Estimation of Indole Acetic Acid and Phosphate Solubilisation by the Yeasts Isolated from the Leguminous Crops

Aim: The present study was aimed to estimate the quantity of IAA production and Phosphate solubilisation by the isolated yeasts from the leguminous crops. Place and Duration of Work: The experiments were carried out in the Department of Agricultural Microbiology, University of Agricultural Sciences, GKVK, Bengaluru during 2019-2020. Methodology: Yeasts were isolated from the leguminous crops such as Red gram, Cowpea, Green gram, Black gram and Bengal gram. Thirty-five yeast isolates were obtained using four media and were subjected to IAA production test and Phosphorus solubilisation by Spectrophotometry method. All the yeast isolates were subjected to the temperature tolerance test at 25, 30, 35 and 40°C. Results: Yeast isolate, CP15SI21 has found to produce the highest IAA under in vitro conditions 30.50 μg/ml and the lowest was found to be 17.16μg/ml by yeast isolate BG20SI29. 24 yeast isolates were found to produce above 20 μg/ml. In the case of Phosphate solubilisation highest was observed in GG7SI9 (25.70 mg/l) and lowest in BG6SI8 (1.20 mg/l). Seven isolates showed Phosphate solubilisation above 10 mg/l. At 35°C all the yeast isolates have shown very good growth compared to other lower temperatures. All the yeast isolates were found to grow in the media supplemented with micronutrients such as zinc and potassium. Conclusion: Our study highlights the potential of yeasts isolated from the leguminous crops that can help in plant growth promotion as the yeast isolates are capable of producing higher amounts of IAA. Some of the yeast isolates can solubilise phosphate under in vitro conditions which in turn helps in the utilization of unavailable P from soils thereby improves plant growth and tolerance to a higher temperature can alleviate abiotic stress.

Isolation and Characterization of Phosphate Solubilising Rhizobia Nodulating Wild Field Pea (Pisum sativum var. abyssinicum) from Southern Tigray, Ethiopia

Hypothesis: Phosphorus is the second limiting nutrients next to nitrogen as well as the least mobile element in the soil. This nutrient is one of the major constraints for low productivity of wild field pea in the study site. Hence, the development of environmental friendly and economically accepted to subsistent farmer is undeniably important. Aims: This experiment was initiated to isolate and characterize inorganic phosphate solubilizing rhizobia from root nodules of field pea (Pisum sativum var. abyssinicum) were characterized for their solubilisation ability on Pikovaskaya liquid and solid media. Study Design: Laboratory experimental design was used. Place and Duration of Study: Field pea root nodules were collected from Southern Tigray and the study was carried out between October, 2015 and June, 2016 at Haremaya University soil microbiology laboratory. Methodology: The presumptive test, qualitative and quantitative phosphate solubilisation of isolates was done in triplicates using the standard procedures. Authentication of the isolates was made using autoclaved and sterilized river sand in pot experiment. Results: The current results revealed that all isolates were gram negative, failed to grow on peptone glucose agar, ketolactose test and did not absorb congo-red upon incubation period. It also showed that phosphate solubilisation index of root nodulating bacteria on in vitro Pikovskaya’s agar medium varied from 1.54 to 2.70. Inorganic phosphate solubilisation in broth medium dissolved insoluble Ca3 (PO4)2 was within the range of 16.59-23.95 mg plant-1 with pH drop from 7.01 to 5.33. Among the tested rhizobia isolates, HUDRI-8 and HUDRI-25 was found to be highest phosphate solubilisation compared to the remaining isolates, served as efficient phosphate solubilizers and could be used for further test under field condition. Conclusion: Finally, the selected isolates which are effective in N2 fixation and able to solubilise inorganic P were found to be effective in promoting nodulation and plant growth under greenhouse condition.