Direct Action Against The Pathogen Genetic Modification Of The Host To Resist Modification Of The Environment To Make It Unfavorable For Diseases Development.

1. PLANT DISEASE CONTROL
T.HARI MURALI KRISHNAA
19PY21
Ayya Nadar Janaki Ammal College, Sivakasi.
Department Of Microbiology.

2. OUTLINE
• The cultivation of crop plants to meet his requirements for food,
clothing, and shelter.
• PRINCIPAL TO DIEASES MANAGEMENT ARE:
• Direct Action Against The Pathogen
• Genetic Modification Of The Host To Resist
• Modification Of The Environment To Make It Unfavorable For Diseases
Development.

3. PLANT QUARATINE
Can be defined as a legal restriction on the movement of agricultural
commodities for the purpose of exclusion, prevention or delay in the
establish of plant pest and disease in areas where they are not
known to occur.
 the first plant quarantine regulation was perhaps promulgated
France in 1660 to suppress and prevent the spread of barberry plant.
• 1912-U.S.A- destructive insect and pest control.
• 1990 – Europe – late blight
• 1940- Netherland – bunchy top
• 1914- India – pest and insect

4. SEED TREATMENT
• Making improvements in managing pests and diseases
like brown rust, and increasing the productivity,
improving sprouting and emergence of buds that are
carried out through seed coating, seed treatment with
solution of sea water and lime, and seed priming
methods respectively.
• Pre-Soaking hydration:
• Treatments of water absorbing type include uncontrolled and controlled
systems.
• Three different techniques are used for controlled absorption of water:
priming with solutions, solid matrix, and manual controlled water.

5. • Seed Coating technologies: (Using polymeric seed coating technique increases the percentage of germination
through direct fertilizing of the soil )
• Applying a film coating on the surface of seeds. (special material covers the surface of
seed ).
• Seeds coating technologies include two methods : pelleting and coating.
• Pre-germination: it takes several weeks or months for knots to be formed by rhizobia
bacteria. However, through seed coating technology the bacteria are close enough to
budding area that lead to an early knot forming.
• Nutrients: in seed coating process seeds are provided with a healthy environment in
which the growing energy during the initial stages will be increased.
• Protection against stress, animals, birds, and fertilizers.
• Smart Seed Coating techniques: (Maize planters know for sure that every minute is
critical during the planting period)
• The coating takes the form of a rigid shell around the seed. When the seeds are put
into the cold soil, no water can penetrates into this shell. So, there will be no budding
unless the temperature reaches to 55 degrees Fahrenheit when the shell loses its
shape and allows penetration of water. This process is reversible and repeatable, thus
will be able to protect the seed against cold weather.

6. • Seed Pelleting or rounding:
• The pelleting process is mostly performed by clay or organic-based
fillers.
• using polymers in pelleting process increases the potassium content in
crops, and also their anti-fungus characteristics minimize any potential
damage to plant.
• germination process accomplishes in three phases:
• 1) Water absorption by seed,
• 2) Delaying phase,
• 3) Radicle growing through emergence of test.
• Found that seed treatment by GA3 with content of 50 ppm carried out prior to planting, can
improve root length, budding proportion, vigor of plant, particularly for fennel seeds of low
quality. (The most common adjusters are Cycocel, Ethephon, Gibberellic, Cytokinin, and Indol
Acetic Acid (IAA).
• Treatment by osmotic solutions:
• Treating maize seeds by polyethylene glycol or potassium salts like KNO3 and
K2HPO4 on speeding the germination process in cold temperatures like 10
degrees Celsius.

7. • Biophysical Methods:
• Applying electricity, magnet, unicolor lights, beams, and ultrasound waves can
widely stimulate the plants growing. This technique is called electroplanting.

8. CULTURAL PRACTICES:
• The term cultural control describes the activities of humans
aimed at controlling disease through the cultural manipulation of
plants.
Selection and preparation of planting materials:
• Destruction of crop residues
• Elimination of living plants that carry pathogens
• Crop rotation
• Tillage practices
• Sowing and harvesting practices
• Intercropping
• Mulching and soil amendments
• Flooding
• Irrigation
• Fertiliser applications and crop nutrition
• Strip farming
• Trap and decoy crops
• MisceIIaneou s practices

9. Destruction of crop residues:
Burying, burning and removal of postharvest crop
residues are important cultural control practices performed during
intercrop periods. If crop residues are buried, some potential
pathogens may be either killed or inhibited in their development.
Fungal pathogens such as Sclerotinia and
CLautcepsw hich produce sclerotia can be controlled to some
extent by burying surface soil.
• Sclerottum oryzae (stem rot)
• Curuul.ariaLunata (black mould)
• Corticium sasaki (sheath blight)
• flag smut (Urocystis agropgri) on wheat
• Septori"a auenae on oats
• Rhyncosporium secalis on barley
• Pgrenophora teres

10. Elimination of living plants that carry pathogens:
• For example- grasses such as Hordeum Leportnum are hosts of the wheat
take-all fungus GaeumannomAces graminis.
Crop rotation:
• Rotations are most likely to be effective in controlling pathogens such as
GaeumannomAces graminis, Pgrenophoratritici-repentis, various
CoLLetotri"chumand Phoma spp. and some pathogenic bacteria which
only survive in the presence of a specific host.
• controlling damping-off and root-rot fungi such as Pythium and
Aphanomgces, Fusartum spp.
Tillage practices:
• Tillage may also influence nutrient release mechanisms and the total effect is often
expressed as increased crop vigor.
• Tillage incorporates various types of organic matter including crop residues, manure,
green manure, volunteer crop plants and weeds into the soil.

11. Sowing and harvesting practices:
• Many crop plants tend to be more susceptible to attacks by various
parasites at certain stages of their development.
Intercropping:
• Intercropping, the growing of a crop or crops between the rows of another
crop, is more common on smaller farms and is very popular in China.
• Bacterial blight (Xanttnmonas carrLpestns pv. manihotis) is decreased.
Mulching and soil amendments:
• Mulching, the application of a covering layer of material to the soil surface,
is a commonly used cultural practice, especially in horticulture. Natural
materials used for mulching include cereal straw and stalks, crop debris,
sawdust, leaves, grass, manure, weeds, reeds, Spanish moss and various
aquatic plants.

12. CHEMICAL CONTROL
SULPHUR:
Is the earliest known fungicide. It is particularly useful
against powdery mildews, used either as dust or as a spray.
COPPER:
Used for fungicide, used in plant protection , mixed with
Bordeaux.
TERRAZOLE:
Effective against certain seedling diseases of maize,
tomato, potato and cucumber.

13. THIABENDAZOLE:
Is effective against post – harvest diseases of sweet orange. It
is also effective against sugar beet leaf spot caused by Cercospora
beticola.
NEMATICIDES:
carbon disulphide is perhaps the earliest chemical used as a
soil fumigant for checking the growth of nematodes. Choropicrin has
been in use in a limited scale in greenhouse and nursery beds for
nearly three decades.
Methyl Bromide
Dichloropropene (DD)
Ethylene Dibromide (EDB)
DD and EDB mixture was intro in after world war

14. OILS:
Banana wilt caused by Mycospharella musicola is controlled by
oils. In light viscosity.
mainly mineral oils from petroleum and to limited extent,
Glyceride oil (from plants)
synthetic oil
SAFENER, SPREADER, and STICKER:
Safener is a chemical which reduce the phytotoxicity of another
chemical. E.g., Copper Sulphate is reduced by lime. Glyceride oils
also good safeners.
which improve the contact between the fungicide and the
sprayed surface. E.g., Glyceride oils , Mineral oils, and Soaps.
sticker is a substance added to spray or dust which improves its
adherence to plant surfaces. E.g., Arabic, Oils, Dextrin are commonly
used as stickers.

15. DEVELOPMENT OF DISEASE
RESISTANT VARIETIES
• In many cases, growing resistant crop varieties is the only method to control diseases,
and perhaps is the ideal one.
HISTORY
• With the rediscovery of Gregor Mendal’s findings by de Vries in Holland, Correns in
Germany and Tschermark in Austria almost simultaneously in 1900, the science of
genetics had a rebirth. Though there are earlier reports on the possibilities of obtaining
varieties resistant to diseases, systematic studies to select varieties for disease
resistance started only during 1900, and the credit for this goes of W.A Orton of the united
states department of agriculture, who for resistant varieties against bunt and smut of
wheat.

16. • Term disease tolerance.
Disease outcome is determined by the three-way interaction of
the pathogen,
plant
environmental conditions.
Defense-activating compounds can move cell-to-cell and
systematically through the plant's vascular system. However, plants don't
have circulating immune cells, so most cell types exhibit a broad suite
of antimicrobial defenses. Although obvious qualitative differences in
disease resistance can be observed when multiple specimens are
compared (allowing classification as “resistant” or “susceptible” after
infection by the same pathogen strain at similar inoculum levels in similar
environments), a gradation of quantitative differences in disease resistance
is more typically observed between plant strains or genotypes. Plants
consistently resist certain pathogens but succumb to others; resistance is
usually specific to certain pathogen species or pathogen strains.

18. Common disease resistance mechanisms:
• Pre-formed structures and compounds
Plant cuticle/surface
Plant cell walls
Antimicrobial chemicals (for
example: glucosides, saponins)
Antimicrobial proteins
Enzyme inhibitors
Detoxifying enzymes that break down pathogen-
derived toxins
Receptors that perceive pathogen presence and activate
inducible plant defences

19. • Inducible post-infection plant defenses
Cell wall reinforcement (cellulose, lignin, suberin, cell wall proteins
Antimicrobial chemicals, including reactive oxygen species such
as hydrogen peroxide or peroxynitrite, or more
complex phytoalexins such as genistein or camalexin.
Antimicrobial proteins such as defensins, thionins, or PR-1
Antimicrobial enzymes such as chitinases, beta-glucanases,
or peroxidases.
Hypersensitive response - a rapid host cell death response
associated with defence mediated by "Resistance genes."

21. BIOLOGYCAL CONTROL
MYCOVIRUSES:
a few viruses present in fungi successfully attack fungi and destroy
them. For example, culture filtrate of Penicillium stoloniferum destroys
Agaricus bisporus.
MYCOPARASITE:
Pseudomononas flurescens when sprayed on rice seedlings effectively
reduce infection by Pyricularia oryzae.
MYCONEMATICIDE:
A few fungi feed on nematodes. Genera of fungi such as Arthrobotrys,
Harposporium are predacious on nematodes and kill them.

22. PGPR
• Plant Growth Promoting Rhizobacteria (PGPR) are a group
of bacteria that enhances plant growth and yield via
various plant growth promoting substances as well as
biofertilizers.
• PGPR as biofertilizers are well recognized as efficient soil
microbes for sustainable agriculture and hold great
promise in the improvement of agriculture yields.
• PGPR genera exhibiting plant growth promoting activity are:
Pseudomonas, Azospirillum, Azotobacter, Bacillus,
Burkholdaria, Enterobacter, Rhizobium, Erwinia,
Mycobacterium, Mesorhizobium, Flavobacterium, etc. This
article presents perspectives on the role of PGPR in agriculture
sustainability.

23. PGPR as Biofertilizers:
Increased yield, solubilization of P (phosphorus) or K
(potassium), uptake of N (nitrogen) and some other elements
through inoculation with PGPR.
Phytohormones PGPR
• Indole-3-acetic acid (IAA) - Acetobacter diazotrophicus
andHerbaspirillum
seropedicae
• Zeatin and ethylene - Azospirillumsp.
• Gibberellic acid (GA3) - Azospirillumlipoferum
• Abscisic acid (ABA) - Azospirillum brasilense

24. PGPR Crop parameters
• Rhizobiumleguminosarum - Direct growth promotion of canola and lettuce
• Pseudomonas putida - Early developments of canola seedlings, growth
stimulation of tomato plant
• Azospirillum brasilense and A. irakense - Growth of wheat and maize plants
• P. flurescens - Growth of pearl millet, increase in growth, leaf nutrient
contents and yield of banana (Musa)
• Azotobacter and Azospirillumspp. - Growth and productivity of canola
• P. alcaligenes, Bacillus polymyxa, - Enhances uptake of N, P and K bymaize crop and
Mycobacterium phlei
• Pseudomonas, Azotobacter - and Stumulates growth and yield of chick pea (Cicer
• Azospirillumspp. arietinum)R. leguminismarum - and Improves the yield and phosphorus uptake in wheat
Pseudomonas spp.
• P. putida, P. flurescens, A. brasilense - Improves seed germination, seedling growth and
• A. lipoferum - yield of maize
• P. putida, P. fluorescens, P. fluorescens, - Improves seed germination, growth parameters of
• P. putida, A. lipoferum, A. brasilense - maize seedling in greenhouse and also grain yield
of field grown maize

25. • Siderophore Production:
• PGPR are reported to secrete some extracellular metabolites called
siderophores.
• The presence of siderophore-producing PGPR in rhizosphere
increases the rate of Fe3+ supply to plants and therefore enhance the
plant growth and productivity of crop. Further, this compound after
chelating Fe3+ makes the soil Fe3+ deficient for other soil microbes and
consequently inhibits the activity of competitive microbes.
• The ability to produce siderophores (as discussed above) that chelate iron, making it
unavailable to pathogens. The capacity to synthesize anti-fungal metabolites such as
antibiotics, fungal cell wall-lysing enzymes, or hydrogen cyanide, which suppress the
growth of fungal pathogens. The ability to successfully compete with pathogens for
nutrients or specific niches on the root; and the ability to induce systemic resistance.

26. PGPR Disease resistance
• Bacillus pumilus, Kluyvera cryocrescens, Cucumber Mosaic Cucumovirus (CMV) of tomato
• B. amyloliquefaciens and B. subtilus (Lycopersicon esculentum)
• B. amyloliquefaciens, B. subtilis and Tomatomottle virus
B. pumilus
• B. pumilus Bacterial wilt disease in cucumber (Cucumis
• sativus), Blue mold disease of tobacco (Nicotiana)
• Pseudomonas fluorescens Sheath blight disease and leaf folder insect in rice
• (Oryza sativa), Reduce the Banana Bunchy Top
• Virus (BBTV) incidence, Saline resistance in
groundnut (Arachis hypogea)
• B . subtilis and B. pumilus Downymildew in pearl millet (Pennisetum
glaucum)
• B. subtilis CMV in cucumber
• B. cereus Foliar diseases of tomato
• Bacillus spp. Blight of bell pepper (Capsicum annuum), Blight
of squash
• Burkholderia Maize (Zea mays) rot
• B. subtilis Soil borne pathogen of cucumber and pepper (Piper)
• Bacillus sp. and Azospirillum Rice blast
• Fluorescent Pseudomonas spp. Rice sheath rot (Sarocladium oryzae)