Studies on association of arbuscular mycorrhizal fungi with gluconacetobacter diazotrophicus and its effect on improvement of sorghum bicolor (L.)

M Meenakshisundaram & K Santhaguru / Int J Cur Sci Res. 2011; 1(2): 23 - 30.

1 pots (four seedlings/ per pot) in to sterilized soil and sand
mixtures. Each seedling received 50g of mycorrhizal inoculum and
5ml of bacterial suspension. Twenty two treatments (three pots
each) resulting from different combinations of G.diazotrophicus
with ten species of AM fungi were established as follows: 1, Control
(without inoculation)2, Entrophospora infrequens 3, Gigaspora
albida 4, Glomus albida 5, Glomus dimorphicum 6, Glomus
tubaeformis 7, Glomus fasciculatum 8, Glomus mosseae 9, Glomus
macrocarpum 10, Scutellospora heterogamma 11, Sclerocystis
pachycaulis 12, G.diazotrophicus 13, G.diazotrophicus +
Entrophospora infrequens 14, G.diazotrophicus + Gigaspora albida
15, G.diazotrophicus + Glomus albida 16, G.diazotrophicus + Glomus
dimorphicum 17,G.diazotrophicus + Glomus tubaeformis 18,
G.diazotrophicus + Glomus fasciculatum 19, G.diazotrophicus +
Glomus mosseae 20, G.diazotrophicus + Glomus macrocarpum 21,
G. diazotrophicus + Scutellospora heterogamma 22,
G,diazotrophicus + Sclerocystis pachycaulis.

Treatments were arranged in a completely randomized design.
After inoculation, plants were grown for 35 days under controlled
conditions. Control and AM inoculated plants received once a week
Hoagland's nutrient solution [21] .Treatments inoculated with
G.diazotrophicus, singularly or in combination with AM fungi,
received once a week a modified Hoagland's solution (without
NH4NO3) and with 1g 1-1CaCO3 added to stabilize the pH).
Deionized water was added when needed.

2.8.Plant measurements and analyses

The plants were harvested at 35 days after inoculation with
G.diazotrophicus and root, stem and leaves were cut in to bits for
determination of dry matter yield, N, P, photosynthetic pigments,
and soluble sugars. Dry matter yield was determined by the drying
plant parts in an oven at 90°C for 3 days, N was measured by
macro-kjeldahl mehod [22] , acid soluble P was estimated by the
modified method of [23], total soluble sugars by anthrone method
[24] and phtosyntetic pigments of fresh leaf tissue was estimated
following the method of Arnon [25].

2.9.Statistical analyses

The data were subjected to statistical analysis by using
IRRISTAT package for one way analysis of variance (ANOVA) and
Duncan's Multiple Range Test (P,<0.05) [26].

3.Results

3.1.Soil characteristics

Soil samples collected from the rhizosphere of S.bicolor grown
in Paravai, Samanatham, Kovilpatti, Dindigul and Kannivadi were
analysed for pH, electrical conductivity, available nitrogen,
availablable phosphorus, and available potassium content (Table-
1). The soil pH ranged from 5.4 to 6.2 and the electrical
conductivity ranged from 0.07 to 0.41dsm-1. The phosphorus (10
to 28mg/ kg soil) and potassium (137 to 500 mg/kg soil) content of
soil were high and the nitrogen content was low (49/to 71 mg/kg
soil).

The FDA guidelines for tuna, mahi-mahi and related fish
specified 5 mg/100 g as defect action level [13] and >50 mg/100 g
as toxicity level [49,13]. The European Economic Community
(ECC) has recently established regulation for species of fish
belonging to the Scombridae and Clupedae families and
fixed a three-class plan for maximum allowable levels of histamine
in fresh fish (n=9; c=2; m = 100 ppm; M = 200 ppm) and
enzymatically ripened fish products (n = 9; c = 2; m = 200 ppm; M =
400 ppm) where n is the number of units to be analyzed from each
lot, m and M are the histamine tolerances, and c is the number of
units allowed to contain a histamine level higher than m but lower
than M [50].

Table 1. Source and Characteristics of soil

EC=Electrical Conductivity

N=Available Nitrogen

P=Available Phosphorus

K=Available Potassium

Nitrogen

0 to 113 mg/kg soil     - Low

113 to 181 mg/kg soil - Medium

181 above mg/kg soil - High

Phosphorus

0 to 4.5 mg/kg soil       - Low

4.6 to 9.0 mg/kg soil     - Medium

9.0 above mg/kg soil     - High

Potassium

0 to 46 mg/kg soil       - Low

47 to 113 mg/kg soil    - Medium

113 above mg/kg soil - High

3.2.Identification of G.diazotrophicus and AM fungi

Effective strains of G.diazotrophicus were assessed in the
sugarcane plant samples collected from Madurai districts, Tamil
nadu, India. For preliminary screening, the cultures were isolated
using LG1, a medium specifically used for G.diazotrophicus
isolation [5]. The formation of orange colour colony on LG1 medium
was taken as prime criterion to identify the G.diazotrophicus
isolates. The isolates were maintained on LG1 agar slants.

Arbuscular Mycorrhizal fungal spores were isolated from
rhizosphere of Sorghum bicolor grown in different localities of
southern districts of Tamil Nadu using wet sieving and decanting
technique and identified as Entrophospora infrequens, Gigaspora
albida, Glomus albida, Glomus dimorphicum, Glomus tubaeformis,
Glomus fasciculatum, Glomus mosseae, Glomus macrocarpum,
Scutellospora heterogamma and Sclerocystis pachycaulis
3.3.Mycorrhizal infection and G.diazotrophicus effect on fungal
colonization

Among the 10 species of AM fungi viz Entrophospora infrequens,
Gigaspora albida, Glomus albida, Glomus dimorphicum, Glomus

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