INTRODUCTION. RESISTANCE TO BIOTIC STRESS. INSECT RESISTANCE. VIRUS RESISTANCE. FUNGAL AND BACTERIAL DISEASE RESISTANCE. NEMATODE RESISTANCE. CONCLUSION. REFERENCE.

1. DISEASE RESISTANT PLANTS
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. SYNOPSIS
INTRODUCTION.
RESISTANCE TO BIOTIC STRESS.
INSECT RESISTANCE.
VIRUS RESISTANCE.
FUNGAL AND BACTERIAL DISEASE
RESISTANCE.
NEMATODE RESISTANCE.
CONCLUSION.
REFERENCE.

3. INTRODUCTION
 The different type of external stresses that
influence the plant growth and development
are biotic and abiotic stresses.
 The biotic stresses are caused by – insects,
pathogen (viruses, fungi, bacteria), and
wounds.
 The abiotic stresses are due to herbicide,
water deficiency, (caused by drought,
temperature, and salinity), ozone and intense
light.
 These stresses lead to diseases.
 This damages the cellular constituents of
plant which is associated with a reduction in
plant yield.

4. The major objective of plant biotechnology is to develop plants that are resistant to biotic and abiotic stresses.

5. RESISTANCE TO BIOTIC
STRESSES
Genetic engineering of plants has led
to the development of crops with
increased resistance to biotic stresses
which is described in three major
categories-
Insect Resistance.
Virus Resistance.
Fungal and bacterial disease
resistance.

6. INSECT (PEST) RESISTANCE
It is estimated that about 15% of the
worlds crop yield is lost to insect or
pests.
The damage to crops is mainly caused by
insect larvae and to some extent adult
insects.
Till sometime ago, chemical pesticides
are the only means of pest control.
Scientist have been looking for alternate
methods of pest control for the following
reason (i.e. limitation of pesticide use).

7. RESISTANCE GENES FROM
MICROORGANISM
BACILLUS THURINGIENSIS (BT) TOXIN.
 Bacillus thuringiensis was first discovered by
Ishiwaki in 1901, although its commercial
importance was ignored until 1951.
 B.thuringiensis is a gram negative, soil
bacterium.
 This bacterium produces a parasporal
crystalline proteinous toxin with insecticidal
activity.
 The protein produce by B.thuringiensis is
referred to as insecticidal crystalline protein
(ICP).

8. BT TOXIN GENES
 Several strains of B. thuringiensis producing
a wide range of crystal (cry) proteins have
been identified.
 The cry genes are classified into large
numbers of distinct families (about 40)
designated as cry1…….cry 40, based on their
sizes and sequences similarities.
 And within same family there may be
subfamily.
 Thus, the total number of genes producing Bt
toxins (cry proteins) is more than 100.
 The molecular weight of cry proteins may be
either large (130 KD) or small (70 KDa).

9. MODE OF ACTION OF CRY
PROTEINS

10. PROBLEM OF INSECT
RESISTANCE TO Bt CROPS
 The major limitation of Bt-gene processing
transgenic plants is the development of Bt-
resistant insects.
 The Bt toxin is a protein, and the membrane
receptor (of the gut) through which the toxin
mediates its action is also a protein.
 It is possible that the appropriate mutations
in the insect gene coding for receptor protein
may reduce the toxin binding and render it
ineffective.
 This may happen within few generations by
repeated growing of Bt crops.

11. ADVANTAGES OF
TRANSGENIC PLANTS WITH
Bt GENES
 Bt genes could be expressed in all parts of
the plants, including the roots and
internal regions of stems and fruits. This is
not possible by any chemical pesticide.
 Toxic proteins are produced within the
plants; hence they are environmental
friendly.
 Bt toxins are rapidly degraded in the
environment.

12. RESISTANCE GENES FROM
HIGHER PLANTS
PROTEINASE (PROTEASE) INHIBITOR
 Proteinase inihibitors are the proteins that
inihibit the activity of proteinase enzyme.
 Certain plants naturally produce proteinase
inihibitors to provide defense against
herbivorous insects.
 Inhibitor when ingested by insects interferes
with the digestive enzymes of the insects.
 This result in the nutrient deprivation
causing death of the insects.
 It is possible to control insects by introducing
proteinase inhibitor genes into crop plants
that normally do not produce these proteins.

13. ADVANTAGES OF PROTEINASE
INHIBITOR
Many insects, not controlled by Bt, can
be effectively controlled.
Use of proteinase gene along with Bt
gene will help to overcome Bt resistance
development in plants.
LIMITATIONS OF PROTEINASE
INHIBITOR
Unlike Bt toxin, high levels of proteinase
inhibitor are required to kill insects.

14. α – AMYLASE INIHIBITOR
 The insect’s larvae secrete a gut/enzyme α
– amylase to digest starch.
 By blocking the activity of this enzyme by
α – amylase inhibitor the larvae can be
starved and killed.
 α – amylase inhibitor gene isolated from
bean has been successfully transferred
and expressed in tobacco.
 It provides resistance against Coleoptera.

15. VIRUS RESISTANCE
 Virus infections of crops may result in
retarded cell division (hypoplasia),
excessive cell division (hyperplasia), and
cell death (necrosis).
 The overall effects of virus infection are
growth retardation, lowered product yield
and sometimes complete crop failure.
 The chemical methods used to control
various plant pathogens will be ineffective
with respond to plant viruses since the
viruses are intracellular obligate parasites.

16. VIRUS COAT PROTEINS
 The virus coat protein mediated approach is the most
successful one to provide virus resistance to plants.
 It was in 1986, transgenic tobacco plant expressing
tobacco mosaic virus (TMV) coat protein gene was
first developed.
TRANSMISION PROTEINS
 It is possible to produce mutated transmission
proteins and block the spread of viruses.
 Thus the spread of insect – transmitted viruses can be
prevented by engineering crops to express a defective
virus – transmission protein.

17. ANTISENCE RNAs
 The antisense RNA approach is design to specifically
interfere with virus replication.
 It is possible to introduce viral antisense gene into plants
and produce m RNAs complementary to viral sequence
involved in viral replication.
 The antisense m RNAs can block the replication of
viruses.
RIBOZYMES
 Ribozymes are small RNA molecules which promotes
the catalytic cleavage of RNA.
 For providing virus resistance, ribozymes in the form of
antisense RNAs capable of cleaving the target viral
RNAs have been developed.

19. FUNGAL AND BACTERIAL
DISEASE
PATHOGENESIS – RELATED (PR)
PROTEINS
 To defend themselves against the invading
pathogens (fungi and bacteria), plants
accumulate low molecular weight proteins.
 Which are collectively regarded as
pathogenesis related (PR) proteins.
 Some of the most important types are
described.

20. CHITINASE
 Chitin is a constituent of fungal cell wall which can be
hydrolyzed by the enzyme chitinase.
 A bacterial chitinase gene obtained from a soil bacterium
(Serratia marcescens) was introduced and expressed in
tobacco leaves.
 The transformed plant was found to be resistant to
infection of the pathogen Rhizoctonia solani.
GLUCANASE
 Glucanase is another enzyme that degrade the cell wall
of many fungi.
 The most widely used glucanase is β – 1, 4 – glucanase.
 The gene encoding for β – 1, 4 – glucanase has been
isolated from barley, introduced, and expressed in
transgenic tobacco plants.
 This gene provided good protection against soil – borne
fungal pathogen Rhizoctonia solani.

21. RIBOSOME INACTIVATING PROTEINS (RIPs)
 Ribosome inactivating proteins offer protection against
fungal infection.
 They act on the large r RNA of eukaryote and
prokaryote ribosome (remove an adenine residue from
a specific site), and thus inhibit protein biosynthesis.
PHYTOALEXINS
 Phytoalexins are secondary metabolites produced in
the plants in response to infection.
 They are low molecular weight and antimicrobial in
nature.
 The phytoalexins usually present in specialized cells
or organelles are mobilized when infection occurs.

22. NEMATODE RESISTANCE
 Nematodes are simple worms found in the soil.
 They possess a complete digestive tract.
 The annual crop loss of the world due to
nematode (roundworm) infestation is very
high.
 It is believed that some chemical compounds
that destroy the gut of the nematode are
produced.
 Biotechnology offers sustainable solution to the
problem of the plant parasite nematode
control.
 Nematode of the family Heteroderidaecause
the most economic damage.

23. ISOLATION OF NEMATODE
RESISTANCE GENES
 Hs1Pro1 – First nematode resistant gene to
be cloned from a wild relative of a sugar
beet that confer resistant against Heterodera
schachtii.
 Mi-1 - The Mi gene of tomato confers
effective resistant against several root knot
nematode species.
 Gpa 2 – confers resistant against some
isolates of the potato cyst nematode
Globodera pallid, was cloned by a
positional cloning strategy.

24. CONCLUSION
The genetic manipulation carried out
in plants for the production of
transgenic plants.
The ultimate goal of transgenic
(involving introduction, integration
and expression of foreign genes) is to
improve the crops, with the desired
traits.

25. REFERENCE
H.S.Chawla: Introduction to plant
biotechnology.
 B.D.Singh, (2004) Biotechnology
Expending Horizons.
Bhojwani SS and Razdan MK – Plant
Tissue Culture.
Google.