Fumigant activity of volatile compounds of Streptomyces philanthi RM-1-138 and pure chemicals (acetophenone and phenylethyl alcohol) against anthracnose pathogen in postharvest chili fruit

Application of volatiles from Streptomyces philanthi RM-1-138 grown on sterile wheat seeds (volatiles RM-1-138) and pure commercial volatile compounds (acetophenone and phenylethyl alcohol) against chili anthracnose pathogen were investigated in vitro and in vivo. Among 42 isolates of Colletotrichum species tested, C. gloeosporioides PSU-NY8 was selected as the most aggressive anthracnose pathogenic strain on chili fruit against the volatiles RM-1-138. The optimum inoculum size (15 g L−1) and spore concentration (107 spore mL−1) of the wheat seed culture of S. philanthi RM-1-138 exhibited the complete suppression (100% inhibition) on C. gloeosporioides PSU-NY8. In addition, the in vivo result indicated the optimum fumigation period of the volatiles RM-1-138 (15 g L−1) was at 6 h. Phenylethyl alcohol showed no antifungal activity at all concentrations tested (10-1000 μL L−1) while acetophenone at 100 μL L−1 of airspace exhibited antifungal activity both in vitro and in vivo after 12 h fumigation. The fumigant activity was evidenced by the damage of cell wall of C. gloeosporioides PSU-NY8 illustrated by SEM. Therefore, the volatiles from S. philanthi RM-1-138 have a high potential for biocontrol of chili anthracnose disease in postharvest system.