6% reduction). PCA quantified a fundamental physiological trade-off, with PC1 (45.5% of variance) clearly separating a yield and quality cluster from a cluster defined by phenylpropanoid metabolism. This was statistically underpinned by significant negative correlations between PAL activity and both fruit yield (r = -0.63) and vitamin C (r = -0.83), confirming the metabolic cost of phenylpropanoid defense activation. It is concluded that 1 mM SA does not rescue yield but serves as a genotype-specific physiological modulator, indicating that management strategies should prioritize cultivars that balance defense expenditure with reproductive sink strength.