1. Seeds contain stored nutrients that make them attractive to pathogens and predators. To protect themselves, seeds have evolved natural defense mechanisms including physical defenses like thick seed coats, and chemical defenses like secondary metabolites and protective proteins. 2. Biological mechanisms also protect seeds, such as beneficial microbes that live within or on seeds and provide disease resistance. Induced systemic resistance is another biological defense where bacteria, chemicals or pathogens induce broad plant defenses. 3. Additional strategies include seed dormancy, dispersal mechanisms, and avoidance techniques like producing seeds at times that avoid peak predator activity. The combination of physical, chemical, and biological defenses helps seeds survive in challenging environments.

1. 1

2. on
Prashanth solabannavar.
PGS10AGR5363 2

3. 3
Why seeds need defense?
Seeds contain Stored protein, lipids and
carbohydrates – seedling growth
These are attractive to pests and
pathogens plus specialized fungal
pathogens which require a specific host
to general feeders such as bacteria,
mammals birds and insects.

4. 4
In general a plant molecule is a defensive mechanism
against pathogens when-
Its synthesis is induced in response to pathogen
challenge.
Its expression level is dependent on specific race –
cultivar interactions and / or
Shows antimicrobial activity either in vivo or more often
in fungal or bacteria growth inhibition assays
(Kombrink and Somssich, 1995)

5. 5
Natural mechanisms employed to
protect seeds against:
Insects, fungi, bacteria, birds and other
predators.
Seeds are extremely valnerable,
particularly to fungal attack and use of
chemical treatment for successful
establishment
(Baskin & Baskin, 1998)

6. 6
Dispersal mechanism.
Avoidance
Physical defense-seed coat
Biological control
Systemic acquired resistance
Chemical defense-secondary metabolites
Protective proteins-enzyme inhibitors
Lectins
Chitinase
seed-Pathogen interactions
NATURAL DEFENSE MECHANISMS OF SEEDS

7. 7
 By the development
of flat, thin, lateral
expansion of wings.
Eg: Spathodea,
Cedrela
 By the development
of tufts of hairs
Eg: Calotropis .
Dispersal by wind

8. 8
By persistent feathery
styles
Eg: Naravelia,clematis
Seed being very
small in size as in
orchids, poppy
and Argemone.
Wind dispersal
of dandelion seeds

9. 9
Fruits and seeds dispersed by water have
thick outer coat.
In some cases pericarp contains airspaces
so that fruits are light and float easily
Eg. coconut, cerbera
In some cases thalamus itself gets
detached and floats in water. Eg: lotus
In some seeds- spongy aril.
Eg: water lily
Dispersal by Water

10. 10
In some sps.seeds are,
coloured in a deceptive manner,
birds mistake these seeds for
insects and carry them away.
Later on they are dropped when
the birds find them of no use.
Eg: Castor- dark purple colour,
Xanthium – spines
Dispersal by Animals
In some cases the fruits are
provided with spines and hooks.
Eg: Bidens – Pappas in the form
of hooks,

11. 11
Seed predation is an important ecological process
that can affect the reproductive success of individual
plants, the dynamics of plant population (Crawly,
1992)
In the defense of seeds from predators, plants have
developed different strategies that could be grouped
in to 3 basic types
o Mechanical
o Chemical
Predation

12. 12
Mechanical predation
 The presence of spiny trunks in some species has been
interpreted as an adoption to prevent climbing rodents
from reaching seeds (Herrera,1984)
 The existence of fleshy or lignified tissues around seeds
could be an efficient barrier that prevents predator
access to seeds.
 Hard, spiny, hairy fruits and those that produce sticky
gum when damaged can protect seeds, reducing the
frequency of attack by predators.
 Presence of hard seed coat reduces the probability of
predation (Alcantara et al., 2000)

13. 13
Chemical Predation
 Some chemicals alter insect hormonal balance
(edycsone and juvenile)
 Other products are toxic with different
actuation mechanisms (cyanogenic glycosides,
alkaloids, proteins)
 Others simply reduce the fruit and seeds
palatability (cucurbitacins) or diminish their
nutritional quality (tannins).

14. 14
 It consists of variations in the temporal
distribution of seed production within a
reproductive season or among different
years.
Eg. producing seeds before or after the best
environment condition exists for predators
may result in a fraction of a seed crop not
beigning exposed to the predation
Albrectsen ( 2000)

15. 15
Devices for survival of seeds
Dormant embroyonic plant with in the seed
of most kinds of plant is protected by a seed
coat until conditions are favourable for new
growth to start.
Struggle for existence is reflected ( shapes,
structures, size of seeds and fruits) on
morphology of seeds.
Some seeds resist prompt germination, so
assures survival if conditions are
unfavourable Eg: gint foxtail.

16. 16
Delayed shedding of the seeds - eg. Achenes
Seeds with impermeable seed coats, which resist
germination for long periods
eg: Legumes
Some produce pods in which one segment remains
indehiscent – closed and the seed within it remains
dormant for a long time
eg: Xanthium
Contd..
Stefferud, (1991)

17. 17
Seeds vary in germination rate both among
species and within individual seed lots.
Longer seeds remain in soil ungerminated
reduced predation by animals or insects.
Seeds that germinate rapidly and establish
healthy seedlings pass through vulnerable
stages quickly, minimizing expose to attack
by seed scavengers and also from seed and
seedling diseases.
Avoidance

18. 18
Seed priming increases germination rate is
credited with reducing susceptibility to seed
diseases, because seeds are vulnerable to
attack for shorter period of time compared to
slower germinating unprimed seeds
Welbaum et al.(1998)

19. 19
Table.1 Effect of pre sowing seed treatment in
Sunflower cv. 7-1A.
Treatments Germination
(%)
Vigour
index
Seed yield
(q/ha)
T1
T2
T3
T4
T5
83.3
77.0
79.0
81.3
80.7
1895
1844
1819
1862
1879
11.02
9.42
8.63
10.86
8.58
CD at 5% 0.6 139 0.52
T1- hydration for 24 hours
T2- cold hydration at 100C for 72 hours and seed drying
T3- Hydration with GA3 and drying
T4- Hydration followed by seed dressing with Thiram
T5- control
Khan et al. (2003)

20. 20
Physical Defense
In seeds – specialized tissues – provide a physical
barrier to protect against pathogenic attack.
Thick seed coats with lignin or trichomes provide
barrier to predation of insects and animals.
Baskin and Baskin (1998)
Structure and architecture of some seed coats delays
or inhibits the growth of hyphae as well.
In muskmelon seeds, microbial growth around the
seed during imbibition is inhibited due to nutrient
leakage from the embryo creates a semi-permeable
endosperm cell wall
Welbaum and Bradford (1990)

21. 21
Thick cell walls of the endosperm
tissue provide a physical barrier to
slow the penetration of fungus in
lettuce and cucurbits.
Yim and Bradford (1998)

22. 22
Resistance system localized to the interior of the
seed coat in cotton
When seed is infected by a fungus, the hyphae
penetrate the chalaza but do not immediately invade
the embryo. Rather they grow on the inner portion of
the seed coat.
Histochemical staining of the nucellus reveals that
there is heavy localization of tannins in that part
attached to the chalaza where the fungus failed to
invade the embryo on entry into the seed.
Halloin, (1983)

23. 23
Contd..
This localized tannin may serve to protect the
embryo from attack by micro-organism.
The cotton phytoalexins gossypol and hemi-
gossypol were produced in cotyledons of
germinating seeds and in seeds exposed to
prolonged rainfall in the field, but were not
produced in the seeds incubated at 20 per cent
seed moisture. Indicating that phytoalexins
important for protection of imbibed or
germinating seeds.
Halloin (1983)

24. 24
 Some of the organisms that are used for biological control
of plants are free living bacteria or fungi in the
rhizosphere.
 Other biological organisms are endophytes that exist inside
the plant that may or may not be seed transmitted.
Sturz and Nowak ( 2000)
 Bacterial endophytes can improve growth and reduce
disease symptoms caused by several plant pathogens
129 sps with more than 54 genera of Pseudomonas,
Bacillus, Enterobacter and agrobacterium being most
commonly isolated genera
Hollman et al.(1997)
Biological Control

25. 25
Beneficial microbes may increase disease
resistance, denovo synthesis of fungi toxic
metabolites at sites of attempted fungal penetration
is increased
Benhamau et al. (1996)
Bacteria Pseudomonas produces metabolites that
are implicated in the control of damping off, flax wilt
and take – all diseases
Dowling and Gara (1994)
Seed endophytes are mainly associated with
protected sites near the seed coats and they may
have colonized this region through small openings
in the coat of cotton and sweet corn
McInory and Kloepper (1995)

26. 26
 Endophytic migration apparently began
as the bacteria moved through the
germination slit into the starchy endosperm
 From the endosperm, the bacteria
colonized the radicle and coleoptile before
spreading systemically through the entire
plant when introduced as seed treatments
Hilton and Bacon( 1995)

27. 27
Hanson (2000)

28. 28
Drum priming technology allows concurrent seed
hydration and application of beneficial microbes
as well
Rowse (1996)
Biological seed treatments are apparently best
suited to augment established consortia of
microbial organisms created as that of long term
strategy of harmonizing crop selection and
management practices
Sturz & Nowak (2000)

29. 29
Table. 2 Effect of treatments with Bacillus spp. and T.harzianium strains
on diseases in pepper plants.
Year Treatment P.Capsici root rot
Severity %
Rhizoct. root rot
Severity%
2000
2001
Not treated
HS93
LS674
T. Harzianium
Not treated+chitin
HS93 + Chitin
LS674 + Chitin
T. Harzianium + Chitin
Not treated
HS93
LS674
T. Harzianium
Not treated+chitin
HS93 + Chitin
LS674 + Chitin
T. Harzianium + Chitin
5.0
3.9
4.8
4.7
5.0
2.95
5.00
4.8
4.8
3.95
4.65
4.5
4.75
2.5
4.6
4.4
2.3
1.6
1.3
1.4
1.3
0.7
0.4
0.5
1.95
1.7
1.15
1.1
1.25
0.6
0.45
0.4
Ahmed et al. (2003)
Healthy plant-0 Dead plant-5.0

30. 30
Induced Systemic Acquired Resistance (SAR) is the
ability of a bacterium, chemical, insect or virus to
induce broad plant defense mechanisms that lead to
the systemic resistance to a number of pathogens
Sticher et al.(1997)
Salicylic acid and its derivatives have been used
extensively in agril. to induce SAR.
Gorlach et al.(1996)
Attempts to induce SAR in ungerminated seeds by
priming or treatment with SAR inducing agents has
produced mixed results
Sher and Wesbaum (1999)
Systemic Acquired Resistance

31. 31
Table. 3 Plant showing defense through SAR and ISR.
Plant Inducer organism SAR ISR Systemic
protection against
Alfalfa Colleto trichum
lindemuthianum
+ - Colleto trichum
lindemuthianum
Aspangus Tobacco necrosis
virus
+ - Tobacco necrosis
virus
Arabidopsis Pseudomonas
flurescens
- + Furasium
oxysporium f.
raphani
Barley Erysiphe/gramins + - Erysiphe/gramins
Carnation Pseudomonas spp. + - Fusarium
Cucumber C lagenarium + - C. lagenarium
Radish P fluresuns - + Fusarium
Oxysporium
Stitcher et al. (1997)

32. 32
Table.4 Signals for SAR.
1. Salicilic acid Decreases Symptoms of TMV
2. Jasmonates Mediation of the plant responses to stresses such as
pathogen and herbivore attack.
Induce proteinase inhibitors, like thionins osmotin,
proline rich cell wall protein and different enzymes
involved in plant defense reactions.
3. Systemin Induces denovo synthesis of proteinase inhibitors.
Induces synthesis of m-RNA for an asparatic protease
in tomato.
4. Ethylene Exogeneous application of ethylene to tobacco
carrying the ‘N’ gene for resistance to TMV results in
resistance to TMV marked by a decrese in the size of
the necrosis.
Can induce some of the PRs such as
β-1, 3 glucaunse and chitinase.
Sticher et al. (1997)

33. 33
A pictorial comparison of the two best characterized forms of induced resistance in plants, both which lead to similar phenotypic responses.
Systemic acquired resistance, induced by the exposure of root or foliar tissues to abiotic or biotic elicitors, is dependent of the phytohormone
salicylate (salicylic acid), and associated with the accumulation of pathogenesis-related (PR) proteins. Induced systemic resistance, induced
by the exposure of roots to specific strains of plant growth-promoting rhizobacteria, is dependent of the phytohormones ethylene and jasmonate
(jasmonic acid), independent of salicylate, and is not associated with the accumulation of PR proteins (or transcripts). However, both responses
are intertwined molecularly, as demonstrated by their reliance on a functional version of the gene NPR1 in Arabidopsis thaliana

34. 34
Seed dormancy
Dormancy of seeds contributes to seed deterioration
resistance and thereby helps in prolonging the longevity.
Although dormancy may not contribute resistance to
microbial degradation, it could aid in preventing
degradative changes of seed origin.
In red wheat, exhibited dormancy and absence of
sprouting damage due to flavanols which functioned not as
direct inhibitors of germination but rather as contributors
to the hypoxia of the embryos.
ABA act as a germination inhibitors in developing wheat
embryos.
Sorghum infected by Fusarium had a higher incidence of
sprouting damage than uninfected heads. Thus, the seeds
resistant to this fungus may be better able to maintain
dormancy and sustain sprouting damage.
Halloin (1983)

35. 35
Seeds contain many minor constituents that are not
used during germination. Many of these compounds
are inhibitors of insect and animal predation.
Alkaloids, such as theobromine, caffeine, strychnine,
brucine and morphine are natural compounds that
protect seeds from insect or animal
Bewley and Black (1994)
Glucosides are bitter componets in some seeds.
Eg: amygdalin in almonds, peaches and plums and
esculin from horse chesmut, saponin in Tung seeds.
Chemical defense: Production of Secondary metabolites

36. 36
Phenolic compounds like coumarin and chlorogenic acid and
their derivatives such as ferulic, caffeic and sinapic acids
occur in the coats of many seeds. These compounds are
germination inhibitors that maintain quiescence in seeds
that contain them and leachout into the soil to inhibit
germination of neighbouring seeds
Bewley and Black (1999)
In barley, Thionin, endochitinases, ribosomal
inactivating proteins, β-glucanase, non-specific lipid transfer
protein, lectin, peroxidase, thaumatin- related antifungal
proteins and inhibitors or α-amylase and proteinases
Shewry and Lucas (1997)

37. 37
Protective proteins- Enzyme Inhibitors
Class I
Directly change the properties of extracellular matrix
and therby strenthens, repairs or alters the cell wall
environment
 HRGPs- Hydroxy Proline rich glycoprotein
 GRPs – Glycine rich proteins
 Suberin,
 Lignin,
 Wall bound phenolics
 Callose
Classes of defense related proteins

38. 38
Class II
Directly act as deterrents and exhibit anti
microbial activities
Amylase & protienase inhibitors
Toxic proteins like lectins & thionins
Hydrolases such as chitinases, β 1,3
glucanases & proteinases
Class III
Proteins which are structurally related to
wound proteins
Protein products of wun 1 & win 1 genes

39. 39
 Of the 12 families of plant proteinases, all
(except 3) of them have been detected in
seeds and all but one of these are serine
proteinases that offer protective mechanism
Shewry (2000)
 Proteinase inhibitors are abundant in
legumes (Soybean) seeds, two classes of
serine proteinase inhibitors have anti-
nutritional effects in feeding trials unless
inactivated by processing
Domoney (1999)

40. 40
Invitro tests and expression in
transgenic plants show that
cysteine proteinases provide
resistance to insects, nematodes
and mollusks that use cysteine
endo-proteinases for digestion
Shewry (1999)

41. 41
RIP-Ribosome inactivating proteins
CHI- chitinase
BGL- β Glucanase
R
o
b
e
r
t
Leah et al. (1991)

42. 42
Lectins
 Lectins are carbohydrate-binding proteins
that bind glycons of glycoproteins, glyolipids
or polysaccharides with high affinity.
 Seed lectins have been shown to kill or
inhibit certain insect pests either in feeding
studies or in transgenic plants. The mode of
action for lectins is not fully understood but
may involve impaired function of membranes
in the digestive tract
Shewry (2000)

43. 43
Table 5. Defense properties of proteins in the PHA
and chitin binding families
Phytohemagglutinin
PHA-E
PHA-L
αAl
Arcelin
Toxic to mammals and birds
Toxic to mammals and birds
Toxic to weevils
Toxic to weevils
Chitin binding
WGA
Rice lectin
Datura lectin
Tomato lectin
Nettle lectin
Hevein
Chitinase
Toxic to weevils, European corn
borer and Southern corn root worm
Toxic to weevils
Toxic to weevils
Toxic to weevils
Toxic to weevils, inhibitory to fungi
lnhibitory to fungi
lnhibitorv to fungi
Maarten et al. (1991)

44. 44
Chitin and plant defense
 Chitin is an insoluble polysacclaride, it is a
compoent of fungal cell walls and also the
cuticles of insects and nematodes.
 Another group of proteins that have a role in
seed defense are endochitinases and
 β-1-3-gluconases which often, but not
alldays occur together
Gomez et al.( 2002)

45. 45
Chitin has not been found in higher plants or
mammals, but plants and mammals produce a
wide array of chitinases that are homologous to
the ones in chitin containing organisms,
some plant chitinases are expressed only during
seed maturation or flower and fruit
development.
These constitutive chitinases are typically
expressed in non vegetative organs such as
seeds.
Takakura et al.( 2000)

46. 46
Major natural role plant chitinases from vegetative
tissues is defensive against pathogens either directly
through their antifungal properties or indirectly through
the release of chitin oligomers .
Chitinase expression is often induced by microbial
attack, causing many chitinases to be classified as
pathogenesis related proteins of the PR-3, PR-4, PR-8 and
PR-11 families
Bol et. al., (1990)
Co-expression of barley chitinase and other defense
proteins in transgenic tobacco incresed quantitative
resistance to fungal diseases
Jach et al. (1995)

47. 47
Family Type member Properties
PR-1 tobacco PR-1a antifungal?, 14-17kD
PR-2 tobacco PR-2
class I, II, and III endo-beta-1,3-
glucanases, 25-35kD
PR-3 tobacco P, Q
class I, II, IV, V, VI, and
VII endochitinases, about 30kD
PR-4 tobacco R
antifungal, win-like proteins,
endochitinase activity,
similar to prohevein C-terminal
domain, 13-19kD
PR-5 tobacco S
antifungal, thaumatin-like proteins,
osmotins, zeamatins, permeatins,
similar to alpha-amylase/trypsin
inhibitors
PR-6 tomato inhibitor I protease inhibitors, 6-13kD
PR-7 tomato P69 Endoproteases
PR-8 cucumber chitinase
class III
chitinases, chitinase/lysozyme
Table. Recommended Classification of Pathogenesis-Related Proteins (PRs)

48. 48
PR-9 lignin-forming peroxidase
peroxidases, peroxidase-like
proteins
PR-10 parsley PR-1
ribonucleases, Bet v 1-related
proteins
PR-11 tobacco class V chitinase endochitinase activity
PR-12 radish Ps-AFP3 plant defensins
PR-13 Arabidopsis THI2.1 Thionins
PR-14 barley LTP4
nonspecific lipid transfer
proteins (ns-LTPs)
PR-15 barley OxOa (germin) oxalate oxidase
PR-16 barley OxOLP oxalate-oxidase-like proteins
Table. Recommended Classification of Pathogenesis-Related Proteins (PRs)

49. 49
Classification and characterization of seed
chitinases
Seed Chitinase isoforms have been
described in distantly related families such
as Apiaceae, Fabaceae poaceae, Fagaceae
and pinaceae
Gomez et al. ( 2002)
Many chitinases are expressed during seed
development with mRNA synthesis typically
beginning at early or mid maturation stages
Leah et. al., (1991)

50. 50
Chitinase inhibition of Insects:
Plants that constitutively expres chitinase
would be anticipated to be resistant to
insects and fungi because this exposure to
chitinase might digest chitin in the gut lining
of herbivores of palnt pathogenic bacteria.
Chitinases isolated from cowpea seeds
apparently have the ability to inhibit the
growth of Collectotrichum lindemuthianum
and C. musae and affect the development of
cowpea weevil in an artificial seed system.
Gomes et al., (1996)

51. 51
OTHER ANTIFUNGAL SEED PROTEINS
Thionins,
Glucanases,
Non specific lipid transfer proteins,
Osmatins,
Ribosome inactivating proteins,
Polygalacturonase-inhibiting proteins,
2S Alburmin storage proteins,
Chitin binding proteins,
 Lectins and
 Other low cysteine rich antimicrobial peptides
Shewry, (2000)

52. 52
Chitin, is an in soluble β(1-4) linked –
acctyl-d-glucosamine, polysaccharide
occurs in wide range of organisms.
It serves a structural role in fungal cell
walls and also in arthropod caticles,
including those of insects, nematodes and
erustaccans.
However, cutin has not been found in
higher plants or in mamals. Nerutheless,
plants produce a wide array of chitinases
homologus to those found in chitin
containing organisms.
Chitinase and seed defense

53. 53
Chitinase expression is often induced by
microbial attack and in fact, many chitinases
have been classified as pathogenesis-related
proteins of the PR-3, PR-4, PR-8 and PR-11
families.
Chitinases are expressed only at well defined
developmental stages, such as seed maturation
or flower and fruit developmet. These are called
constitutive chitinases.
Plant chitinases can be classifical into four
major families encdoded by chia, chib, chic and
chid genes.
Gomez et. al., (2002).

54. 54
Gomez et al. 2002

55. 55
Toxins and seed defense
 Ricin is a powerful protein toxin found in
Ricinus communis.
 Ricin is present in all parts of the plant but is
particularly concentrated in the seeds.
 The toxin could be used as a biological
weapon.
 Purified toxin is found in crystalline form, as
a dry lyophilized powder, or dissolved in
liquid.
 Ricin acts as inhibiting protein synthesis.

56. 56
Seed-Pathogen Interaction
 Plant pathogen usually express several virulence
functions that increase their ability to colonize damage
host plants
 Virulence of the pathogen and resistance of plant are
reciprocal concepts
 General mechanisms such as production of enzymes,
toxins or plant growth regulators that damage or alter
plant cells and provides optimal environment for the
pathogen
Salmond (1994)

57. 57

58. 58

59. 59

60. 60
Conclusion
Seeds are dispersed in nature by wind, water and animals, in turn it
gives protection against predation and other unfavourable
environmental conditions.
Presence of spiny trunks in some species that has been
interrupted to prevent climbing of rodents from reaching seeds.
The existence of fleshy or lignified tissues around seeds could be
an efficient barrier that prevents predator access to seeds
Large seeds usually have a higher probability of being depredated
than smaller ones
Thick seed coats, some with lignin or trachomes provide barrier
that inhibit predation by insects and animals
Biological seed treatment with Tricoderma virens could be reduce
the symptoms of Verticelium wilt in cotton

61. 61
Contd……
Use of high vigour seeds results in rapid establishment and decreases soil
borne diseases and predators.
PR’s like PR-1, β-1,3 glucanases (PR-2), chitinase (PR-3), PR-4 and osmotin
(PR-%) showed antimicrobial activities in tobacco
Salicylic acid reduce the disease symptoms caused by TMV in tobacco
Seed Lectins have been shown to kill or inhibit certain insect pests
Serine protienases act as inhibitors for certain microbes in legume seeds
( soybean )
Secondary metabolited protect seeds from insects and animal predation
Defense gene manipulation will be another tool available for improving
defense responses of seeds

62. THANK YOU