Exploring the biochemical basis of brown rot tolerance in interspecific Prunus spp. populations

Brown rot, caused by Monilinia spp., is one of the most economically important postharvest diseases affecting peaches and nectarines ( Prunus persica L. Batsch). This study investigates the relationship between some biochemical traits (including the antioxidant profile and cuticular wax composition) and brown rot susceptibility. Fruit quality and biochemical traits were evaluated in two interspecific BC1 populations called NT1Ba and NT1Ca, derived from the peach and Prunus davidiana hybrids ‘Barrier’ and ‘Cadaman’, respectively, while cuticular wax composition analyses were performed in the NT1Ba population uniquely. While oxidative stress indicators, including antioxidant capacity (AC), total phenolic content (TPC) and hydrogen peroxide (H₂O₂), did not correlate with disease tolerance, significant differences were detected in cuticle yield and wax composition. Triterpenoids were the most abundant wax compounds, followed by fatty acids, alkanes, alcohols, aldehydes, and sterols. Partial Least Squares Regression (PLSR) analysis revealed that genotypes less susceptible to brown rot had higher cuticle yields and greater levels of acyclic compounds in the wax fraction, suggesting a role in enhancing physical barriers to fungal penetration. In contrast, more susceptible genotypes exhibited higher levels of triterpenes and sterols, together with higher fruit weight and pH, which may have facilitated fungal infection. Although these results require validation across additional genetic backgrounds, they suggest that cuticle traits, particularly the abundance of acyclic wax compounds, may play a key role in brown rot resistance in the NT1Ba population and could represent valuable targets for breeding programs.