Today insect pests have been one of most important problem
in food production. Previous research have been proved that 1/3
of agricultural production of world, prized at several billion dollars
is ruined by damaging of field and storage insect pests every
year. Various toxic, broad-spectrum and synthetic chemicals are
used to control pests. Natural ecosystem, human health and our
environment can be affected due to excessive use of these harmful
chemicals. So now biologically based approaches are developing
to control insect pest instead of toxic and synthetic chemicals
which are ecofriendly, cost-effective and useful and reliable. There
are different types of bio pesticides such as arthropods natural
enemies (predators, parasitoids, and parasites), entomopathogens
(bacteria, fungi, virus and nematodes), insect hormones and plant
derived bio pesticides.
Role of Biotechnology
It is a set of techniques for manipulation of living organisms
or their components to produce useful commercial products such
as new bacterial strains, pest resistant crops. There are various
techniques are used in biotechnology like biological fixation of
nitrogen, tissue culture and organic pest control. Previous research
have been proved that Bacillus thuringiensis (Bt) was discovered
in 1906 by mortality of silkworm larvae. Bacillus thuringiensis
stands out on the world stage since 1938, when first product
was formulated with this pathogen released in France. In 1911 A
German scientist Berliner succeeded to detach and characterize this
bacterium has cylindrical shape and “thuringiensis” named after
German region “Thuringia”. In1938 France formulations having
bacteria colonies was sold as an insecticides. In 1954 Mode of
action was revealed and its usage today. Bt is known as soil bacteria
which is found in different countries, Gram positive, aerobic and its
family is bacilaceae.
It can sporulate to survive when environmental conditions
become adverse and unfavorable. This is found in dead insects,
plants and debris. This produces sporangia containing endospores
and crystalline inclusions of proteins (CRY) which are responsible
for their action against lepidopterans insects. This Crystal is
composed of polypeptide protein that is called endotoxin. When
larvae feed on such proteins initiates the number of reactions that
kills them.
Biotechnology Better Than Insecticides:
Recent researches have been found that insect pests are major
problem for agricultural crops, and losses due to diseases and insect
pests are very high.to manage insect pests we use various harmful
agrochemicals day by day on large scale and use bio pesticides just
on small scale. Survival of natural enemies (predators, parasitoids
and parasites), human health, beneficial insects, and environment
are badly affected by unselective use of chemicals. It also produce
resistance in insects against agro chemicals. On the other hand,
Bio pesticides used over a country which is less harmful for
environment and human beings than synthetic chemicals. To
control insect pests’ new strategy has been developed which
consists of genetically modified plants resistance against insects,
and they are similar and effective like conventional insecticides. In
1986 the first experiments with genetically modified (GM) plants
were made in the United States and in France.
The first variety marketed a vegetable species produced by
genetic engineering was the “FlavrSavr Tomato” developed by
the American company Celgene and marketed from 1994. 1987-
2000 there were more than 11,000 field trials in 45 countries and
tested were corn, tomatoes, soybeans, canola, potatoes and cotton,
and development of safer and more effective technologies genetic
features announced were herbicide tolerance, product quality,
virus-resistance and resistance to insects (Table 1).
Table 1: Worldwide Area of Biotech Crops from 1996-2016.
Area of Biotech Crops in developing and industrial
countries:
In 2016, 19 developing countries cultivated 54% biotech crops
on 99.6 million hectares out of worldwide biotech cultivation area
while 46% biotech crops were planted on 85.5 million hectares
in industrial countries.A new biotech crop rice which is grown in
developing countries (Table 2).
Table 2: Area of Biotech Crops in developing and industrial countries.
Mode of Action of Cry in Bt Cotton:
This protein is inactive protein. This requires Alkaline Ph. (7.5-
8) for activation. This is only harmful for lepidopterist insects and
not for sucking insects and other organisms because lepdopterous
insects have this alkaline ph. medium which is required for
activation of Cry. When insect attacks on cotton plant this toxin
enters into body and become activate. Active toxin binds with
protein receptors on epithelial cells within midgut. Then this toxin
forms pores and puncture the midget so insect will be die due to
starvation.
Major applications of Cry toxins
i. Control of deflator pests
ii. Control of mosquitoes which cause a vector for human
diseases