Development of quality assurance method for biofertilizers using LACz marker

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Date
2004
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CCSHAU
Abstract
Biofertilizers are living microorganisms used to supplement nutritional requirement of plants. Strains of Azotobacter, Rhizobium, Azospirillum, Pseudomonas, Bacillus and Acetobacter have been developed as biofertilizers for various crops and are suppled as carrier based inoculants. The responses of biofertilizers are inconsistent and generally related to the poor quality and poor competitive ability of the inoculants. The quality control methods include standard plate count and most probable number (MPN) by plant infection. Both these methods are not very specific and require at least 10-30 days. Thus, the quality control methods are not strictly followed because producers are not willing to hold their product for 30 days and thus substandard biofertilizers are being supplied to the farmers. Thus, there is an urgent need to develop simple method for quality assurance of biofertilizers, which could be completed with in 6-12 hours. lacZ marked strains of Azotobacter (A-2), Rhizobium (T-19CL and PP1021L), Pseudomonas (P-35) and Bacillus (BPL-2) showed relationship between -galactosidase activity with viable cell number at different stages of growth in liquid medium. The Z buffer with 0.1% Triton X-100 was found to be the best diluent for enumeration of viable cell population in charcoal based inoculants. There was relationship in -galactosidase activity and viable cell number of all these above strains in charcoal based inoculants, which remained stable up to three months. Time for development of yellow colour of ONPG filter paper discs was correlated with viable cell number, thus providing the qualitative method for enumeration of viable cell number in the bioinoculants.
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