Symptoms, Sign and Identification of disease

Course- B.Sc. (Agri.)

Subject- Principles of Plant Pathology

Unit-2

Symptom and sign

Symptom - are the expression of the disease caused by the

manifestation of the physiological reaction of the plant due to

harmful activity of the pathogen

Sign-Physical evidence of the presence of disease agent (e.g.,

mold or fungel spores, bacterial ooze)

Syndrome

Defined as sequential appearance of disease symptoms ona plant during the development of the disease or sum total ofsymptoms exhibited by a disease

Fleck or necrotic spot

Uredial pustule

Telial pustule

Death of organ or plant

Local infection:

An infection affecting a limited part of a plant e.g. leaf spot.

Systemic infection:

infection that spread point of infection to different parts of the

plants e.g. wilts, virus infection, loose smut

Lesion

A localized necrotic or chlorotic areas of diseased tissue/ organ.

Local lesion:

A localized spot produced on a leaf upon mechanical inoculation

with a virus.

Types of symptoms

Morphological symptoms

Histological symptoms

Morphological symptoms

Morphological: (Externally detectable symptoms caused by any

pathogen e.g. blight, leaf spot

– Necrosis

– Hypoplasia

– Hyperplasia & Hypertrophy

Necrosis degeneration of protoplast followed by death of the

tissue or organ or plant

Plesionecrosis (Nearly dead): necrotic symptoms

expressed before the death of the protoplast are calledplesionecrosis.

E.g. yellowing, hydrosis, wilting

Holonecrosis: necrotic symptoms expressed after the death ofthe protoplast are called holonecrosis. In this the affected tissueturns brown in colour

E.g. Rots, spots, blights

Plesionecrotic symptoms

• Yellowing

• Wilting

• Hydrosis

Yellows/ yellowing

• Appearance of uniform or non-

uniform yellowing of leaves due to

infection. it is the result of

breakdown of the chlorophyll

• E.g. fungi (e.g., celery yellows),

viruses (e.g., sugar beet yellows

virus), bacteria (e.g., coconut lethal

yellowing), protozoa (e.g., hart rot),

spiroplasmas or phytoplasmas

http://archive.agric.wa.gov.au/objtwr/imported_images/f06891e.gif

Fig-1

Browning of vascular tissues Wilt

Wilt

A symptom characterized by loss of turgor, which results indrooping of leaves, stems, and flowers.

e.g. bacterial wilt of tomato

Pathological wilt: caused by pathogen-fungus, bacteria and viruses

Physiological wilt: due to water stress and high temperature

http://www.container-gardening-for-you.com//image-files/tomato-wilt-1.jpg

http://uconnladybug.files.wordpress.com/2010/08/dsc01536.jpg

Fig-2

Fig-3

Hydrosis: appearance of watersoaked trnasluscent diseasedtissues whose intercellularspaces contains liquid. This typeof symptoms precedesholonecrotic symptoms

http://www.hawaiiplantdisease.net/glossary/Hydrosis_%28water_soaking%29.htm

Fig-4

Holonecrotic symptoms

May develop on any part of the plant and generally the infected

tissues turns brown.

Holonecrotic symptoms can be divided into three categories

– Necrosis of the green plant parts

– Necrosis of the storage organs

– Necrosis of woody tissues

Necrosis of the storage organs

– Rots

– Leak:

– Mummification:

Necrosis of thegreen plant parts leadsto formation of numberof disease symptomslike:

Restricted necrosis

– Damping off

– Spots

– Shot holes

– Speck or fleck

– Blotch

– Streaks

– stripes

Damping-offIs the collapse and death ofseedlings due to extensivenecrosis of stem tissues beforeor after they emerge from thesoil (pre-emergence andpostemergence damping-off,respectively). caused byPythium and Rhizoctonia ,

http://agropedia.iitk.ac.in/sites/default/files/icrisat/Rhizoctonia_Damping-Off.JPG

Fig-5

Leaf spot: A well defined or self-limiting grey, brownnecrotic lesion on a leaf

http://www.forestryimages.org/browse/detail.cfm?imgnum=5360387

http://www.ipm.iastate.edu/ipm/info/files/images/plantdisease/12/27.jpg

Fig-6Fig-7

Veinal necrosis and local lesions BCMNV

http://cropgenebank.sgrp.cgiar.org/images/management/common_bean_smogs/bsmv.png

http://extension.udel.edu/weeklycropupdate/files/2011/09/SVNV1.jpg

Fig-8

Fig-9

Shot hole- When a necrotic tissue with in a leafspot cracks and

fall off, leaving small holes in their place

http://www.kiwicare.co.nz/content/images/312/255x255crop/shot-hole-1.jpg

Fig-10

Blotch

A necrotic area covered with brown fungus mycelium onleaves, shoots, and stems

http://www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2012/19hrt12a6f3.JPG

http://aces.nmsu.edu/pubs/_circulars/CR538/images/Fig07_Purple_blotch.jpg

Fig-2

Fig-11Fig-12

Streaks and stripe mosaic virus symptoms

http://img.scoop.it/dRMheLe_NSXiYKNogG9MUjl72eJkfbmt4t8yenImKBVvK0kTmF0xjctABnaLJIm9

http://cropgenebank.sgrp.cgiar.org/images/management/wheat_smogs/barley_stripe_mosaic_virus_%28bsmv%29.jpg

Fig-13 Fig-14

Necrosis of woody tissues

Die back: extensive necrosis of shoots from top/ tip to down ward e.g. die back

of chilli/ citrus

Cankers: Necrosis of the bark tissues e.g. citrus canker

Gummosis: Oozing of gum like secretions from the woody tissues: Gummosis of

stone fruits

Guttation

http://www.apsnet.org/publications/apsnetfeatures/Article%20Images/Huanglongbing_Fig01.jpg

Die back: extensive necrosis of

shoots from top/ tip to down

ward e.g. Die back of chilli/

citrus

http://agropedia.iitk.ac.in/sites/default/files/uas%20raichur/Die%20back%20symptoms.jpg Fig-15

Fig-16

Canker

Formation of sharply

delineated, dry, necrotic,

localized lesions on the stem

due to death of cambium

tissue of bark, or (in non-

woody plants)

http://idtools.org/id/citrus/diseases/images/fs_images/04CitrusCanker.jpg

Fig-17

https://c1.staticflickr.com/5/4062/4712129326_8df483a871.jpg

Stem Canker

http://vegetablemdonline.ppath.cornell.edu/Images/Tomato/Tom_BacCanker/Bacterial-cankerNecSpots.jpg

Bacterial canker

of tomato

Fig-19Fig-18

Gummosis

A plant disease in which the lesions exude a sticky

liquid.

http://cdn.c.photoshelter.com/img-get/I0000i9kw_zx62Wo/s/600/600/510205.jpg

http://plant.daleysfruit.com.au/l/citrus-graft-sap-3420.jpeg

Fig-20 Fig-21

Guttation

Exudation of water from plants, particularly along theleaf margin

http://th06.deviantart.net/fs70/PRE/i/2012/018/

3/c/morning_guttation_by_do7slash-

d2qj6xn.jpg Fig-22

Extensive necrosis

Blights

Scald

Scorch

Blast

Anthracnose

Firing

Blight

A disease characterized by rapid and extensive death (Necrosis) of

plant foliage. A general term applied to any of a wide range of unrelated plant

diseases. (e.g., chestnut blight, fireblight, late blight, halo blight)

http://themountaineer.villagesoup.com/media/Common/17/E2/1172128/Early%20Blight.jpg

Fig-23

Blast : it is sudden death of unopened bud or inflorescence

http://agropedia.iitk.ac.in/sites/default/files/13_1.bmphttp://www.greaterkashmir.com/news/2008/N

ov/4/images/news_4_11_2008_2.jpg

Fig24

Fig-25

Anthracnose

Formation of discrete, dark colored, necrotic lesions on the

leaves, stems, and/or fruits. caused by fungus: Colletotrichum sp.

http://www.invasive.org/collections/viewcollection.cfm?id=81953

https://extension.illinois.edu/photolib/lib1

7//midsize/anthracnose%20-

%20silver%20maple.jpg

Fig-26 Fig-27

Necrosis of the storage organs

• Rots

• Leak

• Mummification

Rot

The softening, discoloration, and often decay or disintegrationof a succulent plant tissue as a result of fungal or bacterialinfection.

http://www7.inra.fr/hyp3/images/6032562.jpgFig-28

Leak: exudation of juice from tissues with soft rot is called leak

http://pesticideguy.files.wordpress.com/2013/05/06-fire-blight_-apple.jpg

Fig-29

Hyperplastic & Hypertrophic symptoms

Hyperplasia

A plant overgrowth due to increased cell division.

Hypertrophy

A plant overgrowth due to abnormal cell enlargement.

Wound tumors

• Galls

• Witches Broom

• Enations

Tumor

An uncontrolled growth of tissue or tissues

Gall

An abnormal plant structureformed in response to parasiticattack by certain microorganisms(bacteria, fungi, viruses) or insects.Galls may develop either bylocalized cell proliferation orincrease in cell size.

http://upload.wikimedia.org/wikipedia/commons/9/9e/Agrobacteriumgall.jpg

http://www.delange.org/Fruit_Tree_Disease_Arizona/Blackberry_Crown_Gall_Agrobacterium_tumefaciens.jpg

Fig-30

Fig-31

Enation

A symptom caused by certain plant viruses in which thereare small outgrowths on the plant

Leaves of pea (Pisum sativum cv. Dark Skinned Perfection) infectedwith Pea enation mosaic virus (PEMV)

http://lindagilkeson.com/Book%20Images/foliage_adj/146%20pea%20enation%20mosaic%20virus.jpg

Fig-32

Hypoplastic symptoms

Atrophy/ Hypoplasis/ dwarfing/ Stunting

Rosette: in this the internodes do not enlarge and leaves

are clustered like petals of rose e.g. Peach rosette,

ground rosette

Albication: Complete repression of colour caused by viruses, bacteria, fungi, and iron deficiency

Mosaic; appearance of dark green and light green areas on leaves e.g. Tobacco mosaic

Chlorosis: failure of chlorophyll to develop fully.

Atrophy or stunting

http://bugwoodcloud.org/images/768x512/1235015.jpg

Fig-33

Chlorosis

The loss of chlorophyll from the tissues of a plant, resulting from

microbial infection,

e.g. viral infection, the action of certain phytotoxins, the lack of

light, to magnesium or iron deficiency, etc.

Chlorotic tissues commonly appear yellowish

MosaicAppearance of dark green, light green pattern or sometimeschlorotic areas on leaves due to virus infection

Downy mildew

Formation of superficialcottony hyphal growth withspores generally on underside of the leaf

Powderymildew

http://www.redbudlanenursery.com/portals/0/IDM/DownyMildewLeaf.jpg

Downy mildew

https://ediblesanmarcos.files.wordpress.com/2010/06/100_08631.jpgFig-34

Fig-35

Ergot

Sclerotia that replaces the grain in a diseased inflorescence

Disease of certain grasses and cereals, especially rye, caused by

Claviceps purpurea

Smut

Appearance of masses of dark, powdery, and sometimes odorous

spores on inflorescence

e.g. stinking smut of wheat, common smut of maize.

Rust

Rust A disease giving a “rusty” appearance to a plant and causal

agents form rust-colored spores

Rust

http://hgtv.sndimg.com/HGTV/2012/01/11/RX-DK-LGC11203_rust-disease_s4x3_lg.jpg

ErgotSmut

http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Article%20Images/ergot03.jpg

Fig-36Fig-38Fig-37

http://www.cavalieragrow.ca/wp-content/uploads/2014/08/loosesmutwheatb.jpg

Refererances

Books

Principles of Plant Pathology by R.S. Singh

Web Resources

www.tnau.com

Image Resources

Fig1- http://archive.agric.wa.gov.au/objtwr/imported_images/f06891e.gif

Fig2- http://uconnladybug.files.wordpress.com/2010/08/dsc01536.jpg

Fig3 http://www.container-gardening-for-you.com//image-files/tomato-wilt-1.jpg

Fig 4- http://www.hawaiiplantdisease.net/glossary/Hydrosis_%28water_soaking%29.htm

Fig 5- http://agropedia.iitk.ac.in/sites/default/files/icrisat/Rhizoctonia_Damping-Off.JPG

Fig 6- http://www.forestryimages.org/browse/detail.cfm?imgnum=5360387

Fig 7- http://www.ipm.iastate.edu/ipm/info/files/images/plantdisease/12/27.jpg

Fig 8-http://cropgenebank.sgrp.cgiar.org/images/management/common_bean_smogs/bsmv.png

Fig 9- http://extension.udel.edu/weeklycropupdate/files/2011/09/SVNV1.jpg

Fig 10- http://www.kiwicare.co.nz/content/images/312/255x255crop/shot-hole-1.jpg

Fig 11- http://www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2012/19hrt12a6f3.JPG

Fig 12- http://aces.nmsu.edu/pubs/_circulars/CR538/images/Fig07_Purple_blotch.jpg

Fig 13-http://img.scoop.it/dRMheLe_NSXiYKNogG9MUjl72eJkfbmt4t8yenImKBVvK0kTmF0xjctABnaLJIm9

Fig 14-http://cropgenebank.sgrp.cgiar.org/images/management/wheat_smogs/barley_stripe_mosaic_virus_%28bsmv%29.jpg

Fig 15-http://agropedia.iitk.ac.in/sites/default/files/uas%20raichur/Die%20back%20symptoms.jpg

Fig 16- http://www.apsnet.org/publications/apsnetfeatures/Article%20Images/Huanglongbing_Fig01.jpg

Fig 17- http://idtools.org/id/citrus/diseases/images/fs_images/04CitrusCanker.jpg

Fig 18- https://c1.staticflickr.com/5/4062/4712129326_8df483a871.jpg

Fig 19- http://vegetablemdonline.ppath.cornell.edu/Images/Tomato/Tom_BacCanker/Bacterial-cankerNecSpots.jpg

Fig 20- http://cdn.c.photoshelter.com/img-get/I0000i9kw_zx62Wo/s/600/600/510205.jpg

Fig 21- http://plant.daleysfruit.com.au/l/citrus-graft-sap-3420.jpeg

Fig 22- http://th06.deviantart.net/fs70/PRE/i/2012/018/3/c/morning_guttation_by_do7slash-d2qj6xn.jpg

Fig 23- http://themountaineer.villagesoup.com/media/Common/17/E2/1172128/Early%20Blight.jpg

Fig 24- http://www.greaterkashmir.com/news/2008/Nov/4/images/news_4_11_2008_2.jpg

Fig 25- http://agropedia.iitk.ac.in/sites/default/files/13_1.bmp

Fig 26- https://extension.illinois.edu/photolib/lib17//midsize/anthracnose%20-%20silver%20maple.jpg

Fig 27- http://www.invasive.org/collections/viewcollection.cfm?id=81953

Fig 28- http://www7.inra.fr/hyp3/images/6032562.jpgFig 29- http://pesticideguy.files.wordpress.com/2013/05/06-fire-blight_-apple.jpgFig 30- http://upload.wikimedia.org/wikipedia/commons/9/9e/Agrobacteriumgall.jpgFig 31-

http://www.delange.org/Fruit_Tree_Disease_Arizona/Blackberry_Crown_Gall_Agrobacterium_tumefaciens.jpg

Fig 32-http://lindagilkeson.com/Book%20Images/foliage_adj/146%20pea%20enation%20mosaic%20virus.jpg

Fig 33- http://bugwoodcloud.org/images/768x512/1235015.jpgFig 34- https://ediblesanmarcos.files.wordpress.com/2010/06/100_08631.jpgFig 35- http://www.redbudlanenursery.com/portals/0/IDM/DownyMildewLeaf.jpgFig 36-http://hgtv.sndimg.com/HGTV/2012/01/11/RX-DK-LGC11203_rust-

disease_s4x3_lg.jpgFig 37- http://www.cavalieragrow.ca/wp

content/uploads/2014/08/loosesmutwheatb.jpg

Fig 38- http://www.cavalieragrow.ca/wp-content/uploads/2014/08/loosesmutwheatb.jpg