The document summarizes research on the effect of Bt cotton on soil biota. Some key findings: - Studies found reductions in populations of actinobacteria, bacteria, and fungi in Bt cotton soils compared to non-Bt soils. - Different bacterial and fungal species were identified in the rhizospheres of Bt and non-Bt cotton varieties. - Dehydrogenase enzyme activity, an indicator of soil microbial activity, was lower in Bt cotton soils compared to non-Bt soils. - Counts of total soil bacteria in Bt cotton cultivation fluctuated but were generally lower than in non-Bt cotton soils over time.

2. SeminarTopic
“EFFECT OF Bt COTTON ON SOIL BIOTA”
Submitted by
GADAMBE ARUN GUNAJI
Reg No: – 2018A/105M
Research guide
Dr.R.N.Khandare
Assistant Professor
AICRP on LTFE,
Dept. of SSAC,
VNMKV, Parbhani.
Seminar In-charge
Dr. Syed Ismail
Head of Department of Soil ScienceAnd Agril.Chemistry,
VNMKV, Parbhani.

3. Introduction:-
History:-
1901:- Shigetane Ishiwatari first isolated the bacterium Bacillus thuringiensis as the
cause of the sotto disease.
1915:- Berliner reported the existence of a crystal within Bt,but the activity of this
crystal was not discovered until much later.
1956:- Researchers Hannay,Fitz-James and Angus found that the main insecticidal
activity against moth insect was due to crystal.
1958:- In the US,Bt was used commercially.
1961:- Bt was registered as a pesticide.
1996:-Bt cotton was introduced into US agriculture.

4. Why Bt Cotton?
The sucking pest complex comprising of aphids, jassids, thrips and whitefly are
widespread and fairly serious.
The bollworms are most important tissue feeders and highly damaging. Three types of
bollworms viz. American bollworm (Helicoverpa armigera), Pink bollworm
(Pectionphora gossypiella) and Spotted bollworm (Earias vitella), normally referred as
bollworm complex are by far the most damaging and loss inducing pests of cotton.
 Decrease the damage rate of bollworm complex develop Bt cotton.
(Source:-Mayee C.D. et al.CICR TECHNICAL BULLETIN NO:22)

5. What is Bt?
 The Bt is a short form of ubiquitous soil bacterioum Bacillus thuringiensis. This bacterium is gram
positive and spore forming that forms parasporal crystals during stationary phase of its growth cycle.
The synthesized crystalline proteins called ‘endotoxins’ are highly toxic to certain insects. They kill
the insect by acting on the epithelium tissues of midgut of caterpillars.
 These proteins are characterized by their insecticidal activity and are therefore grouped into four
classes i.e. Lepidoptera-specific (Cry I), Lepidoptera and Diptera-specific (Cry II), Coleoptera-
specific (Cry III) and Diptera-specific (Cry IV).
 Cotton bollworms belong to the order Lepidoptera and therefore are sensitive to Bt Cry I and Cry II
proteins, which are specific to them. Other beneficial insects are unaffected by these proteins.
 popularly and effectively utilized are Cry 1 Ac, Cry 1 Ab in different crops.
(Source:-Mayee C.D. et al.CICR TECHNICAL BULLETIN NO:22)

6. What is Bt cotton?
 A genotype or individual which is developed by the techniques of genetic engineering is referred to as
transgenic.
 In other words, genetically engineered organisms are called transgenics. A transgenic may be a plant, an
animal or a microbe.
 . Transgenic plants contain foreign gene or genetically modified gene of the same species.
 The foreign gene may be from a distantly related species, closely related species or unrelated species or
from micro-organisms such as fungi, bacteria and viruses.
 Bt cotton refers to transgenic cotton which contains endotoxin protein inducing gene from soil
bacterium Bacillus thuringiensis.
(Source:-Mayee C.D. et al.CICR TECHNICAL BULLETIN NO:22)

7. How Bt cotton is developed?
For development of transgenic of any crop, there are five important steps: -
(a)Identification of effective gene or genes.
(b) Gene transfer technology.
(c) Regeneration ability from protoplasts, callus or tissues.
(d) Gene expression of the product at desired level.
(e) Proper integration of genes so that are carried for generations by usual means of
reproduction.
(Source:-Mayee C.D. et al.CICR TECHNICAL BULLETIN NO:22)

8. The major advantage of Bt cotton are summarized below:
1.The Bt cotton has inbuilt genetic resistance to bollworms and is very effective in controlling the yield
losses caused by bollworms to a considerable extent.The resistance is governed by a single dominant
gene.
2.Use of Bt cotton reduces the use of pesticides resulting in reducing the cost of cultivation.
3.It results in improvement of yield levels and also improves margin of profit to the farmers.
4.It provides opportunities to grow cotton in areas of severe bollworm incidence.
5.It promotes ecofriendly cultivation of cotton and allows multiplication of beneficial insects
i.e.parasites and predators of bollworms.
6.It also reduces environmental pollution and risk of health hazards associated with use of insecticides
because in Bt cotton the insecticides are rarely used. An average reduction of 3.6 sprays per crop season
has been reported in Bt varieties as compared to non-Bt.
(Source:-Mayee C.D. et al.CICR TECHNICAL BULLETIN NO:22)

9. Disadvantages of Bt cotton:-
Several advantages with some limitations as well
 High cost of Bt cotton seeds makes not afforded by small and marginal farmers.
 Effectiveness up to 120 days.
 Advers effect on insecticide manufacturing companies.
 Unemployment.
 Ineffective against sucking pests like aphids,whitefly etc.
 Promote malpractices.

10. Soil biota:-
Living component present in soil is called soil biota.
Types of soil biota:-
1.Macrofauna (>2mm)
2.Mesofauna (0.1-2mm)
3.Microfauna(<0.1mm)
Functions of macrofauna :-
1.Pulverize,mix and granulate soil and incorporate o.m.into the lower
horizons.
2.Provide large channels through which air and water can move freely.
3.Partially digest organic residues and leave their excrement for microbial
degradation.

11. Functions of mesofauna:-
1.First line of attack on litter on the forest floor.
2.Important regulators of some microfaunal biomass and composition.
Functions of microfauna :-
1.Soil microfauna is important for the cycling of nutrient in ecosystem.
2.Control populations of microflora.

12. Beneficial Activities of Microorganisms in the Soil:-
1. Humus synthesis.
2. Mineralization of organic nitrogen, sulphur and phosphorus.
3. Increasing Plant Nutrients Availability (P, S, Mn, Fe, Zn and Cu).
4. Symbiotic mycorrhizal associations.
5. Production of organic chelating agents.
6. Increase oxidation-reduction reactions.
7. Increase phosphorus solubilisation.
8. Increase biological Nitrogen Fixation (BNF).
9. Increase free-living bacteria and Cynobacteria.
10.Increase associative microorganisms.
11.Increase symbiotic bacteria with legume and non-legume.
12.Promoting Plant Growth.
13.Production of plant growth hormones.
14.Protection against root pathogens and pseudopathogens.
15.Enhanced nutrient use efficiency.
16.Controlling Deleterious Microorganisms and Plants.

13. Direct and Indirect Effects of Transgenic Plants on soil microbiota:-
FIGURE 1. Direct and indirect effects of transgenic plants on soil microbiota.
(source:- Singh et al.(2016)Current Developments in Biotechnology and Bioengineering: Crop Modification, Nutrition, and
Food Production)

14. With regard to the nature of genes incorporated into the transgenic plant genome, use of an
antibiotic-resistant gene as a marker has been criticized by the World Health Organization , because
antibiotic-resistant genes may transferred to the rhizosphere and soil microbes, and then to linking
groups by horizontal gene transfer .
Deployment of transgenic crops has raised the following scientific concerns:
1. possible adverse effects on nontarget organisms.
2. gene flow into wild plant communities or soil microbiota through horizontal gene
transfer.
3. persistence of gene products or crop residues in the environment.
4. development of resistance in target microorganisms.

15. Case studies

16. Table 1: Average value of microbial counts (N = 25) in Bt and non-Bt cotton soils (vidharbha,MH.)
CFU- Colony forming unit; NS- non significant,*p<0.05;**p<0.01
(source-Tarafdar.et al Applied biological research 14 (1):00-00,2012)
Microorganisms (CFU
g-1)
Non-Bt
Cotton soil
Bt ctton
Soil
Increase(+) or
decrease(-) from
non-Bt
cotton(%)
Level of
significance
No-crop soil
Actinobacteria
( x105 )
52.5±9.7 43.6±7.3 -17.0 ** 31.8±5.9
Bacteria ( x 106 ) 85.9±8.9 73.7±8.5 -14.2 * 59.1±6.2
Fungi (x 104) 31.1±6.9 31.3±5.2 +0.3 NS 19.8±3.4
Nitrifiers (x102 ) 19.7±2.5 18.9±2.4 -4.1 NS 12.9±1.9

17. Table 2 (a)Bacterial isolates identified in rhizosphere soils of non-Bt cotton from four regions in Mahabubnagar
District,Andhra Pradesh. (Achampet, Balnagar, Nagarkurnool and Kalwakurthy)
(Source :- Pindi et al (2013), Bulgarian Journal of Agricultural Science, 19 (No 6) 2013, 1306-1310)
Bacteria
Non Bt cotton Total number
of isolates
Frequency of
isolates, %Kaveri Super nova Super
seeds
N-32
Rhizobium 26 - 26 20 72 14.06
Azospirillum Sp 20 28 22 25 95 18.55
Azotobacter 22 30 - 28 80 15.62
Actinomycetes - 22 27 29 78 15.23
Bacillus Sp 30 27 22 16 95 18.55
Pseudomonas
fluorescence
18 24 21 29 92 17.96
Total 512 100

18. Table 2(b)Bacterial isolates identified in rhizosphere soils of Bt cotton from four regions in Mahabubnagar
District Andhra Pradesh. (Achampet, Balnagar, Nagarkurnool and Kalwakurthy)
(Source :- Pindi et al (2013), Bulgarian Journal of Agricultural Science, 19 (No 6) 2013, 1306-1310)
Bacteria
Bt cotton Total number
of isolates
Frequency
of isolates,
%
Mahyco Marvel Diana Rashi
Rhizobium 18 - 18 19 55 16.17
Azospirillum Sp 15 12 18 18 63 18.57
Azotobacter 14 17 20 - 51 15
Actinomycetes 17 19 - 16 52 15.29
Bacillus Sp 13 11 16 18 58 17.05
Pseudomonas
fluorescence
18 15 14 14 61 17.94
Total 340 100

19. Table 3(a) Fungal isolates identified in rhizosphere soils of non Bt cotton from four regions in Mahabubnagar
District Andhra Pradesh.(Achampet, Balnagar, Nagarkurnool and Kalwakurthy)
(Source :- Pindi et al (2013), Bulgarian Journal of Agricultural Science, 19 (No 6) 2013, 1306-1310)
Fungi
Non Bt cotton Total number
of isolates
Frequency of
isolates, %Kaveri Super nova Super
seeds
N-32
Aspergillus Sp 22 18 22 16 78 15.11
Penicillium 23 - 25 17 65 12.59
Rhizopus 14 20 23 15 72 13.95
Fusarium 19 26 25 21 91 17.63
Trichoderma 25 24 - 17 66 12.79
Alternaria 20 19 16 18 73 14.14
Rhizoctonia 18 15 18 20 71 13.75
Total 516 100

20. Table 3(b) Fungal isolates identified in rhizosphere soils of Bt cotton from four regions in Mahabubnagar
District Andhra Pradesh.(Achampet, Balnagar, Nagarkurnool and Kalwakurthy)
(Source :- Pindi et al (2013), Bulgarian Journal of Agricultural Science, 19 (No 6) 2013, 1306-1310)
Fungi
Bt cotton Total number
of isolates
Frequency of
isolates, %
Mahyco Marvel Diana Rashi
Aspergillus Sp 10 11 12 6 39 12.95
Penicillium 10 12 16 - 38 12.62
Rhizopus 13 14 9 11 47 15.61
Fusarium 15 13 16 13 57 18.93
Trichoderma 12 17 8 9 46 15.28
Alternaria 10 10 - 8 28 9.3
Rhizoctonia 15 10 10 11 46 15.28
Total 301 100

21. Table No.4 Dehydrogenase activity (lg TPF g-1 h-1) in the rhizosphere soils under Bt (Bt) and non-Bt (NBt) cotton
crops. NC indicates no crop (IARI,New Delhi)
(Source:- Sarkar et al.(2008) Journal of Agronomy & Crop Science (2008)194,289-296).
Treatments
Crop growth period (days)
0 60 90 120 Mean
NBt 20.7 33.0 43.4 28.0 31.3
Bt 19.4 33.0 22.8 28.6 26.0
NC 20.5 27.8 21.1 25.3 23.7
Mean 20.2 31.3 29.1 27.3
LSD (P = 0.05): treatment (T) = 1.90; days (D) = 2.20; T · D = 3.81

22. Table No.5 Number (CFU’s) of total soil bacteria observed in cultivation of Bt and non-Bt cotton by replicate
and mean(Brazil)
(source:- Farnandes et al.(2019) Journal of Agricultural Science; Vol. 11, No. 4; 2019)
Soil Collection
Time
Rep 1 Rep 2 Rep 3 Mean 1 Mean 2
CFU/mL
Bt 0 D.A.S 2.75 × 10-5 3.0 × 10-5 2.5 × 10-5 2.75 × 10-5 Aa
30 D.A.S 2.5 × 10-5 2.0 × 10-5 1.8 × 10-5 2.10 × 10-5 Aab
60 D.A.S 2.9 × 10-5 2.9 × 10-5 2.0 × 10-5 2.60 × 10-5 Aab
90 D.A.S 1.7 × 10-5 1.9 × 10-5 1.9 × 10-5 1.83 × 10-5 Ab
120 D.A.S 2.0 × 10-5 2.1 × 10-5 2.1 × 10-5 2.07 × 10-5 Aab
150 D.A.S 2.7× 10-5 2.9 × 10-5 2.9 × 10-5 2.83× 10-5 Aa 2.36 ×
10-5 a
Non-Bt 0 D.A.S 2.7 × 10-5 1.3 × 10-5 2.5 × 10-5 2.17× 10-5 Aa
30 D.A.S 2.6 × 10-5 1.7 × 10-5 3.0 × 10-5 2..43 × 10-5 Aa
60 D.A.S 2.4× 10-5 1.7 × 10-5 1.5 × 10-5 1.87 × 10-5 Aa
90 D.A.S 1.4 × 10-5 2.2 × 10-5 2.1 × 10-5 1.90 × 10-5 Aa
120 D.A.S 2.3 × 10-5 2.1× 10-5 1.5 × 10-5 1.97 × 10-5 Aa
150 D.A.S 2.6 × 10-5 2.9 × 10-5 2.2 × 10-5 2.75 × 10-5 Aa 2.15 ×
10-5 a

23. Table no.6 Effects of Transgenic cotton on Soil Microbiota(Varanasi).
(source:- Singh et al.(2016)Current Developments in Biotechnology and Bioengineering: Crop Modification, Nutrition, and Food
Production)
Protein/gene plant Method Organisms Impact
Cry1Ac Cotton Plate count,enzymatic activities Soil microbes Negative effect
Cry1Ac Cotton Plate count Soil bacterial and fungal
communities
Transient effect
Cry1Ac Cotton RCR-RFLP Soil bacterial and fungal
communities
Transient effect
Cry1Ac Cotton Soil microbial biomass, enzymatic
activities
Soil bacterial, fungal and
actinomycetal communities
Cry1Ac negatively affects soil
microbial and biochemical
properties
Cry1Ac Cotton AMF colonization Mycorrizal fungi No effect on AMF colonization
Cry1Ac Cotton Plate count Rhizosperic microbial
community
Transient effect
Cry1Ab Cotton Plate count Soil microbial community Transient effect

24. Fig. 2 Activities of phosphatase, urease, dehydrogenase, phenol oxidase and protease in rhizosphere soil of a Bt transgenic
cotton and its non-Bt near-isogenic counterpart following different growth periods and in a control soil incubated without
a growing cotton plant. P1: vegetative period; P2: reproductive period; P3: senescing period; P4: whole life cycle. Vertical
bars represent – SD (n = 3)
(source:- Shen et al.(2006) Plant soil (2006)285:149-159) (China)
non-Bt Bt CK-no straw

25. Fig.3 Enzyme activities in soil incubated with different amounts of biomass from Bt and non Bt cotton and in
soil without biomass addition.Vertical bars represent ± SD (n=3). (China).
(source:- Shen et al.(2006) Plant soil (2006)285:149-159)
non-Bt Bt CK-no straw

26. Table No.7 Aerobic, Heterotrophic Microbial population density of Bt Rhizosphere soil (Tirupati)
(source:- Audiseshamma et al.(2014)International Journal of Current Microbiology and Applied
Sciences(2014)3(5):289-294)
S. No Sample
Microbial population Density (Cfu / gm soil)
Bacteria Fungi Actinomycetes Yeasts
1. Bt Rhizosphere
soil
27(±3)×104 29×104 27×102 48×104
2. Non Bt
Rhizosphere Soil
41×104 18×104 32×102 18×104

27. Table no.8 Beneficial Microbial population Density in Rhizosphere soils of Bt and Non Bt cotton(Tirupati)
(source:- Audiseshamma et al.(2014)International Journal of Current Microbiology and Applied
Sciences(2014)3(5):289-294)
S.
No
Types of organisms
Bt Rhizosphere
(Cfu/gm soil)
Non Bt Rhizosphere (Cfu/gm soil)
1 Symbiotic Nitrogen fixing bacteria 7×106 11×106
2 Asymbiotic nitrogen fixing bacteria
Azospirillum
Azatobacter
15×103
78×104
28×103
20×104
3 Phosphate Solubilizing bacteria 35×104 43×104
4 Cellulase degrading bacteria 28×104 27×104

28. Figure.4a Distribution of Microbial populations in Bt cotton soils(Tirupati)
Figure.4b Distribution of Microbial populations in Non Bt cotton soils
(source:- Audiseshamma et al.(2014) International Journal of Current Microbiology and Applied Sciences(2014)3(5):289294)

29. Fig.5A Distribution of beneficial microbial population in Bt Cotton soils(Tirupati)
Fig.5B Distribution of beneficial microbial population in Non Bt Cotton soils
(source:- Audiseshamma et al.(2014) International Journal of Current Microbiology and Applied Sciences(2014)3(5):289294)

30. Table no. 9. Effect of cultivation of Bt cotton on soil microbial population (log10 CFU g-1) (Warangal,TS.)
(source:-Surapaneni et al.(2015) Green Farming Vol. 6 (6) : 1297-130
Microbial
population
(log 10
CFU g-1)
Soil under
non-Bt
cotton
Soils under
Bt cotton
for
2-5 years
Soils under
Bt cotton
for >8
years
Significan
ce
Range Mean±Std
dev
Range Mean ±Std
dev
Range Mean ±Std
dev
Total
microbial
population
3.2-7.3 4.8-±1.3 3.2-8.8 6.2±1.9 3.0-9.3 6.25±1.8 NS
Pseudomon
as (PSB)
3.3-5.3 4.1±0.7 3.1-5.6 3.6±0.7 3.1-7.4 4.4±1.5 NS
Azotobacter 4.0-5.4 4.6±0.6 3.0-5.3 4.1±0.5 4.0-6.7 4.8±0.8 NS
MBC(mg kg
-1)
74.8-186.0 141.4±34.8 125.1-
250.9
150.9±34.3 96.7-385.2 173.3±68.6 NS

31. Table 10: Effect of Bt and non Bt cotton on soil microbial population in Perambalur district,Tamilnadu (Mean
values of ten villages in eachtalukas).
(Source:- Sherene et al.(2018) Biological Forum – An International Journal 11(1): 18-23(2019)
Sr.
No
Talukas General microflora in Bt cotton
grown soils (CFU /g)
General microflora in non Bt cotton
grown soils (CFU /g)
Bacteria
× 106
Fungi × 103 Actinomycete
s × 10 3
Bacteria
× 106
Fungi × 103 Actinomycetes
× 10 3
1. Veppanthattai 42 15.0 4.8 29 14.7 3.8
2. Perambalur 58 14.3 4.0 33 13.8 2.8
3. Alathur 30 14.8 5.2 25 12.0 2.9
4. Veppur 35 16.5 5.7 25 14.3 3.1
Range values 30-58 14.3-16.5 4.0-5.7 25-33 12.0-14.7 2.8-3.8
SD 8.034 1.491 0.56 4.877 1.913 0.814

32. Table 11: Effect of Bt and non Bt cotton on soil microbial respiration and Dehydrogenase activity in soils of
Perambalur district,Tamilnadu (Mean values of ten villages in eachtaluks).
(Source:- Sherene et al.(2018) Biological Forum – An International Journal 11(1): 18-23(2019).
ss
S.No. Talukas Bt cotton grown soils Non Bt cotton grown soils
DHA
(µg TPF/ g / h
Soil respiration
µg of CO2/ g / h
DHA
(µg TPF/ g / h
Soil respiration
µg of CO2/ g / h
1. Veppanthattai 0.2137 224 0.071 164
2. Perambalur 0.2281 264 0.068 181
3. Alathur 0.1983 308 0.075 202
4. Veppur 0.1739 286 0.079 201
Rangevalues 0.174 -0.228 224-308 0.068-0.079 168-202
SD 0.024 26.464 0.006 16.494

33. Table no. 12 Impact of GM cotton on soil biochemical and biological characteristics (IARI,New Delhi)
MBC microbial biomass C, MBN microbial biomass N, MBP microbial biomass P, TOC total organic carbon, MQ
microbial quotient, PNM potential nitrogen mineralization, NS not significant.
(source:- Sarkar et al.(2008)Environment Monit Asses(2009)156:595-604)
Biological and biochemical Percent increase (+)
characteristics or decrease (−)
MBC +44.6
MBN +53.6
MBP +104
TOC NS
MQ +37
PNM +21.5
Nitrification +11.4
Nitrate reductase +35.3
Alk-phosphatase +24.1
Acid-phosphatase +16.3

34. Figure 6 a&b. Effects of Bt and non-Bt cotton on soil enzyme activities (a) soil urease; (b) soil dehydrogenase.
**P < 0.01. Error bars (± SD) with the same letters within the cotton genotypes do not differ significantly.
(CICR,Nagpur)
(source:- Velmourougane et al.(2013) Plant soil Environment Vol.59,2013,No.3:108-114).

35. Table No. Bacterial populations in soil rhizosphere of 06Z604D expressing both cry1Ac and cry2Ac genes at
five different crop growth stages at
(source: Swilla et al.(2015)African Journal of BiotechnologyVol.15(21) pp.930-939)
(source: Swilla et al.(2015)African Journal of Biotechnology Vol.15(21) pp.930-939)
Mean rhizosphere culturable bacterial population (Cells/g
dry Soil)
Treatment Sampling
time (DAS)
0 64 110 154 175
06Z604D (Bt) 1.85x105 3.32x105 4.32x105 5.74x105 5.46x105
99M03 (Isoline) 1.97x105 2.92x106 8.12x104 9.58x105 1.06x106
HART89M
(Conventional)
1.78x105 3.56x105 8.91x104 5.21x105 6.23x105
Table no.13. Bacterial populations in soil rhizosphere of 06Z604D expressing both
cry1Ac and cry2Ac genes at five different crop growth stages at Thika CFT
site(Thika ,Kenya).

36. Table 14. Comparisons of colony counts on soils from the rhizosphere of the three different cotton lines (Miles
and Misra drop plate method). (Thika,Kenya)
(source: Swilla et al.(2015) African Journal of Biotechnology Vol.15(21) pp.930-939)
Treatment Bacteria Actinomycetes Fungi
06Z604D (Bt) 2.38x105 4.81x105 5.61x105
99M03(Isoline) 4.48x105 5.98x105 4.91x105
HART 89M
(Conventional)
CD (p=0.05)
3.77x105 5.72x105 5.43x105

37. Table no.15.Effect of cry proteins on soil microbial population and diversity(CICR,Nagpur)
(source:- Velmourougane et al.(2017)CAB Reviews 2017 12,No.046)
Microorganisms
Cry protein
Experimentation Conclusions
Culturable bacteria and fungi Cry1Ac Bt and non-Bt cotton A significant, increase in numbers in soil with Bt
cotton
Microbial population and diversity Cry1Ac Bt and non-Bt cotton Higher microbial population and diversity in Bt
cotton
Total microbial population Cry1Ac Bt and non-Bt cotton No adverse effects
Microbial functional diversity Cry1Ac Bt and non-Bt cotton No adverse effects
Culturable functional bacteria Cry1Ac Bt and non-Bt cotton No significant differences in numbers after the
growing season
Methylobacteria Cry1Ac Bt and non-Bt cotton No adverse effects
Microbial diversity Cry1Ac Bt and non-Bt cotton No adverse effects
Culturable functional bacteria Cry1Ac Multiple-year cultivation of Bt
cotton
No adverse effects
Composition of soil microbiota Cry1Ac Bt and non-Bt cotton More extensive fungal colonization, higher
ratios of fungi to bacteria, and different types of
fungal spores in soil with Bt cotton

38. Table no.16. Estimation of Microbial Population by Viable Plate Count method and MPN method (Nagpur)
(source:- Ekta et al.(2016) International Journal of Agriculture Sciences Vol.8,Issue 53,2016,pp-2708-2710)
Sr.No.
Soil sample with different
treatment/ variety
MPN method/gm of soil
(dilution factor)
Viable Plate Count /gm of soil (dilution
factor)
Total Associative
Nitrogen Fixers (10 5)
Heterotrophic
population
(10 7)
Phosphate
Solubilizers(10 2)
1 Bt cotton V1 3.9 x 10 5 38 x 10 7 15 x 10 2
2 Non Bt cotton V1 2.0 x 10 5 28 x 10 7 11 x 10 2
3 Bt cotton V2 6.3 x 10 5 86 x 10 7 7 x 10 2
4 Non Bt cotton V2 3.3 x 10 5 19 x 10 7 4.3 x 10 2
5 Bt cotton V3 16.0 x 10 5 55 x 10 7 12 x 10 2

39. Figure 7. Bacterial population (cFu log10 g−1 of soil) at four locations (Punjab)
Non Bt cotton varieties –CIM-591 and CIM-573
(source:-Yasin et al.(2016) plant production science,2016)
Bt cotton varieties –CIM-602 and CIM-599

40. Photos 1 A-D: Scanning electron micrographs of conventional or non-Bt (A and C) and Bt cotton stubble
residues (B and D) retrieved from field incubation after 4 weeks (A and B) and 12 weeks (C and B) at
Narrabri(Kenya).
Fig. A (non-Bt) Fig.B (Bt)
s
(source:-Watson et al.(2004) Ecological Impacts of Genetically Modified Organisms)

41. Fig.C (non Bt)
(source:-Watson et al.(2004) Ecological Impacts of Genetically Modified Organisms)
Fig.D (Bt)

42. Photo 2C. Close-up SEM picture of Bt and non-Bt cotton stubble showing fungal spores (Kenya)
Fig.E (non-Bt) Fig.D(Bt)
(source:-Watson et al.(2004) Ecological Impacts of Genetically Modified Organisms)

43. Conclusion:-
 Some studies indicate that Bt cotton has no negative effect on soil biota and may even have beneficial
effects,while some have reported adverse effect.
 Some soil specific microbial populations were affected by Bt cotton and some specific microbial populations
were unaffected.
 Cultivation of Bt cotton expressing Cry1Ac gene had no adverse effect on soil biological activities such as
microbial population,soil respiration,dehydrogenase activity.
 Bt toxins from Bt and transgenic crops had no apparent effect on soil microorganisms such as
bacteria,fungi,algae,nematode and protozoa.
 Bt cotton had no harmfull effects on soil enzyme activities.
 Growth of Bt cotton has a positive effect on most of the microbial,biochemical indicators and enzyme
activities.
 Some soil specific microbial populations were affected by Bt cotton and some specific microbial populations
were unaffected.

44.  Studies based on Cry1Ac –expressing proteins in the laboratory and field based studies reported “ no” ,
“significant” and a “ transient effect” of Bt crop on soil microbial communities.
 Cultivation of Bt cotton either for prolonged period (> 8 years ) or for short terms (2-5 years) did not bring out
any significant change in the population of total microbes, Azatobacter, Psuedomonas and soil enzyme activity
in rhizosphere soil, when compared to non Bt cotton cultivation.
 Cultivation of Bt cotton did not affect the diversity of the soil bacterial population.