1Department of Microbiology, Osmania University, Hyderabad-500 007, Andhra Pradesh.
2Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru 502 324, Andhra Pradesh.
*E-mail: gopalred@hotmail.com, Tel: 91 40 27682246 (O), 91 40 27017431 (R).
Two hundred and seven bacteria were isolated from four different sources viz. farm waste compost (FWC), rice straw compost (RSC), Gliricidia vermicompost (GVC) and macrofauna (earthworms, centipedes, slugs and snails). All the isolates were tested for antagonistic activity on four soil borne plant pathogenic fungi, Sclerotium rolfsii, Macrophomina phaseolina, Fusarium solani and Fusarium oxysporum. Percentage of antagonistic bacteria varied from 19 in FWC to 39 in GVC. Of the 207 isolates, eighteen were antagonistic to all four soil borne plant pathogenic fungi. Inhibition was maximum on Kings B medium (63%), followed by glycerol casamino yeast extract (GCY) (49%) and potato dextrose agar (PDA) (46%). Identification of the 18 antagonistic isolates revealed that twelve belonged to genus Bacillus and six were Pseudomonas. B. licheniformis (EB 13) and Pseudomonas sp. (CDB 35) showed anti-fungal effect higher than other bacteria in plate culture conditions. These strains also showed significant reduction in fungal biomass when grown in broth culture. PDA amended with zinc sulphate further improved antifungal activity of EB 13 and CDB 35. In glass house conditions, soil amended with glucose and/or zinc in combination with EB 13 or CDB 35 reduced M. phaseolina infection in sorghum roots and improved shoot weight.
antagonistic bacteria, composts, pathogenic fungi, soil borne, sorghum
