Research Article

Assessment of Rhizobial and Phosphobacteria biofertilizer to overcome the moisture stress in the Vigna mungo

A.Bharathi and M.Buvaneswri1*

Published 06/19/2015 .
Email: bharathi141@gmail.com

INTRODUCTION

Biofertilizers are widely thought as important owing to their nitrogen fixation or phosphate solubilizing ability. It protects the crop from pathogenic infection by production of Siderophores,  thereby it act as a biological control to increase the crop yield and produce growth promoting substances like auxins, Vitamins, Gibberlins etc. The   pivotal role played by Biofertilizers is their ability to protect the plants from moisture stress, even though   the microbes require water for their multiplication. This study will open a new horizon in the area of biofertilizer application imparting drought tolerance. The presence of trehalose is a non-reducing sugar which accumulates in the bacteroids to overcome moisture stress(6). The second one is nutrient interaction of the plant by uptake of potassium due to silicate solubilizing culture(5).

Materials and Methods

Pot culture study

                The pots were filled with soils. Five treatments with five control pots were carried out in different moisture regimes and five seeds were sown on each pot. In each treatment, the pots were filled with Rhizobium, Phosphobacterial biofertilizer and silicate solubilizing organisms. The five treatments include soil moisture maintained at Hygroscopic coefficient, Wilting coefficient, Field capacity, Saturation and Super saturation.

Methods for measuring soil moisture

                First the different moisture content of soil was determined by the Gravimetric method. A known volume of the moist soil sample was taken and dried in an oven at a temperature of 100-110°C. After drying, the content was weighed again. The moisture lost by heating represent the soil moisture content. It was calculated by

 

        Loss wt of soil

Soil moisture % =    ------------------------- x100

          Dry Weight of soil

 

Determination of Potassium

                To determine the potassium level in the plant tissue, the fresh tissues from the plant part was collected and decontaminated from dust and another foreign material by washing with detergent solution and deionized water. Then it was subjected to Diacid, Triacid digestion and dryashing. After the preparation of the plant tissue, the potassium level is determined by     Flamephotometry. 

The level of potassium found in the plant tissue was analyzed by introducing in to the flame photometer in solution form. The atoms get excited by taking energy from flame and the emitted radiation was measured by photocell and photomultiplier tube. The concentration of potassium was measured by comparing the radiation emitted by a known standard with that of the sample.

Estimation of Trehalose

                The trehalose sugar present in the rhizobial cells was determined by the following test.

Osazone formation-The sample (rhizobial culture) in the YEMA broth was taken in clean test tube. To this a mixture of phenyl hydrazine hydrochloride and sodium acetate was added and heated in aboiling water bath for 15 minutes.

Hydrolysis-The sample was taken in a test tube and added two drops of 0.1N HCL and iodine solution. The colour change was checked and it was further confirmed by Barfoed’s, Fouglars and Fehling’s solution.

Result and discussion

                In the pot culture study a pulse crop was taken owing to fact that the long tap root system of leguminous crops could help in overcoming moisture stress during the initial period. The five treatments were applied with mixed biofertilizer containing Rhizobium, Phosphobacteria and silicate solubilizing bacteria. Then they were evaluated against five similar set of controls without biofertilzer application. The soil moisture percentage and moisture tension was determined by gravimetric method and by using Tensiometer( table-1& table-2).

Table-1 Soil moisture percentage

S.No

Treatment

Moisture level in percentage (%)

1

T1 Hygroscopic coefficient

10.2

2

T2 Wilting percentage

14.4

3

T3 Field capacity

30.2

4

T4 Saturation

52.2

5

T5 Super saturation

86.4

 

 

Table-2 Moisture Tension

S.No

Treatment

Moisture tension(bars)

1

Hygroscopic coefficient

33

2

Wilting percentage

16

3

Field capacity

0.4

4

Saturation

0.3

5

Super saturation

0.1

 

 

 

Then the plants were observed for their growth, turbidity and overall performance. The observations made were based on the physical viewing by the crop presentation in both treatments as well as in control. The plants were maintained at optimum moisture level upto 15 days and then the treatment condition was imposed. The duration of the Blackgram crop was 90 days. When results were compared  treatment with biofertilizer had prolonged to longevity of Blackgram for a few days (Table-3).

Table-3 Observation on death of plants due to different moisture level

S.No

Parameters

Death of plants(in days)

Treatment

Control

1

 Hygroscopic coefficient

21

18

2

 Wilting percentage

26

24

3

 Field capacity

78

75

4

 Saturation

79

75

5

 Super saturation

65

60

 

 

 

In case of treatment with combined biofertilizers recorded increased potassium status than in control. Hence it is another clear indication that the enhanced potassium content in plant might be one of the reasons for the plant to be more drought tolerant (Table-4).

Table-4 Effect of Nutrient (K) status on Blackgram

S.No

Parameters

Nutrient status in (%)

Treatment

Control

1

Hygroscopic coefficient

3.21

2.98

2

Wilting percentage

3.22

3.01

3

Field capacity

3.21

2.98

4

Saturation

3.18

2.95

5

Super saturation

3.15

2.91

 

 

Further the effect of trehalose in enhancing drought tolerance is well documented. Rhizobium is known for its trehalose production. The utilization of Rhizobium in the mixed culture under water stress would release the trehalose from the cell into soil. The presence would have imparted the tolerance for water stress. It was identified by Osazone test here trehalose does not form osazone because it does not contain a functional carbomyl group. There were no crystals formed. It confirms trehalose is one of the nonreducing sugar. On hydrolysis it yields 2 moles of D glucose. It was confirmed by Barfoed’s test: The sugar present in the test sample reduced cupric acetate to Cuprous oxide to form reddish brown precipitate.

 

Conclusion

                Biofertilizer application increases the tolerance of Blackgram to water stress compared with control and the plants treated with Rhizobium and Phosphobacterial biofertilizer contain higher level of potassium in their tissues. It might have a role in imparting stress tolerance to water. The next important is the use of Rhizobium, which produces trehalose might be another possible factor to enhance tolerance of the plant to water stress.

REFERENCES        

Alagawadi A.R., Gaur A .1988. Associative effect of Rhizobium and Phosphate solubilizing bacteria on the yield of nutrient uptake of chickpea. Plant and soil 105:241-246

Bhagwat A.1999. Biosynthesis of trehalose from maltooligosaccharides in Rhizobia. Canadian j microbial 45(8):716-721 

 Briggs LJ.1899. Electrical instrument for determining the moisture, temperature and soluble content of soils. U.6.D.A-Bull.15:200-220

Dudija S., Rahuram AL and Kundu BS.1981.Effect of Rhizobium and phosphobacteria on the  yield and nutrient uptake in chickpea. Current science.50:503-505

Perrenoud S.1990. Potassium and plant health2 nd edi.IPI Research topic.No.3 INP.Berne.

Streeter JG.1985. Accumulation of alpha, alpha –trehalose by Rhizobium bacteria and bacteroids. J. Bacteriol. 164(1):78-84  

 

CONFLICTS OF INTEREST

“The authors declare no conflict of interest”.

            

© 2015 by the authors; licensee SKY FOX Publishing Group, Tamilnadu, India. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).