The root rot pathogen M. Phaseolina was isolated from coleus
plants showing typical root rot symptoms and pure cultures of the
pathogen were obtained by the single hyphal tip method [6]. The
biocontrol agent P. fluorescens strain Pf1 was obtained from the culture
collection section, Department of Plant Pathology, Centre for Plant
Protection Studies, Tamil Nadu Agricultural University, India.
Other native coleus rhizobacterial P. fluorescens (CPF1 to CPF10)
strains were isolated from soil samples obtained from different parts of
Tamil Nadu state. One gram of rhizosphere soil adhering to root surface
was collected and transferred to a 250 ml conical flask containing
100 ml of sterile water. After thorough shaking for 15 minutes in a
shaker, different dilutions were prepared. One ml of each 10-5 and 10-6
dilution was pipetted out and poured into the sterile petridishes. Later
King's medium B (KB) [7] was poured, rotated and incubated at room
temperature (28 ± 2°C) for 24 hours. After 24 hours of incubation, the
bacterial growth was purified by the dilution plate technique [8]. The
bacterial culture was maintained in King's B broth (KB) in 30 percent
(v/v) glycerol at -80°C.
Characterization of the different cultures of antagonistic bacteria