Biological control of Rhizopus rot of peach fruits by Candida guilliermondii

The biocontrol capability of Candida guilliermondii (Cast) Langeroret Guerra against Rhizopus stolonifer (Ehrenb. ex Fr.) Vuill. postharvest rot of peach fruits was studied in vitro and in vivo under different storage temperatures. C. guilliermondii at 5.0 x 10⁸ CFU (colony-forming unit)/mL of washed cells provided complete control of 5 x 10⁴ spores / mL of R. stolonifer during storage at 25 °C for 4 d, 15 °C for 7 d and 3 °C for 30 d. Temperature had no significant effect on the biocontrol efficacy. Antagonist population increased 45.6, 34.4 and 33.1 times per site at 25 °C, 15 °C and 3 °C for 3, 3 and 7 d, respectively, then the population stabilized for the remaining storage period. Cell-free culture filtrate of C. guilliermondii was not effective in preventing decay and resulted in even greater lesion diameter than those of sterile distilled water at 3 °C. These results showed that competition for nutrient, not antibiotic production, plays a major role in the biocontrol capability of C. guilliermondii against rhizopus rot of peach fruits. As the interval between wounding and inoculation with the pathogen increased from 0 to 72 h, susceptibility of wounds to decay by R. stolonifer decreased from 100% of 0 h to 5% of 4 h and 0% of 24 h, then increased to 10% of 48 h and 40% of 72 h.