Efficacy of antagonistic yeasts in the control of brown rot of nectarines and effect on fruit microbiome.

Monilinia fructicola, the causal agent of brown rot, is one of the most important pathogens affecting nectarines during storage. Current management strategies include preventive treatments with synthetic fungicides, posing technical, environmental and toxicity issues. We aimed to evaluate the efficacy of treatments with antagonistic yeasts to control brown rot of nectarines. A screening trial was set up by treating inoculated fruits with 14 yeast strains. The most effective strains (MS, Metschnikowia sp., AP47, M. fructicola, FR4A, Aureobasidium sp.) were tested in semi-commercial conditions. Fruits were maintained in storage rooms at 1 °C for 28 days, followed by 4 days of shelf-life at 25 °C. After storage, all treatments showed a significant rot reduction compared to the control. The efficacy of MS strain was comparable to the chemical control treatment, making the antagonist as competitive as fungicides. All strains maintained a significative rot reduction at the end of shelf-life. The evaluation of postharvest quality parameters, including firmness, total soluble solids and titratable acidity showed that none of the three tested yeasts affected nectarine quality. A metabarcoding analysis was conducted to evaluate the effect of the treatments on the microbial population of the nectarines. Results proved that treatments with antagonistic yeasts represents a promising tool for reducing postharvest losses preserving the fruit quality.