Colloidal chitin (Sigma chemicals Co., USA) was used as a substrate for chitinase assay (Wen et al. 2002). Bacteria were seeded onto LB plate supplemented with 0.2% col- loidal chitin and solidified with 1.5% agar. After incubation at 35 °C for 72–96 h, the zones of clearing of the chitin could be seen around the colonies.
In addition, plant growth promoting abilities including auxin production, phosphate solubilisation, siderophore and HCN production were determined for these two strains. Auxin production was checked in the presence (50, 100 and 500 μg/ml) and absence of L-tryptophan and estimated using Salkowski reagent (Patten & Glick 2002). The indole acetic acid concentration in culture was calculated using a calibration curve of pure IAA as a standard. The pattern of production of indole acetic acid was also determined at dif- ferent times. The Pikovaskyas medium with insoluble tricalcium phosphate Ca3(PO4)2 (Pikovaskyas, 1948) or CaHPO4 compound (Bashan et al. 2013) was used to determine the potential of bacterial strains in solubilising mineral phosphate. A qualitative assay of siderophore production was conducted in Chrome Azurole’s (CAS) agar medium according to Schwyn and Neilands (1987). Micro-organisms exhibiting an orange halo were considered positive for the production of siderophores. Cyanogenesis was deter- mined as described by Donate-Correa et al. (2004). Petri plates containing TSA medium inoculated with bacterial cultures and incubated at 28 °C for 3 days. Before incubating a piece of filter paper impregnated with 1% picric acid and 2% sodium carbonate had been placed in the lid of each petri plates. A change in colour from yellow to orange- brown on the filter paper indicated the production of cyanide.