Testing Efficacy Of Screened Phosphate Solubilisers Under In Vitro Conditions

Phosphate solubilising bacteria (PSB) and fungi (PSF) were enumerated by employing Pikovskaya and Modified Pikovskaya agar supplemented with Tricalcium phosphate (TCP) as insoluble phosphate source. The P solubilisers formed yellow halos around their colonies on Modified Pikovskaya agar (MPVK) using Bromophenol blue. The frequency of PSB was highest in the Kharar soil (5.1%) and the least in Model Town, Ludhiana soil (2.2%) in rhizosphere zone. The population of PSF was maximum in Kharar soil (15%) followed by Pakhowal Road, Ludhiana soil (10%) and the least in Model Town, Ludhiana soil (5.6%). The PSB reported belonged to Bacillus and Micrococcus sp. while the PSF belonged to the Aspergillus niger, Aspergillus fumigatus and Penicillium sp. The population of PSM was highest in the rhizosphere than that of non-rhizosphere. The maximum halo size on Modified Pikovskaya agar was reported in Bacillus sp. (5 mm). PSM were screened to observe their efficacy to solubilise P on PVK broth. Penicilliu sp. was found to solubilise maximum TCP (54.2 µg/ml) followed by the Aspergillus fumigatus (51.4 µg/ml) and the least in Aspergillus niger (11.2 µg/ml). The inverse trend in the rate of P solubilisation with that of final pH of broth was observed. The maximum decrease pH was reported in Penicillium sp. (4.5) followed by Aspergillus fumigatus (5.5) and Aspergillus niger (6.0).