WELCOME TO
ALL
DISPERSAL OF PLANT PATHOGENS
COURSE NO. PPATH 322
COURSE TITLE: PRINCIPLES OF PLANT PATHOLOGY AND DISEASES OF FIELD CROPS
...
Topics
1. What is DISSEMINATION of plant
pathogens
2. Necessity of dissemination
3. Types of dispersal
4. Modes of pathoge...
Dissemination/dispersal/transmission
Transport of spores or infectious bodies, acting as
inoculum, from one host to anothe...
EFFECTIVE DISPERSAL
If displacement occurs on a susceptible host and where
the environment is suitable, the pathogen can g...
Why Pathogen Disseminate

•Food and nutrition
•Survival
•Complete life cycle
•Reproduction
6
Agents of dissemination
1.
2.
3.
4.
5.
6.
7.
8.

Wind-----------------------------------------Anemochory
Water------------...
The dispersal of infectious plant pathogens in space occurs
through two ways:
Disease

1. Autonomous or direct or active ...
Wind as a means of dispersal
Short distance dissemination
sporangia of downy mildew fungi,
conidia of powdery mildew fungi...
Wind

Wind disseminating fungi
Bacteria
•Numerous spore
•discharge of spores with sufficient force X. malvacearum, Erwinia...
Factors affecting wind disemination
•

•
•

Periodicity of wind
– Diurnal
– Nocturnal
Turbulance in air
Air current
– Stea...
Some Example:
•P.Graminis tritici
• Horizontal---600Km
• Altitude-------500m above of the infected field
•P. Infestans
• H...
International Dispersal
From America to Europe ---------------------------Puccinia Striformis
From Newzealand to Austrslia...
Dispersal by water

Surface running water
after heavy rains
during irrigation: canals and wells
Ex: The mycelial fragme...
By rain splash ------------splash dispersal
•
•

•
•

Most efficient meas for bacteria.
Rain drops falling with force on s...
1) Animate agents
Insects
Fungal pathogens:
honey secretions having attractive odours.
Ex: Sugary disease of sorghum
Bacte...
•

Mechanical
– Fungi-----------------------------Legs
– Bacteria--------------------------Bristles
– Viruses-------------...
e) Human beings- more direct than indirect
•
•
•
•
•
•
•

Transportation of seeds (seed trade): Ex: Late blight of potato,...
f) Dispersal by phanerogamic parasites:
• Phanerogamic parasites transmit the viruses by acting as a
bridge between the di...
g) Role of birds
• Disperse flowering parasites and certain fungi.
• Stem segments of dodder are carried by birds for prep...
Farm and wild animals:
Cattle feeding on diseased fodder ingest the
viable fungal propagules (spores or oospores
or sclero...
Books Recommended

Mehrotra & Aggarwal

V. N. Pathak
22
Two more books
• Plant disease –R.S. Singh-India
• A text book of plant pathology- H.
Ashrafuzzaman-Bangladesh

23
24
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Dispersal of Plant Pathogens

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Dispersal of Plant Pathogens

  1. 1. WELCOME TO ALL
  2. 2. DISPERSAL OF PLANT PATHOGENS COURSE NO. PPATH 322 COURSE TITLE: PRINCIPLES OF PLANT PATHOLOGY AND DISEASES OF FIELD CROPS K. M. GOLAM DASTOGEER LECTURER DEPARTMENT OF PLANT PATHOLOGY BANGLADESH AGRICULTURAL UNIVERSITY
  3. 3. Topics 1. What is DISSEMINATION of plant pathogens 2. Necessity of dissemination 3. Types of dispersal 4. Modes of pathogen dissemination a. Winds, Water, Human, Birds, Insects, Animals—Indirect b. Seed, plant parts, Soil-----direct 3
  4. 4. Dissemination/dispersal/transmission Transport of spores or infectious bodies, acting as inoculum, from one host to another host at various distances resulting in the spread of the disease. or Displacement of a plant pathogen from its place of production or origin to a suitable place where it can grow/establish 4
  5. 5. EFFECTIVE DISPERSAL If displacement occurs on a susceptible host and where the environment is suitable, the pathogen can grow and multiply Ineffective Dispersal When plant pathogen does not get any medium for its survival. For example, if it falls on a stone
  6. 6. Why Pathogen Disseminate •Food and nutrition •Survival •Complete life cycle •Reproduction 6
  7. 7. Agents of dissemination 1. 2. 3. 4. 5. 6. 7. 8. Wind-----------------------------------------Anemochory Water----------------------------------------Hydrochory Soil Seed Animal---------------------------------------Zoochory Human-------------------------------------- Anthropochory Mechinary used in agriculture Transport system 7
  8. 8. The dispersal of infectious plant pathogens in space occurs through two ways: Disease 1. Autonomous or direct or active dispersal In this method the dispersal of plant pathogens takes place through soil, seed and planting material during normal agronomic operations. There is no major role of external agencies like insects, wind, water, etc. in this type of dispersal. 2. Indirect or passive dispersal------- insects, wind, water, etc. in this type of dispersal insects, wind, water, Human 8
  9. 9. Wind as a means of dispersal Short distance dissemination sporangia of downy mildew fungi, conidia of powdery mildew fungi and basidiospores of rust fungi Long Distance •Uredospores of rust fungi, Chlamydospores of smut fungi and conidia of Alternaria, Helminthosporium and Pyricularia,
  10. 10. Wind Wind disseminating fungi Bacteria •Numerous spore •discharge of spores with sufficient force X. malvacearum, Erwinia amylovora • Light in weight Nematode • smaller size Anguina tritici, Heterodera •Thich outer wall •Less affinity to water Virus Vector •19 Viruses and phytoplasmas – •E.g. Most fungi except synchytriaceae, • insect and mite vectors by wind Plasmodiophoromyces, fusarium
  11. 11. Factors affecting wind disemination • • • Periodicity of wind – Diurnal – Nocturnal Turbulance in air Air current – Steady-horizontal – Breeze & turbulance-Vertical – Irregular-Multidimensional Record of air velocity and direction tells the direction and distance of spore dispersal and thereby helps to forecast neww disease outbreak is likely to occur 11
  12. 12. Some Example: •P.Graminis tritici • Horizontal---600Km • Altitude-------500m above of the infected field •P. Infestans • Horizontal---200m to 600Km •Spores of Molds •Aspergillus •Penicillium •Cladosporium • Altitude----------2000m above
  13. 13. International Dispersal From America to Europe ---------------------------Puccinia Striformis From Newzealand to Austrslia--------------------P. Striformis From England to Denmark--------------------------Powdery Mildew of Barely Glass with glycerine Microscope Fig. Spore Trap 13
  14. 14. Dispersal by water Surface running water after heavy rains during irrigation: canals and wells Ex: The mycelial fragments, spores or sclerotia of fungi, Colletotrichum falcatum, Fusarium, Ganoderma, Macrophomina, Pythium, Phytophthora, Sclerotium, etc.,  Long distance ------ floods
  15. 15. By rain splash ------------splash dispersal • • • • Most efficient meas for bacteria. Rain drops falling with force on sori, pustules, cankers or even soil surface may splash the propagules – in small droplets and enable them to land on neighbouring healthy susceptible surfaces or – the water droplets may be carried to long distances by air. Ex: Bacterial leaf spot of rice (Xanthomonas campestris pv. oryzae), Bacterial leaf streak of rice (Xanthomonas campestris pv. oryzicola) Fungal spores and bacteria present in the air or plant surface are washed downward by rain splash or drops from overhead irrigation and are deposited on susceptible healthy plants. 15
  16. 16. 1) Animate agents Insects Fungal pathogens: honey secretions having attractive odours. Ex: Sugary disease of sorghum Bacterial pathogens Cucumber wilt- E. tracheiphila --------stripped cucumber beetles (Acalymma vittata) a---------spotted cucumber beetle (Diabrotica undecimipunctata). Viral pathgens: • More than 80 % of viral and phytoplasmall diseases • Laegest family- Homoptera- Aphids and leaf hoppers • mealy bugs and scale insects (Coccoidae) • whiteflies (Aleurodidae) • hoppers (Membracidae) in Homoptera also transmit virus diseases. •
  17. 17. • Mechanical – Fungi-----------------------------Legs – Bacteria--------------------------Bristles – Viruses---------------------------Wings – Mycoplasma--------------------Abdomen • Biological Transmit through sexual process from generation to generation Insect Specificity of Insect Transmission Aphids----------------Mosaic group---------------Tomato mosaic, Papaya mosaic, potato leaf roll, chilli mosaic Leaf Hopper---------Yellows ---------------------------------Tungro of rice Thrips------------------Spots with concentric ring---------Pineaple yellow spots Whiteflies-------------Thickening of veins/veinlets------Tobacco leaf curl, Tomato leaf curl 17
  18. 18. e) Human beings- more direct than indirect • • • • • • • Transportation of seeds (seed trade): Ex: Late blight of potato, Downy mildew of grapevine, Citrus canker, Fusarium wilt of banana, etc. Planting diseased seed materials: Planting diseased bulbs, bulbils, corms, tubers, rhizomes, cuttings, etc., of During adoption of normal farming practices: Cultivation, planting, irrigation, weeding, pruning etc., Spores can be carried by workers clothing’s, shoes, and hands etc., By use of contaminated implements: By use of diseased grafting and budding material
  19. 19. f) Dispersal by phanerogamic parasites: • Phanerogamic parasites transmit the viruses by acting as a bridge between the diseased and healthy plants. • Ex: Dodder(Cuscuta California, C. campesris, C. subinclusa etc.) • Cuscuta subinclusa----Cucumber mosaic virus • Cuscuta california -----Tobacco mosaic virus, Tobacco rattle virus, Tomato spotted wilt virus • Cuscuta campestris - Tomato bushy stunt virus 19
  20. 20. g) Role of birds • Disperse flowering parasites and certain fungi. • Stem segments of dodder are carried by birds for preparing their nests • Seeds of Loranthus • Spores of chestnut blight fungus • Cleistothecia of many powdery mildew fungi are carried by feathers of birds. 20
  21. 21. Farm and wild animals: Cattle feeding on diseased fodder ingest the viable fungal propagules (spores or oospores or sclerotia) and pass out as such in the dung. soil inhabiting fungi especially sclerotia adhere to the hoofs and legs of animals and get transported to other places. 21
  22. 22. Books Recommended Mehrotra & Aggarwal V. N. Pathak 22
  23. 23. Two more books • Plant disease –R.S. Singh-India • A text book of plant pathology- H. Ashrafuzzaman-Bangladesh 23
  24. 24. 24

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