Postharvest application of natural compounds and biocontrol agents to manage brown rot of stone fruits

Postharvest losses caused by fungal decay seriously affect globally fresh fruit production. The main pathogens causing postharvest disease on stone fruit are Monilinia laxa, M. fructicola and M. fructigena, causal agents of brown rot. The effectiveness of formulations based on natural compounds and biocontrol agents to manage brown rot on peach cultivars ‘+5Tardibelle’ and ‘Extreme 486’ was tested. Commercial formulations of chitosan, sweet orange essential oil, Bacillus subtilis, Aureobasidium pullulans, chito-oligosaccharides (COS-OGA) and a mixture of thymol, geraniol and eugenol were applied by dipping fruit, using as a reference a synthetic fungicide (fludioxonil) and an untreated control. Fruits were immersed for 30 s in the solutions, then cold stored at 2°C respectively 7 days for ‘+5Tardibelle’ and 14 days for ‘Extreme 486’, then exposed to shelf life. Brown rot evaluation at 3 and 7 days shelf life showed a significant reduction of disease incidence by fludioxonil. Among alternative compounds, tendency toward disease reduction on ‘+5Tardibelle’ was observed with application of chitosan and of B. subtilis, and on ‘Extreme 486’ with application of Aureobasidium pullulans. A sensory quality assessment was carried out to evaluate aroma and taste. The results showed the highest preference for peaches treated with fludioxonil, describing them as sweeter and tastier, followed by mixture of thymol, geraniol and eugenol and B. subtilis. These results suggest that the application of alternative substances could contribute to the management of postharvest diseases of peaches. Additional trials are needed to adjust concentrations and treatment time to make significant progress toward replacement of synthetic fungicides.