The combination of curing with either chitosan or Bacillus subtilis CPA-8 to control brown rot infections caused by Monilinia fructicola

Recently, it has been reported that brown rot in peaches and nectarines can be effectively controlled by exposing fruit to 50 °C for 2 h and 95-99% relative humidity (RH). This treatment was effective at reducing infections that had become established in the field. However, it did not provide protection for further Monilinia fructicola infections, indicating that fruit was susceptible to subsequent infections after the treatment process and before cool storage. Chitosan and Bacillus subtilis (strain CPA-8) were evaluated for their ability to prevent M. fructicola infections and for their ability to complement the heat treatment. Two chitosan concentrations (0.5% or 1%) were applied at three temperatures (20, 40 or 50 °C) for 1 min to wounded and unwounded fruit that were artificially inoculated with M. fructicola. One percent chitosan applied at 20 °C had a preventive effect against further M. fructicola infections on heat-treated fruit that had been previously inoculated: brown rot incidence was reduced to 10%, in comparison with the control (73%). However, chitosan applied to wounded fruit had a poor preventive effect. The antagonist, B. subtilis CPA-8, had a preventive effect in controlling M. fructicola infections: the incidence of brown rot was reduced to less than 15% for both varieties evaluated (‘Baby Gold 9’ and ‘Andros’ peaches), in comparison with the control fruit (higher than 98%). In contrast, when fruit were stored at 0 °C, this preventive effect was not detected. These findings indicate that heat-treated fruit can be protected from subsequent fruit infection after heat treatment by use of chitosan or B. subtillis CPA-8, thereby providing packinghouses with an effective biologically based, combined approach to the management of postharvest brown rot.