Dr. Rupa G. Nandi


Suitability of gum liquid inoculums for the commercial production of biofertilizer for Glycin max by temperature tolerant strains.
Fund Granted : Rs. 95,000/-.


Executive Summary:

In present study an attempt was made to formulate gum liquid inoculums in which gum was taken as carrier. Strains of Rhizobium are isolated which can tolerate temperature and was taken as the main microorganism to produce bio-fertilizer for soybean.

18 isolates of Rhizobium japonicum out of which four isolates was selected as temperature tolerant strains from different parts of M.P. All the isolates were gram negative with good growth on congo red yeast extract mannitol agar medium. All the test isolates gave negative results for casein hydrolysis and starch hydrolysis. All the test isolates gave positive results for gum production and glucose consumption.

A pH range of 4.5 to 12.0 was found to be common for the growth of most of test isolates and Ph   range from 6.5 to 8.0 were found to be most suitable for the growth multiplication and nodulation of Rhizobium japonicum. The number of colonies of Rhizobium japonicum decreases with increase in acidity or alkalinity. A temperature range of 27ºC to 40ºC was found to be favourable for most of the test isolates. Optimum temperature was recorded at 35ºC. Temperature above 35ºC caused significant decrease in the colony count.
Gum as a carrier was found best. The count was recorded 10-8 cells/ml upto10 months after that the count was 10-7cells/ml which reduced to nil after sometime. In yeast extract mannitol broth the count was recorded 10-7 cells/ml upto 12 months and beyond this period the count was not very satisfactory.
Accordingly gum liquid inoculum was found to be best carrier. Poor survival of Rhizobium japonicum was recorded in lignite and was not satisfactory.
Pot trials revealed increase in the number of nodules due to seed bacterialization by gum liquid inoculum with Rhizobium Japonicum as strain was used. Results showed that dry weights of shoots and yield also increased due to seed bacterialization by Rhizobium Japonicum. The maximum yield of soybean over control was noted in treatment with isolates Rj(S)TAL102. The percentage increase in grain yield ranged from 20% to 50% with gum liquid inoculum than powdered inoculant (lignite as carrier).
In the field trial to seed bacterialization by gum liquid inoculum with 5 test isolates was performed. In this field trial comparison was made between gum liquid inoculum bio-fertilizer in which the carrier was gum and the other carrier lignite as control. The result of field trial revealed that liquid inoculum which was prepared with modified media increased not only the number of nodule, but also grain yield, number of pods and the total biomass per plot. Increase in grain yield was recorded from 17% to 50%. The application of Rhizobium japonicum with carrier gum enhanced grain and straw yield. On the basis of results obtained in the present investigation, it can be concluded that Rj(S)TAL102, Rj(S), Rj(S) and Rj(S) which were found to be the effective strains of Rhizobium japonicum can be used as inoculant for commercial production of soybean bio-fertilizer.
The most important finding of the investigation is that unsatisfactory result by carriers like lignite and peat can be overcome by the use of gum liquid inoculum. Previously traditional carriers like lignite, peat was used which did not give satisfactory result. So to overcome this problem formulation of liquid inoculum is recommended in which gum is used as a carrier and according to the present investigation the result showed that liquid inoculum with gum as carrier was more efficient to enhance the growth of microorganisms than the powdered inoculant. Gum liquid inoculum increases the shelf life of the strain or bio-fertilizer.
So, gum liquid inoculum was found to be the efficient carrier and can be used for commercial production of soybean bio-fertilizer for enhanced production of soybean. The best gums found are Guar and Locust bean and amongst the modified media the once are G2 and G6 in which the count found to be the high.