In vitro Screening of Native Bacillus Isolates for Plant Growth Promoting Attributes

Bacillus spp. are well known rhizosphere residents of many crops and usually show plant growth promoting (PGP) activities that include biocontrol capacity against some phytopathogenic fungi. In this study, a total of thirty Bacillus isolates were obtained from the rhizospheric soils of groundnut and redgram crops growing in Rangareddy district, India and identified based on their colony morphology, cell morphology and biochemical characteristics. These thirty isolates were screened for PGP attributes like phosphate solubilization and Indole Acetic Acid (IAA) production. Isolates showing PGP properties were further screened for in vitro antagonism against soil borne phytopathogens viz., Sclerotium rolfsii, Rhizoctonia solani and Fusarium solani. Results revealed that 50% (15 out of 30 isolates) reacted positively for one or more PGP properties. A high prevalence of antagonists was found against the three fungal pathogens. Majority of the bacterial isolates (33%) displayed antagonism through the production of siderophores or HCN and the remaining isolates showed antagonism with negative results for siderophores and HCN indicating that, other mechanisms such as production of mycolytic enzymes and Antibiosis etc. may be involved. It was suggested that the rhizospheric soils are the rich source of Bacillus fungal antagonists, which have a potential to be used in the future as PGP inoculants.