Biological control of postharvest diseases of peach with phyllosphere isolates of Pseudomonas syringae

Commercially ripe peaches were wounded and co-inoculated with phylloplane isolates of Pseudomonas syringae (MA-4 and NSA-6), Pseudomonas fluorescens (BAP-3), or an isolate of Candida sp. (NSD-4) in combination with either conidia of Monilinia fructicola (cause of brown rot) or sporangiospores of Rhizopus stolonifer (cause of rhizopus rot). Isolates NSA-6 and MA-4 at a concentration of 1 x 107 CFU/mL reduced brown rot to 28% and 73%, respectively, from 98% in the inoculated check after 5 days incubation at 22°C. Both isolates reduced rhizopus rot to 5% and 8% from 53% in the inoculated check after 5 days incubation. The P. syringae isolates when used in 2-min soak treatments were less effective against natural, preharvest M. fructicola infections of late-harvested peaches. Isolates MA-4 and NSA-6 suppressed brown rot from 63% to 30% and from 95% to 71-81%, respectively, after 3 and 4 days incubation at 22°C. The use of 0.5% CaCl2 in the soak suspension significantly improved the activity of P. syringae but...