Identification of some Biocontrol agents on Potato Soft Rot Bacterium

One of the most important factors causing damage to potato is the soil-borne soft rot bacteria which have a wide host range and produce pectinase enzyme causing soft rot in potato tubers. Use of antagonistic bacteria is important as an alternative to chemical in control of pathogens. In this study, 30 samples of potato tubers suspected to be infected with soft rot bacteria along with surrounding soil samples were collected from potato farms in East Azarbaijan province. Then the soft rot bacteria were isolated from potato tuber samples. Pathogenic bacterial isolates were identified as Pectobacterium carotovorum subsp. carotovorum using biochemical and molecular methods. The antagonistic bacteria were isolated from soil samples around the tubers then screening test was performed on pathogen bacterium under laboratory conditions. Seven of 250 antagonists isolated from soil, formed inhibition zone on the pathogen. Two of them, 37G and 41E, with more than 50% inhibition on pathogen growth, show the most effective antibiosis and other three isolates 37B, 36A and 34B showed inhibition of nearly 50% but 11A isolate with 40% inhibition was excluded because of pathogenic activity on potato tubers. The antagonistic bacteria were identified as Streptomyces sp using biochemical, morphological and molecular methods. Streptomyces are good potential for control of plant pathogenic bacteria due to different biocontrol mechanisms, including the induction of host plant resistance and the ability to destroy the AHL.