Post harvest biological control of apple bitter rot by soil-borne Actinomycetes and molecular identification of the active antagonist

• Soil Actinomycetes antagonists against Colletotrichum gloeosporioides were screened.
• Six antagonists with significant inhibitory effects against the fungus were found.
• Bitter rot of apple was inhibited by direct use of active Actinomycetes.
• Bitter rot of apple was inhibited by using crude extract of Actinomycetes.
• Production of hydrolytic enzymes by antagonists was studied.
• Most effective antagonist was identified by sequencing of 16S rDNA.

Apple bitter rot is a destructive fruit rot of apple worldwide. Because of recent advances in postharvest biological control as an eco-friendly and a potent alternative of fungicides, the present study evaluated the antagonistic activities of more than 100 Actinomycetes isolated from apple orchard soils of Kerman city (Iran) against causal agent of the disease. In vitro bioassays revealed that six of the isolates had significant inhibitory effects against the mycelial growth of the pathogen. Postharvest in vivo experiments were performed with either direct application of antagonists spore and mycelial mat or suspensions of their crude extracts. Statistical results indicated that antagonists inhibited rotting of apple fruit (p < 0.01) either by inhibition of disease onset or preventing further expanse of diseased fruit-lesions. Molecular identification of the antagonist performed based on 16S rDNA nucleotide sequence, and identified as Amycolatopsis sp. The present study is a preliminary step toward production of an applicable eco-friendly biocontrol product. Future larger scale postharvest evaluations would reveal such feasibility.