Inhibitory effects of non-chemical agents on Penicillium expansum and other decay fungi in apple

Blue mold caused by Peniciliium expansum Link. is a major postharvest decay agent in apple fruit.  In this research, the efficacy of two non-chemical compounds including chitosan and carnoba coating wax and Imazalil in inhibiting blue mold in apple cvs. Golden delicious and Red delicious and their association with polyphenol content was studied in laboratory condition. Additionally, the effect of two antagonistis (Trichoderma atroviride and T. haziamum) on a number of decaying fungi including Rhizopus stolonifer, Alternaria  alternata, P. expansum, Ulocladium sp., Aspergilus sp., Cladosporium fulvum and Monilia sp. was determined. Fungicide Imazalil and distilled water were used as controls. Based on the results, Golden delicious was more susceptible to P. expansum than Red delicious. In both cultivars, chitosan treatment reduced P. expansum decay in fruit and its growth in culture medium. The least to the most decay severities were observed in Imazalil, chitosan+Imizalil, chitosan, chitosan+wax and wax treatments and chitosan treatment reduced it up to 97% Polyphenol concentration was higher in Red delicious than Golden delicious and the most to the least polyphenol concentration were detected in chitosan, chitosan+Imizalil, chitosan+wax, Imizalil, wax and control (distilled water) treatments, respectively. Negative correlations were found between polyphenol concentration and P. expansum susceptibility and treatment (R=-0.989and -0.68, respectively). Accordingly, inducible and constitutive polyphenols might contribute in apple resistance to blue mold and in chitosan-induced protection. Both Trichoderma species in particulr T. atroviride inhibited all decaying agents. Based on these results, chitosan can be recommended as an effective nonchemical agent for apple protection against blue mold but carnoba wax has no protective effect.