6.130
EVALUATION OF CIETINASE PRODUCTION AND ACC UTILIZATION AS PARAMETERS FOR SELECTION OF GROUNDNUT RHIZOBACTERIA FOR BIOCONTROL AND PLANT GROWTH PROMOTION
C V S S RAJESH and A.R PODILE

Biotechnology Programme, School of Life Sciences, University of Hyderabad, Hyderabad - 500 046, India


Background and objectives
Rliizobacterial isolates have the ability to promote growth and protect the plants from phylopathogenic fungi. Ability to produce chitinase and utilization of 1 -arnino cyclopropane - 1 -carboxylic acid (ACC) were thought to be direct orindirect indicators conferring antifungal property and plant growth promotion, respectively. The objective of the present study was to isolate, characterise, screen and select for the PGPRs which are antifungal and also to see whether ACC utilisation by an isolate could be a direct indicator of it's PGPR property (Glick et al. 1994).


Materials and methods
Bacteria were isolated from the groundnut rhizosphere samples collected from different localities. Groundnut seeds were then bacterised using 150 different bacterial isolates and pot trials were done in duplicates to observe their PGPR activity against appropriate control. All these bacterial isolates were tested for the presence / absence of chitinase by epiflourescence method (O'Biren and Colwell, 1987). The antifungal property of these strains was checked against Aspergillus niger in a dual culture test on potato dextrose agar plates. An attempt was made to correlate chitinase production with the antifungal property of the isolates. All the isolates were tested for ACC utilisation in M9 minimal medium with ACC as the sole source of nitrogen in triplicates. The experiment was repeated.


Results and conclusions
More than 150 bacteria from groundnut rhizosphere were isolated. Colonies showing distinctly different morphological charecterestics were selected on nutrient agar and king's B media plates. In dual culture tests they have shown different degrees of antifungal property against A. niger. Based on the observations they were categorised into 4 classes, siz., not inhibiting, inhibiting only mycelial growth inlfibiting only sporulation and inhibiting both sporulation and mycelial growth. The total of 37 isolates, including the latter three classes, were treated as antifungal isolates. The test for the presence or absence of chitinase indicated that only about 50% of the total isolates were chitinase producers. Among the antifungal isolates, 13 were found to produce chitinase. We also noticed that a few of the isolates produce cbitinase which have not shown antifungal property. Of the 87 isolates that produce chitinase only 15 isolates showed antifungal property. We therefore conclude that all chitinase producers are not antifungal. The results with ACC utilization test inidicated that ACC utilization cannot be taken as a direct indicator of PGPR property.


References
Glick, BR., Jacobson, C.B. Schwarze, M.M.K., and Pasternak, J.J. 1994. Can. J. Microbiol. 40, 911-915 O' Brien, M. and Colwell, R.R- 1987. Appl. Environ. Nficrobiol. 53, 1718-1720.