ABSTRACT
During the isolation of bacterial plant pathogen from diseased plant samples, several nonpathogenic and saprophytic bacterial colonies also grow in the isolation plates. Generally, such colonies appear much earlier than plant pathogenic bacterial colonies. Sometimes the saprophytic bacterial colonies are intermingled with plant pathogenic bacterial colonies. Therefore, picking the pathogenic bacteria and their purification is an important step to obtain pure culture of bacterial plant pathogen. Further, during the preservation of bacterial cultures, sometimes the cultures are contaminated with other microbes and therefore purification is a necessary aspect in the maintenance of these cultures. However, many times the colonies of saprophytic bacteria develop along with plant pathogenic bacteria. Further, the colonies that came up more slowly are likely to be that of pathogenic bacteria. The cultures obtained by single colony transfer are checked for purity. Make a dilute suspension of the culture in distilled sterilized water and streak on the nutrient agar plates.
